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χ3–borophene-based detection of hydrogen sulfide via gas nanosensors
Journal Pre-proofs Research paper χ3 –borophene-based detection of Hydrogen Sulfide via gas nanosensors Mohammad Fazilaty, Majid Pourahmadi, Mohammad Reza Shayesteh, Saeedeh Hashemian PII: DOI: Reference:
S0009-2614(19)31047-4 https://doi.org/10.1016/j.cplett.2019.137066 CPLETT 137066
To appear in:
Chemical Physics Letters
Received Date: Revised Date: Accepted Date:
31 October 2019 22 December 2019 28 December 2019
Please cite this article as: M. Fazilaty, M. Pourahmadi, M. Reza Shayesteh, S. Hashemian, χ3 –borophene-based detection of Hydrogen Sulfide via gas nanosensors, Chemical Physics Letters (2019), doi: https://doi.org/ 10.1016/j.cplett.2019.137066
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier B.V.
χ3 –borophene-based detection of Hydrogen Sulfide via gas nanosensors
Mohammad Fazilaty1,*Majid Pourahmadi1, Mohammad Reza Shayesteh1, Saeedeh Hashemian2 1Department
of Electrical Engineering, Yazd Branch, Islamic Azad University, Yazd, Iran 8916871967
2Department
of Chemistry, Yazd Branch, Islamic Azad University, Yazd, Iran 8916871967 [email protected] [email protected] [email protected] [email protected]
Abstract A combination of non-equilibrium Green’s function (NEGF) method and density functional theory was employed to explore a χ3-borophene nanoribbon placed between two χ3-borophene nanoribbon electrodes. This study demonstrates that the Hydrogen Sulfide (H2S) molecule transfers a fraction of charges to the χ3-borophene nanoribbon, thus resulting in highly visible changes in the Density of states (DOS), transmission spectrum and I-V curve. Moreover, changes in the sub-bands of electrodes caused by gas adsorption were found accountable for the current variation. Hence, they are proved to be sensitive nanosensors with high selectivity and the capability to show dramatic industrial application capabilities. Introduction Borophene, a structure consisting of a single layer of the boron atoms, has recently been synthesized by two independent groups [1]. Interestingly, the outcome of these experiments is different and indicates two-dimensional boron polymorphs [2]. Most of the all-boron quasi-planar clusters and nano-surfaces, including nanosheets, are made of triangular atomic rings [3]. In 2015, Ihsan Boustani et al [4] and Mannix et al. [1][5] synthesized borophene as a 2D-boron sheet on Ag (111) under ultrahigh vacuum conditions. Over the past two years, several studies have been conducted on the outstanding features of borophene sheets. The synthesized structure represented a strong anisotropy [6]. Precise analysis of the Scanning Tunneling Microscopy (STM) and Density Functional Theory (DFT)-based simulation showed that three phases of the borophene [6], i.e., 2Pmmn, χ3, and β12, are synthesized in two above-mentioned experiments. Compared with other theoretically proposed models of the boron sheet, neither β12 nor χ3 can be the ground-state structure [1]. Also, both β12 and χ3 demonstrate a triangular lattice characterized by varying arrangements of periodic holes [6]. Moreover, they are flat without clear vertical undulation, observable through scanning tunneling microscopy [7]. Finally, the β12 and χ3 sheets have very adjacent hole densities [6]. The dense composition of these sheets well justifies the smooth transition between the two structures during the annealing process [1]. Contrary to the above semimetals or semiconductors, β12 and χ3 borophenes are metallic in nature [8]. The β12 and χ3 sheets have tight hole densities, which well explains the easy exchanges between the two structures at the time of annealing [9]. Both borophenes are planar and devoid of any vertical undulation. Despite such a crucial characteristic, many periodic boron vacancy distribution patterns are detected in the course of experiments and first principles of calculations. Meanwhile, χ3-sheet (Fig. 1a) enjoys the largest fraction of boron with a coordination number of 5(CN=5). In this regard, χ3 borophene is prepared through growing boron from an electron beam evaporator under a substrate temperature of ≈750 K [10]. Contrary to the β12 phase, the χ3 phase has a weaker substrate-over layer hybridization [1]. Consequently, a quasi-freestanding borophene sheet has been detected in this sheet. The anisotropic behavior of χ3 can be justified on the account of the directionality of its vacancy arrangement [11]. Observing the χ3 sheet in the x-direction, it is seen that the atoms are more densely packed than when considered in the y-direction. Furthermore, upon close consideration, the mechanical properties of the sample were found to be substantial. On the other hand, due to nanoscale features, like a high surface area to volume ratios, high crystallinity was evident in χ3 sheets [12]. Regarding the possibility of functionalization by the *
Correspond author
1
application, nanomaterial-based sensors are assumed to have the potential of offering a high ratio of detection sensitivity to cost, a considerably increased speed of response, miniaturized size sensors and most importantly operating with low power demands [13]. In general, a sensor converts a measurable physical or chemical quantity into a signal that can be noticed by an observer or the apparatus [14]. Sensors are a domain of applications that are growingly evolving [14]. The more technology offers improved products, the more will demand from technology would be. Furthermore, the higher miniaturization demands are, the smarter the processing techniques would be and more miniaturized interfaces will emerge [13][14]. Within the miniaturization process, the electromagnetic crosstalks will remain non-trivial. Thus, we need sensing approaches that are immune to electromagnetic variations. One solution for this purpose is the optic fiber sensor [14]. Environmental monitoring, chemical, textile, food, medical diagnosis, pharmaceutical industries, military applications, and gas sensing, especially ammonia sensing, are highly demanded in the industrial sector [15]. With rapid development in modern industrial technology, environmental pollution caused by harmful gases has become an increasingly serious issue [15]. Therefore, studies on adsorption and detection of harmful gases are becoming very significant. Low power consumption and higher performance are compelling demands in the electronic systems. As a result, it is necessary to find new materials capable of addressing these demands [16]. Also, Hydrogen sulfide (H2S) gas has been identified as a health hazard to human beings and swine in deep-pit production systems, emanated mainly from gasoline, natural gases, and urban sewage. H2S gas is colorless, corrosive, flammable, extremely toxic and potentially lethal even at low concentrations [17]. Typically, it exists as low as few parts per million (ppm). The damaging effects of H2S depend on the amount of the inhaled gas and the time length. Acute exposure to high concentrations of hydrogen sulfide is potentially lethal during manure agitation and removal events in deep-pit swine housing [18]. This research aims to investigate the sensing and adsorption of H2S gas phenomena in the χ3 borophene based on the density functional theory. Moreover, it is tried to analyze the external bias voltage using nonequilibrium Green’s function formalism. First-principle DFT Calculations Density Functional Theory (DFT) calculations have been employed to investigate the electronic properties and the energetics of H2S/3-XBNR [19]. These computations were performed using SIESTA ab-initio Package [20] owing its efficiency to the strictly localized basis sets and pseudopotential method for treating core electrons of each atomic type. We used Generalized Gradient Approximation (GGA) with Perdew-Burke-Ernzerhof [21] exchangecorrelation functional and norm-conserving Troullier-Martins [22] pseudopotential as our approximations. Also, the double zeta polarization basis set was chosen for calculating the electronic properties. The kinetic energy cut-off was considered as 300 Rydberg. Also, the first Brillouin Zone was sampled using a 20×1×1 regular Monkhorst-Pack grid [23] for nanoribbon calculations with fermi-Dirac smearing method to determine electron occupancies with an electronic temperature of 300K. The electronic self-consistent iteration convergence threshold was set to 10-6eV and the ionic relaxations overall this paper was performed via conjugate gradient method. Thus, the maximum of the total force component on each atom in the supercell became less than 0.01 eV/Å. The mentioned criteria were applied to calculate the surface energetics of the H2S molecule on χ3 Brophene nanoribbon cut along x-direction (χ3-XBNR). For non-periodic directions (z and y-directions) of the ribbon, a vacuum region with a length of 20 Å was set. In the past two decades, non-equilibrium Green Function (NEGF) [24] has been introduced as a remarkable technique to calculate transport properties. Numerous papers can be found that apply the technique successfully to estimate the transport properties of different devices at a maximum level of accuracy. NEGF indebts most of its success to the definition of an open system and calculation of transport properties of the essential part of the device. This simple estimate combines several techniques with DFT to provide an effective tool to calculate the transport properties of devices with exceptionally favorable results. Various software packages such as TranSiesta [20] are used to investigate the transport properties of the structure. TranSiesta employs a procedure to solve the electronic structure of a system formed by a finite material sandwiched between two metallic leads. In this approach, Green function techniques are used to find electronic density from DFT Hamiltonian for an open system instead of diagonalization. To investigate the transport properties of the system, we considered a setup consisting of three main parts (Fig. 5a), with left and right leads and a central scattering region. Left and right leads are considered as ideal χ3-borophene nanoribbon, which represents long pristine structures indeed. The scattering region is comprised of an edge-hydrogenated χ3-borophene nanoribbon. Using a double zeta-polarized basis set, this study compares the I-V characteristics of the system with/without the H2S molecule. Using the Landauer-Buttiker formula [24], the electric current through the central scattering region is as follows:
2
∫
𝐼(𝑉𝑏) = 𝐺0
𝜇𝑅
𝑇(𝐸,𝑉𝑏)[𝑓(𝐸 ― 𝜇𝐿) ― 𝑓(𝐸 ― 𝜇𝑅)]𝑑𝐸, (1)
𝜇𝐿
where G0=2e2/h is unit of quantum conductance, T(E, Vb) is transmission probability of electrons through potential Vb, f is fermi-Dirac distribution, and μ (μ ) is the chemical potential of right (left) lead. Furthermore, in this R
L
research, the cut-off energy for transport calculation is considered to be 300 Rydberg, and the k-sampling was performed with a 1×1×101 Monkhorst-Pack grid. To study the adsorption mechanism of the H2S molecule on different sites of the ribbon, we may calculate adsorption energy defined as Eads = EH-BNR/gas – (EH-BNR + Egas). The adsorption energy (Eads) of an adsorbate to the surface was calculated as the energy difference between the molecule-surface system and the system of isolated clean surface and gas molecule. Negative Eads indicates an attractive interaction between the adsorbate and the surface. Also, the relative stability of the ribbon can be investigated by formation energy defined as E = [EH-XBNR − mEsheet – nEH2/2]/m+n. Here, Esheet is the total energy of χ3-borophene sheet per atom, EH2 corresponds to hydrogen molecule energy, and (m,n) are the number of boron and hydrogen atoms in hydrogenated χ3-borophene nanoribbon, respectively. Moreover, there are two important factors for determining the performance of a gas sensor: sensitivity and selectivity. The sensitivity [27] of gas sensors is defined as S(%)=|C-C0|/C0, where C0 (in units of 2e2/h) is the conductance of a clean ribbon’s surface and C is the conductance after surface exposure to the gas at Fermi energy. Selectivity [27] is the capacity of a sensor to discriminate between gases in a mixture. A good sensor will detect a particular signal by allowing adsorption of the desired gas while remaining insensitive to others. The selectivity coefficient (K) of ‘target gas’ to another gas is defined as K=SA/SB, where SA and SB are the sensitivities of ‘target gas’ and the other gas, respectively. Results and Discussion The optimized primitive cell of χ3-borophene sheet is demonstrated in Fig. 1a which is composed of four B atoms. The lattice constants of the sheet for A and B are equal to 2.94 Å and 4.49 Å respectively, which is in good agreement with other experimental and theoretical works [25]. χ3-borophene sheet owes its flat structure to the presence of hexagonal vacancies [6,26]. The band structure in Fig. 1c (left) shows metallic behaviour along all symmetry lines in Brillouin zone. According to Density of States shown in Fig. 1c (right) The largest contribution of electrons close to the Fermi level are attributed to p orbitals. These orbitals are mostly of and types. orbitals represent strong in-plane bonds; orbitals have out-of-plane two-headed parallel bonds and play an important role in making the structure stable. 4
KA
c
a
b
2
X
S
B
E-Ef(eV)
A
S+Px+Py Pz
Y
0
-2
KB -4
X
S
Y
0
0.5
1
DOS(States/eV)
(a)
(b)
(c)
Fig.1 (a) The primitive cell of the χ3-borophene sheet (up) (b) first Brillouin zone, and (c) band structure of the sheet along high symmetry points in BZ To understand the adsorption of H2S on χ3-borophene nanoribbon, one should primarily conduct a relaxation study. In order to make borophene nanoribbon cut along B (XBNR), we change the primitive cell to a rectangular unit cell
3
x
with r1 = 2A − B and r2 = B lattice vectors (Fig. 2a), repeat the unit cell 5 times along r1, and then cut along r2direction (Fig. 2b).
b
c
a
(a)
(b)
Fig. 2. The schematic of top views of (a) rectangular unit cell of 3-borophene sheet and (b) edge-hydrogenated χ3borophene nanoribbon cut along r2-direction (3-XBNR)
y
z
To remove the effect of dangling bonds, hydrogen atoms are used on both the top and bottom edges of the χ3borophene nanoribbon in an armchair structure (Fig. 2b). The supercell is small enough to be adequate for computations. The formation energy of the ribbon is E=0.183 eV, which shows a stable structure with respect to the χ3-borophene sheet. According to the literature [25], the stability of the ribbon may get better by increasing its width. In this work, we relaxed the adsorption configurations at different sites. We started with multiple initial guesses at the center of the ribbon and approached the edge. We found out that adsorption is more favorable near the edges of the ribbon. Meanwhile, we tried different orientations of the H2S molecule and each time the structure relaxed to S-down geometry in all configurations. Let us analyze the bonding characteristics of the gas with the borophene surface in detail. The adsorption energy (Eads) of H2S adsorbate to the surface is calculated to be -5.35 eV. Figs. 3a-3d illustrate the relaxed geometry of an H2S on χ3-XBNR and charge density difference defined as Δρ = ρtot(r) – ρribbon(r) − ρgas(r), where ρtot(r) is the charge distribution on relaxed ribbon with the adsorbed gas, ρribbon(r) is the charge distribution on borophene, and ρgas(r) is the charge distribution on the isolated gas. Conceptually, Δρ depicts the charge accumulation/depletion in the system by which we can easily visualize the charge transfer. According to Fig. 3a-3d, when the H2S molecule approaches the surface of the sulfur atom, it slightly deforms the edge of the ribbon and a charge transfer occurs from molecule to the surface that represents a strong bonding with the surface. x
z
(a)
x
y
(b)
4
(c)
(d)
Fig. 3. The relaxed structure of H2S molecule adsorbed on the ribbon: (a) top view and (b) side view and charge density difference with isosurface level of 0.0006 eV/ Å 3 on χ3-XBNR: (c) top view (d) side view; blue surface denotes electron gain while the red surface represents electron loss. Another quantity that elaborates the dramatic change in the electronic properties of the ribbon before and after gas adsorption is the total density of states (DOS). Fig. 4 depicts the metallic behavior of the pristine ribbon and the ribbon with adsorbed gas and the tolerable DOS near the Fermi energy. As can be inferred from this figure, this molecule induces a significant change in DOS of the system. DOS(states/eV)
16
14
12
10
8
6
4
2
0 -6 -4 -2 2 4
hydrogenated 3-XBNR
H2S + hydrogenated 3-XBNR
0
Energy(eV)
6
Fig. 4. The DOS near-zero energy for the relaxed situation of hydrogenated χ3-XBNR (solid line) and the system of H2S + hydrogenated χ3-XBNR (dash-dotted line) The instrument shown in Fig. 5a was used to detect the alteration in the transport properties as a result of the H2S adsorption on χ3-borophene nanoribbon. We considered the transport along the z-direction. Fig. 5b shows the current-voltage (I-V) characteristics, where a noticeable effect of H2S adsorption is observed. Therefore, so the resistance of the device is different in the presence of gas compared to the pristine ribbon, as implied from Fig. 5b. Current(A)
100
80
60
40
20
0 0 1
hydrogenated 3-XBNR
H2S + hydrogenated 3-XBNR
0.5
Voltage(V)
1.5 2
(a)
(b)
Fig. 5 (a) illustration of the device setup (top view) showing the semi-infinite left and right electrode regions and the central scattering region. (b) Current (μA) -Voltage (V) characteristics of hydrogenated χ3-XBNR (black) and the system of H2S + hydrogenated χ3-XBNR (red)
5
Zero bias transmission spectra T(E) in the presence and absence of gas molecules are presented in Fig. 6. The results show that adsorption of the gas molecules results in decreased transmission of incident electrons. Transmission(G/G ) 0
8
7
6
5
4
3
2
1
0 -2 -1.5 -1 0.5 1 1.5
hydrogenated 3-XBNR
0
H2S + hydrogenated 3-XBNR
-0.5
Energy(eV)
2
Fig. 6. The transport spectrum at zero bias is plotted in terms of energy for the absorption state with the minimum absorption energy Fig. 6 shows T(E) for the minimum absorption energy state in terms of energy. Physically, borophene is placed between electrodes, forming a potential barrier for electronic transport. At the time of absorption, the electronic structure changes cause the electronic transport coefficient to alter. As can be seen, there is no band gap adjacent to the Fermi energy and the conduction mechanism is made purely through electron transport near the Fermi energy. the electron transport coefficient adjacent to the fermi energy for ribbon with adsorbed gas experiences a reduction with respect to the bare ribbon. Therefore, the sensitivity of the gas sensor is S=31.35%. The basic problem of most gas sensors is that the conductivity value can be almost the same for different gas species and concentrations. Moreover, they suffer from a lack of selectivity and drift [27]. Various sophisticated and very costly techniques could be used for enhancing the sensor selectivity [28]. The difficulty consists that they are very often influenced by water vapor and thus the changes in the moisture content of the ambiance could interfere considerably the gas sensing. To determine the selectivity of the sensor or amount of interference from other gases, we first examined H2O and NO sensitivities. According to the definition of selectivity, the ratio of the target gas (H2S) sensitivity and other gases’ sensitivities (H2O and NO) are 2672.64 and 2.51, respectively. So, H2O plays a negligible role in the transport channels of the device and NO have a sensitivity of 12.48% which is 2.51 times smaller than that of H2S. This observation proves that the device resistance is increased and can be a very ideal candidate for a nanosensor. Eigen Channel analysis was used for a better understanding of electron transport. Graphical illustration of scattering modes helps to gain a better understanding of the modes (especially channels) of the system. These special modes can be useful in understanding the band structure of the borophene nanoribbon. At zero bias, the electrical conductivity is obtained from the sum of the eigenvalues of each channel eigenvalue. We calculated these channel properties using the simulation results obtained by TranSIESTA and Inelastic Package. Fig. 7a shows a dominant channel passing through the left electrode at Fermi energy and Fig. 7b shows a decreased channel passing in the presence of the H2S molecules, which shows the high sensitivity of the device. Furthermore, the figure shows that the scattering modes vary widely across the strips. The more localized (non-localized) modes are distributed along the channel, causing less (more) electrical conductivity.
6
b
c
a
y
z
x
(a)
(b)
Fig. 7. The Eigen channel analysis specifically used for passing from the left electrode direction in the Fermi energy: (a) before and (b) after gas adsorption Conclusion This study focuses on the adsorption of Hydrogen Sulfide (H2S) molecules on χ3-borophene nanoribbon using nonequilibrium Green’s function (NEGF) coupled with density functional theory and the transport property model. We demonstrated that the hydrogen sulfide molecules in the system have remarkable effects on the transmission of an electron from the scattering region. The data analysis results showed that H2S molecule can reverse the correlation of orbitals and cause changes in the transmission spectrum. Moreover, this molecule made a significant current reduction in the I-V curve of the χ3-borophene nanoribbon. We further computed transmission functions, sensitivity and selectivity in the presence of H2O and NO for this device and observed a lower sensitivity compared to H2S. The results confirm that the system is a proper structure for the H2S gas sensor and can show immense capabilities for industrial usage. References 1.
Mannix, Andrew J., Xiang-Feng Zhou, Brian Kiraly, Joshua D. Wood, Diego Alducin, Benjamin D. Myers, Xiaolong Liu et al. "Synthesis of borophenes: Anisotropic, two-dimensional boron polymorphs." Science 350, no. 6267 (2015): 1513-1516. 2. Feng, Baojie, Jin Zhang, Qing Zhong, Wenbin Li, Shuai Li, Hui Li, Peng Cheng, Sheng Meng, Lan Chen, and Kehui Wu. "Experimental realization of two-dimensional boron sheets." Nature Chemistry 8, no. 6 (2016): 563. 3. Chkhartishvili, Levan, Ivane Murusidze, and Rick Becker. "Electronic Structure of Boron Flat Holeless Sheet." Condensed Matter 4, no. 1 (2019): 28. 4. Boustani, Ihsan. "New quasi-planar surfaces of bare boron." Surface science 370, no. 2-3 (1997): 355-363. 5. Ranjan, Pranay, Tumesh Kumar Sahu, Rebti Bhushan, Sharma SRKC Yamijala, Dattatray J. Late, Prashant Kumar, and Ajayan Vinu. "Borophene: Freestanding Borophene and Its Hybrids (Adv. Mater. 27/2019)." Advanced Materials 31, no. 27 (2019): 1970196. 6. Zhang, Zhuhua, Evgeni S. Penev, and Boris I. Yakobson. "Two-dimensional boron: structures, properties and applications." Chemical Society Reviews 46, no. 22 (2017): 6746-6763. 7. Luo, Zhifen, Xiaoli Fan, and Yurong An. "First-principles study on the stability and STM image of borophene." Nanoscale research letters 12, no. 1 (2017): 514 . 8. Adamska, Lyudmyla, and Sahar Sharifzadeh. "Fine-tuning the optoelectronic properties of freestanding borophene by strain." ACS Omega 2, no. 11 (2017): 8290-8299. 9. Feng, Baojie, Jin Zhang, Ro-Ya Liu, Takushi Iimori, Chao Lian, Hui Li, Lan Chen et al. "Direct evidence of metallic bands in a monolayer boron sheet." Physical Review B 94, no. 4 (2016): 041408. 10. Wu, Rongting, Ilya K. Drozdov, Stephen Eltinge, Percy Zahl, Sohrab IsmailBeigi, Ivan Božović, and Adrian Gozar. "Large-area single-crystal sheets of borophene on Cu (111) surfaces." Nature nanotechnology 14, no. 1 (2019): 44. 11. Wang, Zhiqiang, Tie-Yu Lü, Hui-Qiong Wang, Yuan Ping Feng, and JinCheng Zheng. "High anisotropy of fully hydrogenated borophene." Physical Chemistry Chemical Physics 18, no. 46 (2016): 31424-31430.
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12. Wu, Xin, Fengwen Mu, Yinghui Wang, and Haiyan Zhao. "Graphene and Graphene-Based Nanomaterials for DNA Detection: A Review." Molecules 23, no. 8 (2018): 2050. 13. Nazemi, Haleh, Aashish Joseph, Jaewoo Park, and Arezoo Emadi. "Advanced micro-and nano-gas sensor technology: A review." Sensors 19, no. 6 (2019): 1285. 14. Aliofkhazraei, M., and N. Ali. "Recent developments in miniaturization of sensor technologies and their applications." (2014): 245-306. 15. Singh, Eric, M. Meyyappan, and Hari Singh Nalwa. "Flexible graphene-based wearable gas and chemical sensors." ACS applied materials & interfaces 9, no. 40 (2017): 34544-34586. 16. Fiori, Gianluca, Francesco Bonaccorso, Giuseppe Iannaccone, Tomás Palacios, Daniel Neumaier, Alan Seabaugh, Sanjay K. Banerjee, and Luigi Colombo. "Electronics based on two-dimensional materials." Nature nanotechnology 9, no. 10 (2014): 768. 17. Shah, Mansi S., Michael Tsapatsis, and J. Ilja Siepmann. "Hydrogen sulfide capture: From absorption in polar liquids to oxide, zeolite, and metal–organic framework adsorbents and membranes." Chemical reviews 117, no. 14 (2017): 9755-9803. 18. Chou, C. H., and World Health Organization. Hydrogen sulfide: human health aspects. World Health Organization, 2003. 19. Kohn, Walter, and Lu Jeu Sham. "Self-consistent equations including exchange and correlation effects." Physical review 140, no. 4A (1965): A1133. 20. Soler, José M., Emilio Artacho, Julian D. Gale, Alberto García, Javier Junquera, Pablo Ordejón, and Daniel Sánchez-Portal. "The SIESTA method for ab initio order-N materials simulation." Journal of Physics: Condensed Matter 14, no. 11 (2002): 2745. 21. Perdew, John P., Kieron Burke, and Yue Wang. "Generalized gradient approximation for the exchangecorrelation hole of a many-electron system." Physical Review B 54, no. 23 (1996): 16533. 22. Troullier, Norman, and José Luís Martins. "Efficient pseudopotentials for plane-wave calculations." Physical review B 43, no. 3 (1991): 1993. 23. Monkhorst, Hendrik J., and James D. Pack. "Special points for Brillouin-zone integrations." Physical review B 13, no. 12 (1976): 5188. 24. Datta, S. "Quantum Transport: Atom to Transistor Cambridge University Press." (2005). 25. Vishkayi, Sahar Izadi, and Meysam Bagheri Tagani. "Freestanding χ 3-borophene nanoribbons: a density functional theory investigation." Physical Chemistry Chemical Physics 20, no. 15 (2018): 10493-10501. 26. Peng, Bo, Hao Zhang, Hezhu Shao, Zeyu Ning, Yuanfeng Xu, Gang Ni, Hongliang Lu, David Wei Zhang, and Heyuan Zhu. "Stability and strength of atomically thin borophene from first principles calculations." Materials Research Letters 5, no. 6 (2017): 399-407. 27. Moseley, Pat T. Solid state gas sensors. Taylor & Francis, 1987. 28. Williams, David E., and Patrick T. Moseley. "Dopant effects on the response of gas-sensitive resistors utilising semiconducting oxides." Journal of Materials Chemistry 1, no. 5 (1991): 809-814.
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There is no conflict of Interest between authors absolutely .
Transmission(G/G0)
hydrogenated 3-XBNR
0
0.5
1
1.5
H2S + hydrogenated 3-XBNR
-0.5
2
100
80
60
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0 0
hydrogenated 3-XBNR
Voltage(V)
1
H2S + hydrogenated 3-XBNR
0.5
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-1.5
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Energy(eV)
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An ab-initio study of 3-borophene nanoribbon using DFT and NEGF for H 2S sensing. Large transfer of charge from molecules to the edges of ribbon with high adsorption energies. significant reduction of current in I-V characteristics of the device and strong sensitivity of sensor to hazardous H2 S molecule. The sensor demonstrated a high level of selectivity of H 2 S compared to NO molecule and water vapor (H2O).
S0009-2614(19)31047-4 https://doi.org/10.1016/j.cplett.2019.137066 CPLETT 137066
To appear in:
Chemical Physics Letters
Received Date: Revised Date: Accepted Date:
31 October 2019 22 December 2019 28 December 2019
Please cite this article as: M. Fazilaty, M. Pourahmadi, M. Reza Shayesteh, S. Hashemian, χ3 –borophene-based detection of Hydrogen Sulfide via gas nanosensors, Chemical Physics Letters (2019), doi: https://doi.org/ 10.1016/j.cplett.2019.137066
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2019 Published by Elsevier B.V.
χ3 –borophene-based detection of Hydrogen Sulfide via gas nanosensors
Mohammad Fazilaty1,*Majid Pourahmadi1, Mohammad Reza Shayesteh1, Saeedeh Hashemian2 1Department
of Electrical Engineering, Yazd Branch, Islamic Azad University, Yazd, Iran 8916871967
2Department
of Chemistry, Yazd Branch, Islamic Azad University, Yazd, Iran 8916871967 [email protected] [email protected] [email protected] [email protected]
Abstract A combination of non-equilibrium Green’s function (NEGF) method and density functional theory was employed to explore a χ3-borophene nanoribbon placed between two χ3-borophene nanoribbon electrodes. This study demonstrates that the Hydrogen Sulfide (H2S) molecule transfers a fraction of charges to the χ3-borophene nanoribbon, thus resulting in highly visible changes in the Density of states (DOS), transmission spectrum and I-V curve. Moreover, changes in the sub-bands of electrodes caused by gas adsorption were found accountable for the current variation. Hence, they are proved to be sensitive nanosensors with high selectivity and the capability to show dramatic industrial application capabilities. Introduction Borophene, a structure consisting of a single layer of the boron atoms, has recently been synthesized by two independent groups [1]. Interestingly, the outcome of these experiments is different and indicates two-dimensional boron polymorphs [2]. Most of the all-boron quasi-planar clusters and nano-surfaces, including nanosheets, are made of triangular atomic rings [3]. In 2015, Ihsan Boustani et al [4] and Mannix et al. [1][5] synthesized borophene as a 2D-boron sheet on Ag (111) under ultrahigh vacuum conditions. Over the past two years, several studies have been conducted on the outstanding features of borophene sheets. The synthesized structure represented a strong anisotropy [6]. Precise analysis of the Scanning Tunneling Microscopy (STM) and Density Functional Theory (DFT)-based simulation showed that three phases of the borophene [6], i.e., 2Pmmn, χ3, and β12, are synthesized in two above-mentioned experiments. Compared with other theoretically proposed models of the boron sheet, neither β12 nor χ3 can be the ground-state structure [1]. Also, both β12 and χ3 demonstrate a triangular lattice characterized by varying arrangements of periodic holes [6]. Moreover, they are flat without clear vertical undulation, observable through scanning tunneling microscopy [7]. Finally, the β12 and χ3 sheets have very adjacent hole densities [6]. The dense composition of these sheets well justifies the smooth transition between the two structures during the annealing process [1]. Contrary to the above semimetals or semiconductors, β12 and χ3 borophenes are metallic in nature [8]. The β12 and χ3 sheets have tight hole densities, which well explains the easy exchanges between the two structures at the time of annealing [9]. Both borophenes are planar and devoid of any vertical undulation. Despite such a crucial characteristic, many periodic boron vacancy distribution patterns are detected in the course of experiments and first principles of calculations. Meanwhile, χ3-sheet (Fig. 1a) enjoys the largest fraction of boron with a coordination number of 5(CN=5). In this regard, χ3 borophene is prepared through growing boron from an electron beam evaporator under a substrate temperature of ≈750 K [10]. Contrary to the β12 phase, the χ3 phase has a weaker substrate-over layer hybridization [1]. Consequently, a quasi-freestanding borophene sheet has been detected in this sheet. The anisotropic behavior of χ3 can be justified on the account of the directionality of its vacancy arrangement [11]. Observing the χ3 sheet in the x-direction, it is seen that the atoms are more densely packed than when considered in the y-direction. Furthermore, upon close consideration, the mechanical properties of the sample were found to be substantial. On the other hand, due to nanoscale features, like a high surface area to volume ratios, high crystallinity was evident in χ3 sheets [12]. Regarding the possibility of functionalization by the *
Correspond author
1
application, nanomaterial-based sensors are assumed to have the potential of offering a high ratio of detection sensitivity to cost, a considerably increased speed of response, miniaturized size sensors and most importantly operating with low power demands [13]. In general, a sensor converts a measurable physical or chemical quantity into a signal that can be noticed by an observer or the apparatus [14]. Sensors are a domain of applications that are growingly evolving [14]. The more technology offers improved products, the more will demand from technology would be. Furthermore, the higher miniaturization demands are, the smarter the processing techniques would be and more miniaturized interfaces will emerge [13][14]. Within the miniaturization process, the electromagnetic crosstalks will remain non-trivial. Thus, we need sensing approaches that are immune to electromagnetic variations. One solution for this purpose is the optic fiber sensor [14]. Environmental monitoring, chemical, textile, food, medical diagnosis, pharmaceutical industries, military applications, and gas sensing, especially ammonia sensing, are highly demanded in the industrial sector [15]. With rapid development in modern industrial technology, environmental pollution caused by harmful gases has become an increasingly serious issue [15]. Therefore, studies on adsorption and detection of harmful gases are becoming very significant. Low power consumption and higher performance are compelling demands in the electronic systems. As a result, it is necessary to find new materials capable of addressing these demands [16]. Also, Hydrogen sulfide (H2S) gas has been identified as a health hazard to human beings and swine in deep-pit production systems, emanated mainly from gasoline, natural gases, and urban sewage. H2S gas is colorless, corrosive, flammable, extremely toxic and potentially lethal even at low concentrations [17]. Typically, it exists as low as few parts per million (ppm). The damaging effects of H2S depend on the amount of the inhaled gas and the time length. Acute exposure to high concentrations of hydrogen sulfide is potentially lethal during manure agitation and removal events in deep-pit swine housing [18]. This research aims to investigate the sensing and adsorption of H2S gas phenomena in the χ3 borophene based on the density functional theory. Moreover, it is tried to analyze the external bias voltage using nonequilibrium Green’s function formalism. First-principle DFT Calculations Density Functional Theory (DFT) calculations have been employed to investigate the electronic properties and the energetics of H2S/3-XBNR [19]. These computations were performed using SIESTA ab-initio Package [20] owing its efficiency to the strictly localized basis sets and pseudopotential method for treating core electrons of each atomic type. We used Generalized Gradient Approximation (GGA) with Perdew-Burke-Ernzerhof [21] exchangecorrelation functional and norm-conserving Troullier-Martins [22] pseudopotential as our approximations. Also, the double zeta polarization basis set was chosen for calculating the electronic properties. The kinetic energy cut-off was considered as 300 Rydberg. Also, the first Brillouin Zone was sampled using a 20×1×1 regular Monkhorst-Pack grid [23] for nanoribbon calculations with fermi-Dirac smearing method to determine electron occupancies with an electronic temperature of 300K. The electronic self-consistent iteration convergence threshold was set to 10-6eV and the ionic relaxations overall this paper was performed via conjugate gradient method. Thus, the maximum of the total force component on each atom in the supercell became less than 0.01 eV/Å. The mentioned criteria were applied to calculate the surface energetics of the H2S molecule on χ3 Brophene nanoribbon cut along x-direction (χ3-XBNR). For non-periodic directions (z and y-directions) of the ribbon, a vacuum region with a length of 20 Å was set. In the past two decades, non-equilibrium Green Function (NEGF) [24] has been introduced as a remarkable technique to calculate transport properties. Numerous papers can be found that apply the technique successfully to estimate the transport properties of different devices at a maximum level of accuracy. NEGF indebts most of its success to the definition of an open system and calculation of transport properties of the essential part of the device. This simple estimate combines several techniques with DFT to provide an effective tool to calculate the transport properties of devices with exceptionally favorable results. Various software packages such as TranSiesta [20] are used to investigate the transport properties of the structure. TranSiesta employs a procedure to solve the electronic structure of a system formed by a finite material sandwiched between two metallic leads. In this approach, Green function techniques are used to find electronic density from DFT Hamiltonian for an open system instead of diagonalization. To investigate the transport properties of the system, we considered a setup consisting of three main parts (Fig. 5a), with left and right leads and a central scattering region. Left and right leads are considered as ideal χ3-borophene nanoribbon, which represents long pristine structures indeed. The scattering region is comprised of an edge-hydrogenated χ3-borophene nanoribbon. Using a double zeta-polarized basis set, this study compares the I-V characteristics of the system with/without the H2S molecule. Using the Landauer-Buttiker formula [24], the electric current through the central scattering region is as follows:
2
∫
𝐼(𝑉𝑏) = 𝐺0
𝜇𝑅
𝑇(𝐸,𝑉𝑏)[𝑓(𝐸 ― 𝜇𝐿) ― 𝑓(𝐸 ― 𝜇𝑅)]𝑑𝐸, (1)
𝜇𝐿
where G0=2e2/h is unit of quantum conductance, T(E, Vb) is transmission probability of electrons through potential Vb, f is fermi-Dirac distribution, and μ (μ ) is the chemical potential of right (left) lead. Furthermore, in this R
L
research, the cut-off energy for transport calculation is considered to be 300 Rydberg, and the k-sampling was performed with a 1×1×101 Monkhorst-Pack grid. To study the adsorption mechanism of the H2S molecule on different sites of the ribbon, we may calculate adsorption energy defined as Eads = EH-BNR/gas – (EH-BNR + Egas). The adsorption energy (Eads) of an adsorbate to the surface was calculated as the energy difference between the molecule-surface system and the system of isolated clean surface and gas molecule. Negative Eads indicates an attractive interaction between the adsorbate and the surface. Also, the relative stability of the ribbon can be investigated by formation energy defined as E = [EH-XBNR − mEsheet – nEH2/2]/m+n. Here, Esheet is the total energy of χ3-borophene sheet per atom, EH2 corresponds to hydrogen molecule energy, and (m,n) are the number of boron and hydrogen atoms in hydrogenated χ3-borophene nanoribbon, respectively. Moreover, there are two important factors for determining the performance of a gas sensor: sensitivity and selectivity. The sensitivity [27] of gas sensors is defined as S(%)=|C-C0|/C0, where C0 (in units of 2e2/h) is the conductance of a clean ribbon’s surface and C is the conductance after surface exposure to the gas at Fermi energy. Selectivity [27] is the capacity of a sensor to discriminate between gases in a mixture. A good sensor will detect a particular signal by allowing adsorption of the desired gas while remaining insensitive to others. The selectivity coefficient (K) of ‘target gas’ to another gas is defined as K=SA/SB, where SA and SB are the sensitivities of ‘target gas’ and the other gas, respectively. Results and Discussion The optimized primitive cell of χ3-borophene sheet is demonstrated in Fig. 1a which is composed of four B atoms. The lattice constants of the sheet for A and B are equal to 2.94 Å and 4.49 Å respectively, which is in good agreement with other experimental and theoretical works [25]. χ3-borophene sheet owes its flat structure to the presence of hexagonal vacancies [6,26]. The band structure in Fig. 1c (left) shows metallic behaviour along all symmetry lines in Brillouin zone. According to Density of States shown in Fig. 1c (right) The largest contribution of electrons close to the Fermi level are attributed to p orbitals. These orbitals are mostly of and types. orbitals represent strong in-plane bonds; orbitals have out-of-plane two-headed parallel bonds and play an important role in making the structure stable. 4
KA
c
a
b
2
X
S
B
E-Ef(eV)
A
S+Px+Py Pz
Y
0
-2
KB -4
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S
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0
0.5
1
DOS(States/eV)
(a)
(b)
(c)
Fig.1 (a) The primitive cell of the χ3-borophene sheet (up) (b) first Brillouin zone, and (c) band structure of the sheet along high symmetry points in BZ To understand the adsorption of H2S on χ3-borophene nanoribbon, one should primarily conduct a relaxation study. In order to make borophene nanoribbon cut along B (XBNR), we change the primitive cell to a rectangular unit cell
3
x
with r1 = 2A − B and r2 = B lattice vectors (Fig. 2a), repeat the unit cell 5 times along r1, and then cut along r2direction (Fig. 2b).
b
c
a
(a)
(b)
Fig. 2. The schematic of top views of (a) rectangular unit cell of 3-borophene sheet and (b) edge-hydrogenated χ3borophene nanoribbon cut along r2-direction (3-XBNR)
y
z
To remove the effect of dangling bonds, hydrogen atoms are used on both the top and bottom edges of the χ3borophene nanoribbon in an armchair structure (Fig. 2b). The supercell is small enough to be adequate for computations. The formation energy of the ribbon is E=0.183 eV, which shows a stable structure with respect to the χ3-borophene sheet. According to the literature [25], the stability of the ribbon may get better by increasing its width. In this work, we relaxed the adsorption configurations at different sites. We started with multiple initial guesses at the center of the ribbon and approached the edge. We found out that adsorption is more favorable near the edges of the ribbon. Meanwhile, we tried different orientations of the H2S molecule and each time the structure relaxed to S-down geometry in all configurations. Let us analyze the bonding characteristics of the gas with the borophene surface in detail. The adsorption energy (Eads) of H2S adsorbate to the surface is calculated to be -5.35 eV. Figs. 3a-3d illustrate the relaxed geometry of an H2S on χ3-XBNR and charge density difference defined as Δρ = ρtot(r) – ρribbon(r) − ρgas(r), where ρtot(r) is the charge distribution on relaxed ribbon with the adsorbed gas, ρribbon(r) is the charge distribution on borophene, and ρgas(r) is the charge distribution on the isolated gas. Conceptually, Δρ depicts the charge accumulation/depletion in the system by which we can easily visualize the charge transfer. According to Fig. 3a-3d, when the H2S molecule approaches the surface of the sulfur atom, it slightly deforms the edge of the ribbon and a charge transfer occurs from molecule to the surface that represents a strong bonding with the surface. x
z
(a)
x
y
(b)
4
(c)
(d)
Fig. 3. The relaxed structure of H2S molecule adsorbed on the ribbon: (a) top view and (b) side view and charge density difference with isosurface level of 0.0006 eV/ Å 3 on χ3-XBNR: (c) top view (d) side view; blue surface denotes electron gain while the red surface represents electron loss. Another quantity that elaborates the dramatic change in the electronic properties of the ribbon before and after gas adsorption is the total density of states (DOS). Fig. 4 depicts the metallic behavior of the pristine ribbon and the ribbon with adsorbed gas and the tolerable DOS near the Fermi energy. As can be inferred from this figure, this molecule induces a significant change in DOS of the system. DOS(states/eV)
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0 -6 -4 -2 2 4
hydrogenated 3-XBNR
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Fig. 4. The DOS near-zero energy for the relaxed situation of hydrogenated χ3-XBNR (solid line) and the system of H2S + hydrogenated χ3-XBNR (dash-dotted line) The instrument shown in Fig. 5a was used to detect the alteration in the transport properties as a result of the H2S adsorption on χ3-borophene nanoribbon. We considered the transport along the z-direction. Fig. 5b shows the current-voltage (I-V) characteristics, where a noticeable effect of H2S adsorption is observed. Therefore, so the resistance of the device is different in the presence of gas compared to the pristine ribbon, as implied from Fig. 5b. Current(A)
100
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0 0 1
hydrogenated 3-XBNR
H2S + hydrogenated 3-XBNR
0.5
Voltage(V)
1.5 2
(a)
(b)
Fig. 5 (a) illustration of the device setup (top view) showing the semi-infinite left and right electrode regions and the central scattering region. (b) Current (μA) -Voltage (V) characteristics of hydrogenated χ3-XBNR (black) and the system of H2S + hydrogenated χ3-XBNR (red)
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Zero bias transmission spectra T(E) in the presence and absence of gas molecules are presented in Fig. 6. The results show that adsorption of the gas molecules results in decreased transmission of incident electrons. Transmission(G/G ) 0
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Fig. 6. The transport spectrum at zero bias is plotted in terms of energy for the absorption state with the minimum absorption energy Fig. 6 shows T(E) for the minimum absorption energy state in terms of energy. Physically, borophene is placed between electrodes, forming a potential barrier for electronic transport. At the time of absorption, the electronic structure changes cause the electronic transport coefficient to alter. As can be seen, there is no band gap adjacent to the Fermi energy and the conduction mechanism is made purely through electron transport near the Fermi energy. the electron transport coefficient adjacent to the fermi energy for ribbon with adsorbed gas experiences a reduction with respect to the bare ribbon. Therefore, the sensitivity of the gas sensor is S=31.35%. The basic problem of most gas sensors is that the conductivity value can be almost the same for different gas species and concentrations. Moreover, they suffer from a lack of selectivity and drift [27]. Various sophisticated and very costly techniques could be used for enhancing the sensor selectivity [28]. The difficulty consists that they are very often influenced by water vapor and thus the changes in the moisture content of the ambiance could interfere considerably the gas sensing. To determine the selectivity of the sensor or amount of interference from other gases, we first examined H2O and NO sensitivities. According to the definition of selectivity, the ratio of the target gas (H2S) sensitivity and other gases’ sensitivities (H2O and NO) are 2672.64 and 2.51, respectively. So, H2O plays a negligible role in the transport channels of the device and NO have a sensitivity of 12.48% which is 2.51 times smaller than that of H2S. This observation proves that the device resistance is increased and can be a very ideal candidate for a nanosensor. Eigen Channel analysis was used for a better understanding of electron transport. Graphical illustration of scattering modes helps to gain a better understanding of the modes (especially channels) of the system. These special modes can be useful in understanding the band structure of the borophene nanoribbon. At zero bias, the electrical conductivity is obtained from the sum of the eigenvalues of each channel eigenvalue. We calculated these channel properties using the simulation results obtained by TranSIESTA and Inelastic Package. Fig. 7a shows a dominant channel passing through the left electrode at Fermi energy and Fig. 7b shows a decreased channel passing in the presence of the H2S molecules, which shows the high sensitivity of the device. Furthermore, the figure shows that the scattering modes vary widely across the strips. The more localized (non-localized) modes are distributed along the channel, causing less (more) electrical conductivity.
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b
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(a)
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Fig. 7. The Eigen channel analysis specifically used for passing from the left electrode direction in the Fermi energy: (a) before and (b) after gas adsorption Conclusion This study focuses on the adsorption of Hydrogen Sulfide (H2S) molecules on χ3-borophene nanoribbon using nonequilibrium Green’s function (NEGF) coupled with density functional theory and the transport property model. We demonstrated that the hydrogen sulfide molecules in the system have remarkable effects on the transmission of an electron from the scattering region. The data analysis results showed that H2S molecule can reverse the correlation of orbitals and cause changes in the transmission spectrum. Moreover, this molecule made a significant current reduction in the I-V curve of the χ3-borophene nanoribbon. We further computed transmission functions, sensitivity and selectivity in the presence of H2O and NO for this device and observed a lower sensitivity compared to H2S. The results confirm that the system is a proper structure for the H2S gas sensor and can show immense capabilities for industrial usage. References 1.
Mannix, Andrew J., Xiang-Feng Zhou, Brian Kiraly, Joshua D. Wood, Diego Alducin, Benjamin D. Myers, Xiaolong Liu et al. "Synthesis of borophenes: Anisotropic, two-dimensional boron polymorphs." Science 350, no. 6267 (2015): 1513-1516. 2. Feng, Baojie, Jin Zhang, Qing Zhong, Wenbin Li, Shuai Li, Hui Li, Peng Cheng, Sheng Meng, Lan Chen, and Kehui Wu. "Experimental realization of two-dimensional boron sheets." Nature Chemistry 8, no. 6 (2016): 563. 3. Chkhartishvili, Levan, Ivane Murusidze, and Rick Becker. "Electronic Structure of Boron Flat Holeless Sheet." Condensed Matter 4, no. 1 (2019): 28. 4. Boustani, Ihsan. "New quasi-planar surfaces of bare boron." Surface science 370, no. 2-3 (1997): 355-363. 5. Ranjan, Pranay, Tumesh Kumar Sahu, Rebti Bhushan, Sharma SRKC Yamijala, Dattatray J. Late, Prashant Kumar, and Ajayan Vinu. "Borophene: Freestanding Borophene and Its Hybrids (Adv. Mater. 27/2019)." Advanced Materials 31, no. 27 (2019): 1970196. 6. Zhang, Zhuhua, Evgeni S. Penev, and Boris I. Yakobson. "Two-dimensional boron: structures, properties and applications." Chemical Society Reviews 46, no. 22 (2017): 6746-6763. 7. Luo, Zhifen, Xiaoli Fan, and Yurong An. "First-principles study on the stability and STM image of borophene." Nanoscale research letters 12, no. 1 (2017): 514 . 8. Adamska, Lyudmyla, and Sahar Sharifzadeh. "Fine-tuning the optoelectronic properties of freestanding borophene by strain." ACS Omega 2, no. 11 (2017): 8290-8299. 9. Feng, Baojie, Jin Zhang, Ro-Ya Liu, Takushi Iimori, Chao Lian, Hui Li, Lan Chen et al. "Direct evidence of metallic bands in a monolayer boron sheet." Physical Review B 94, no. 4 (2016): 041408. 10. Wu, Rongting, Ilya K. Drozdov, Stephen Eltinge, Percy Zahl, Sohrab IsmailBeigi, Ivan Božović, and Adrian Gozar. "Large-area single-crystal sheets of borophene on Cu (111) surfaces." Nature nanotechnology 14, no. 1 (2019): 44. 11. Wang, Zhiqiang, Tie-Yu Lü, Hui-Qiong Wang, Yuan Ping Feng, and JinCheng Zheng. "High anisotropy of fully hydrogenated borophene." Physical Chemistry Chemical Physics 18, no. 46 (2016): 31424-31430.
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12. Wu, Xin, Fengwen Mu, Yinghui Wang, and Haiyan Zhao. "Graphene and Graphene-Based Nanomaterials for DNA Detection: A Review." Molecules 23, no. 8 (2018): 2050. 13. Nazemi, Haleh, Aashish Joseph, Jaewoo Park, and Arezoo Emadi. "Advanced micro-and nano-gas sensor technology: A review." Sensors 19, no. 6 (2019): 1285. 14. Aliofkhazraei, M., and N. Ali. "Recent developments in miniaturization of sensor technologies and their applications." (2014): 245-306. 15. Singh, Eric, M. Meyyappan, and Hari Singh Nalwa. "Flexible graphene-based wearable gas and chemical sensors." ACS applied materials & interfaces 9, no. 40 (2017): 34544-34586. 16. Fiori, Gianluca, Francesco Bonaccorso, Giuseppe Iannaccone, Tomás Palacios, Daniel Neumaier, Alan Seabaugh, Sanjay K. Banerjee, and Luigi Colombo. "Electronics based on two-dimensional materials." Nature nanotechnology 9, no. 10 (2014): 768. 17. Shah, Mansi S., Michael Tsapatsis, and J. Ilja Siepmann. "Hydrogen sulfide capture: From absorption in polar liquids to oxide, zeolite, and metal–organic framework adsorbents and membranes." Chemical reviews 117, no. 14 (2017): 9755-9803. 18. Chou, C. H., and World Health Organization. Hydrogen sulfide: human health aspects. World Health Organization, 2003. 19. Kohn, Walter, and Lu Jeu Sham. "Self-consistent equations including exchange and correlation effects." Physical review 140, no. 4A (1965): A1133. 20. Soler, José M., Emilio Artacho, Julian D. Gale, Alberto García, Javier Junquera, Pablo Ordejón, and Daniel Sánchez-Portal. "The SIESTA method for ab initio order-N materials simulation." Journal of Physics: Condensed Matter 14, no. 11 (2002): 2745. 21. Perdew, John P., Kieron Burke, and Yue Wang. "Generalized gradient approximation for the exchangecorrelation hole of a many-electron system." Physical Review B 54, no. 23 (1996): 16533. 22. Troullier, Norman, and José Luís Martins. "Efficient pseudopotentials for plane-wave calculations." Physical review B 43, no. 3 (1991): 1993. 23. Monkhorst, Hendrik J., and James D. Pack. "Special points for Brillouin-zone integrations." Physical review B 13, no. 12 (1976): 5188. 24. Datta, S. "Quantum Transport: Atom to Transistor Cambridge University Press." (2005). 25. Vishkayi, Sahar Izadi, and Meysam Bagheri Tagani. "Freestanding χ 3-borophene nanoribbons: a density functional theory investigation." Physical Chemistry Chemical Physics 20, no. 15 (2018): 10493-10501. 26. Peng, Bo, Hao Zhang, Hezhu Shao, Zeyu Ning, Yuanfeng Xu, Gang Ni, Hongliang Lu, David Wei Zhang, and Heyuan Zhu. "Stability and strength of atomically thin borophene from first principles calculations." Materials Research Letters 5, no. 6 (2017): 399-407. 27. Moseley, Pat T. Solid state gas sensors. Taylor & Francis, 1987. 28. Williams, David E., and Patrick T. Moseley. "Dopant effects on the response of gas-sensitive resistors utilising semiconducting oxides." Journal of Materials Chemistry 1, no. 5 (1991): 809-814.
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There is no conflict of Interest between authors absolutely .
Transmission(G/G0)
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An ab-initio study of 3-borophene nanoribbon using DFT and NEGF for H 2S sensing. Large transfer of charge from molecules to the edges of ribbon with high adsorption energies. significant reduction of current in I-V characteristics of the device and strong sensitivity of sensor to hazardous H2 S molecule. The sensor demonstrated a high level of selectivity of H 2 S compared to NO molecule and water vapor (H2O).