Structural, optical and photoelectrochemical properties of electrodeposited CdSe thin films

Cadmium Selenide thin films have been electrodeposited from an acidic bath using CdSO₄ as a cadmium source and SeO₂ as a selenium source at pH=3 on to stainless steel and fluorine-tin oxide coated glass substrates. The CdSe films have been characterized by X-ray diffraction, scanning electron microscopy and optical absorption. X-ray diffraction spectra showed that CdSe is polycrystalline with single hexagonal phase. The intensity of the (0 0 2) peak increases remarkably by annealing in nitrogen atmosphere. A microstructural study revealed that the films were uniform and well covered the substrate. Optical absorption studies showed that the bandgap of the CdSe is 1.70 eV. It is observed that the conductivity of the CdSe films increases by annealing in nitrogen atmosphere. The photoelectrochemical activities of CdSe films deposited on stainless steel and fluorine-tin oxide coated glass have been studied by using CdSe/ 1 M NaOH-1 M Na₂S-1 MS / C cell configuration and it is found that films deposited on stainless steel give better performance, photoelectrochemical (PEC) studies also reveal that the CdSe has n-type conductivity.     

Structural and optical properties of electron beam evaporated CdSe thin films

Thin films of cadmium selenide (CdSe) as a semiconductor is well suited for opto-electronic applications such as photo detection or solar energy conversion, due to its optical and electrical properties, as well as its good chemical and mechanical stability. In order to explore the possibility of using this in optoelectronics, a preliminary and thorough study of optical and structural properties of the host material is an important step. Based on the above view, the structural and optical properties of CdSe films have been studied thoroughly in the present work. The host material, CdSe film, has been prepared by the physical vapour deposition method of electron beam evaporation (PVD: EBE) technique under a pressure of 5 × 10⁻⁵ mbar. The structural properties have been studied by XRD technique. The hexagonal structure with a preferred orientation along the (0 0 2) direction of films has been confirmed by the X-ray diffraction analysis. The films have been analysed for optical band gap and absorbed a direct intrinsic band gap of 1·92 eV.     

Investigation of structural,electrical and optical properties of nickel substituted CdSe thin films

The technologically important Cd_1−xNi_xSe thin films with variable compositions (0 ≤ x ≤ 1) have been developed by a chemical deposition method. The structural, compositional, optical and electrical properties were studied by X-ray diffraction, Scanning electron microscopy, Atomic absorption spectroscopy, UV–visible double beam spectrophotometer and d.c. two probe method. XRD studies indicate polycrystalline in nature with hexagonal phase for all the samples. The lattice constants decrease with increase in nickel content in CdSe host lattice. The surface morphology study of all samples reveals uniform and spherical grains. An optical study of the samples shows that band gap value decreases with nickel content. Electrical measurements depict semiconducting properties of all samples.     

Structural and optical properties of nanocrystalline CdSe and Al:CdSe thin films for photoelectrochemical application

Nanocrystalline CdSe and Al:CdSe semiconductor thin films have been successfully synthesized onto amorphous and FTO glass substrates by spray pyrolysis technique. Aqueous solutions containing precursors of Cd and Se have been used to obtain good quality films. The optimized films have been characterized for their structural, morphological, wettability and optical properties. X-ray diffraction (XRD) studies show that the films are polycrystalline in nature with hexagonal crystal structure. Scanning electron microscopy (SEM) studies show that the film surface is smooth, uniform and compact in nature. Water wettability study reveals that the films are hydrophilic behavior. The formation of CdSe and Al:CdSe thin film were confirmed with the help of FTIR spectroscopy. UV–vis spectrophotometric measurement showed a direct allowed band gap lying in the range 1.673–1.87 eV. Output characteristics were studied by using cell configuration n- CdSe/Al:CdSe |1 M (NaOH + Na₂ + S)|C. An efficient solar cell having a power conversion efficiency of 0.38% at illumination 25 mW cm⁻² was fabricated.     

Structural,optical and photoconducting properties of sprayed CdSe films

CdSe films were grown by the pyrolytic decomposition of a mixture of aqueous solutions of selenourea (NH₂CSeNH₂) and CdCl₂·5H₂O. The effect of changes in the selenium-to-cadmium ion ratio on the photoconductivity was examined. The as-grown films had low resistance and showed poor photoconductivity gain. When the films were annealed in air the resistance as well as the gain increased appreciably. These changes have been attributed to chemisorption of oxygen. The samples with one part CdCl₂·5H₂O and one part NH₂CSeNH₂ were found to be the most photosensitive, the ratio of dark resistance to light resistance being of the order of 10⁵. The spectral response of the resistance of these films shows a dip in the region of 690 nm, which is in close agreement with the band gap determined from optical absorption measurements.     

X-ray line broadening and photoelectrochemical studies on CdSe thin films

Cadmium Selenide (CdSe) thin films have been prepared on Indium doped tin oxide coated conducting glass (ITO) substrates at various deposition potential and solution pH values using potentiostatic cathodic electrodeposition technique. The deposited films are characterized using X-ray diffraction, scanning electron microscopy, energy dispersive analysis by X-rays, optical absorption, and photoelectrochemical techniques, respectively. X-ray diffraction pattern revealed that the deposited films are found to exhibit hexagonal structure with preferential orientation along (002) plane. X-ray line profile analysis technique by the method of variance has been used to evaluate the microstructural parameters such as crystallite size, rms microstrain, dislocation density, and stacking fault probability. The variation of microstructural parameters with deposition potential, solution pH values, and annealing temperature are studied. Surface morphology and film composition are investigated by scanning electron microscopy and energy dispersive analysis by X-rays, respectively. Optical absorption analysis has been carried out to evaluate the optical parameters such as refractive index, extinction coefficient, real and imaginary dielectric constants, and packing density, respectively. Photoelectrochemical solar cells are constructed using as-deposited and annealed CdSe thin films as photocathode, and their power output characteristics are studied. The experimental observations are discussed in detail.     

Structural, compositional, thermoelectrical and photoelectrochemical properties of CdSe thin films

Cadmium selenide thin films have been deposited on non-conducting glass and stainless steel substrates. Films were characterized by X-ray diffraction, atomic absorption spectroscopy. The electrical and thermoelectrical properties also studied. The X-ray diffraction analysis shows that the film samples are in cubic crystal structure. Film was found to be cadmium deficient. The efficiency of photoelectrode was found to be 1.15 % using sulphide-polysulphide electrolyte.     

Structural, optical and photoelectrochemical properties of brush plated CdSe x Te1 − x thin films

CdSe _x Te_{1 – x} films have been deposited by the brush plating technique for the first time, on titanium and conducting glass substrates at room temperature. These films were annealed in argon atmosphere at 475°C for 15 min. Their structural, optical and photoelectrochemical (PEC) properties are presented and discussed. The power conversion efficiency has been found to be 9.0% at 60 mW cm^–2white light illumination. A peak quantum efficiency of 0.7 has been obtained for the films of composition CdSe_0.7Te_0.3. Donor concentration of 10¹⁷cm^–3and electron mobility of 60 cm²V^–1sec^–1were obtained.     

Investigation of size dependent structural and optical properties of thin films of CdSe quantum dots

Cadmium selenide (CdSe) quantum dots were grown on indium tin oxide substrate using wet chemical technique for possible application as light emitting devices. The structural, morphological and luminescence properties of the as deposited thin films of CdSe Q-dot have been investigated, using X-ray diffraction, transmission electron microscopy, atomic force microscopy and optical and luminescence spectroscopy. The quantum dots have been shown to deposit in an organized array on ITO/glass substrate. The as grown Q-dots exhibited size dependent blue shift in the absorption edge. The effect of quantum confinement also manifested as a blue shift of photoluminescence emission. It is shown that the nanocrystalline CdSe exhibits intense photoluminescence as compared to the large grained polycrystalline CdSe films.     

Studies on photoelectrical,optical and galvanomagnetic properties of CdSe films

CdSe films were deposited onto glass substrates by the hot wall technique at a system pressure of 10^–6torr. The optimum deposition conditions for obtaining device grade films were determined. Photoelectrical and optical properties of the films deposited at the optimum conditions were studied. Information on the refractive index and absorption coefficient were derived from the above measurements and the data were analysed in the light of the existing theories. Direct transitions corresponding to band gaps of 1.7 and 1.92 eV were obtained. Measurement of mobility of CdSe films as a function of temperature indicated ionized impurity scattering to be predominant in our temperature range of measurements. The scattering parameter and the effective massm _e ^* of carriers was determined from thermoelectric power measurements.     

Optical properties of CdSe and CdO thin films electrochemically prepared

The present work comparatively studies the optical properties of CdO against CdSe samples potentiostatically electrodeposited onto fluorine-doped tin oxide/glasses (FTO). The films were prepared by electrochemical reduction processes in dimethyl sulfoxide (DMSO) solution. The optical properties are studied by transmittance measurements and diffuse reflectance spectra (DRS). Structural properties of the films were also studied by X-ray diffraction spectroscopy (XRD). For CdSe the direct bandgap energy obtained from both transmittance measurements and first derivative peak position of the DRS is 1.69 ± 0.01 eV. In the case of CdO both direct and indirect gaps were found. Careful deconvolution of the spectra allows assigning the direct bandgap energy at 2.52 eV. A first indirect bandgap appears at 2.03 eV, while it is possible to have a second one at 0.46 eV.     

Effect of thickness on structural,optical, electrical and morphological properties of nanocrystalline CdSe thin films for optoelectronic applications

This paper presents effect of thickness on the physical properties of thermally evaporated cadmium selenide thin films. The films of thickness 445 nm, 631 nm and 810 nm were deposited employing thermal evaporation technique on glass and ITO coated glass substrates followed by thermal annealing in air atmosphere at temperature 300 °C. The as-deposited and annealed films were subjected to the XRD, UV–Vis spectrophotometer, source meter, SEM and EDS to find the structural, optical, electrical, morphological and compositional analysis respectively. The structural analysis shows that the films have cubic phase with preferred orientation (1 1 1) and nanocrystalline nature. The structural parameters like inter-planner spacing, lattice constant, grain size, number of crystallites per unit area, internal strain, dislocation density and texture coefficient are calculated. The optical band gap is found in the range 1.69–1.84 eV and observed to decrease with thickness. The electrical resistivity is found to increase with thickness for as-deposited films and decrease for annealed films. The morphological studies show that the as-deposited and annealed films are homogeneous, smooth, fully covered and free from crystal defects like pin holes and voids. The grains in the as-deposited films are densely packed, well defined and found to be increased with thickness.     

Structural,optical and electrical properties of CdZnS thin films

The thin films of Cd_1-x Zn _x S (x?=?0, 0.2, 0.4, 0.6, 0.8 and 1) have been prepared by the vacuum evaporation method using a mechanically alloyed mixture of CdS and ZnS. The structural, optical and electrical properties have been investigated through the X-ray diffractometer, spectrophotometer and Keithley electrometer. The X-ray diffraction patterns of these films show that films are polycrystalline in nature having preferential orientation along the (002) plane. In the absorption spectra of these films, absorption edge shifts towards lower wavelength with the increase of Zn concentration. The energy band gap has been determined using these spectra. It is found that the energy band gap increases with increasing Zn concentration. The electrical conductivity of so prepared thin films has been determined using a I–V characteristic curve for these films. The result indicates that the electrical conductivity decreases with increasing Zn content and increases with temperature. An effort has also been made to obtain activation energy of these films which increases with increasing Zn concentration in CdS.     

Nonlinear optical and acoustic properties of thin films

The nonlinear optical and acoustic properties of thin films have been studied experimentally. The following nonlinear effects have been investigated: acoustic wave generation; stimulated light scattering due to acousto-optic interaction; and the influence of excitation conditions, film structure, and film composition on the above effects.     

Structural and optical properties of GaGeTe thin films

Smooth and pinhole-free thin films of Ga₅Ge₁₉Te₇₆ have been obtained by vacuum evaporation. The as-deposited films are amorphous. Thermal annealing at 222°C leads to an amorphous-to-crystalline transition. A maximum contrast of 30% in reflectivity (measured at 1 µm) has been obtained on phase transition from amorphous to crystalline state. The optical constants and the bandgap are reported.     

Electrical and optical properties of TiN thin films

TiN thin films have been grown by reactive magnetron sputtering. It has been shown that an Ohmic contact to TiN thin-film can be made from indium. The TiN thin films have been shown to be n-type semiconductors with a carrier concentration of 2.88 × 10²² cm^?3 and resistivity of ρ = 0.4 Ω cm at room temperature. The activation energy for conduction in the TiN films at temperatures in the range 295 K < T < 420 K is 0.15 eV. The optical properties of the TiN thin films have been investigated. The material of the TiN thin films has been shown to be a direct gap semiconductor with a band gap E _g = 3.4 eV.     

Preparation,characterization and optical properties of nanostructured ZnO thin films

Nanostructured ZnO thin film on a glass slide has been prepared by the spin-coating method together with calcining at 500 °C for 2 h in flowing oxygen atmosphere. The grain size of the ZnO nanoparticles is estimated to be ca. 12 nm as determined by the absorption spectrum and powder X-ray diffraction analysis. The photoluminescent peaks that centered at ca. 379 and 388 nm are assigned to the spontaneous emission and exciton–exciton emission, respectively. The thin film also shows frequency-tripled properties for the output when the laser beam of 1.06 μm is input in convergent beam.