The influence of substrate temperature on the morphology, optical and electrical properties of thermal-evaporated ZnSe thin films
13 Nov 2009-Journal of Alloys and Compounds (Elsevier)-Vol. 487, Iss: 5, pp 280-285
TL;DR: In this paper, structural, morphological, optical and electrical properties of ZnTe films were investigated as a function of substrate temperature (at −123 and 27°C) and post-deposition annealing temperature ( at 200, 300 and 400°C).
Abstract: The structural, morphological, optical and electrical properties of ZnTe films deposited by evaporation were investigated as a function of substrate temperature (at −123 and 27 °C) and post-deposition annealing temperature (at 200, 300 and 400 °C). It was determined that films deposited at both substrate temperatures were polycrystalline in nature with zinc-blende structure and a strong (1 1 1) texture. A small Te peak was detected in XRD spectra for both substrate temperatures, indicating that as-deposited ZnTe films were slightly rich in Te. Larger grains and a tighter grain size distribution were obtained with increased substrate temperature. Scanning electron microscopy (SEM) studies showed that the microstructures of the as-deposited films agreed well with the expectations from structure zone model. Post-deposition annealing induced further grain growth and tightened the grain size distribution. Annealing at 400 °C resulted in randomization in the texture of films deposited at both substrate temperatures. Optical spectroscopy results of the films indicated that the optical band gap value increased from 2.13 to 2.16 eV with increased substrate temperature. Increasing the annealing temperature sharpened the band-edge. Resistivity measurements showed that the resistivity of films deposited at substrate temperatures of −123 and 27 °C were 32 Ω cm, and 1.0 × 104 Ω cm, respectively with corresponding carrier concentrations of 8.9 × 1015 cm−3 and 1.5 × 1014 cm−3. Annealing caused opposite changes in the film resistivity between the samples prepared at substrate temperatures of −123 and 27 °C.
TL;DR: In this article, transition metal selenides (TMSs) are proposed as potential materials for electrochemical energy storage systems and their properties, preparation methods, and applications are discussed.
Abstract: Electrochemical energy storage devices (lithium ion batteries, sodium ion batteries, magnesium ion batteries, and super capacitors) with high power and energy densities are considered the most promising equipment for large-scale applications of portable electronic devices and electric vehicles. These devices can be realized by exploring nanostructured materials with high capacity, favorable cycling stability, and superior rate capability. Transition metal selenides (TMSs) are potential materials for electrochemical energy storage systems. In this paper, we summarized the nanostructured transition metal selenides and indicated their properties, preparation methods, and applications in electrochemical energy storage systems. We discussed the electronic properties of TMSs and showed that these materials have tunable electronic properties. We enumerated the 10 most-used preparation methods of TMSs as well as their composites with other functional materials. Subsequently, we systematically reviewed their applications in lithium ion batteries, sodium ion batteries, magnesium ion batteries, and super capacitors. Finally, we proposed the challenges and opportunities of their applications in energy storage.
TL;DR: In this article, thin films of ZnSe were deposited on soda lime glass substrates by thermal evaporation and annealed in vacuum at various temperatures in the range of 100-300°C. Structural and optoelectronic properties of these films were investigated and compared with the available data.
Abstract: Thin films of ZnSe were deposited on soda lime glass substrates by thermal evaporation and annealed in vacuum at various temperatures in the range of 100–300 °C. Structural and optoelectronic properties of these films were investigated and compared with the available data. XRD studies revealed that as-deposited films were polycrystalline in nature with cubic structure. It was further observed that the grain size and crystallinity increased, whereas dislocations and strains decreased with the increase of annealing temperature. The optical energy band gap estimated from the transmittance data was in the range of 2.60–2.67 eV. The observed increase in band gap energy with annealing temperature may be due to the quantum confinement effects. Similarly, refractive index of the films was found to increase with the annealing temperature. The AFM images revealed that films were uniform and pinhole free. The RMS roughness of the films increased from 1.5 nm to 2.5 nm with the increase of annealing temperature. Resistivity of the films decreased linearly with the increase of temperature.
TL;DR: In this paper, polycrystalline ZnX and CdTe thin films were prepared by rf magnetron sputtering and by thermal vacuum evaporation (CdTe), respectively.
Abstract: Polycrystalline ZnX (X = S, Se) and CdTe thin films were prepared by rf magnetron sputtering and by thermal vacuum evaporation (CdTe films), respectively. The structural properties were studied by X-ray diffraction (XRD), which revealed that ZnX films are polycrystalline with a marked (111) texture. After irradiation with protons crystallite sizes decreased while mechanical strains increased. Thicknesses of ZnX films and surface roughness have been measured by X-ray reflectometry (XRR) with thickness values between 58 nm and up to 163 nm and with surface roughness between 1.7 nm and 2.4 nm. Morphological investigations were made by scanning electron microscopy (SEM), drops - free surfaces with compact and uniform aspect being deposited. Absorption and transmission measurements were carried out for all samples deposited on optical glass substrates. Experimentally determined bandgap energies were between 2.31–2.75 eV for ZnSe layers, respectively, 3.10–3.65 eV for ZnS films. Optical transmissions in VIS-NIR regions are higher than 60% for both ZnSe and ZnS films. Glass/ITO/ZnS/ZnSe/CdTe/Cu:Au structures in superstrate configuration were produced by depositing CdTe absorber layers by thermal vacuum evaporation (TVE). Action spectra of the external quantum energy (EQE) and the current-voltage (I-V) characteristics in AM 1.5 conditions (the density power of the incident light is equal with 100 mW/cm2) corresponding for double-heterojunction ZnS/ZnSe/CdTe photovoltaic structures were investigated before and after irradiations with high energy protons (3 MeV).
TL;DR: In this article, a post-deposition annealing of ZnSe thin films was carried out in air at various temperatures to refine the crystalline phase refinement, which resulted in an increase of conductivity and optical bandgap of the samples.
Abstract: Zinc selenide (ZnSe) thin films are deposited by physical vapor deposition on indium tin oxide (ITO) substrates with different thicknesses. The crystalline phase refinement is studied by carrying out post-deposition annealing in air at various temperatures. The composition analyses carried out by the Rutherford backscattering spectroscopy have shown the ratios of Zn:Se to be 1:1. As-deposited samples have shown predominant crystalline phase with a small inclusion of the amorphous phase. The contribution of amorphous phase diminishes after the post-deposition annealing of the samples in air. However, the peaks of tin oxide and ITO begin to appear in the X-ray diffraction patterns after post-deposition annealing, showing that substrate material has started reacting with ZnSe films. The crystallinity of the ZnSe samples increases with annealing temperature, which results in the increase of conductivity and optical bandgap of the samples. It is proposed that as-prepared un-annealed samples grow with a large population of trapping centers filled with electrons near the top edge of the valance band. These electrons are elevated to the conduction band when exposed to the light, resulting in a very high photo current in as-prepared samples in comparison with post-annealed samples. The population of the localized trapping centers near the top edge of the valence band of ZnSe diminishes significantly with the post-annealing that refines the band gap; optimize their electrical and optical properties.
TL;DR: In this paper, annealing the precursors via a solvothermal process with different amount of ethylenediamine (EN) was used to obtain different morphologies of ZnSe nanoparticles and nanosheets.
Abstract: ZnSe nanocrystals with different morphologies were obtained by annealing the precursors via a solvothermal process with different amount of ethylenediamine (EN) (30 ml, 40 ml, and 50 ml). When EN was increased from 30 ml to 50 ml in the mixed solution, the morphologies changed from isotropic nanoparticles to highly anisotropic nanosheets. The X-ray diffraction (XRD) results showed that both the ZnSe nanoparticles and nanosheets were in the metastable wurtzite crystal phase. The large-scaled ZnSe nanosheets were composed of nanoparticles due to the template effect of the EN. The nanoparticles were found to be uniform with an average size of approximately 7 nm, while the large-scale nanosheets had a length of up to 4 μm and a width of up to 3 μm, and also exhibited a single crystalline nature. Both the nanoparticles and nanosheets showed an near band-edge emission peak centered at 422 nm, which was blue-shifted compared to the bulk wurtzite (WZ) structure of ZnSe. The investigation of the photocatalytic activity of the ZnSe nanoparticles and nanosheets showed that the nanosheets were more suitable for the degradation of Rhodamine B under UV radiation.
01 Jan 2001
01 Jan 1956
TL;DR: In this article, the authors present a chemical analysis of X-ray diffraction by Xray Spectrometry and phase-diagram Determination of single crystal structures and phase diagrams.
Abstract: 1. Properties of X-rays. 2. Geometry of Crystals. 3. Diffraction I: Directions of Diffracted Beams. 4. Diffraction II: Intensities of Diffracted Beams. 5. Diffraction III: Non-Ideal Samples. 6. Laure Photographs. 7. Powder Photographs. 8. Diffractometer and Spectrometer. 9. Orientation and Quality of Single Crystals. 10. Structure of Polycrystalline Aggregates. 11. Determination of Crystal Structure. 12. Precise Parameter Measurements. 13. Phase-Diagram Determination. 14. Order-Disorder Transformation. 15. Chemical Analysis of X-ray Diffraction. 16. Chemical Analysis by X-ray Spectrometry. 17. Measurements of Residual Stress. 18. Polymers. 19. Small Angle Scatters. 20. Transmission Electron Microscope.
01 Jan 1969
01 Mar 2009
01 May 1994
TL;DR: In this paper, the authors present thin film technology, thin film characterisation, and high energy techniques for thin film. But they do not discuss the effects of these technologies on the performance of the film.
Abstract: Thin Film Technology. Gas Kinetics. Vacuum Technology. Evaporation. Deposition. Epitaxy. Chemical Vapor Deposition. High-Energy Techniques. Plasma Processes. Film Characterization.