Contribution study of properties of copper indium diselenide thin films

Stoichiometric powder of CuInSe₂ (CIS) was prepared from molten stoichiometric quantities of the elements. The structure analyzed by X-ray diffraction powder (XRD), shows mainly the chalcopyrite phase. CIS polycrystalline thin films deposited from this powder have been grown on glass substrates in vacuum by thermal evaporation method. The structural and electrical properties of both as-deposited and annealed films were studied using X-ray diffraction and dark conductivity measurements respectively. As-prepared films at room temperature showed an amorphous structure. However, the chalcopyrite structure with (112) preferential orientation was observed after annealing in vacuum at 400 °C during 30 min. The influence of the annealing process on the dark conductivity of the films was also discussed.     

Structural,optical, and electrical properties of flash-evaporated copper indium diselenide thin films

Copper indium diselenide (CuInSe₂) compound was synthesized by reacting its elemental components, i.e., copper, indium, and selenium, in stoichiometric proportions (i.e., 1:1:2 with 5% excess selenium) in an evacuated quartz ampoule. Structural and compositional characterization of synthesized pulverized material confirms the polycrystalline nature of tetragonal phase and stoichiometry. CuInSe₂ thin films were deposited on soda lime glass substrates kept at different temperatures (300–573 K) using flash evaporation technique. The effect of substrate temperature on structural, morphological, optical, and electrical properties of CuInSe₂ thin films were investigated using X-ray diffraction analysis (XRD), atomic force microscopy (AFM), optical measurements (transmission and reflection), and Hall effect characterization techniques. XRD analysis revealed that CuInSe₂ thin films deposited above 473 K exhibit (112) preferred orientation of grains. Transmission and reflectance measurements analysis suggests that CuInSe₂ thin films deposited at different substrate temperatures have high absorption coefficient (~10⁴ cm⁻¹) and optical energy band gap in the range 0.93–1.02 eV. Results of electrical characterization showed that CuInSe₂ thin films deposited at different substrate temperatures have p-type conductivity and hole mobility value in the range 19–136 cm²/Vs. Variation of energy band gap and resistivity of CuInSe₂ thin films deposited at 523 K with thickness was also studied. The temperature dependence of electrical conductivity measurements showed that CuInSe₂ film deposited at 523 K has an activation energy of ~30 meV.     

Properties of pulse electrodeposited copper indium selenide films

Copper Indium Selenide films were deposited by the pulse plating technique at different bath temperatures in the range of 30–80 °C and at 50 % duty cycle (15 s ON and 15 s OFF). X-ray diffraction studies indicated the formation of single phase chalcopyrite copper indium selenide films. The band gap of the films decreased from 1.17 to 1.05 eV with decrease of duty cycle. Atomic force microscope studies indicated that the surface roughness and grain size increased with duty cycle. Room temperature resistivity of the films is in the range of 0.01–2.0 ohm cm. Films deposited at 50 % duty cycle have exhibited a V_oc of 0.59 V, J_sc of 15 mA cm^?2, FF of 0.75 and efficiency of 6.64 %.     

Study of electrochemically grown copper indium diselenide (CIS) thin films for photovoltaic applications

CIS thin films have been grown electrochemically from an aqueous electrolyte at room temperature on fluorine doped tin oxide coated glass substrate at different deposition potentials ranging from ?0.7 to ?1.0 V versus Ag/AgCl reference electrode. Cyclic voltammetry was studied at slow scan rate to optimize the deposition potential. The thin film samples were selenized in a tubular furnace at 400 °C for 20 min. X-ray diffraction and Raman analysis was used to study the structural properties. Optical absorption, scanning electron microscopy and energy dispersive X-ray analysis (EDAX) have been used to investigate the band-gap, surface morphology and compositional analysis. Electrical properties were studied with the help of current–voltage measurements. Conductivity type for CIS thin films was studied by using photo-electrochemical study. The prominent reflections (112), (204/220) and (312/116) of tetragonal chalcopyrite CIS have been revealed for all as-grown and selenized samples. The energy band gap of the selenized CIS thin film deposited at various deposition potentials was found to be ~1.03 to 1.24 eV. Granular, uniform and void free surface was observed in as-prepared sample, while large clusters were noticed in selenized samples. EDAX results reveal that the stoichiometric CIS thin film are deposited ?0.8 V, however, Cu-rich and In-rich CIS layers were grown at lower and higher cathodic deposition potentials, deviated from ?0.8 V. The values ideality factor (η) calculated from I–V measurements were found to be decreased upon selenization. The Raman spectra of stoichiometric CIS thin film shows dominant A1 mode with spectral features sensitive to the microcrystalline quality of the layers. A ordered defect compound layer and secondary phases of CuSe are observed in In-rich and Cu-rich CIS layers, respectively.     

Structural and optical properties of electrodeposited indium selenide thin films

Journal of Materials Science Letters -     

Electrochemical etching of copper indium diselenide surface

CuInSe₂ thin films were grown onto ITO surface by electrodeposition and annealed in the hydrogen atmosphere at 400 °C. The influence of traditional chemical etching (KCN etchant) and electrochemical etching at various potentials and values of solution pH (0.8-13) on the surface composition and morphology was studied using the EDX and SEM methods. The mechanism of CuInSe₂ decomposition at various pH values was examined by cycling voltammetry. The influence of chemical and electrochemical etchings on electrical and optical characteristics of thin films was analyzed.     

Copper indium gallium diselenide thin films for sun angle detectors in space applications

This work reports on processing, analysis and characterization of copper indium gallium diselenide (CIGS) used as a photosensitive layer for sensors such as sun angle detectors in space applications. CIGS-based solar cell devices with different CIGS layer thicknesses and the pn-junction located on the opposite side of the incidence of light were illuminated through their ultra-thin transparent molybdenum back contacts. The results from the current density versus voltage and quantum efficiency measurement indicate that the CIGS absorber layer may not exceed 750 nm at backside illumination, due to the limited CIGS diffusion length.     

Reproducibility studies on thin-film copper indium diselenide prepared from copper indium oxide

Thin-film copper indium diselenide was prepared by selenization of copper indium oxide deposited by spray pyrolysis of an aqueous solution containing copper and indium salts. The degree of reproducibility in thickness, composition and electrical parameters was found to be good. The electrical parameters could be controlled and tuned for photovoltaic applications reproducibly by means of this cost-efficient fabrication technique. This revised version was published online in November 2006 with corrections to the Cover Date.     

Structural, optical and electrical properties of chemically deposited nonstoichiometric copper indium diselenide films

Thin films of copper indium diselenide (CIS) were prepared by chemical bath deposition technique onto glass substrate at temperature, 60°C. The studies on composition, morphology, optical absorption, electrical conductivity and structure of the films were carried out and discussed. Characterization included X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray analysis (EDAX) and absorption spectroscopy. The results are discussed and interpreted.     

Surface modification of electrodeposited p-CulnSe2 thin films with selenium and ruthenium

Changes in the surface composition of electrodeposited p-CulnSe₂ (CIS) thin films with electrodeposited selenium and ruthenium chemically adsorbed, improve the cathodic photocurrent response in sulphuric acid solution. The structural and chemical composition of the as-deposited and modified surface have been determined by X-ray diffraction and atomic absorption spectrometry before and after illumination. The estimates of the optical band gap have been analysed and discussed in terms of bulk modifications arising from the indium released, and its substitution by selenium or ruthenium.     

The optical and electrical properties of copper indium di-selenide thin films

Thin films of copper indium di-selenide (CIS) with a wide range of compositions near stoichiometry have been formed on glass substrates in vacuum by the stacked elemental layer (SEL) deposition technique. The compositional and optical properties of the films have been measured by proton-induced X-ray emission (PIXE) and spectrophotometry (photon wavelength range of 300–2500 nm), respectively. Electrical conductivity (σ), charge-carrier concentration (n), and Hall mobility (μ_H) were measured at temperatures ranging from 143 to 400 K. It was found that more indium-rich films have higher energy gaps than less indium-rich ones while more Cu-rich films have lower energy gaps than less Cu-rich films. The sub-bandgap absorption of photons is minimum in the samples having Cu/In ≈ 1 and it again decreases, as Cu/In ratio becomes less than 0.60. Indium-rich films show n-type conductivities while near-stoichiometric and copper-rich films have p-type conductivities. At 300 K σ, n and μ_H of the films vary from 2.15 × 10⁻³ to 1.60 × 10⁻¹ (Ω cm)⁻¹, 2.28 × 10¹⁵ to 5.74 × 10¹⁷ cm⁻³ and 1.74 to 5.88 cm² (V s)⁻¹, respectively, and are dependent on the composition of the films. All the films were found to be non-degenerate. The ionization energies for acceptors and donors vary between 12 and 24, and 3 and 8 meV, respectively, and they are correlated well with the Cu/In ratios. The crystallites of the films were found to be partially depleted in charge carriers.     

Characterization of electrosynthesized iron diselenide thin films

Iron diselenide (FeSe₂) is an interesting p-type semiconductor with a band gap of 1 eV suitable for solar cell applications. Deposition of FeSe₂ thin films by electrodeposition from aqueous solutions is a low temperature and inexpensive technique. In the present work, FeSe₂ thin films were deposited onto tin oxide coated conducting glass substrates by cathodic electrodeposition technique. The deposited films were characterized by X-ray diffraction, Energy dispersive X-ray analysis, Scanning electron microscope and optical absorption techniques. The effects of electrolyte concentration and deposition potential on the structural, compositional, morphological and optical properties of FeSe₂ thin films are studied. The experimental observations are discussed in detail.     

Preparation and characterization of nanostructured copper bismuth diselenide thin films from a chemical route

Thin films of copper bismuth diselenide were prepared by chemical bath deposition technique ontoglass substrate below 60°C. The deposition parameters such as time, temperature of deposition and pH of the solution, were optimized. The set of films having different elemental compositions was prepared by varying Cu/Bi ratio from 0·13–1·74. Studies on structure, composition, morphology, optical absorption and electrical conductivity of the films were carried out and discussed. Characterization includes X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive X-ray analysis (EDAX), absorption spectroscopy, and electrical conductivity. The results are discussed and interpreted.     

Synthesis and studies on effect of indium doping on physical properties of electrodeposited CdSe thin films

Semiconducting CdSe and indium doped CdSe (In: CdSe) thin films have been synthesized on stainless steel and fluorine doped tin oxide coated glass substrates in an aqueous medium using a potentiostatic mode of electrodeposition. The doping concentration of indium has been optimized to 0.15 vol% using the reliable photoelectrochemical technique. To study the effect of indium doping these films are characterized using X-ray diffraction, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, elemental mapping, Raman spectroscopy, contact angle measurement and UV–visible spectrophotometry techniques. CdSe and In: CdSe thin films are low crystalline with a cubic crystal structure. The valence states of CdSe and In: CdSe thin films are analyzed by means of XPS. Undoped CdSe thin film shows fiberlike morphology, which transforms into a beautiful web of nanofibers upon doping. The Elemental composition of both films analyzed by means of energy dispersive X-ray spectroscopy. Raman studies show transverse optical and longitudinal optical modes of phonon. Indium doping improves the hydrophilic nature of CdSe photoanode. The optical band gap (direct) found to be decreased from 2.02 to 1.67 eV upon indium doping. Both films are photoactive in nature.     

Structural, electrical, and optical properties of copper indium diselenide thin film prepared by thermal evaporation method

Stoichiometric compound of copper indium diselenide (CuInSe₂) was synthesized by direct reaction of high-purity elemental copper, indium and selenium in an evacuated quartz ampoule. The phase structure and composition of the synthesized pulverized material analyzed by X-ray diffraction (XRD) and energy dispersive analysis of X-rays (EDAX) revealed the chalcopyrite structure and stoichiometry of elements. Thin films of CuInSe₂ were deposited onto organically cleaned soda lime glass substrates held at different temperatures (i.e. 300 K to 573 K) using thermal evaporation technique. CuInSe₂ thin films were then thermally annealed in a vacuum chamber at 573 K at a base pressure of 10^− 2 mbar for 1 h. The effect of substrate temperature (T_s) and thermal annealing (T_a) on structural, compositional, morphological, optical and electrical properties of films were investigated using XRD, transmission electron microscopy, EDAX, atomic force microscopy (AFM), optical transmission measurements and Hall effect techniques. XRD and EDAX studies of CuInSe₂ thin films revealed that the films deposited in the substrate temperature range of 423-573 K have preferred orientation of grains along the (112) plane and near stoichiometric composition. AFM analysis indicates that the grain size increases with increase of T_s and T_a. Optical and electrical characterizations of films suggest that CuInSe₂ thin films have high absorption coefficient (10⁴ cm^− 1) and resistivity value in the interval 10^− 2-10¹ Ω cm influenced by T_s and T_a.     

Recrystallization and interdiffusion in thin bimetallic films

Diffusion-induced recrystallization phenomena in thin bimetallic films are described. For specimens consisting of a copper layer vapour deposited onto an electropolished nickel substrate, diffusion experiments were carried out in situ in the electron microscope in the temperature range 450–600°C. It is concluded from the observations that new grains were formed by self-induced recrystallization. These new grains were curved in order to accomodate the misfit still present. The degrees of interdiffusion of the curved grains and the matrix were determined respectively from the curvature and from the increase in the average moiré spacing. It was found that the curved grains, compared with the matrix, were in a much more advanced stage of homogenization. Assuming that this was caused by grain boundary diffusion occuring in the recrystallization front while it swept through the material, a realistic value for the grain boundary diffusion coefficient was obtained. It is demonstrated that the driving force on the recrystallization front cannot be supplied by the difference in strain energy between the matrix and the curved grains. Instead, it is shown that the driving force can be provided by the chemical Gibbs free energy for the reaction between the matrix and the recrystallized material.     

Growth of selenium thin films

Quantitative measurements of the formation and growth of selenium films on sapphire, glass, aluminium and nickel substrates have been made for various substrate temperatures (T) and evaporation times (t) using a scanning electron microscope (SEM). The film formation and growth process was thought to be a mechanism of the adsorption of impinging selenium atoms on the stable clusters, and the growth of these clusters as evaporation continues. The difference in the values of the activation energies for the growth of selenium on different substrates was explained by considering them as apparent energies which contain the adsorption, desorption, surface diffusion and binding energy terms. The experimental results also indicated an increase in there-evaporation of adatoms from the substrates at higher temperatures.     

Electrical properties of electrodeposited CdTe thin films

The electrical properties of electrodeposited CdTe thin films have been studied. The temperature-dependent electrical conductivity data obtained have been used to determine the conductivity type and semiconductor parameters (E _g, B, and α) of the films.     

Characteristics of pulse electrodeposited PbS thin films

PbS thin films were deposited for the first time using the pulse electrodeposition technique at different duty cycles in the range of 9 to 50% and at room temperature using lead nitrate and sodium thiosulphate. The thickness of the films increased from 0.5 to 1.0 μm with increase of duty cycle. The films were polycrystalline and exhibited cubic structure. The band gap of the films deposited at 50% duty cycle is 0.42 eV. The resistivities of the films decreased from 0.9 to 0.5 × 10⁵ ohm cm as the duty cycle increased. Films with grain size in the range of 20 to 35 nm were deposited. Films with refractive index varying in the range of 4.45–3.75 with increase of wavelength were obtained. Films with higher photosensitivity and higher detectivity compared to earlier reports were obtained.