Film thickness effect on structural,optical and electrical properties of indium oxide (In 2 O 3 ) thin films grown via sol-gel method

Abstract

In this work, we investigated the effect of the thickness on structural, morphological, optical, and electrical properties of In₂O₃ thin films synthesized via by sol–gel spin coating technique. The prepared samples were characterized by various techniques including X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray (EDX) spectra, UV-Vis-NIR spectrophotometer as well as the electrical measurements via the four-probe technique. The XRD analysis reveals that the films have a cubic crystalline structure, with (222) preferential orientation. The crystallite size values of the films were varied from 14 to 27 nm. The (SEM) images indicated that the homogenous and smooth surface with better adherent to the substrate surface. The EDX spectrum reveals the presence of In and O element necessary for In₂O₃ films for film formation. Excess of oxygen is observed due to the substrate contribution. The transmittance results exhibit that the films are highly transparent, more than 75% in the visible range from 400 nm to 800 nm is measured. The estimated band gap energy is found to increase with increasing film thickness (3.37–3.7 eV). The electrical resistivity of the In₂O₃ thin films substantially decreases with the increasing film thickness from 1.48×10^-4 to 1.3×10^-3 Ω.cm.

Keywords

Sol–gel spin coating method film thickness physical properties.

1 Introduction

In the last few years, human existence is becoming semiconducting thin films dependant. The latter play important role in all fields especially field of optoelectronic, microelectronic and communication technologies [1]. Among them, the transparent conductive oxides (TCO) such as SnO₂, CdO, ZnO, In₂O₃, TiO₂ etc [2 –4] have been extensively studied, because of their unique physical and chemical properties, they found a large number of applications, such as photovoltaic solar cells [5], sensor devices [6], light-emitting diode devices [7] and flat panel displays [8]. Among these oxides, In₂O₃ is an important one, it is well known as a suitable material for many electronic applications due to its excellent physical properties. It is an n-type semiconductor with a wide band gap (E_g ∼ 3.65 eV) [9], a high refractive index (2–2.1) [10] as well, high optical transmittance (in the visible region) and good electrical conductivity [11]. Thus these properties allow for photovoltaic devices, solar cell, transparent windows, liquid crystal displays, light emitting diode (LED) and gas sensors to be realized [12 –14].

Several researchers have studied the effect of several parameters on the structural, optical and electrical properties of Indium (III) oxide (In₂O₃) in order to improve their properties [15 –20], using different method. The films thickness is one of the most important decisive factors for film physical properties. The lack of thin In₂O₃ film thickness in the literature motivated us to study the influence film thickness on physical properties of In₂O₃ films. Few published papers emphasized that the film thickness has a significant effect on the physical properties of In₂O₃ film [21, 22]. However, only a few studies have been devoted to the influence of large film thickness (d > 800 nm) on the physical properties of In₂O₃ films deposited by sol gel spin coating process.

By the way, several deposition techniques have been widely used to produce In₂O₃ thin films including RF magnetron sputtering [23], chemical vapor deposition (CVD) [24], spray ultrasonic [25], thermal evaporation [26], spray pyrolysis [27], pulsed laser deposition (PLD) [28] and sol-gel methods [29]. Among these, sol–gel method is one of the most used techniques for In₂O₃ thin films preparation compared to others deposition methods, due to its significant advantages such as simple, economical relatively cost-effective process. It allows the easy and precise control of material composition and films production with a good quality [30 –32].

This paper reports the effect of film thickness on structural, morphological, optical and electrical properties of In₂O₃ thin films prepared by sol–gel spin coating process.

2 Experimental details

2.1 Materials and In₂O₃ thin film preparation

The undoped indium oxide (In₂O₃) thin films have been grown by sol-gel spin coating technique. Indium (III) nitrate hydrate (In(NO₃)₃·H₂O), 99.98% pure (Sigma–Aldrich) (0.43 g), that was used as source material of In⁺³ and it was dissolved in appropriate amount of ethanol (C₂H₆O) (9 ml) and acetylacetone (C₅H₈O₂) (1 ml) as the stabilizer, with 0.15 M concentration. The volume ratio of acetyl-acetone to ethanol was maintained at 1:10. The starting solution was stirred for 2 h at 50° C, then mixed and stirred with a magnetic stirrer for 24 h at room temperature to obtain a transparent solution. Soda lime glass (SLM) slides were used as substrates with the size of (2.5 cm×2.5 cm×0.15 cm). Before the deposition, the glass substrate was cleaned followed by rinsing in methanol and acetone for 10 min then cleaned with deionized water for 5 min and dried in air.

The prepared solution was dropped onto cleaned glass substrate, with rotation speed of 4000 rpm for 30 s in order to obtain a well coated thin film on glass substrates. Subsequently, the coated films were dried at 250° C for 10 min after each successive coating in a furnace to evaporate the organic solvent. The procedures was repeated 4, 6, 8, 10 and 15 times (number of layers) in order to achieve various In₂O₃ thin film thicknesses. Finally, the film was annealed at 550° C in the furnace for 1 h. A schematic drawn representing the In₂O₃ thin film preparation steps are sketched in Fig. 1.

Fig. 1

Flow chart showing the schematic diagram for In₂O₃ thin film preparation procedure.

2.2 Characterization methods

The structural, morphological, optical and electrical characterizations of all the films were treated by using various techniques. The crystallinity of the samples was characterized by X-ray diffraction (Model: Bruker D8) using Cu Kα (λ= 1.5418 Å) radiation within the 2θ range of 10°–90°. Moreover, observation of surface morphology was achieved using a scanning electron microscope (SEM JEOL model VEGAS3 TESCAN). The films composition was analyzed by energy dispersive analysis using X-rays (EDAX) equipped in “VEGAS3 TESCAN”. The optical transmittance was recorded using UV-Visible spectrophotometer (Perkin Elmer Lambda 950 UV/VIS) in the wavelength range 200 to 1000 nm. Finally, the measurements of electrical resistivity were carried out by a four-point configuration, using “Jandel RM 3000” apparatus at room temperature. Carrier concentration and mobility were measured by Hall effect measurements system using gold contact electrodes with applying the magnetic field 0.6 T and current 3 mA.

3 Results and discussion

3.1 Structural properties

To films thicknesses of In₂O₃ thin film was controlled by varying the number of the layers from 4 to 15 layers. The film thickness was determined using SEM cross sections by calculating the average thickness from one end to the other as depicted in Fig. 2. As shown in Fig. 3, the thickness of the films increases with the number of the layers, the variations follow a quasi linear behavior with a rate of 58 nm per cycle. Form the linearity depence one can choose the number of cycle suitable to obtain a desired thickness.

Fig. 2

Direct thickness measurement of the film of In₂O₃ from the cross sectional SEM images.

Fig. 3

Variation of the film Thickness with the number of layers.

The crystal structure and orientation of the In₂O₃ thin film were investigated by X-ray diffraction (XRD) pattern. The XRD pattern of all In₂O₃ films prepared at different film thickness (175, 330, 520, 690 and 910 nm) on glass substrate are shown in Fig. 4. As can be observed in the graphic, the samples have a polycrystalline structures with five peaks shown in Fig. 4, assigned to (211), (222), (400), (440) and (622) diffraction planes, matching with a body cantered cubic (BCC) phase of In₂O₃ with a space group of Ia3(206) (JCPDS Card No. 06-0416, space group, a = 10.118 Å) [33]. However, no peak related to a secondary phases such as In or InO is observed. Similar result has been observed in our earlier work and other work [34, 35]. Moreover, Fig. 4 reveals that the samples have an intense peak originating from the (222) diffraction plane, it becomes narrower, intense when the film thickness increases, suggesting the films crystallinity improvement. The preferential growth along (222) direction may be due to the reasons that the plan (222) requires the lowest free surface energy formation [36, 37]. The data also shows that the peak position slightly shifts to a lower 2θ value as shown in Fig. 5, this is probably due to stress created during the films growth.

Fig. 4

XRD patterns of nano-crystalline In₂O₃ thin films for different film thickness.

Fig. 5

Variation of peak (222) position of In₂O₃ thin films at different film thickness.

To describe the preferred growth orientation (h k l), we calculated the texture coefficient from the X-ray data using the following equation [38]: $TC (hkl) = \frac{I (hkl) / - I_{0} (hkl)}{\frac{1}{N} \sum I (hkl) / - I_{0} (hkl)}$ (1)

Where I (h k l) is the measured intensities of the plane, I₀(h k l) is intensities of the standard plane (h k l) (JCPDS data card (6–416)) and N is the number of diffraction peaks. The obtained results summarized in the Fig. 6. It is clear that the (222) direction has the highest texture coefficient comparing with other peaks, which increases drastically with increasing film thickness. It is well known that the films texturation is usually related to two factors: the growth and nucleation. The increase in the preferred orientation of (222) plane is attributed to the increasing in the growth along this direction on the detriment other planes.

Fig. 6

The texture coefficient of In₂O₃ thin films as function of film thickness along (222), (400) and (440) directions.

The crystallite size (D) was estimated from the FWHM of the high intense peaks, namely the one corresponding to (222) crystallographic plane, using the Debye–Scherrer formula [39]: $D = \frac{0.94 λ}{β cos θ}$ (2)

Where λ is the wavelength of the X-ray (λ= 1.5418 Å), β is the full width half maximum of the diffraction peak expressed in radians and θ is the Bragg diffraction angle.

The dislocation density (δ) and strain (ɛ) were calculated using the following equations [40, 41]:

$δ = \frac{1}{D^{2}}$ (3)

$β_{hkl} \cdot cos θ = \frac{K . λ}{D} + 4 . ɛ . sin θ$ (4)

The calculated crystallite sizes, strain and dislocation density is listed in Table 1.

Table 1

Crystallite sizes, dislocation density and strain values of In₂O₃ thin films extracted from XRD analysis

Thickness (nm)	Peak (hkl)	2θ°	FWHM (β°)	D (nm)	δ× 10¹⁵ (Lines /m²)	ɛ× 10^–4
175	(222)	30.66	0.61	14±0.2	5.1	7.3
330	(222)	30.62	0.45	19±0.2	2.77	5.38
520	(222)	30.59	0.42	20.5±0.2	2.38	5.01
690	(222)	30.57	0.38	23±0.2	1.89	4.54
910	(222)	30.54	0.32	27±0.2	1.37	3.83

It is evident from the contents of Table 1 and Fig. 7, that as the films thickness increases, the crystallite size enlarges, while the strain decreases. The same behavior is reported by Goswami et al. in his study on In₂O₃ thin films prepared by pulsed laser deposition technique [42]. On opposite, in our previous work [43] we have noticed a decrease in crystallite size with molar concentration increase. The observed improvement in crystallite sizes is commonly attributed to sufficient supply of thermal energy to the coalescence the atoms over the surface substrate and this facilitate the merging of the smaller particles into larger ones, as the results, the crystallite sizes increases [44, 45]. The decrease in strain formed in the crystal could be related to improvement of the crystallinity, which result to produced more organised films with less point defects.

Fig. 7

The evolution of grain size and strain of In₂O₃ thin films at different film thickness.

The inter-planar distances d_hkl and the lattice constant a for a body-centered cubic structure of In₂O₃ films were estimated according to Bragg’s law as Equation [46]: $d_{hkl} = \frac{n λ}{2 sin θ_{hkl}}$ (5) $a = d . \sqrt{h^{2} + k^{2} + l^{2}}$ (6)

Where θ _hk is the diffraction angle and λ is the X-ray wavelength (1.5418 Å) and hkl is the Miller indices.

In order to calculate the deformation in the lattice parameters of bulk, the internal stress needs to be determined. For cubic crystals, the internal stress (σ) in the plane of the film can be estimated using the following equation: $σ = \frac{E}{2 . γ} (\frac{a - a_{0}}{a_{0}})$ (7)

Where a is the lattice constant measured from the XRD, a₀ is that of bulk lattice constant (10.118 Å), E is Young’s modulus of In₂O₃ (145 GPa) [47], γ is the Poisson’s ratio (0.31) for In₂O₃ [48].

The calculated structural parameters from XRD pattern of In₂O₃ films are summarized in Table 2. As can be seen from Table 2 the a lattice parameter of pure In₂O₃ thin films increases with the films thickness. At the same time, the internal stress changes from compressive (negative) to tensile (positive). The similar result observed in previous study [49, 50]. It can be seen that the compressive stress in the films decreases and in contrary, the tensile stress increases with increasing films thickness.

Table 2

Structural parameters information of prepared In₂O₃thin films for different films thickness

Thickness (nm)	h k l planes	2θ (degree)	Calculated parameters		Reference parameter (JCPDS card No 06-0416)	Stress (Gpa)
			Lattice constant a (Å)	d-spacing (Å)
175	(222)	30.66	10.101	2.916		–0.39
330	(222)	30.62	10.112	2.919	a₀ = 10.118 Å	–0.14
520	(222)	30.59	10.122	2.922	d = 2.921 Å	0.09
690	(222)	30.57	10.129	2.924	2θ= 30.58	0.25
910	(222)	30.55	10.136	2.926		0.42

3.2 Morphological properties

The surface morphology images of as grown In₂O₃ thin film having different thickness is presented in Fig. 8 (a)-(e). It can be seen that all the films have a uniform, smooth, continuous and homogenous surface morphology with particle distribution consisting of spherical and triangular shapes without any voids and cracks. However, with the increases of film thickness, a large number of granular and dense grains are formed on top of the film. As can be seen, the grain size increases with increasing of film thickness. This result is supported by obtained results in the XRD analysis.

Fig. 8

SEM micrographs of the In₂O₃ thin films at different film thickness: (a) 175 nm, (b) 330 nm, (c) 520 nm, (d) 690 nm and (e) 910 nm.

3.3 Compositional analysis

The EDX spectra of In₂O₃ thin film deposited with different films thicknessare reported in Fig. 9. The EDX study confirms the presence of indium (In) and oxygen (O) necessary for In₂O₃ formation. The silicon originates from the glass substrate. In a stoichiometric In₂O₃ the atomic percentage shoud be 60% and 40% for Oxygen and Indium, respectively. However, according to the EDX spectra (Fig. 9) the films contain an excess of oxygen, this might be due to the contribution of oxygen originating from the substrate as well as Si atoms. On the other hand the excess of oxygen may also originate from the existence of oxygen vacancies [51].

Fig. 9

EDX spectrum of the In₂O₃ thin films at different film thickness: (a) 175 nm, (b) 330 nm, (c) 520 nm, (d) 690 nm and (e) 910 nm.

3.4 Optical properties

The transmittance spectra of the indium oxide thin films in the wavelength range of 200–1000 nm are shown in Fig. 10. All of the samples exhibit high optical transmittance more than 75% in the visible wavelength region (400 to 800 nm). The high transmittance of these films can be appropriated as transparent electrode of the solar cell application [52]. Interference fringes are noticeable in the visible region, this indicatives of uniform and homogenous obtained films which are characteristically smooth [53, 54]. Hence, the reduction in the light scattering losses due to the films smoothness is the principal reason of the films transmittance improvement. Besides, the transmittance spectra of our samples revealed strong absorption edges in the UV region (λ< 380 nm), which suggesting the blue-shifted absorption edge with the increasing films thickness, as shown in the inset of Fig. 10. This phenomenon has been reported in other TCO thin films [55, 56].

Fig. 10

The transmittance spectra of In₂O₃ thin films prepared with various film thickness.

From the curve of (αhν)² as function (hν) which depicted in Fig. 11, the optical band gap (E_g) can be determined by the extrapolation of the linear region of the curves to intersect at hν axis following Tauc relationship [57]:

Fig. 11

The plot of (αhν) ² against hν of In ₂O₃ thin films and inset shows the variation of optical band gap (E_g) as a function of film thickness.

${(ahv)}^{2} = A (hv - E_{g})$ (8)

Where A is a constant, hν is the photon energy, E_g is the optical band gap energy and α is the absorption coefficient, which calculated as [58]: $α = \frac{1}{d} Ln (\frac{1}{T})$ (9)

Where d is the thickness of the sample.

The inset image as shown in Fig. 11, represents the calculated band gap values dependence on the films. The observed band gap values are in good agreement with the reported value for the ITO films deposited by electron beam evaporated and RF sputtering technique [59, 60]. The broadening of band gap energy with the increasing films thickness can be due to the Burstein–Moss effect [61, 62]. This phenomenon is related to increased carrier concentration which lead to shifts the Fermi level to higher energy [63, 64].

3.5 FTIR Spectroscopic Analysis

FTIR spectroscopy was used to reveal the chemical bond present indium oxide (In₂O₃) thin films. Figure 12 represents the FTIR spectra of indium oxide (In₂O₃) thin films with various films thickness. A sharp absorption peak centered at 2354 cm^–1 is attributed to the O–H stretching vibration from absorbing water molecules (H₂O) in In₂O₃ lattice [65]. However, we can also recognize absorption band at 906 cm^–1 related to C–H bending vibration. The weak intense bands around 766 cm^–1 are ascribed to In–O lattice stretching vibrations [66], because the In–O stretching vibration modes are usually observed in the region of 800–300 cm^–1 as reported by many authors [67, 68].

Fig. 12

FTIR spectra for In₂O₃ thin films deposited as a function of film thickness.

3.6 Electrical properties

Table 3 illustrates the variation in resistivity (ρ), carrier concentrations (n), and Hall mobility (μ) of In₂O₃ thin films as a function of films thickness. As shown in Table 2, the resistivity decreased from 1.5×10^–3 Ω·cm at 175 nm to 1.5×10^–4 Ω.cm at 910 nm. At the same time, both of the carrier concentration and mobility of the films rapidly increase from 1.24×10²¹ cm^–3 to 6.43×10²¹ cm^–3 and 0.65 cm²/V.S to 33.7 cm²/V.S with increasing thickness, respectively. Similar results were reported in previous literature [69 –71]. The resistivity reduced can be attributed to the films crystallization improvement, which leads to the enlargement in crystallite sizes which consequently reduces the free electron scattering at grain boundaries [72] and then the carriers mobility enhancement. On other hand, the presence of oxygen vacancies and/or interstitial indium acts as charge donor centers in the system consistent with the observed increase of the charge carrier density and mobility [73, 74]. The free carriers enhancement with the thickness is in good agreement with the films band gap broadening as deduced from the optical characterization results.

Table 3
Electrical resistivity, carrier concentration and carrier mobility values of In₂O₃ thin films deposited using sol-gel spin coating method

Thickness (nm) Resistivity Carrier concentration Carrier mobility

ρ (Ω.cm) n (cm^-3) μ (cm²/VS)

175 1.50×10^-3 1.24×10²¹ 0.65

330 1.03×10^-3 1.63×10²¹ 1.78

520 5.20×10^-4 2.16×10²¹ 5.56

690 2.80×10^-4 3.41×10²¹ 13.70

910 1.50×10^-4 6.43×10²¹ 33.70

Thickness (nm)	Resistivity	Carrier concentration	Carrier mobility
175	1.50×10^-3	1.24×10²¹	0.65
330	1.03×10^-3	1.63×10²¹	1.78
520	5.20×10^-4	2.16×10²¹	5.56
690	2.80×10^-4	3.41×10²¹	13.70
910	1.50×10^-4	6.43×10²¹	33.70

4 Conclusion

In summary, high transparent conducting In₂O₃ was successfully prepared on glass substrates using a sol-gel spin coating technique. The structural, morphological, optical and electrical properties of In₂O₃ thin films have been investigated and analysis as a function of the thickness. The X-ray diffraction analysis indicated that the deposited thin films have a cubic polycrystalline structure with (222) as preferential growth direction. In addition, the crystallite sizes rises with the films thickness it increases from 14 to 27 nm. SEM images revealed that the prepared films are voids and cracks free and also the homogeneity and the smoothness of the films surface. The EDX spectra confirmed the presence of In and O elements. Furthermore, the prepared films have a good transmittance in the visible region above 75% with blue shift in band gap energy from 3.37 to 3.7 eV attributed to Burstein–Moss effect due to free carriers concentration enhancement with the films thickness increase. The FTIR spectroscopy measurements have have provided evidence of functional groups (In-O) proposed to be present in the chemical bonding. Electrical properties show that the films resistivity is reduced with increasing the film thickness. In conclusion we inferred that the film thickness is important parameter controlling In₂O₃ films physical properties.

References

Kennedy

, Viswanathan

and Pradeev raj

, Study of the influence of substrate temperature on structural, optical, and electrical properties of Zn-doped MnIn₂S₄ thin films prepared by chemical spray pyrolysis, Physics Letters A 380 (2016), 2842–2848.

Sanchez-Juarez

, Tiburcio-Silver

and Ortiz

, Properties of fluorine-doped ZnO deposited onto glass by spray pyrolysis, Solar Energy Materials and Solar Cells 52 (1998), 301–311.

Jeong

J.S.

, Kim

Y.H.

and Lee

J.Y.

, Morphology and Structure of Nano-Sized In₂O₃ Crystals Synthesized by Wet Reaction, Journal of the Korean Physical Society 42 (2003), S254–S257.

Kashyout

A.B.

, Soliman

and Fathy

, Effect of preparation parameters on the properties of TiO₂ nanoparticles for dye sensitized solar cells, Renewable Energy 35(12) (2010), 2914–2920.

Yüzüak

G.D.

and Coşkun

Ö.D.

, The effect of annealing on the structural, electrical, optical and electrochromic properties of indium-tin-oxide films deposited by RF magnetron sputtering technique, Optik 142 (2017), 320–326.

Sudha

, Sharma

and Gupta

, Achieving sensitive and stable indium oxide thin films for gamma radiation monitoring, Sensors and Actuators A: Physical 285 (2019), 378–385.

Huang

C.J.

, Su

Y.K.

and Wu

S.L.

, The effect of solvent on the etching of ITO electrode, Materials Chemistry and Physics 84(1) (2004), 146–150.

Cho

and Yun

Y.-H.

, Characterization of indium tin oxide (ITO) thin films prepared by a sol–gel spin coating process, Ceramics International 37(2) (2011), 615–619.

Flores-Mendoza

, Influence of the annealing temperature on the properties of undoped indium oxide thin films obtained by the sol–gel method, Thin Solid Films 517(2) (2008), 681–685.

10.

Bouhdjer

, Attaf

, Saidi

, Bendjedidi

, Benkhetta

and Bouhaf

, Correlation between the structural, morphological, optical, and electrical properties of In₂O₃ thin films obtained by an ultrasonic spray CVD process, Journal of Semiconductors 36(8) (2015), 082002(1-6).

11.

Ding

, An

, Li

, et al., Preparation of ITO nano-particles by liquid phase co-precipitation method, Journal of Nanomaterials, vol. 2010, Article ID 543601, pp. 5, 2010.

12.

Girtan

, Cachet

and Rusua

G.I.

, On the physical properties of indium oxide thin films deposited by pyrosol in comon with films deposited by pneumatic spray pyrolysis, Thin Solid Films 427 (2003), 406–paris.

13.

Kim

H.S.

, Na

H.G.

, Yang

J.C.

, Lee

and Kim

H.W.

, Synthesis, Structure, Photoluminescence, and Raman of Indium Oxide Nanowires, Acta Physica Polonica A 119(2) (2011), 143–145 Spectrum.

14.

Korotcenkov

, Brinzari

, Cerneavschi

, Ivanov

, Golovanov

, Cornet

, Morante

, Cabot

and Arbiol

, The influence of film structure on In₂O₃ gas response, Thin Solid Films 460 (2004), 315–323.

15.

Fellahi

, Addou

, Kachouane

, El Jouad

and Sofiani

, Optical properties of undoped and tin-doped nanostructured In₂O₃ thin films deposited by spray pyrolysis, Eur Phys J Appl Phys 74 (2016), 24611.

16.

Lau

L.N.

, Ibrahim

N.B.

and Baqiah

, Influence of precursor concentration on the structural, optical and electrical properties of indium oxide thin film prepared by a sol–gel method, Appl Surf Sci 345 (2015), 355–359.

17.

Zhang

, Dong

, Xu

, Zhao

and Wu

, Characteristics of zirconium-doped indium tin oxide thin films deposited by magnetron sputtering, Sol Energy Mater Sol Cells 92 (2008), 1224–1229.

18.

Kaleemulla

, Reddy

A.S.

, Uthanna

and Reddy

P.S.

, Physical properties of pure In₂O₃ thin films, Optoelectron Adv Mater Rapid Commun 2 (2008), 782–787.

19.

Tripathi

, Rath

, Ganesan

and Choudhary

R.J.

, Growth dynamics of pulsed laser deposited indium oxide thin films: a substrate dependent study, Appl Surf Sci 256 (2010), 7091–7095.

20.

Sariket

, Shymal

, Hajra

, Mandal

, Bera

, Maity

, Kundu

and Bhattacharya

, Temperature controlled fabrication of chemically synthesized cubic In₂O₃ crystallites for improved photo-electrochemical water oxidation, Materials Chemistry and Physics 201 (2017), 7–17.

21.

, et al., Preparation and characterization of ITO thin films on glass by a sol–gel process using metal salts, International Journal of Nanoscience 3(04n05) (2004), 447–454.

22.

Ghamari

, Raoufi

and Arjomandi

, Influence of Thickness on Crystallographic, Stereometric, Optoelectronic, and Electmical Characteristics of Electron-Beam Deposited Indium Tin Oxide thin Films, Materials Chemistry and Physics 260 (2021), 124051–roche.

23.

Yeom

H.Y.

, Popovich

, Chason

and Paine

D.C.

, A study of the effect of process oxygen on stress evolution in d.c. magnetron-deposited tin-doped indium oxide, Thin Solid Films 411(1) (2002), 17–22.

24.

Daoudi

, Canut

, Blanchin

M.G.

, Sandu

C.S.

, Teodorescu

V.S.

and Roger

J.A.

, Tin-doped indium oxide thin films deposited by sol–gel dip-coating technique, Materials Science and Engineering: C 21(1-2) (2002), 313–317.

25.

Lee

J.-H.

and Park

B.-O.

, Transparent conducting In₂O₃ thin films prepared by ultrasonic spray pyrolysis, Surf Coat Technol 184 (2004), 102–107.

26.

Chu

Chia-Pu

, Ko

Tsung-Shine

, Chang

Yu-Cheng

, Lu

Tien-Chang

, Kuo

Hao-C.

and Wang

S.C.

, Thermally evaporated In₂O₃ nanoloquats with oxygen flow dependent optical emissions Mater, Sci Eng B 147 (2008), 276.

27.

Kumari

, Pate

Sanjaykumar R.

and Gohel

Jignasa V.

, Optical and structural properties of ZnO thin films prepared by spray pyrolysis for enhanced efficiency perovskite solar cell application, Opt Quant Electron 50 (2018), 180: pp(1-22).

28.

Tripathi

, et al., Growth dynamics of pulsed laser deposited indium oxide thin films: a substrate dependent study, Applied Surface Science 256(23) (2010), 7091–7095.

29.

Mohammadi

, Abdizadeh

and Golobostanfard

M.R.

, Opto-electronic properties of molybdenum doped indium tin oxide nanostructured thin films prepared via sol–gel spin coating, Ceramics International 39(6) (2013), 6953–6961.

30.

Ilican

, Caglar

and Caglar

, Preparation and characterization of ZnO thin films deposited by sol-gel spin coating method, Journal of Optoelectronics and Advanced Materials 10(10) (2008), 2578–2583.

31.

Al-Ghamdi

, et al., Structure and optical properties of nanocrystalline NiO thin film synthesized by sol–gel spin-coating method, Journal of Alloys and Compounds 486(1-2) (2009), 9–13.

32.

Baqiah

, Ibrahim

N.B.

, Halim

S.A.

, Chen

S.K.

, Lim

K.P.

and Awang Kechik

M.M.

, Physical properties of Fe doped In₂O₃ magnetic semiconductor annealed in hydrogen at different temperature, Journal of Magnetism and Magnetic Materials 401 (2017), 102–107.

33.

Majeed Khan

M.A.

, Khan

, Ahamed

and Alhoshan

, Structural and optical properties of In₂O₃ nanostructured thin film, Materials Letters 79 (2012), 119–121.

34.

Bouhdjer

, Saidia

, Attaf

, Aida

M.S.

, Jlassi

, Bouhaf

, Benkhetta

and Bendjedidi

, Structural, morphological, optical, and electrical properties of In₂O₃ nanostructured thin films, Optik 127 (2016), 7319–7325.

35.

Koh

S.K.

, Han

Y.G.

, Lee

J.H.

, Yeo

Un. J.

and Cho

J.S.

, Material properties and growth control of undoped and Sn-doped In₂O₃ thin films prepared by using ion beam technologies, Thin Solid Films 496 (2006), 81–88.

36.

Zhang

K.H.L.

, Walsh

, Catlow

C.R.A.

, et al., Surface energies control the self-organization of oriented In₂O₃ nanostructures on cubic zirconia, Nano Lett 10 (2010), 3740.

37.

Kashyout

Abd El-Hady B.

, Fathy

and Soliman

M.B.

, Studying the Properties of RF-Sputtered Nanocrystalline Tin-Doped Indium Oxide, International Journal of Photoenergy, Volume (2011), Article ID 139374, pp. 6.

38.

Khelifi

, et al., Investigation of F doped SnO₂ thin films properties deposited via ultrasonic spray technique for several applications, Surfaces and Interfaces 15 (2019), 244–249.

39.

Bendjedidi

, Attaf

, Saidi

, Aida

M. S.

, Semmari

, Bouhdjar

and Benkhetta

, Properties of n-type SnO₂ semiconductor prepared by spray ultrasonic technique for photovoltaic applications, Journal of Semiconductors 36(12) (2015), 123002(1-4)

40.

Messemeche

, et al., Elaboration and characterization of nano-crystalline layers of transparent titanium dioxide (Anatase-TiO₂) deposited by a sol-gel (spin coating) process, Surfaces and Interfaces 19 (2020), 100482.

41.

Benamra

, Saidi

, Attaf

, Aida

M.S.

, Derbali

and Attaf

, Physical properties of Al-doped ZnS thin films prepared by ultrasonic spray technique, Surfaces and Interfaces 21 (2020), 100645.

42.

Goswami

and Sharma

A.K.

, Investigation of the optical behavior of indium oxide thin films with the aid of spectroscopic ellipsometry technique, Applied Surface Science 495 (2019), 143609.

43.

Yahia

, Attaf

, Saidi

, Dahnoun

, Khelifi

, Bouhdjer

, Saadi

and Ezzaouia

, Structural, optical, morphological and electrical properties of indium oxide thin films prepared by sol gel spin coating process, Surfaces and Interfaces 14 (2019), 158–165.

44.

Yuan

, Zhu

, Wang

, Cai

, Zhang

, Qiu

and Wu

, Annealing effect of In₂O₃ thin films on electrical properties and application in thin film transistors, Thin Solid Films 519 (2011), 3254–3258.

45.

Baqiah

, Ibrahim

N.B.

, Halim

S.A.

, Chen

S.K.

, Lim

K.P.

and Awang Kechik

M.M.

, Physical properties of Fe doped In₂O₃ magnetic semiconductor annealed in hydrogen at different temperature, Journal of Magnetism and Magnetic Materials 401 (2016), 102–107.

46.

Derbali

, Saidi

, Attaf

, Benamra

, Bouhdjer

, Attaf

, Ezzaouia

, Derbali

and Aida

M.S.

, Solution flow rate influence on ZnS thin films properties grown by ultrasonic spray for optoelectronic application, Journal of Semiconductors 39(9) (2018), 093001(1-7).

47.

Bartolomé

, Hidalgo

, Maestre

, Cremades

and Piqueras

, In-situ scanning electron microscopy and atomic force microscopy Young’s modulus determination of indium oxide micro-rods for micromechanical resonator application, Applied Physics Letter 104 (2014), 161909:1–161909:5.

48.

Zhang

, Regoutz

, Palgrave

, Payne

, Egdell

, Walsh

, Collins

, Wermeille

and Cowley

, Determination of the Poisson ratio of (100) and (111) oriented thin films of In₂O₃ by synchrotron-based X-ray diffraction, Physics Review B 84 (2011), 233301:1–233301:4.

49.

Nishimura

, Sasabayashi

, Norihiro

ITO

, Sato

, Utsumi

, Yano

, Kaijo

, Inoue

and Shigesato

, Structure and Internal Stress of Tin-Doped Indium Oxide and Indium–Zinc Oxide Films Deposited by DC Magnetron Sputtering, Japanese Journal of Applied Physics 46(12) (2007), 7806–7811.

50.

Sasabayashi

, Song

P.K.

, Shigesato

, Utsumi

, Kaijo

and Mitsui

, Internal Stress of ITO, IZO and GZO Films Deposited by RF and DC Magnetron Sputtering, Japanese Journal of Applied Physics, MRS Online Proceeding Library 666 (2001), F2.4:1–6.

51.

Ennaceri

, Boujnah

, Erfurt

, Rappich

, Lifei

, Khaldoun

, Benyoussef

, Ennaoui

and Taleb

, Influence of stress on the photocatalytic properties of sprayed ZnO thin films, Solar Energy Materials and Solar Cells 201 (2019), 110058.

52.

Gulen

, Yildirim

, Bal

, Varilci

, Belenli

and Oz

, Role of annealing temperature on microstructural and electro-optical properties of ITO films produced by sputtering, J Mater Sci: Mater Electron 24 (2013), 467–474.

53.

Beji

, Souli

, Azzaza

, Alleg

and Turki

N.K.

, Study on the zinc doping and annealing effects of sprayed In₂O₃ thin films, J Mater Sci: Mater Electron 27 (2016), 4849–4860.

54.

Hegazy

Ahmed R.

, Salameh

and Alsmadi

A.M.

, Optical transitions and photoluminescence of fluorine-doped zinc tin oxide thin films prepared by ultrasonic spray pyrolysis, Ceramics International 45 (2019), 19473–19480.

55.

Wang

F.H.

and Chang

C.L.

, Effect of substrate temperature on transparent conducting Al and Fco-doped ZnO thin films prepared by rf magnetron sputtering, Applied Surface Science 370 (2016), 83–91.

56.

Ben Miled

, Jlas si

, Sta

, Dhaouadi

, Ha jji

, Mousdis

, Kompitsas

and Ezzaouia

, Influence of In-doping on microstructure, optical and electrical properties of sol–gel derived CdO thin films, J Mater Sci.: Mater Electron 29 (2018), 11286–11295.

57.

Derbali

, Attaf

, Saidi

, Benamra

, Nouadji

, Aida

M.S.

, Attaf

and Ezzaouia

, Investigation of structural, optical and electrical properties of ZnS thin films prepared by ultrasonic spray technique for photovoltaic applications, Optik 154 (2018), 286–293.

58.

Attaf

, Derbali

, Saidi

, Benamra

, Aida

M.S.

, Attaf

, Ezzaouia

and Derbali

, Physical properties of Pb doped ZnS thin films prepared by ultrasonic spray technique, Physics Letters A 384 (2020), 126199.

59.

George

and Menon

C.S.

, Electrical and optical properties of electron beam evaporated ITO thin films, Surf Coat Technol 132 (2000), 45–48.

60.

Malathy

, Sivaranjani

, Vidhya

V.S.

, Balasubramanian

, Joseph Prince

, Sanjeeviraja

and Jayachandran

, Role of substrate temperature on the structural, optoelectronic and morphological properties of (400) oriented indium tin oxide thin films deposited using RF sputtering technique, J Mater Sci: Mater Electron 21 (2010), 1299–1307.

61.

Obulapathi

, Kumar

A.G.S.

, Sarmash

T.S.

, Rani

D.J.

, Rao

G.V.V.

and Rao

T.S.

, Effect of film thickness on physical properties of CuCrO2 thin films, J Australas Ceram Soc 52 (2016), 102e105.

62.

Chen

L.Y.

, Chen

W.H.

, Wang

J.J.

, Hong

F.C.N.

and Su

Y.K.

, Hydrogen-doped high conductivity ZnO films deposited by radio-frequency magnetron sputtering, Appl Phys Lett 85 (2004), 5628–5630.

63.

Tsai

D.C.

, Chang

Z.C.

, Kuo

B.H.

, Wang

Y.H.

, Chen

E.C.

and Shieu

F.S.

, Thickness dependence of the structural, electrical, and optical properties of amorphous indium zinc oxide thin films, Journal of Alloys and Compounds 743 (2018), 603–609.

64.

Han

, Mayer

J.W.

and Alford

T.L.

, Band gap shift in the indium tine oxide films on polyethylene napthalate after thermal annealing in air, J Appl Phys 100 (2006), 083715.

65.

Thirumoorthi

and Thomas Joseph Prakash

, A study of Tin doping effects on physical properties of CdO thin films prepared by sol–gel spin coating, Journal of Asian Ceramic Societies 4 (2016), 39–45.

66.

Gerbier

M.M.

, Baraton

M.I.

, Machet

and Quintard

, Ion plated indium oxide: infrared and optical study, Journal of Molecular Structure 115(1-2) (1984), 103–106.

67.

Baranauskas

, Fontana

, Guo

Z.J.

, Ceragioli

H.J.

and Peterlevitz

A.C.

, Fielde mission properties of nanocrystalline tin oxide films, Sens Actuat B Chem 107 (2005), 474.

68.

Yang

and Gao

, Facile and Surfnt-Free Route to Nanocrystalline Mesoporous Tin Oxide, J Am Ceram Soc 89(5) (2006), 1742–acta.

69.

Biswas

P.K.

, De

, Ortner

and Korder

, Study of sol–gel-derived high tin content indium tin oxide (ITO) films on silica-coated soda lime silica glass, Mater Lett 58 (2004), 1540–1545.

70.

Salvador

, Sanchez

, Watts

B. E.

, Klimm

, Baraldi

, Parisini

, Vantaggio

and Fornari

, Sol-gel growth and characterization of In₂O₃ thin films, Thin Solid Films 645 (2018), 383–390.

71.

Voisin

, Ohtsuka

, Petrovska

, Sergiienko

and Nakamura

, Structural, optical and electrical properties of DC sputtered indium saving indium-tin oxide (ITO) thin films, Optik 156 (2018), 728–737.

72.

Jlassi

, Sta

, Hajji

and Ezzaouia

, Effect of nickel doping on physical prop-erties of zinc oxide thin films prepared by the spray pyrolysis method, Appl Surf Sci 301 (2014), 216–224.

73.

Solieman

, Effect of sintering temperature on the structural, optical and electrical properties of sol–gel derived indium oxide thin films, J Sol-Gel Sci Technol 60 (2011), 48–57.

74.

Tomita

, Yamashita

, Hayafuji

and Adachi

, The origin of nn-type conductivity in undoped In₂O₃, Applied Physics Letters 87 (2005), 051911–051913.

Film thickness effect on structural,optical and electrical properties of indium oxide (In 2 O 3 ) thin films grown via sol-gel method

Abstract

Keywords

1 Introduction

2 Experimental details

2.1 Materials and In2O3 thin film preparation

3 Results and discussion

3.1 Structural properties

References

2.1 Materials and In₂O₃ thin film preparation