Lithium ion beam impact on selenium nanowires

Physica E 87 (2017) 37–43

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Lithium ion beam impact on selenium nanowires ⁎

Suresh Panchal , R.P. Chauhan

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Department of Physics, National Institute of Technology, Kurukshetra 136119 Haryana, India

A R T I C L E I N F O

A BS T RAC T

Keywords: Ion irradiation Selenium nanowires Texture analysis Electrical properties Impedance

This study is structured on Li3+ ion irradiation effect on the different properties of selenium (Se) nanowires (NW's) (80 nm). Template technique was employed for the synthesis of Se nanowires. Exploration of the effect of 10 MeV Li3+ ions on Se NW's was done for structural and electrical analysis with the help of characterization tools. X-ray diffraction revealed the variation in peak intensity only, with no peak shifting. The grain size and texture coefficients of various planes were also found to vary. Current-Voltage characteristics (IVC) show an increment in the conductivity up to a fluence of 1×1012 ions/cm2 and a decrease at the next two fluences. The effects of irradiation are presented in this paper and possible reasons for the variation in properties are also discussed in this study.

1. Introduction In the recent years, a great deal of interest has been found in the synthesis of nanomaterials and nanodevices because of their unique properties. A development in semiconducting based nano-devices of small dimension and uniformity is a necessary stair toward developing the next generation technology. Apart from 2D or 3D materials, 1D nanostructures holds different properties. These are the smallest dimensional structure that can efficiently transport electrical carriers, and thus can be used as bases for the construction of new generation integrated nanoscale electronic and photonic devices. Semiconducting nanowires possess massive application in nano-electronics and photoelectric elements like solar cells, photo detectors, leasers and sensors [1–4]. Selenium is an important VI group p-type semiconductor, having energy band gap of the order of 1.6 eV. Due to high catalytically activity, high photoconductivity (8×104 scm−1) and functional properties in superconductivity [5,6] one dimensional selenium nanowires have been studied extensively. Selenium nanowires find utility in the area of solar batteries, photoelectric cells, light-measuring devices, xerography and their spectral response to entire visible range is much needed characteristic required for photoconductor. Synthesis of 1D nanostructures can be achieved by various techniques like, sonochemical approach, self-seeding process, hydrothermal method, vapor phase growth, template based method and many more. Among these, template assisted electro-deposition is a versatile and efficient technique for the growth of nanowires with controlled diameter, length and shape [7].

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Irradiation of nanomaterial with swift heavy ions (SHI) is a unique tool for engineering the properties of nanostructures and involved a lot of attention in last few years. Modification in nanostructures can be achieved by low or high energy ions. SHI irradiation can be used to enhance the structural, photo electronic and optical properties of the materials. Energy of SHI in target material imparted through two mechanisms: (a) nuclear energy loss (Sn), which involves transfer of energy to target atom through elastic collision and dominates at low energy ( < 1 MeV) and (b) electronic energy loss (Se) which is inelastic collision between incident ion and electron of target atom and dominate at higher energy ( > 1 MeV) [8]. In case of swift heavy ions irradiation, electronic energy loss (Se) is dominating process due to inelastic collision. Energetic ion piercing crystal lattice creates excitation and ionization process which leads to creation of wide variety of defects like; defect clusters, vacancies and dislocations which affect the energy levels and changes their physical properties in controlled way [9–11]. The creation of defects mainly depends upon mass, energy and fluence of the incident ion [12]. In the performance of the devices like, solar cells, sensors, schottky diodes etc. these defects play an important part with trapping and recombination of current carriers. Distributions of defects in material are mainly responsible for modification of the electrical and optical properties of the material [13,14]. A number of studies on irradiation of bulk and thin films were reported, but only a few papers in literature were found which provides much information about the irradiation induced modification in the properties of semiconducting nanowires [15–18]. But not so much work had done on the irradiation of selenium nanowires [19,20], which motivate us to move forward in this direction so that we gain much more information

Corresponding author. E-mail addresses: [email protected] (S. Panchal), [email protected] (R.P. Chauhan).

http://dx.doi.org/10.1016/j.physe.2016.11.030 Received 10 August 2016; Accepted 25 November 2016 Available online 27 November 2016 1386-9477/ © 2016 Elsevier B.V. All rights reserved.

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S. Panchal, R.P. Chauhan

2.4. Characterization

about effect of irradiation on selenium nanowires properties. Present study deals with the study of modification in structural, electrical and optical properties of 10 MeV Li3+ ion irradiated selenium nanowires (80 nm) synthesized via template assisted electro-deposition.

Rigaku Mini-Flex diffractometer equipped with CuKα radiation (λ=1.54 Å) was used for structural analysis of pristine and irradiated samples at a scan speed of 2̊/min. Estimation of crystal size was made from peak broadening by Scherrer method. SEM image provide morphological information and were recorded by using JEOL JSM6390 LV. Before morphological analysis, template was dispersed using dichloromethane, ethanol and de-ionised water. To make sample surface conducting, sample was coated with gold platinum alloy in JEOL JFC-1600 Auto Fine coater unit. I-V measurements were carried out with the help of Keithley-2400 series source meter and Ecopia Probe station using two probes.

2. Experimental details 2.1. Synthesis All the chemicals used for synthesis purpose are of AR grade and used without any further purification. Se nanowires used in the present study were synthesized by electro deposition with a three electrode set up using electrolyte, containing selenium dioxide (SeO2) and boric acid (H2BO3) having pH around 2. Ion track etched polycarbonate membrane (whatman make) having pore diameter 80 nm, coated with thin layer of gold-palladium alloy, were used for deposition of selenium nanowires. Deposition was carried out at room temperature (30 ± 2 °C) in a Perspex cell having a hole (1 cm diameter) at the bottom for 7 min. Deposition voltage was optimized using cyclic voltammetry. Deposition was carried with the help of SP-240 Biologic Potentiostat via chronoampereometery technique. All the potentials were applied with respect to Ag/AgCl reference electrode. A thin platinum wire of diameter around 5 mm served as counter electrode and a copper substrate on which template was placed acted as working electrode and filling of pores took place during electro chemical deposition. After completion of deposition electrolyte was poured off and sample was removed carefully from working electrode.

3. Results and discussion 3.1. Morphological analysis Surface morphology of pristine samples was investigated by SEM as shown in Fig. 2. The length of wires was estimated around 10 µm which confirms the complete and uniform deposition of pores. Dissolution of membrane affects the wires like wires gets slanted ormay be breaking can takes place. 3.2. Structural analysis For structural analysis XRD spectra of irradiated nanowires was compared with pristine, as shown in Fig. 3. The presence of a number of peaks from different family suggests the polycrystalline nature of pre- and post-irradiated samples. The observed XRD spectra closely match with the JCPDS card no. 020677 which confirms the Hexagonal structures of as prepared nanowires with lattice constants a=0.443 nm and c=0.511 nm, which are in the range of the standard values given in the JCPDS card. On comparing the XRD spectra of pre- and postirradiated samples, no shifting in the “2θ” position was observed but variation in the peak intensity was noticeable. This variation in the peak intensity is a directly reflection of the crystallographic orientations of the planes [21]. Estimation of preferred orientations can be done on the basis of texture coefficients (T.C.) [22] of the peaks given by

2.2. SRIM calculations The range of Li3+ ion in selenium nanowires was calculated with the help of SRIM software and was found to be 21.75 µm which is larger than length of nanowires (10 µm), so probability of implantation is negligible. 10 MeV Li3+ ions in selenium nanowires have electronic stopping power 37.733 eV/Å whereas nuclear stopping power was 30.061×10−3 eV/Å. So in present case, modifications in target material were mainly due to electronic excitation. Inside targeted material, the trajectories of incident ions strongly depends upon their energy. At low energy, the trajectories follow zigzag pattern showing large random deviation from initial direction and a significant straggling. On the other hand, at high energy where electronic stopping dominates, the trajectories basically remain straight with small straggling and well simulated by SRIM 2008 programmer shown in Fig. 1. TRIM calculation for damage inside Se material during Li ion bombardment are shown in Fig. 1, which confirms that mostly lithium ions ionizes the target material with only a few amount of target vacancies. Some restrictions are also there with TRIM calculation as it calculates only for smooth surface and no consideration was made on damages produced by previous incident ion.

T. C. = 1

I(hkl)/ I ˳ (hkl)

ΣI(hkl)/ I ˳ (hkl) n

where I(hkl) is the relative peak intensity as observed in XRD spectra, I˳(hkl) is the relative intensity of peaks as given in the standard JCPDS card and n stands for number of miller planes. The value of T.C. for different peaks is as shown in Table 1. The maximum value of T.C. never exceed n and a value of texture coefficient greater than one for any peak indicate the preferred orientation of grains in the sample [23]. T.C. values mentioned in bold (Table 1) illustrated the preferred orientation of the crystal planes. Mentioned values of T.C. shows that the ion fluence affects the crystallographic orientation. Energy imparted by incident ions also affects the strain and reflection (R) of the material [24]. In pristine case, planes (110) and (400) show preferred orientation but after irradiation there is a decrease in the T.C. of these planes and a significant increase in the value of T.C. of (213) plane was observed. As the radiation passes through material, it imparts its energy to the target material which results in the form of planes movement, variation in the average grain size and strain. From X-Ray line broadening, the average grain size of pre- and post-irradiated samples was determined from Scherrer's formula [25],

2.3. Irradiation parameters Selenium nanowires were irradiated with 10 MeV Li3+ ions from Inter University Accelerator Centre (IUAC), New Delhi, India for different fluences ranging from 1×1011 to 1×1013 ions/cm2. The samples were mounted on a copper ladder having four faces perpendicular to the ion beam flux. The samples were irradiated in vacuum chamber (6×10−6 Torr) by ion beam magnetically scanned over an area of 1×1 cm2. Ion beam current was maintained constant at 1pnA (particle nano Ampere) at the time of experiment. The reason of using such low current was to avoid burning of polycarbonate membrane due to rise of temperature.

D=

38

kλ βCos θ

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Fig. 1. (a) Ion trajectories (Depth vs. Y-axis) in Se nanowires; (b) Ions Distribution with depth; (c) Distribution of ionization losses; (d) Collisions events.

δ=

1 −2 m D2

Dislocation density (δ) contains information about perfection of crystal structure, which is the length of dislocation lines per unit volume of the crystal. Value of average grain size, dislocation density and strain is as shown in Table 2. From Table 2, an increase in the average grain size was observed from 20.38 to 32.38 nm up to third fluence after that a decrease in the average grain size was observed. The decrease in the dislocation density may be due to the increase in average grain size which results in decrease in number of grain boundaries. A decrease in the lattice strain was also observed which shows relaxation of crystal lattice of selenium nanowires [28]. However at higher fluence (5×1012 and 1×1013 ions/ cm2) decrease in average grain size and increase in dislocation density and lattice strain was observed which may be due to either grain splitting effect or ion beam induced dislocation and defects [29–32].

Fig. 2. SEM image of selenium nanowires of 80 nm diameter.

3.3. Electrical analysis

where D is the average grain size, λ is the characteristic wavelength of Cu-Kα (1.5406 Å), k is the constant having value 0.94, β is the full width half maxima (FWHM) and θ be the angle of diffraction. The strain induced in nanowire arrays due to passage of ions through nanowires, which is related to the lattice damages, can be determined using relation [26,27].

Fig. 4, depicted the effect of irradiation on current-voltage characteristics (IVC) of selenium nanowires. A Keithley 2400 series source meter and Ecopia probe station, with fine tungsten tip (10 µm diameter) was used to record IV characteristic of pristine and irradiated nanowires in voltage range −3V to +3 V and is an mutual outcome of a collection of 480 parallel nanowires. For pristine nanowire, the I–V characteristics display almost symmetric and nonlinear behavior, however an increment in the current with the increase in ion fluence up to 1×1012 ions/cm2 was observed. Here, we are dealing with a non-linear behavior of IVC and looking

ε = β/4tanθ s where, ε stands for weighted average strain, βs is integral breadth of peak and θ is the angle of diffraction peak. Evaluation of dislocation density was done by using the relation [27] 39

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Fig. 3. XRD spectrum of pristine and irradiated selenium nanowires. Table 1 Texture coefficient (T.C.) of pristine and irradiated samples. Planes

101 110 102 112 103 213 310 312 400

Pristine

0.576 3.902 0.187 0.287 0.276 0.491 0.182 0.101 2.998

Ion fluence (ions/cm2) 1×1011

5×1011

1×1012

5×1012

1×1013

0.728 4.939 0.188 0.433 – 0.430 – 0.091 0.190

0.684 4.685 0.183 0.436 – 0.557 – 0.166 0.288

0.573 3.627 0.139 0.297 – 1.460 – 0.192 0.711

0.420 3.046 0.143 0.282 0.176 2.333 – 0.149 1.451

0.416 2.390 0.127 0.204 – 2.144 – 0.668 1.082

Table 2 Average grain size, dislocation density and strain for pristine and irradiated samples. Fluence (ions/ cm2)

Average grain size (nm)

Dislocation density (×1015)

Strain (×10−3)

Pristine 1×1011 5×1011 1×1012 5×1012 1×1013

20.38 28.42 31.66 32.02 27.46 24.12

2.407 1.238 1.039 0.975 1.326 1.719

9.05 6.90 6.70 6.40 6.28 7.98

Fig. 4. IV Characteristic of pristine and irradiated selenium nanowires.

tunneling behavior at the contacts. Fig. 6 shows graph for log (I) versus log (V) for pristine and irradiated nanowires. It is clear from the plots, at low voltage current shows first order dependence on voltage which shows ohmic conduction is dominating, but at higher voltage transition to quadratic dependence of current on voltage is a clear indication of space charge limiting current (SCLC). The variation in the linear portion must also be noticed where it is found to increase at first three fluences and later is reduced at the last two fluences. In SCLC system, an excess of charge carriers is injected from the contacts, but the material of interest must possess either low free carrier concentration or low carrier mobility. With the increasing

for possible model of transport which can explain this type of behavior. It is noticed that at low voltage the plots are nearly linear but at higher voltage non-linear nature was perceived. A more precise explanation was obtained by plotting I/V versus V shown in Fig. 5. A linear graph between I/V versus V is an indication of I∝V2. This type of behavior cannot be explained on the basis of Schottky or

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(1) is suitable for describing the SCLC in material having low aspect ratio but not valid for the materials having high aspect ratio such as nanowires. Application of Eq. (1) to nanomaterial leads to ambiguous conclusions. Talin et. al developed a model for nanowires in which current density is given by [36].

J = ζ (R / L )ε μ

V2 L3

(2)

ζ(R/L) is a scaling factor depending upon the aspect ratio and R is the radius of nanowires. For materials having R/L < 1, SCLC follows the following expression;

J = ζ (R / L )−2 εμ

voltage, the injected charge carrier's concentration becomes dominating over free charge carrier concentration and consequently transition from ohmic to SCLC or nonlinear behavior takes place. Literature also suggest that SCL current in bulk materials (Semiconducting and insulator), leads to non-linear IVC [33,34]. In case of bulk solids SCLC was first analyzed by Mott, and derived the following relation for current density [35]

9 V2 εμ 8 L3

(3)

This gives the quadratic dependence of current on voltage. SCLC is more effective for nano sized materials due to their poor electrostatic screening experienced by injected carriers, carrier depletion and incorporation of charge traps during synthesis [37–39]. With the passage of energetic ion through a material, generation of charge carrier and formation of intermediate energy state in the forbidden energy band is a common phenomenon [40], which results in the band gap reduction. This trimming of band gap modifies the barriers height. The generation of current carriers and reduction of barrier height on irradiation resulted into an increase in conductivity of the nanowires along with the increase in ohmic region as is depicted in Log I verses Log V graphs for initial fluences (Fig. 6). Increase in the crystallite size, as evident from XRD analysis, also is another possible cause of increase in conductivity of selenium nanowires. During the flow of current carriers, grain boundaries act as potential barrier and tunneling of carriers through these boundaries depends on the potential barrier introduced by grain boundaries. Increase in the crystallite size resulting in the decrease of grain boundaries on account of which charge carrier encountered with a lesser amount of scattering and hence increase in the conductivity of nanowires takes place. On the

Fig. 5. Plots of I/V as a function of voltage for pristine and irradiated Se nanowires.

J=

V2 L3

(1)

where µ is the mobility of carriers, ε is the permittivity of the material, V and L is the applied voltage and length of nanowires respectively. Eq.

Fig. 6. og (I) versus log (V) for pre- and post- irradiated Se nanowires.l

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properties remain almost unaltered on irradiation. Electrical properties are explained on the basis of SCLC model of transport. Electrical characteristics manifest an increase in the conductivity at initial fluences that may be attributed to the generation of charge carrier and reduction in barrier height during irradiation. But a decrease in the conductivity was also observed at higher fluences (5×1012 ions/cm2 and 1×1013 ions/cm2) which may be due to the irradiation induced defects and grain fragmentation. It can be concluded that Li3+ ion irradiation can be used to tailor the transport properties of Se nanowires with optimum choice of fluence and energy, which is the demand of future nano based electronic and microelectronic devices. Acknowledgement Authors are thankful to IUAC, New Delhi, India, for providing required beam line for irradiation of the samples. The assistance provided from Pelletron group during irradiation experiment is also thankfully acknowledged. The financial support in the form of project, No. IUAC/XIII.7/UFR-56303 is also thankfully acknowledged. Fig. 7. Variation of a real part (Z´) of impedance as a function of frequency at different fluence.

References

other hand at higher fluence (5×1012 and 1×1013 ions/cm2) a reverse effect was observed that is decrease in current and grain size was observed. At higher fluence irradiation induced defects and grain fragmentation dominates due to which decrease in crystallite size takes place, resulting in decrease of current [20,32]. This decrease in current can be illustrated from Fig. 6 where the reduction in the ohmic region is seen at these fluences. So we can conclude that at lower fluence (1×1011 to 1×1012 ions/ 2 cm ) generation of charge carrier's and formation of intermediate energy state dominates which results in the increase in the current while at higher fluence grain fragmentation and irradiation induced defect cause decrease in current. Thus it appears that irradiation at fluence 1×1012 ions/cm2 is optimum to increase the conductivity for selenium nanowires for positive enhancement of electrical conductivity nanowire arrays.

[1] Z. Yao, H.W.C. Postma, L. Balents, C. Dekker, Carbon nanotube intramolecular junctions, Nature 402 (6759) (1999) 273–276. [2] R.S. Wagner, W.C. Ellis, Vapor‐liquid‐solid mechanism of single crystal growth, Appl. Phys. Lett. 4 (5) (1964) 89–90. [3] A.M. Morales, C.M. Lieber, A laser ablation method for the synthesis of crystalline semiconductor nanowires, Science 279 (5348) (1998) 208–211. [4] T.J. Trentler, K.M. Hickman, S.C. Goel, A.M. Viano, Solution-liquid-solid growth of crystalline III-V semiconductors: an analogy to vapor-liquid-solid growth, Science 270 (5243) (1995) 1791. [5] Y. Qian, Solvothermal synthesis of nanocrystalline III–V semiconductors, Adv. Mater. 11 (13) (1999) 1101–1102. [6] C.R. Martin, Template synthesis of electronically conductive polymer nanostructures, Acc. Chem. Res. 28 (2) (1995) 61–68. [7] A. Huczko, Template-based synthesis of nanomaterials, Appl. Phys. A 70 (4) (2000) 365–376. [8] A. Solanki, S. Choudhary, V.R. Satsangi, R. Shrivastav, S. Dass, Enhanced photoelectrochemical properties of 100MeV Si 8+ ion irradiated barium titanate thin films, J. Alloy. Compd. 561 (2013) 114–120. [9] N.V. Doan, G. Martin, Elimination of irradiation point defects in crystalline solids: sink strengths, Phys. Rev. B 67 (13) (2003) 134107. [10] I.P. Jain, G. Agarwal, Ion beam induced surface and interface engineering, Surf. Sci. Rep. 66 (3) (2011) 77–172. [11] D.K. Avasthi, Modification and characterisation of materials by swift heavy ions, Def. Sci. J. 59 (4) (2009) 401. [12] D. Kanjilal, Swift heavy ion-induced modification and track formation in materials, Curr. Sci. 80 (12) (2001) 1560–1566. [13] M. McPherson, Infrared photoconduction in radiation-damaged silicon diodes, J. Opt. A: Pure Appl Opt. 7 (6) (2005) S325. [14] V.R. Pillai, S.K. Khamari, V.K. Dixit, T. Ganguli, S. Kher, S.M. Oak, Nucl. Instrum. Methods A 685 (2012) 41. [15] E.F. Pecora, A. Irrera, F. Priolo, Ion beam-induced bending of silicon nanowires, Phys. E 44 (6) (2012) 1074–1077. [16] R.P. Chauhan, P. Rana, C. Narula, S. Panchal, R. Choudhary, Variation in electrical properties of gamma irradiated cadmium selenate nanowires, Nucl. Instrum. Methods B 379 (2016) 78–84. [17] K. Makise, Y. Matsubara, S. Tasaki, K. Mitsuishi, B. Shinozaki, Superconductivity of In/Mo narrow wires fabricated using focused Ga-ion beam, Phys. E 75 (2016) 235–240. [18] P. Rana, R.P. Chauhan, Structural, optical and electrical properties of ion beam irradiated cadmium selenate nanowires, J. Mater. Sci. Mater. Electron. 25 (12) (2014) 5630–5637. [19] K.M. Chintala, S. Panchal, P. Rana, R.P. Chauhan, Structural, optical and electrical properties of gamma-rays exposed selenium nanowires, J. Mater. Sci. Mater. Electron. 27 (2016) 8087–8093. [20] N. Kumar, R. Kumar, S. Kumar, S.K. Chakarvarti, Modifications in optical and electrical properties of selenium nanowire arrays using ion beam irradiation, Appl. Phys. A 121 (2) (2015) 571–579. [21] B.D. Cullity, Elements of X-Ray Diffraction, 2nd ed., Addison-Wesley Publishing Company, USA, 1978. [22] G.B. Harris, X. Quantitative measurement of preferred orientation in rolled uranium bars, Lond. Edinb. Dublin Philos. Mag. J. Sci. 43 (336) (1952) 113–123. [23] T.W. Cornelius, J. Brötz, N. Chtanko, D. Dobrev, G. Miehe, R. Neumann, M.T. Molares, Controlled fabrication of poly-and single-crystalline bismuth nanowires, Nanotechnology 16 (5) (2005) S246. [24] D. Gehlawat, R.P. Chauhan, Swift heavy ions induced variation in the electronic transport through Cu nanowires, Mater. Chem. Phys. 145 (1) (2014) 60–67. [25] B.D. Cullity, S.R. Stock, Elements of X-ray Diffraction, 3rd ed., Prentice-Hall, New

3.4. Impedance analysis To study the impedance of selenium nanowires a graph between real impedance (Z′) and frequency was plotted for pristine and irradiated nanowires. Impedance measurement was carried out in a frequency range from 20 Hz to 7 MHz with sinusoidal amplitude of 200 mV. A decrease in impedance for pristine nanowires was observed after a frequency of 100 kHz as shown in Fig. 7. This decrease in the impedance may be due to the high capacitive coupling at higher frequency [41]. In the frequency range of less than 105 Hz, Z′ is independent of frequency but shows a variation with irradiation fluence. The frequency at which the value Z´ starts decreasing shift towards to higher frequency with the fluence up to 1×1012 ions/cm2, which shows an decrease in impedance and shift toward lower frequency for next two fluence that is for 5×1012 ions/cm2 and 1×1013 ions/cm2, showing increase in impedance. This decrease in Z´ value for initial three fluences denotes the enhanced ac conductivity of the sample and increase in Z´ value for last two fluences confirms decrease in conductivity. These results are in well agreement with the result obtained in I-V characteristics of the wires. 4. Conclusion Irradiation has significant impact on the properties of nanostructures. In the present study, modifications induced by high energy lithium ion irradiation on selenium nanowires are analyzed. Structural 42

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Nucl. Instrum. Methods B 266 (9) (2008) 1987–1992. [33] A.A. Grinberg, S. Luryi, M.R. Pinto, N.L. Schryer, Space-charge-limited current in a film, IEEE Trans. Electron Dev. 36 (6) (1989) 1162–1170. [34] A. Rose, Space-charge-limited currents in solids, Phys. Rev. 97 (6) (1955) 1538. [35] N.F. Mott, R.W. Gurney, Electron. Process. Ion. Cryst. (1940). [36] A.A. Talin, F. Léonard, B.S. Swartzentruber, X. Wang, S.D. Hersee, Unusually strong space-charge-limited current in thin wires, Phys. Rev. Lett. 101 (7) (2008) 076802. [37] F. Léonard, J. Tersoff, Novel length scales in nanotube devices, Phys. Rev. Lett. 83 (24) (1999) 5174. [38] Y. Gu, L.J. Lauhon, Space-charge-limited current in nanowires depleted by oxygen adsorption, Appl. Phys. Lett. 89 (14) (2006) 143102. [39] A.D. Schricker, F.M. Davidson III, R.J. Wiacek, B.A. Korgel, Space charge limited currents and trap concentrations in GaAs nanowires, Nanotechnology 17 (10) (2006) 2681. [40] P. Kannappan, K. Asokan, J.B.M. Krishna, R. Dhanasekaran, Effect of SHI irradiation on structural, surface morphological and optical studies of CVT grown ZnSSe single crystals, J. Alloy Compd. 580 (2013) 284–289. [41] W. Veit, H. Diestel, R. Pregla, Coupling of crossed planar multiconductor systems, IEEE Trans. Microw. Theor. Tech. 38 (3) (1990) 265–269.

Jersey, 2001, pp. 167–171. [26] A.R. Stokes, A.J.C. Wilson, The diffraction of X rays by distorted crystal aggregatesI, Proc. Phys. Soc. 56 (3) (1944) 174. [27] G.K. Williamson, W.H. Hall, X-ray line broadening from filed aluminium and wolfram, Acta Metall. 1 (1) (1953) 22–31. [28] A.A. Khurram, F. Jabar, M. Mumtaz, N.A. Khan, M.N. Mehmood, Effect of light, medium and heavy ion irradiations on the structural and electrical properties of ZnSe thin films, Nucl. Instrum. Methods B 313 (2013) 40–44. [29] S. Hemon, F. Gourbilleau, C. Dufour, E. Paumier, E. Dooryhee, A. Rouanet, TEM study of irradiation effects on tin oxide nanopowder, Nucl. Instrum. Methods B 122 (3) (1997) 526–529. [30] A. Berthelot, S. Hemon, F. Gourbilleau, C. Dufour, B. Domenges, E. Paumier, Behaviour of a nanometric SnO2 powder under swift heavy-ion irradiation: from sputtering to splitting, Philos. Mag. A 80 (10) (2000) 2257–2281. [31] Y.S. Chaudhary, S.A. Khan, R. Shrivastav, V.R. Satsangi, S. Prakash, D.K. Avasthi, S. Dass, A study on 170 MeV Au13+ irradiation induced modifications in structural and photoelectrochemical behavior of nanostructured CuO thin films, Nucl. Instrum. Methods B 225 (3) (2004) 291–296. [32] S. Rani, N.K. Puri, S.C. Roy, M.C. Bhatnagar, D. Kanjilal, Effect of swift heavy ion irradiation on structure, optical, and gas sensing properties of SnO2 thin films,

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