Effect of phosphoric acid treatment on the physical properties of zinc telluride thin films (original) (raw)
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Zinc Telluride Thin Films: A Review
Asian Journal of Chemistry
Extensive research has been carried out on the deposition and characterization of polycrystalline thin films by several researchers [1-32]. These materials are used in optical instruments, solar cells, telecommunications terminals, in-vehicle equipment, traffic lights, magnetic films, diamond films, microelectronic devices, solar selective coatings, sensor devices, optical mass memories and superconducting films. In recent years, binary semiconductor material such as zinc telluride has been studied by many scientists. Recent investigations have shown that zinc telluride thin films show absorption in the spectrum range from visible to near infrared (as widely reported in the literature). The II-VI (ZnTe) compound semiconductors have a direct transition at 2.26 eV. Therefore, ZnTe is capable of green light emission at 550 nm, i.e. in spectral region corresponding to the maximum sensitivity of the human eye. This makes ZnTe an appealing candidate for the production of bright light-emitting diodes and diode lasers. There are several reports available on the growth of zinc telluride thin films by different deposition methods such as electro-deposition method [33-35], closed space sublimation technique [36,37], screen printing technique [38], spray pyrolysis [39], radio frequency magnetron sputtering [40], thermal evaporation [41], electron beam evaporation [42], physical vapour deposition [43] and molecular beam epitaxy [44]. Each technique has strengths and weaknesses as described by researchers.
2012
ZnTe thin films were prepared by Stacking of elemental (Zn and Te) layers (SEL) followed by inert gas annealing. The optical parameters were calculated from the transmission spectra. The bandgap of the annealed samples was found between 1.95 eV and 2.06 eV. The change in film thickness after annealing was observed using cross sectional SEM image of the annealed samples. The surface morphology of the annealed Te/Zn stack was also analyzed and observed as very smooth, compact and dense surface. The prepared film was Zn rich evidenced by EDAX. The observed result encourages in pursuing the SEL method for the preparation of compound semiconductor from II-VI group materials.
Journal of Crystal Growth, 2011
ZnTe thin films were deposited by the two-source evaporation technique on amorphous glass substrate. The deposited films were annealed under nitrogen ambient pressure. The resistivity of the film annealed under nitrogen pressure of 100 mbar was found to be less than that of as-deposited film by more than four orders of magnitude. The films structures were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The films' thickness and the optical properties such as refractive index, absorption coefficient and optical band gap of the films were determined from transmittance spectra in the wavelength range of 400-2000 nm. The dark electrical conductivity of the films was studied as a function of temperature to determine the DC conductivity activation energy of the films.
Journal of Engineering Technology and Applied Physics
ZnTe bilayer thin films were deposited onto soda-lime glass by a thermal vacuum evaporation technique using the NANO 36 thermal evaporator under a vacuum pressure of 2.9 x 10-5 torr. The optical characteristics of the film were measured using an AVANTEX UV spectrophotometer in the wavelength range from 239.534 nm to 999.495 nm. Also, the electrical characteristics of the thin films were investigated using KEITHLEY four-point probe techniques. The investigation of the optical properties of the thin films as-deposited and annealed at different temperatures showed high transmission in the NIR region with good absorption in the visible and UV regions. The extrapolated band gap energies were 2.60 eV and 3.20 eV for annealed and as-deposited samples, respectively. electrical resistivity decreased as the annealing temperature increases. The images of the film as-deposited and on annealing have a uniform distribution on the glass slides.
Fabrication and characterization of Zinc Telluride (ZnTe) thin films grown on glass substrates
Physica B: Condensed Matter, 2019
In this paper we highlight the fabrication of Zinc Telluride (ZT) thin films grown onto glass substrates at 300 o C with varying thickness, in the range of 200 nm to 1000 nm, by adopting the simplistic thermal evaporation technique with base pressure of 10-6 m bar. In addition, their structural and optical characterizations are also studied by exploring the influence of substrate annealing temperature and thickness of the samples. The morphology, crystalline nature and composition analysis of the thin films were done by X-ray diffraction and scanning electron microscopy. These results revealed that the sample having thickness around 1000 nm show crystalline nature while the samples having lower thickness demonstrate amorphous structure. The optical characterizations are described in the form of transmission spectra, refractive index, and absorption coefficient. The band gap values obtained by probing optical data, show that all the samples have direct band gaps in the vicinity of 2.25 eV. This suggests possible applications of ZnTe in optoelectronics devices in the visible region of electromagnetic spectra.
Zinc telluride films by photoenhanced metalorganic chemical vapor deposition
Journal of Electronic Materials, 1991
Polycrystalline films of zinc telluride (ZnTe) have been deposited on glass and conducting semiconductor coated glass substrates at 270~176 C by photoenhanced metalorganic chemical vapor deposition (PECVD) using the reaction of dimethylzinc (DMZn) or diethylzinc (DEZn) and diisopropyltellurium (DIPTe) in hydrogen under atmospheric pressure. The deposited films are always of p-type conductivity. Their properties are affected by the DMZn/DIPTe or DEZn/DIPTe molar ratio in the reaction mixture. The optimum DMZn/DIPTe ratio has been found to be approximately 0.9 on the basis of the open-circuit voltage of ZnTe/CdS heterojunctions and photoconductivity measurements. Without intentional doping, the deposited films are of high resistivity (>107 ohm-cm) at room temperature, and the resistivity of these films has been controlled by using arsine as a dopant. The structural, optical, and electrical properties of ZnTe films have been characterized.
OPTICAL AND ELECTRICAL CHARACTERISTICS OF VACUUM EVAPORATED ZINC TELLURIDE THIN FILMS
IASET, 2020
These films of ZnTe compound of varying thickness ranging from 191.3 nm to 248.4 nm have been deposited by vacuum evaporation technique on the clean glass substrates. Optical method (Tolansky method) was employed to measure the thickness of the deposited thin films. The optical properties of the ZnTe thin films were investigated by UV-VIS spectrophotometer and the electrical resistivity have been studied as a function of thickness by Four Probe Kit. The results of all these studied parameters are presented and discussed in this paper.
Improvement of physical properties of ZnO thin films by tellurium doping
Applied Surface Science, 2014
This investigation addressed the structural, optical and morphological properties of tellurium incorporated zinc oxide (Te-ZnO) thin films. The obtained results indicated that Te-doped ZnO thin films exhibit an enhancement of band gap energy and crystallinity compared with non-doped films. The optical transmission spectra revealed a shift in the absorption edge toward lower wavelengths. X-ray diffraction measurement demonstrated that the film was crystallized in the hexagonal (wurtzite) phase and presented a preferential orientation along the c-axis. The XRD obtained patterns indicate that the crystallite size of the thin films, ranging from 23.9 to 49.1 nm, changed with the Te doping level. The scanning electron microscopy and atomic force microscopy results demonstrated that the grain size and surface roughness of the thin films increased as the Te concentration increased. Most significantly, we demonstrate that it is possible to control the structural, optical and morphological properties of ZnO thin films with the isoelectronic Te-incorporation level.
Synthesis and characterization of copper doped zinc telluride thin films
Solid-State Electronics, 2005
Copper doped zinc telluride (ZnTe:Cu) thin films have been synthesized by an electrodeposition technique from acidic aqueous bath containing ZnSO 4 , TeO 2 and CuSO 4. The reaction mechanism has been studied by cyclic voltammetry to identify the deposition potential of ZnTe and ZnTe:Cu. X-ray diffraction as well as SEM techniques have been employed to investigate the structure and surface morphology of as-deposited and doped films. Optical properties, such as transmission, refractive index and band gap have been analyzed. The drastic change in resistivity has been observed due to incorporation of Cu dopent and the results are discussed in detail.
Study of Optical Properties of Nanocrystalline Zinc Phosphide Thin films
Silicon, 2018
Zinc phosphide (Zn 3 P 2), a II-V group semiconductor compound has long been considered as a very interesting and suitable candidate for several applications especially in photovoltaics. Nanocrystalline Zn 3 P 2 thin films were successfully synthesized on glass and different silicon-based substrates by a combined physico-chemical method. The properties and morphology of Zn 3 P 2 films were investigated. SEM images showed that all films displayed a nanoscale granular, polycrystalline morphology. It depends dramatically on the surface state of the substrate and follows the substrate its morphology. X-ray diffraction (XRD) spectra revealed a preferred orientation of the Zn 3 P 2 nanocrystalline film along the (102) and (405) direction. The transmittance of the Zn 3 P 2 films was found to be high of the order of 87%. The optical gap of the film was determined using the optical transmission spectra and the obtained optical band gap value is 1.96 eV. A decrease of the average reflectance from 15% to 4.25%, after deposition of the nanocrystalline Zn 3 P 2 on a textured Si substrate, was observed. This result was compared to the one obtained with SiN x layer deposited on the same Si substrate. A difference of 1% was noticed. We assume that the combination of nanocrystalline Zn 3 P 2 thin film and a textured Silicon surface could increase the efficiency of photovoltaic silicon solar cell by using Zn 3 P 2 as an antireflection layer.