Growth and vacuum post-annealing effect on the properties of the new absorber CuSbS2 thin films

Post-growth treatments in vacuum atmosphere were performed on CuSbS₂ films prepared by the single-source thermal evaporation method on glass substrates. The films were annealed in vacuum atmosphere for 2 h in temperature range 130-200 °C. The effect of this thermal treatment on the structural, optical and electrical properties of the films was studied. X-ray diffraction (XRD) patterns indicated that the films exhibited an amorphous structure for annealing temperature below 200 °C and a polycrystalline structure with CuSbS₂ principal phase. For the films annealed at temperatures below 200 °C one direct optical transition in range 1.8-2 eV was found. For the films annealed at 200 °C, two optical direct transitions emerged at 1.3 and 1.79 eV corresponding to the CuSbS₂ and Sb₂S₃ values respectively. The electrical measurements showed a conversion from low resistivities (3.10^− 2-9.10^− 2) Ω cm for the samples annealed at temperatures below 200 °C to relatively high resistivities (2 Ω cm) for the samples annealed at 200 °C. In all cases the samples exhibited p-Ztype conductivity.     

The structure and optical properties of ZnO films on various LiNbO3 substrates

ZnO films thin films have been deposited on glass and three different LiNbO₃ (LNO) substrates at room temperature using radio frequency magnetron sputtering. The structure and optical properties of the films were investigated by X-ray diffraction (XRD), optical transmission spectroscopy and spectro-photometry. XRD analysis shows that all the films are hexagonal wurtzite structure, and there is compressive strain in the films. Typical optical transmittance values in the order of 80% were obtained for all the films, and the band gaps are in the range of 3.273-3.282 eV. The Photo-Luminescence (PL) spectra results indicate that the type of substrate affects the photoluminecence of ZnO films significantly, and the films on rotated Y-cut 128° LNO substrates have strong UV emission at room temperature.     

Structural and optical studies of nanocrystalline V2O5 thin films

We report the structural and optical properties of nanocrystalline thin films of vanadium oxide prepared via evaporation technique on amorphous glass substrates. The crystallinity of the films was studied using X-ray diffraction and surface morphology of the films was studied using scanning electron microscopy and atomic force microscopy. Deposition temperature was found to have a great impact on the optical and structural properties of these films. The films deposited at room temperature show homogeneous, uniform and smooth texture but were amorphous in nature. These films remain amorphous even after postannealing at 300 °C. On the other hand the films deposited at substrate temperature T_S > 200 °C were well textured and c-axis oriented with good crystalline properties. Moreover colour of the films changes from pale yellow to light brown to black corresponding to deposition at room temperature, 300 °C and 500 °C respectively. The investigation revealed that nanocrystalline V₂O₅ films with preferred 001 orientation and with crystalline size of 17.67 nm can be grown with a layered structure onto amorphous glass substrates at temperature as low as 300 °C. The photograph of V₂O₅ films deposited at room temperature taken by scanning electron microscopy shows regular dot like features of nm size.     

Nickel diffusion in polycrystalline CuInSe2 thin films with a <112> fiber texture

Nickel diffusion in CuInSe₂ thin films was studied in the temperature range 430-520 °C. Thin films of copper indium diselenide (CuInSe₂) were prepared by selenization of CuInSe₂-Cu-In multilayered structure on glass substrate. A thin film of Nickel was deposited and annealed at different temperatures. Surface morphologies of the Ni diffused and undiffused CuInSe2 films were investigated using scanning electron microscope. The alteration of Nickel concentration in the CuInSe₂ thin film was measured by Energy Dispersive X-Ray Fluorescence (EDXRF) technique. These measurements were fitted to a complementary error function solution and the diffusion coefficients at four different temperatures were evaluated. The diffusion coefficients of Ni in CuInSe₂ films were estimated from concentration profiles at temperatures 430-520 °C as D = 1.86 × 10^− 7(cm²s^− 1)exp[− 0.68(eV)/kT].     

Role of oxygen in enhancing N-type conductivity of CuInS2 thin films

Post-growth treatments in air atmosphere were performed on CuInS₂ films prepared by the single-source thermal evaporation method. Their effect on the structural, optical and electrical properties of the films was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), optical reflection and transmission and resistance measurements. The films were annealed from 100 to 350 °C in air. The stability of the observed N-type conductivity after annealing depends strongly on the annealing temperature. Indeed it is shown that for annealing temperatures above 200 °C the N-type conductivity is stable. The resistance of the N-CuInS₂ thin films correlates well with the corresponding annealing temperature. The samples after annealing have direct bandgap energies of 1.45-1.50 eV.     

Structural, thermal and optical characterization of TiO2:ZrO2 thin films prepared by sol-gel method

We have studied the structural and optical properties of thin films of TiO₂, doped with 5% ZrO₂ and deposited on glass substrate (by the sol-gel method). The dip-coated thin films have been examined at different annealing temperatures (350 to 450 °C) and for various layer thicknesses (63-286 nm). Refractive index and porosity were calculated from the measured transmittance spectrum. The values of the index of refraction are in the range of 1.62-2.29 and the porosity is in the range of 0.21-0.70. The coefficient of transmission varies from 50 to 90%. In the case of the powder of TiO₂, doped with 5% ZrO₂, and aged for 3 months in ambient temperature, we have noticed the formation of the anatase phase (tetragonal structure with 14.8 nm grains). However, the undoped TiO₂ exhibits an amorphous phase. After heat treatments of thin films, titanium oxide starts to crystallize at the annealing temperature 350 °C. The obtained structures are anatase and brookite. The calculated grain size, depending on the annealing temperature and the layer thickness, is in the range (8.58-20.56 nm).     

Thermal treatment effect on the optical properties of ZrO2 thin films deposited by thermionic vacuum arc

This paper shows the ex situ thermal treatment effects of the ZrO₂ thin films obtained by TVA (thermionic vacuum arc) technique on the optical properties (e.g., transmittance, refractive index and band-gap energy) of ZrO₂ thin films. The crystal structure, surface and optical properties were investigated for ZrO₂ thin films deposited on glass substrates by thermionic vacuum arc (TVA) method. The thermal treatment effect on the optical properties of the thin films was determined. The XRD analysis showed that the deposited ZrO₂ thin films have baddeleyite (monoclinic) and zirconium (hexagonal) structures. The thicknesses and refractive index were determined by interferometric measurements. The thin films were thermal treated at different temperatures (350 °C, 450 °C and 550 °C), and the analysis showed that the optical properties of ZrO₂ deposited thin films were improved by thermal treatment at 450 °C.     

Synthesis and electrochromic study of sol-gel cuprous oxide nanoparticles accumulated on silica thin film

In this study, electrochromic properties of cuprous oxide nanoparticles, self-accumulated on the surface of a sol-gel silica thin film, have been investigated by using UV-visible spectrophotometry in a lithium-based electrolyte cell. The cuprous oxide nanoparticles showed a reversible electrochromic process with a thin film transmission reduction of about 50% in a narrow wavelength range of 400-500 nm, as compared to the bleached state of the film. Using optical transmission measurement, we have found that the band gap energy of the films reduced from 2.7 eV for Cu₂O to 1.3 eV for CuO by increasing the annealing temperature from 220 to 300 °C in an N₂ environment for 1 h. Study of the band gaps of the as-deposited, colored and bleached states of the nanoparticles showed that the electrochromic process corresponded to a reversible red-ox conversion of Cu₂O to CuO on the film surface, in addition to the reversible red-ox reaction of the Cu₂O film. X-ray photoelectron spectroscopy indicated that the copper oxide nanoparticles accumulated on the film surface, after annealing the samples at 200 °C. Surface morphology of the films and particle size of the surface copper oxides have also been studied by atomic force microscopy analysis. The copper oxide nanoparticles with average size of about 100 nm increased the surface area ratio and surface roughness of the silica films from 2.2% and 0.8 nm to 51% and 21 nm, respectively.     

Optimization of parameters of chemical spray pyrolysis technique to get n and p-type layers of SnS

SnS thin films were prepared using automated chemical spray pyrolysis (CSP) technique. Single-phase, p-type, stoichiometric, SnS films with direct band gap of 1.33 eV and having very high absorption coefficient (> 10⁵/cm) were deposited at substrate temperature of 375 °C. The role of substrate temperature in determining the optoelectronic and structural properties of SnS films was established and concentration ratios of anionic and cationic precursor solutions were optimized. n-type SnS samples were also prepared using CSP technique at the same substrate temperature of 375 °C, which facilitates sequential deposition of SnS homojunction. A comprehensive analysis of both types of films was done using x-ray diffraction, energy dispersive x-ray analysis, scanning electron microscopy, atomic force microscopy, optical absorption and electrical measurements. Deposition temperatures required for growth of other binary sulfide phases of tin such as SnS₂, Sn₂S₃ were also determined.     

Optical and structural properties of sol-gel prepared MgZnO alloy thin films

Mg_xZn_1−xO (x = 0-0.5) alloy thin films were prepared by a sol-gel dip-coating method. Mg_0.1Zn_0.9O and Mg_0.5Zn_0.5O films prepared were annealed in the range of 400-900 °C to investigate their thermal stability and temperature-dependent optical properties. The Mg_0.1Zn_0.9O films were thermally stable in the investigated annealing temperature range and exhibited the maximum ultraviolet emission at 800 °C. The segregation of MgO occurred in the Mg_0.5Zn_0.5O films, and the near-band-edge ultraviolet emission of this alloy was enhanced with increasing annealing temperature. The Mg saturation content in the sol-gel prepared MgZnO alloys was found to be about 0.23 where the band gap extended to 3.48 eV.     

The influence of the precursor concentration on CuSbS2 thin films deposited from aqueous solutions

The paper discusses the influence of precursor concentration on the morphology and the structure of CuSbS₂ thin films obtained from aqueous solutions and used as absorber for three-dimensional (3D) solar cells. CuSbS₂ films are obtained by Spray Pyrolysis Deposition, varying the precursor weight ratio (CuCl₂·2H₂O: H₂NCSNH₂: (CH₃COO)₃Sb) between 2.57: 1: 5.71-6.86: 1: 5.71, at 240 °C. The films were analyzed by XRD, I-V dark measurements and SEM. Enriching the films in antimony proved to be a control method of the films morphology and structure.     

Preparation and characterization of novel CuClSe2 semiconductor thin film

CuClSe₂ was synthesized by solid-state reaction between copper chloride and selenium at 300 °C. CuClSe₂ thin film was prepared on a glass substrate by pulsed laser deposition (PLD) method. XRD (X-ray diffraction) analysis revealed that the CuClSe₂ thin film has a preferred surface orientation parallel to (006). The transmittance and reflectance spectra of the film indicated that the compound is an indirect band gap material; the energy band gap is about 1.45 eV; its absorption coefficients are in the range of 10⁴-10⁵ cm^− 1 when the wavelength is shorter than 720 nm. The melting point of CuClSe₂ is about 328 °C. These results show that CuClSe₂ is a potential absorber layer material applied in solar cells.     

Transparent conducting indium oxide thin films grown by low-temperature metal organic chemical vapor deposition

We have grown indium oxide thin films on silicon substrates at low temperature by metal organic chemical vapor deposition. Polycrystalline film growth could only be obtained at temperatures below 400 °C. Above 400 °C, metallic indium deposition dominated. We have investigated the effect of substrate temperature and reactor pressure on the film growth and structural properties in the range of 250-350 °C and 5 ^? 10³-4 ^? 10⁴ Pa. The film grown at 300 °C exhibited a resistivity of about 3.6 × 10^− 3 Ω cm and a maximal optical transmittance of more than 95% in the visible range. The film showed an optical band gap of about 3.6 eV.     

Highly conducting and transparent tin-doped CdO thin films for optoelectronic applications

Highly conducting and transparent thin films of tin-doped cadmium oxide were deposited on quartz substrate using pulsed laser deposition technique. The effect of growth temperature on structural, optical and electrical properties was studied. These films are highly transparent (78-89%) in visible region, and transmittance of the films depends on growth temperature. It is observed that resistivity increases with growth temperature after attaining minimum at 150 °C, while carrier concentration continuously decreases with temperature. The lowest resistivity of 1.96 × 10^− 5 Ω cm and carrier concentration of 5.52 × 10²¹ cm³ is observed for the film grown at 150 °C. These highly conducting and transparent tin-doped CdO thin films grown via pulsed laser deposition could be an excellent candidate for future optoelectronic applications.     

Influence of substrate temperature on structural,optical, and electrical properties of flash evaporated CuIn0.81Al0.19Se2 thin films

Chalcopyrite copper indium aluminum diselenide (CuIn_0.81Al_0.19Se₂) compound is prepared by direct reaction of high purity elemental copper, indium, aluminum and selenium in their stoichiometric proportion. Structural and compositional characterizations of pulverized material confirm the formation of a single phase, polycrystalline nature. CuInAlSe₂ (CIAS) thin films are deposited on organically cleaned soda lime glass substrates using flash evaporation technique by varying the substrate temperatures in the range from 423 K to 573 K. Influence of substrate temperature observed by X-ray diffraction (XRD), scanning electron microscope (SEM), optical and electrical measurement. CIAS Films grown at different substrate temperatures are polycrystalline in nature, exhibiting a chalcopyrite structure with lattice parameters a = ∼0.576 nm and c = ∼1.151 nm. The crystallinity in the films increases with increasing substrate temperature up to 473 K, and tend to degrade at higher substrate temperatures. Optical band gap is in the range of 1.20 eV–1.38 eV and the absorption coefficient is close to 10⁵ cm⁻¹. Electrical characterization reveals p-type conductivity and the structural, morphological and optical properties indicate potential use of CIAS thin films as an absorber layer for thin film solar cell applications.     

Growth of Cu2SnS3 thin films by solid reaction under sulphur atmosphere

Cu₂SnS₃ thin film have been synthesized by solid state reaction under vapour sulphur pressure at 530 °C, during 6 h, via a sequentially deposited copper and tin layers Cu/Sn/Cu…Sn/Cu/Sn. The structure and the composition were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Electron Probe Micro Analysis (EPMA). X-ray diffraction revealed that as the deposited film crystallizes in the cubic structure and the crystallites exhibit preferential 111 orientation of the grains. Moreover, EPMA analysis confirmed that the obtained film is stoichiometric. The SEM study shows the presence of spherical particles of ≈100-120 nm diameters. The optical absorption coefficient and band gap of the film were estimated by means of transmission and reflection optical measurements at room temperature. A relatively high absorption coefficient in the range of 10⁴ cm⁻¹ was indeed obtained and the band gap value is of the order of 1.1 eV. On the other hand, the electrical conductivity of Cu₂SnS₃ film prepared in the present experiment is suitable for fabricating a thin film solar cell based on not cheaper and environmental friendly material.     

Influence of deposition regime on physical properties of gallium doped zinc oxide films

Zinc oxide films doped by gallium were deposited using RF diode sputtering from a ceramic ZnO + 2% Ga₂O₃ target on Corning glass in argon atmosphere. Samples were supported in three different positions against a substrate holder - horizontal, and at 60 and 80° to the horizontal position. Two series of samples 700-1000 nm in thickness were prepared: one at room temperature (RT) and the second at 200 °C. XRD, optical and electrical experiments indicated that the films are polycrystalline having average crystallite sizes from 30 to 80 nm, integrated transmittances in the range of 400-1000 nm increased from 85 to 90 per cent and optical band-gap values increased from 3 to 3.2 eV with higher deposition temperature. The resistivity of the obliquely sputtered samples positioned at 80° to the substrate holder was one order lower than the horizontally positioned samples. No significant changes were observed in case of optical properties of the films in dependence on the tilt-angle.     

Effect of temperature on structural, optical and photoluminescence properties of antimony (Sb) doped polycrystalline CuInS2 thin films prepared by spray pyrolysis

Copper indium disulphide (CuInS₂) is an absorber material for solar cell and photovoltaic applications. By suitably doping CuInS₂ thin films with dopants such as Zn, Cd, Na, Bi, Sn, N, P and As its structural, optical, photoluminescence properties and electrical conductivities could be controlled and modified. In this work, Sb (0.01 mole (M)) doped CuInS₂ thin films are grown in the temperature range 300-400 °C on heated glass substrates. It is observed that the film growth temperature, the ion ratio (Cu/In = 1.25) and Sb-doping affects the structural, optical and photoluminescence properties of sprayed CuInS₂ films.The XRD patterns confirm that the Sb-doping suppresses the growth of CuInS₂ polycrystalline thin films along (1 1 2) preferred plane and in other characteristic planes. The EDAX results confirm the presence of Cu, In, S and Sb. About 60% of light transmission occurs in the wavelength range 350-1100 nm. The absorption coefficient (α) is found to be in the order of 10⁵ cm⁻¹. The band gap energy increases as the temperature increases from 300-400 °C (1.35-1.40 eV). SEM photographs depict that large sized crystals of Sb-doped CuInS₂ (1 μm) are formed on the surface of the films. Well defined sharp blue and green band emissions are exhibited by Sb-doped CuInS₂ thin films. Defects-related photoluminescence emissions are discussed. These Sb-doped CuInS₂ thin films are prepared by the cost effective method of spray pyrolysis from the aqueous solutions of CuCl₂, InCl₃, SC(NH₂)₂ and SbCl₃ on heated glass substrates.     

Optical properties of In2O3 films prepared by spray pyrolysis

In₂O₃ thin films have been deposited on glass substrates by spray pyrolysis. InCl₄ was used as the solute to prepare the starting solution with a concentration of 0.1 M. The films were grown at different substrate temperatures ranging from 300 to 400 °C. The as-grown layers were optically characterized in order to evaluate the absorption coefficient, optical band gap, refractive index, extinction coefficient and other optical parameters. The influence of substrate temperature on these parameters was reported and discussed.     

Single-step sputtered Cu2SnSe3 films using the targets composed of Cu2Se and SnSe2

Cu₂SnSe₃ thin films were prepared by single-step D.C. sputtering at 100-400 °C for 3 h using targets composed of Cu₂Se and SnSe₂ in three different ratios of 2/1 (target A), 1.8/1 (target B), and 1.6/1 (target C). The advantages of self-synthesized SnSe₂ instead of commercially available SnSe for depositing Cu₂SnSe₃ thin films were demonstrated. Effects of target composition and substrate temperature on the properties of Cu₂SnSe₃ thin films were investigated. Structure, surface morphology, composition, electrical and optical properties at different process conditions were measured. The 400 °C-sputtered films obtained from target B display with direct band gap of 0.76 eV, electrical resistivity of 0.12 Ω cm, absorption coefficient of 10⁴-10⁵ cm^− 1, carrier concentration of ∼ 1.8 × 10¹⁹ cm^− 3, and electrical mobility of 2.9 cm²/V s.