Jet nebuliser spray pyrolysed indium oxide and nickel doped indium oxide thin films for photodiode application

Journal Pre-proof JET NEBULISER SPRAY PYROLYSED INDIUM OXIDE AND NICKEL DOPED INDIUM OXIDE THIN FILMS FOR PHOTODIODE APPLICATION Narmada A, Kathirvel P, Lakshmi Mohan, Saravanakumar S, Marnadu R, Chandrasekaran J

PII:

S0030-4026(19)31599-2

DOI:

https://doi.org/10.1016/j.ijleo.2019.163701

Reference:

IJLEO 163701

To appear in:

Optik

Received Date:

5 July 2019

Revised Date:

30 October 2019

Accepted Date:

5 November 2019

Please cite this article as: A N, P K, Mohan L, S S, R M, J C, JET NEBULISER SPRAY PYROLYSED INDIUM OXIDE AND NICKEL DOPED INDIUM OXIDE THIN FILMS FOR PHOTODIODE APPLICATION, Optik (2019), doi: https://doi.org/10.1016/j.ijleo.2019.163701

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JET NEBULISER SPRAY PYROLYSED INDIUM OXIDE AND NICKEL DOPED INDIUM OXIDE THIN FILMS FOR PHOTODIODE APPLICATION Narmada Aa, Kathirvel Pb, Lakshmi Mohana,c,*, Saravanakumar Sd, Marnadu Re, Chandrasekaran J e a)

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Department of Sciences, Amrita School of Engineering, Coimbatore, Amrita Vishwa Vidyapeetham, India b) Department of Physics, PSG College of Technology, Coimbatore, 641004, Tamil Nadu c) Research and Development center, Bharathiar University, Coimbatore, 641046 d) Department of Physics, N.S.S College, Pandalam, 689501, Kerala, India e) Department of Physics, Sri Ramakrishna Mission Vidyalaya College of Arts and Science, Coimbatore-641020, Tamil Nadu, India *

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Corresponding author. Tel: +91 8870642558 Email address: [email protected]

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Abstract

Indium oxide thin films at different substrate temperatures (250-450 °C) and nickel

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doped indium oxide films with various doping concentration of 10 and 15 wt% were coated (at 400 °C) using jet nebulizer spray pyrolysis technique confirmed the cubic phase of the films from X-ray diffraction analysis. The micro-strain effects were also verified by Williamson-Hall

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method. Field emission scanning electron microscopy (FE-SEM) confirmed temperature dependence in the formation of octahedron layered geometry. The influence of temperature on

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surface irregularity and its effect on band gap shift confirmed using optical characterization was attributed to Burstein-Moss shift. The influence on doping was reinforced with the emission peak shift of photoluminescence spectra in ultra violet, violet and blue regions (394, 421 and 467 nm). Based on confirmations from these characterizations, n-In2O3/p-Si junction diodes were fabricated for as prepared In2O3 and 10 and 15 wt% concentrations nickel doped In2O3 at 400 °C.

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P-N junction diodes fabricated and analyzed showed high sensitivity for 15 wt% nickel doped indium oxide under illumination condition. On account of this 15 wt% nickel doped junction diode is a good candidate for optoelectronic devices.

Keywords: Jet Nebulizer Spray Pyrolysis, Recrystallization, Williamson-Hall method, Burstein Moss shift, p-n junction diode 1. Introduction

Indium oxide (INO) is an n type direct bandgap semiconductor with band gap of about 3.8 eV [1]. The optical transparency in visible region and the conducting nature of indium oxide makes it a suitable candidate for optoelectronic applications [2]. The conducting nature of INO is due to the deviations from its stoichiometric compositions[3]. This post transition metal has various desirable properties for optoelectronic applications including resistivity, sensitivity, catalytic action, thermal stability etc. The conductivity and optical properties of n type INO can be tuned by doping [4-7]. There are reported works describing the properties of sensitivity and

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conductivity of nickel oxides [8–10]. Ni atoms with high solubility and low ionic radii than Indium ion shows the highest possibility of getting incorporated within the acceptor sites of INO [3–6].

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The various methods for thin film preparations includes pulsed laser deposition

(PLD)[11], spin coating[12] , ion beam implantation[13], sputtering[14]. Being a cost effective

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and simple technique, our choice of thin film preparation was Jet nebulizer spray pyrolysis technique[15]. Owing to the effect of high pressure from compressed air the precursor solution

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in the nebulizer transforms to aerosol and hence deposited layer will have improved quality of thin film a [7]. The work reported here mainly focuses on the variations in structural, optical and

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morphological properties of Ni doped on INO thin films and also the sensitivity analysis of In2O3 and Ni doped In2O3 photodiode under dark and light conditions. 2. Materials and methods

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The indium oxide thin film depositions were carried out by jet nebulizer spray pyrolysis technique. The chemicals indium (III) chloride and nickel (II) chloride of AR grade having purity greater than 98% were used. The coating was performed on the well cleaned glass substrate [1,7]. Compressed air released into the nozzle of nebulizer containing homogenous solution of InCl3 via a tube, converts the liquid particles to sub-micron size droplets or aerosol

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mist. These aerosols gets delivered from the nebulizer to the glass substrate[15]. The chemical dissociation and decomposition follows as below [1], InCl3 + 3H2 O →

In(OH)3 + 3HCl

250-450 °C

(1)

In(OH)3 + 3HCl →

In2 O3

(2)

INO thin films at different substrate temperatures were deposited (250 to 450 °C). The decomposition process causes the evaporation of solvent solution evaporates forming uniform oxide layer of indium. Nickel doping was also performed with same procedure, by adding appropriate amount of nickel (II) chloride (NiCl2) into InCl3 solutions for 10 wt% and 15 wt% Ni doped INO thin films[16]. Table 1 shows the conditions maintained during thin film preparation. Various characterization techniques were employed for analyzing the deposited oxide thin films.

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The structural analysis of films were carried out by X-ray diffractometer XPERT-PRO with Cu Kα radiation (k = 1.54056˚A). The optical characterization of thin films were examined through

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UV-diffused reflectance spectra recorded within the wavelength range of 200-900 nm, using JASCO UV Vis NIR spectrometer (model name; V-770). The room temperature

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Photoluminescence (PL) studies was performed done using a JASCO FLUOROSCENCE spectrum (model name; FP-8300) with Xenon lamp with an excitation wavelength of 310nm.

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Surface morphology of samples was obtained by Field emission scanning electrons microscopy (Carl Zeiss microscope). P-N junction diodes were fabricated and analyzed under dark and light (100 mW/cm2) condition using portable solar simulator (PEC-L01).Also the dark and

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photocurrent of the junction diode were measured by applying bias voltage ranging from -3 to +3 V (step of 0.15 V) using Keithley electrometer.

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3. Result and discussion 3.1 X-Ray diffraction analysis

The structural analysis of In2O3 thin films were performed in θ-2θ geometry in the range of 20° to 70°. The Figure 1 represents XRD patterns of five spray deposited In2O3 films with temperature ranging from 250-450 °C with 50 °C increments [2]. At lower temperatures of 250

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°C and 300 °C, the pattern shows a diffraction peak centered at 22.41° corresponding to rhombohedra indium oxide (JCPDS card number 22-0336) with space group R3c. The diffraction peaks are weaker and wider for films deposited at substrate temperature 250 °C and 300 °C. Films deposited above 300 °C started crystallizing and were indexed by comparing with JCPDS 060-416 having space group Ia3 and orientated along (222) plane of cubic phase. As substrate temperature increased above 300 °C, the sharper crystalline phases indicated a switch

from rhombohedra to cubic In2O3 [17]. The peak arising at 56.588° indicated the partial thermal decomposition of In(OH)3 [18]. The growths of BCC crystallized In2 O3 samples were verified by estimating the crystalline size and lattice parameters were mentioned elsewhere [4,5,19]. Table 2 represents the lattice parameters, which are in comparison with the standard reported values (a=10.11 A, V=1.035 nm3, d=2.930 A) [20]. The stable orientation of intense peaks indicated that the samples are polycrystalline. Peak broadening was observed at 350 °C, which further increased at 400 °C

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and again decreased at 450 °C. At favorable energies above 350 °C, the increase of mobility and diffusion co-efficient would have caused activated atoms to move towards favorable energy sites

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resulting in nucleation and with the increase of temperature further diffusion through grain

boundaries caused recrystallization to occur [19]. Thus at 400° C recrystallization might have

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happened which resulted in decreased grain size.

The decrease in (222) peak intensity witnessed for temperature above 350 °C might be

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due to the consummated thermal decomposition [21]. The grain growth observed with the increase of temperature after 400 °C which might have induced a strain in the crystal have

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resulted in lattice parameter variations. Thus for comprehensive crystallization and grain growth to happen more energy is required and hence the crystal growth got arrested at 400 °C. The Xray diffraction pattern of Ni doped In2 O3 thin films at 400 °C substrate temperature is shown in

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Figure 2. All the peaks corresponded with cubic phase of In2 O3 thin films deposited at 400 °C. On increasing the doping concentration, the peak intensity and the broadening increased. The calculated values of crystalline size and lattice parameters of 10 wt% and 15 wt% Ni doped indium oxide are listed in Table 2. From the data values, a consistent decrease in the crystalline size and lattice parameters can be observed on increasing doping concentration. The ionic radii

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of Ni2+ (0.83A֯) is smaller when compared with In3+ (0.94 A֯) confirms the possibility of Ni2+ being substituted into lattice sites [22-23]. The bond energy of Ni2+ O2- (382 KJ/mol) being higher compared to that of In2+ O2- (320 KJ/mol) as reported by You Ran Luo et.al also confirms the arrested growth [24, 25]. 3.1.1 Micro-strain analysis

XRD peak profile analysis was done using Williamson-Hall method which is powerful method to evaluate the peak broadening effect due to crystallite size and micro-strain is shown in Figure 3-4 [26,27]. The Williamson–Hall (W–H) considers the peak width 2θ, which gets influences by crystallite size and lattice strain [28]. The strain-induced broadening arising from crystal imperfections and distortions and can be related by [29], β

𝜀 = 4 tan θ Kλ

D = β cos θ

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(2) (3)

1

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The equation 11 and 12 shows the direct dependence of tan θ on micro strain and cos θ on crystalline size. The total peak broadening is the sum of influence due to crystalline size and β = βD +β𝐬

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micro strain. (4)

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The W-H plot using uniform deformation Model (UDM) [28, 30], uniform stress deformation Model (USDM) [31-33], uniform deformation energy density model (UDEDM)

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[17,34] for INO films deposited at different temperatures and 10 and 15 wt% Ni doped In2O3 thin films are shown in Figure 3 & 4. The strain values estimated are compared and tabulated in Table 3. The elastic compliances of In2O3 with values 4.84x10-3, -1.5637x10-3 and 0.013085

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GPa-1 were chosen respectively [31,32] and Young’s modulus Yhkl, for cubic In2O3 nanoparticles was estimated as 202.639 GPa [33] for USDM and UDEDM model calculations. The decrease in the strain with increasing temperature for the crystallized models confirms that thermal stress does not contribute significantly to the strain for INO films

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deposited at different temperatures. The negative value of micro strain at 400 °C refers to compressive strain which can be regarded as a part of the possibility of strain induced defects created, which makes it a suitable candidate for diode applications [35]. From the graphs shown in Figure 4, it is observed that the compressive strain at 400 °C increases and switches to tensile strain with 15% doping. The 10 wt% Ni doping has large number of residual points, which indicates the inhomogeneity developed in crystal on doping. The variation from compressive to tensile strain affirms the Ni incorporation in the grain

boundaries. The incorporation of 15wt% of Ni increases the grain density, normalizing a tensile strain distribution. 3.2 Field emission scanning electron microscope The FE-SEM image in Figure 5 represents thin film prepared at 400 and 450 °C showing a octahedra layerd geometry. The vapor phase mechanism was used for the formation of such geometry. The layers of octahedrons were formed due to the anisotropic crystal growth along different planes [36]. As reported by Maghraby et.al, the surface energy relationships among

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three low-index crystallographic planes should correspond to γ{111} < γ{100} <γ{110} for a cubic phased INO [36].

At a favorable energy of 400 °C, vertical growth of INO crystal occurs along the (001)

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plane. Simultaneously some of the adsorbed species with tipped geometries got incorporated into the side planes along (111) and (110). However by elevating the temperature to 450 °C, growth

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along (001) plane got disappeared and oriented along (111) and (110) planes. Thus temperature plays an important role in extensively controlling and influencing the structure and morphology

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of thin films. As temperature increased, the layered structure oriented well along [111] and [110] direction which has been already reported [36]. Thus by combining the results of other

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characterization techniques, the role of temperature on crystallization and grain growth was consistent with the observations from structural analysis [37]. The higher crystalline size value estimated the grain growth at 450 °C with improved crystallinity was justified from

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morphological analysis.

Figure 5 represents FE SEM images of 10 wt% and 15 wt% Ni doped INO thin films. The imaging of 10% Ni doping on INO shows the dopant particles occupying the grain boundaries. The latter image of 15% Ni doping clearly exhibits that as the concentration of impurities increases the probability of Ni atoms getting incorporated into the lattice sites is also

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high. From the peak profile analysis, there was a compressive strain developed for 10 wt% Ni doping. This strain developed might be due to dopant particles occupying in the boundaries region, which was reconfirmed using FESEM image. Moreover, EDAX spectra of all films prepared at 400 °C and 450 °C of INO shows the presence of In and O and the presence of Ni along with In and O in Figure 5. The EDAX represents the energy of x-ray is a characteristics of elements from which the x-rays gets emitted. The thin films deposited at 400 oC and 450 oC have

the Indium and oxygen emitted from L and K shell. EDAX spectra of Ni doped indium oxide had the peaks of Ni and O arising from K series whereas In from L series [16, 38].

3.3 UV-DRS Spectroscopy The optical characterization of In2O3 thin films were examined through UV-diffused reflectance spectroscopy with in the wavelength range of 200-900 nm [26]. The band gaps of

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In2O3 thin films treated at 350°C, 400°C and 450 °C and the Ni doped thin films of 10 and 15 wt% concentrations at 400 °C were determined. The absorbance and reflectance (R %) of thin

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films against wavelength plots are shown in Figure 6 and 7. The absorbance/reflectance of the thin films showed a small shift in the absorbance edge and reflectance edge. The absorbance peaks were centered at 315, 319 and 307 nm. The 10 and 15 wt% Ni doped In2O3 thin films

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showed peak at 300 and 307 nm, confirming the interaction between both molecules. The irregular and inhomogeneous materials will generally have diffuse reflected beams, which were

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analyzed using Kubelka–Munk theory. Based on it a Kubelka-Munk function F (R ∞ ) [8], the band gap value determined by extrapolating graph onto x axis from Tauc plot as shown in Figure

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8. The estimated values of band gaps are tabulated in Table 4.

The variation in band gap value is consistent with variation in absorbance and reflectance

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spectra. The shift in the band gap was seen on an increasing side of wavelength, which resulted in lower band gap value for INO at 400 °C. This might be due to effect of substrate temperature to maintain crystallinity [27]. The decrease in band gap value (Eg) at 400 °C might be due to increased surface irregularity and interfaces at grain boundaries arising due to recrystallization. The variation in bandgap value again at 450 °C concludes that, as temperature increases the

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crystallinity improves and thereby has an influence in the band gap [39]. The widening of bandgap for 10 wt% Ni doped can be ascribed to Burstein Moss shift [40] and the slight narrowing of band gap at 15% doping can be attributed to the effects of the electron and impurity scattering [7]. As the doping concentration increases, shallow energy states of impurities formed will intend to form a reduced band gap region. The blue shift of Eg with bulk values (3.8 eV) along with the obtained band gap values confirms the formation of direct band gap In2O3 thin films [37]. The refractive index of In2O3 thin films were calculated based on Moss and Single

oscillator models[1,41].The constant value of the single effective oscillator energy E0 and the dispersion energy Ed for inter band optical transitions were estimated to be 6.85 and 17.06 eV. From Table 5 the average of refractive index value obtained was 2.16. The values were found to be consistent with reported values [42]. The theoretical calculation of thickness for the both as prepared indium oxide and 10 and 15 wt% Ni doped at 400 °C thin films were estimated using the model reported by Mancifer

t=

λ1 λ2

(5)

2n(λ1 )λ2 −2n(λ2 )λ1

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[43] and the values were obtained as shown in Table 6.

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The observed values of thickness of thin films shows a decrease in value with substrate

temperature owing to the vaporization of aerosols at high temperature [1]. The addition of dopant

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also shows a fall in thickness. The lower thickness at 10 wt% might be due to the inhomogeneous substitution of nickel at Indium recrystallized boundaries at 400 °C substrate

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temperature. As Ni concentration increases this inhomogeneity reduces, which was also verified

3.4 Photoluminescence

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with peak broadening analysis.

The room temperature Photoluminescence (PL) of In2O3 thin films were verified using

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Xenon source with an excitation wavelength of 310 nm. The Figure 9 shows the PL spectra of In2O3 thin films deposited at 350,400 and 450 °C. The observed peaks were at 394.25 nm, 421.3 nm, 467.1 nm. The standard indium oxide has highest emission peak around 338 nm (3.67 eV)[44]. The peak around 390 nm aroused due to exciton recombination, which has a major role in influencing the optical emission [22, 23]. The emission peaks at 423 nm and 467 nm has been

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already reported before by Jothibas et.al [17]. These peaks can be attributed to electrons transitions mediated by oxygen vacancies. According to Feng Gu et.al , the recombination of conduction band electron with oxygen sites can yield high emission peaks. Since bulk indium oxide does not support emissions at room temperature, the PL spectra indicates the formation crystalline nanoparticles. Indium hydroxide gets thermally decomposed into In2O3 by releasing HCl as vapor along with formation of oxygen vacancies. Thus the recombination of oxygen

vacancies (deep trap charges) and photo generated electrons from conduction band gave rise to peak centered at 466nm. The comparison PL plot of 10 and 15 wt% Ni doped In2O3 at 400°C is demonstrated in Figure 9 (b). The peak intensities of undoped INO were high when compared to doped thin films. Generally on doping the negative charges will get compensated as an oxygen vacancy in the lattice sites. But here on nickel incorporation at 400 °C, the luminescence of peaks decreased. On doping, the reduction in peak intensity and peak shift on comparison with as prepared In2O3 at

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400 °C confirms the incorporation of Ni in acceptor sites of In2O3. The emission peaks centered around 416 nm and 466 nm got quenched on doping. Owing to the high surface to volume ratio

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the presence of unsaturated bonds of atoms expected in the surface sites is more. Hence the surface with O2- ions will play an important role in the quenching of the luminescence. The

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trapping rate of electron from conduction band to vacant deep traps (oxygen vacancies) would have decreased. There are chances for the Ni ions to reside at surface grain boundaries. The

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quenching of luminescence is associated with Ni at grain boundaries of crystal resulted in recombination of electrons and holes in surface of particles for non radiative process[23].

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3.5 Junction diode fabrication

The n-In2O3/p-Si junction diode were fabricated on p-type silicon wafers with (100) orientation. The thickness and resistivity of the wafer is 279 μm (± 25 μm) and 0 - 60 Ω.cm

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respectively. For removing unwanted impurities like dust, grease, oil, etc. The silicon wafers were cleaned using standard procedures [45]. After the cleaning process, 3 ml of pure In2O3 and Ni doped In2O3 homogeneous solution were deposited on the p-Si wafer using JNSP technique at an optimized substrate temperature of 400 ºC. The schematic diagram of the fabricated junction

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diode is shown in Figure 10. For contact purpose, the silver (Ag) paste was applied on either side of the n-In2O3/p-Si junction diode. Then it was dried at 5 hour in room temperature. 3.5.1 Current –voltage (I-V) characterization of n-In2O3/p-Si junction diode Figure 11 shows the current-voltage (I-V) characteristics for pure In2O3 and Ni doped In2O3 junction diode fabricated with various Ni concentrations like 10 and 15 wt%. P-N junction diode parameters such as n, ФB, and Io of the n-In2O3/p-Si junction diode were analyzed under dark and light (100 mW/cm2) condition using portable solar simulator (PEC-L01).The dark and

photocurrent of the junction diode were measured by applying bias voltage ranging from -3 to +3 V (step of 0.15 V) using Keithley electrometer. The forward current values of the junction diodes were found to increase exponentially with bias voltage under light condition when compared to dark as shown in Figure 11. Result suggests that the fabricated diodes has higher photoconducting nature and very sensitive in illumination. The current conduction mechanism of the fabricated n-In2O3/p-Si junction diode was explained based on thermionic emission theory (TET) [43, 44]. The Ideality factor and barrier height of the diodes were calculated using the following q(V−IRs )

I = I0 [exp (

nKB T

) − 1]

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relation and are summarized in Table 7. (6)

qϕB

I0 = AA∗ T 2 exp (− K

BT

)

(7)

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Here,

Where Io is the saturation current, q is the electron charge, V is the bias voltage, n is the ideality

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factor, ΦB is the effective barrier height, KB is the Boltzmann constant, T is the temperature, the IRs term is voltage drop on the Rs and effective Richardson constant. It is obviously seen from 7

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Table 7, that the saturation current (Io) of the undoped junction diode was found to be 1.45 × 10A. Interestingly, this was increased to 2.16 × 10-3 A after Ni doping particularly under light

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condition. This is an indication that the Ni doping concentrations strongly improve the saturation current (Io) of the diode. The ideality factor (n) and effective barrier height of the diode were calculated by the following the equations [46]. q

(

d(V)

)

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n=

kB T d(ln(I))

ϕB =

KB T q

AA∗ T2

In (

I0

)

(8) (9)

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The ideality factor (n) of the diode was deduced from the intercepts of semi-logarithmic plots (ln J vs voltage (V)) as shown in Figure 12. In general, the ideality factor (n) is less than 1 which indicated that the fabricated diode was ideal diode. However, the ideality factor (n) of the n-In2O3/p-Si junction diode was varying from 3.38 to 1.35 with Ni concentration. The minimum ideality factor of n=1.35 was obtained for the diode fabricated with 15 wt% of Ni under light. This result may be attributed due to increase the photo-generated charge carrier under light condition [47,48]. Moreover, the higher ideality factor such as n=4.42 and 3.38 ascribed due to

the weak photo-generated charge carrier, recombination of e- - h+ pairs in space charge region, existence of a native oxide layer between n-In2O3 and p-Si wafer and tunneling [49,50]. The effective barrier height (ΦB) of the pure In2O3 diodes is calculated to be high of 1.10 eV which was found to decrease continuously both dark and light condition after incorporating Ni atoms in In2O3 matrix. The 15 wt% of Ni doped In2O3 junction diodes show the lower barrier height of 0.89 eV. The barrier height values of the diode mostly influenced by the contact or thickness between the p-type and n-type layer along with the carrier tunneling traps, which are

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localized in the n-type layer nearer to the p-Si surface [51]. Based on the diodes results, it could be concluded that the fabricated n-In2O3/p-Si junction diode was very sensitive both light and Ni

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doping concentrations particularly 15 wt%. Hence, the 15 wt% Ni doped junction diode has most appropriate for optoelectronic device application.

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4. Conclusion

The indium oxide and nickel doped indium oxide thin films have been successfully deposited by

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jet nebulizer spray pyrolysis at various substrate temperatures. The peak width shift in XRD confirms the factors influencing the formation and micro strain effects of the spray deposited thin

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films which were also verified by Williamson-Hall method. Optical characterization using UVDRS spectra confirmed the influence of temperature on surface irregularity and band shift. The increase in the direct band gap on Ni doping was attributed to Burstein Moss shift. The

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photoluminescence spectra of INO prepared at 350 °C, 400 °C and 450 °C showed the presence and influence of oxygen vacancy. The FESEM analysis ensured the octahedral layered geometry. The presence of Indium and oxygen in crystal sites has been confirmed from EDAX spectra. By adopting the optimum condition at 400 °C, a photodiode was fabricated on p type silicon wafer. The I-V characteristics show the high sensitivity on light illumination for 15 wt% Ni doped INO

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diode.

Declaration of interests The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper

Acknowledgment Authors acknowledge the support received from to Department of Physics, Alagappa University for XRD measurements . AN and LM acknowledges Coimbatore Institute of Technology (Department of Physics) and The South India Textile Research Association (SITRA),

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Coimbatore for FESEM and EDAX measurements.

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Fig. 1. XRD pattern of INO thin film prepared at different substrate temperatures

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Figure 2 XRD pattern of Ni doped of INO thin film at 400 °C substrate temperatures

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(a )

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(c )

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(b )

Fig. 3 (a) UDM (b) USDM (c) UDEDM for In2O3 thin film at 350 °C, 400 °C and 450 °C

(b)

(c )

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Fig. 4. W-H plot of Ni doped In2O3 thin film at 400 C (a) UDM (b) USDM (c) UDEDM

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INO at 400 °C

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10 wt% Ni

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INO at 450 °C

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15 wt%

Fig. 5 FE-SEM image of spray coated undoped and doped Indium oxide thin film.

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(b)

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(a)

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Fig 6: Absorbance plot of In2O3 thin film prepared at (a) 350, 400, 450 °C and (b) Ni doped In2O3 400 °C

(b)

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(a)

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Fig 7: Reflectance plot of In2O3 thin film prepared at (a) 350, 400 and 450 ° C (b) Ni doped In2O3 at 400 °C

(a)

(a)

(b)

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Fig. 8 Tauc plot of INO thin film coated at (a) 350 °C, 400 °C and 450 °C (b) 10 and 15 % Ni doped INO thin film

(b)

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Fig 9: (a) PL spectra of In2 O3 thin films at 350 °C, 400 °C and 450 °C (b) PL spectra of Ni doped In2O3 thin films at 400 °C

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Fig 10: Schematic diagram of the n-In2O3/p-Si junction diode

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Fig 11: I-V characterization of n-In2O3/p-Si junction diode for various doping concentration of Ni

of ro -p re lP ur na Jo Fig 12: Semi-logarithmic plot of ln J vs V for n-In2O3/p-Si junction diode with different Ni doping concentration.

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Parameters

Values

Diameter of the nozzle Distance between substrate and nozzle Substrates temperature Pressure maintained Flow rate

0.5 mm 5 cm

Time of spray

20 min

400 °C 3.5 kg cm−2 0.5 ml min−1

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Deposition conditions of thin film

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Table 1:

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Highest peak (2θ)

Plane

FWHM (degree)

Volum e (nm3)

Inter planar spacing d (A°)

1.0061

1.0184

2.904

41.847

1.0068

1.0205

D(nm)

a=b=c (nm)

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Samples

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Table 2 Lattice parameter values of indium oxide and Ni doped indium oxide thin films at various temperatures

Dislocation density X 10-3 (nm)-2

Bond length

2.342

0.6258

0.2515

2.906

3.1249

1.1125

0.2517

Strain ε (X

L (nm)

10-3)

30.7461

(222)

0.1476

In2 O3 (400°C)

30.7252

(222)

0.1968

In2 O3 (450°C)

30.6821

(222)

0.1476

55.799

1.0082

1.0248

2.910

2.3381

0.6234

0.2520

10 wt% Ni doped In2 O3 (400 °C)

30.7711

(222)

0.1968

41.851

10.053

1.0159

2.9020

3.120

1.112

0.2513

(222)

0.2460

33.485

10.036

1.0108

2.897

3.893

1.737

0.2509

55.799

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15% Ni doped 30.8259 In2 O3 (400 °C)

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In2 O3 (350°C)

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USDM Strain Ε (×10-3)

In2 O3 (350 °C)

55.799

66.34

0.67133

In2 O3 (400 °C)

41.847

38.07

Ni doped In2 O3 (15 wt%)

Strain Ε (×10-3)

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66.34

0.6713

38.07

-0.324

Stress (σ) MPa 136.04

-65.71

78.49

UDEDM D (nm)

66.34

Energy density (u) (KJm-3) 45.69

Strain Ε (×10-3)

Stress(σ) MPa

0.67158

136.08

38.07

10.62

0.3237

65.60

58.87

17.22

0.4122

83.54

55.799

58.87

0.38735

58.87

.3873

41.851

27.2

-0.943

27.2

-0.943

-191.2

27.2

90.25

0.943

191.2

74.72

2.04

74.72

2.04

413.95

74.72

422.7

2.04

413.9

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Ni doped In2 O3 (10 wt%)

-0.3242

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In2 O3 (450 °C)

D (nm)

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D (nm)

Samples

Scherrer’s formula D (nm)

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UDM

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Table 3 Strain and crystalline size values of Indium oxide and Ni doped INO thin film at 400 °C substrate temperatures

33.485

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Table 4: Optical band gap of as prepared and Ni doped thin films

In2 O3 (350 °C)

3.82

In2 O3 (400 °C)

3.80

In2 O3 (450 °C)

3.94

4.03

15wt % Ni doped In2 O3

3.91

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10wt % Ni doped In2 O3

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Eg (eV)

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Table 5 Refractive index of as prepared and Ni doped INO thin films

Samples

Moss model

Single oscillator model

2.23

2.148

In2 O3 (400 °C)

2.23

2.146

In2 O3 (450 °C)

2.21

2.173

10wt % Ni doped In2 O3

2.20

2.192

15wt % Ni doped In2 O3

2.22

2.166

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In2 O3 (350 °C)

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Table 6: Theoretical thickness values of In2 O3 thin films at 350 °C, 400 °C and Ni doped In2O3 thin films at 400 °C.

Samples

104.64

In2 O3 (400 °C)

78.95

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In2 O3 (350 °C)

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Thickness (d) (nm)

74.37

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In2 O3 (450 °C)

50.2

15wt % Ni doped In2 O3

77.79

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10wt % Ni doped In2 O3

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Table 7: Significant diode parameters of n, ФB and Io for n-In2O3/p-Si junction diode.

Doping concentration of Ni ( wt%)

Ideality factor

Barrier height

(n)

(ФB)

Saturation current density (Io)

Light

Dark

Light

Dark

Light

0

3.38

4.42

1.10

0.93

1.45 × 10-7

2.01 × 10-4

10

2.12

1.91

1.02

0.91

15

2.87

1.35

0.92

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Dark

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1.89 × 10-6 2.64 × 10-4

2.16 × 10-3

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0.89

8.92 × 10-4

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