Single Source Vacuum Thermal Evaporation Research Articles

Synthesis and Characterization of Next Generation Cu2ZnxFe1−xSnS4 (x = 0, 0.25, 0.5, 0.75 and 1) Compounds

In this paper, we investigate the effect of Zn/Fe ratio on the properties of Cu2ZnxFe1−xSnS4 (CZFTS) compounds. Multicomponent CZFTS powders were prepared by direct melting of the constituent elements taken in stoichiometric compositions. After that, CZFTS thin films were fabricated using a single source vacuum thermal evaporation method. After that, CZFTS thin films were annealed in sulfur atmosphere under nitrogen flow at 400°C for 30 min. Structural properties of CZFTS powders and thin films were studied by elemental composition measurement, x-ray diffraction (XRD) and Raman spectroscopy. Analysis of chemical compositions reveals that the synthesized CZFTS powders are close to the expected stoichiometry. XRD patterns and Raman spectra of CZFTS powders showed that only polycrystalline CZFTS phase is present and a possible transition phase from stannite to kesterite structure had occurred by reducing Fe content. Using XRD data, the crystal parameters of CZFTS powders were estimated. Structural properties of CZFTS thin films indicate an enhancement of crystallinity after annealing. Some microstructural parameters of the prepared films were evaluated. However, morphological analysis of CZFTS crystals showed compact surfaces. Also, micrographs of CZFTS thin films indicate an improvement of crystallinity films followed by the increases of average roughness values after a sulfurization process. Moreover, hot probe method indicates that CZFTS ingots and prepared films exhibit an obvious p-type semiconductor.

Growth and Characterization of the Evaporated Quaternary Absorber Cu2FeSnS4 for Solar Cell Applications

Cu2FeSnS4 (CFTS) was synthesized by direct fusion of high-purity elemental copper, iron, tin and sulfur. CFTS thin films were deposited on glass substrates heated by single source vacuum thermal evaporation, after which the obtained samples were annealed under a sulfur atmosphere in a sealed quartz tube at 400°C for 1 h in order to optimize the CFTS stannite phase. The substrate temperature was varied from room temperature to 200°C. The formation of a stannite structure with (112), (200) and (004) planes in the powder and thin films was confirmed using x-ray diffraction measurements and the crystallites were found to have a preferred orientation along the (112) direction. Optical measurements analysis showed that after the sulfurization process the layers have a relatively high absorption coefficient close to 105 cm−1 in the visible spectrum. The films show a direct optical band gap in the range 1.30–1.63 eV for substrate temperature varied from room temperature to 200°C. All samples revealed p-type conductivity as determined by the hot probe method.

Investigation on the AC and DC electrical conductivity of Sn3Sb2S6 thin films prepared by glancing angle deposition

Sn3Sb2S6 thin films were deposited by single source vacuum thermal evaporation using glancing angle deposition technique. The incident angle α between the particle flux and the normal to the substrate was varied from 0° to 85°. The structural, morphological and electrical properties were investigated by X-ray diffraction, scanning electron microscopy, and impedance spectroscopy, respectively. The effect of these properties as a function of the incident angle has been studied. The AC conductivity exhibited a Jonscher’s universal power law. It is observed that exponent s decreases with increasing measurement temperature. Further analysis revealed that, samples AC conductivity follows the correlated barrier hopping model. The Cole–Cole plot showed a single semicircle, indicating an equivalent circuit with a single parallel resistor R and capacitance C network. The activation energy obtained from both angular relaxation frequency and DC conductivity suggests that the carrier transport mechanism is a hopping mechanism thermally activated in the band gap.

Investigation of physical properties and impedance spectroscopy study of Cu3SbS3 thin films

Cu3SbS3 ingot material was successfully grown by direct melting of the constituent elements taken in stoichiometry compositions using high-purity copper, antimony and sulfide elements. Cu3SbS3 thin films were prepared by single source vacuum thermal evaporation method under vacuum (10−5 Torr) onto no heated glass substrates. The X-ray diffraction experimental data revealed that the Cu3SbS3 powder exhibiting an orthorhombic structure and lattice parameters a, b and c were calculated. It has been shown that the as-deposited Cu3SbS3 thin films were overall amorphous and the film thicknesses were around 400 nm. The absorption spectra of the films showed that the Cu3SbS3 compound is a direct band gap material and the gap value is closed to 1.46 eV. The as-deposited Cu3SbS3 films show absorption coefficients of about 2 × 105 cm−1 near the absorption edge. The as-deposited Cu3SbS3 films exhibit p-conductivity type by using hot probe method. A Schottky diode (Al/p-Cu3SbS3/Mo) was fabricated by simple deposition of pure Aluminum on the front side of the Cu3SbS3 thin film. I–V characteristics show that the Al makes Schottky contact with p-Cu3SbS3. Impedance spectroscopy technique was used to evaluate the conduction processes of the samples as a function of temperature (598–673 K) in the range 1 Hz–13 MHz. We found a decrease with temperature of the entire serial resistance Rs, the parallel resistance Rp and the capacitance Cp. In effort to modeling these results an equivalent electrical circuit was used. From the Arrhenius diagram, we estimated activation energy at 0.16 eV which represents the energy difference between the trap level and the valence band.

Structural and electrical properties of the new sulfosalt Sn2Sb6S11 thin films prepared by vacuum thermal evaporation

Sulfosalts SnxSbySz materials were known as promising candidates in photovoltaic applications. So, a member of this family Sn2Sb6S11 material was synthesized by direct melting of the constituent elements and Sn2Sb6S11 thin films were deposited by single source vacuum thermal evaporation method at different substrates temperatures in the range 30–200 °C. A good homogeneity of the films with thicknesses in the range 216–471 nm was obtained. X-ray diffraction. Atomic force microscopy and AC impedance spectroscopy were used to characterize the structural, morphological and electrical properties respectively. The effect of these properties as a function of the substrate temperature has been studied. Frequency measurements, in the range from 5 Hz to 13 MHz, were performed in order to evaluate the effect of the substrate temperature on the conduction mechanism. Impedance spectroscopy appears as a very useful technique for discerning between grain boundary capacitance (C gb) and grain boundary resistance (R gb) contributions.

Effect of substrate temperature on the structural, morphological, and optical properties of Sb2S3 thin films

Sb2S3 thin films have been deposited by single source vacuum thermal evaporation onto glass substrates. The substrate temperature was varied in the range of 25–270°C. X-ray diffraction (XRD) showed that films deposited at substrate TS<250°C have an amorphous structure, while those prepared at TS≥250°C have a polycrystalline structure. XRD investigations showed that the crystallite size dimension increases with increasing substrate temperature. The effect of substrate temperature on grain size and surface roughness was studied by atomic force microscopy (AFM). The optical constants of the films were determined from optical transmission recorded in the 500–1800nm wavelength range. The dispersion parameters and the high-frequency dielectric constant were determined by modeling the refractive index using the Wemple–Di Domenico model. The optical band gap energy of the films decreases from 1.98 to 1.74eV as the substrate temperature varies from 25 to 270°C.

Optical properties of the new material Sn2Sb6S11 thin films deposited by thermal vacuum evaporation

The purpose of this work was to investigate the effect of substrate temperature on the structural and optical properties of Sn2Sb6S11 thin films. Sn2Sb6S11 thin films have been deposited by single source vacuum thermal evaporation onto glass substrates at various substrate temperatures in the range 30–200°C. By X-ray diffraction analysis, an improvement on the structural properties by increasing the substrate temperature was observed. The reflectance and transmittance of the films are measured in the incident wavelength range 300–1800 nm. The absorption coefficients of the Sn2Sb6S11 thin films are in the range of 105–106 cm−1. The analysis of the absorption coefficient in the high absorption region revealed two direct forbidden band gaps Eg1 and Eg2 in the ranges 1·58–1·72 and 1·75–1·88 eV respectively. It has been found that the refractive index dispersion data obeyed the single oscillator of the Wemple–DiDomenico model. Using this model, the dispersion parameters and the high frequency dielectric constant were determined. The low value of the extinction coefficient is a qualitative indication of excellent surface smoothness of the films. The electric free carrier concentration on the effective mass ratio was estimated according to the model of Spitzer–Fan.

The Effect of the Growth Condition on the Properties of the New Material Sn3Sb2S6 Thin Films

Sulfosalt Sn3Sb2S6 material was synthesised by the horizontal Bridgman method. X-rays diffraction analysis of the powder showed that only homogenous Sn3Sb2S6 phase is present in the ingot. Sn3Sb2S6 thin films were deposited by a single source vacuum thermal evaporation with different thicknesses on glass substrates. Th e optical and structural properties of the films were studied as a function of thicknesses and temperature substrates. It is interest to no te that Sn3Sb2S6 films exhibit polycrystalline structures along (416) preferred plane without heating the substrates. In addition, we no te that as the thickness increases from 150 nm to 430 nm the average grain size increases from 190 to 350 ˚ A. The samples have direct bandgap energies of 1.5 - 1.75 eV. Furthermore, we found that the absorption coefficient in all cases reached 10 4 cm −1 . So, Sulfosalt Sn3Sb2S6 thin films could be used as a potential candidate in

A comparative study of the properties of thermally evaporated CuIn 2n + 1 S 3n + 2 (n = 0, 1, 2 and 3) thin films

CuInS 2, CuIn 3S 5, CuIn 5S 8 and CuIn 7S 11 compounds were synthesized by the horizontal Bridgman method using high-purity copper, indium and sulphur elements. Crushed powders of these ingots were used as raw materials for the vacuum thermal evaporation. So, CuIn 2n + 1 S 3n + 2 (n = 0, 1, 2, and 3) thin films were deposited by single source vacuum thermal evaporation onto glass substrates heated at 150 °C. The structural, compositional, morphological, electrical and optical properties of the deposited films were studied using X-ray diffraction (XRD), energy dispersive X-ray, atomic force microscopy and optical measurement techniques. XRD results revealed that all the films are polycrystalline. However, CuInS 2 and CuIn 3S 5 films had a chalcopyrite structure with preferred orientation along 112 while CuIn 5S 8 and CuIn 7S 11 films exhibit a spinel structure with preferred orientation along 311. The absorption coefficients of the all CuIn 2n + 1 S 3n + 2 films are in the range of 10 −4 and 10 −5 cm −1. The direct optical band gaps of CuIn 2n + 1 S 3n + 2 layers are found to be 1.56, 1.78, 1.75 and 1.30 eV for n = 0, 1, 2, and 3, respectively. CuIn 3S 5 and CuIn 5S 8 films are p type with electrical resistivities of 4 and 12 Ω cm whereas CuInS 2 and CuIn 7S 11 are highly compensated with resistivities of 1470 and 1176 Ω cm, respectively.

Study of the Optical Properties of Sn-doped Sb2S3 Thin Films

Sn doped Sb2S3 thin films have been deposited by single source vacuum thermal evaporation onto glass substrates at substrate temperature Ts= 240°C. The optical constants were obtained from the analysis of the experimental recorded transmission and reflectance spectral data over the wavelength range 300–1800nm. It has been found that the refractive index dispersion data obeyed the single oscillator of the Wemple-DiDomenico model. By using this model, the dispersion parameters and the high-frequency dielectric constant were determined. The electric free carrier susceptibility and the carrier concentration on the effective mass ratio were estimated according to the model of Spitzer and Fan.

Fabrication and characterization of In 2S 3 thin films deposited by thermal evaporation technique

Indium sulphide, In 2S 3, thin films present an alternative to conventional CdS films as buffer layer for CIS-based thin film solar cells. The objective is to eliminate toxic cadmium for environmental reasons. Indium sulphide is synthesized and deposited by single source vacuum thermal evaporation method on glass substrates. The films are analyzed by X-ray diffraction (XRD) and spectrophotometric measurements. They have a good crystallinity, homogeneity and adhesion. The X-ray diffraction analysis confirmed the initial amorphous nature of the deposited InS film and phase transition into crystalline In 2S 3 formed upon annealing at free air for 250 °C substrate temperature for 2 h. The optical constants of the deposited films were obtained from the analysis of the experimental recorded transmission and reflectance spectral data over the wavelength range of 300–1800 nm. We note that the films annealed at 250 °C for 2 h show a good homogeneity with 80% transmission. An analysis of the optical absorption data of the deposited films revealed an optical direct band gap energy in the range of 2.0–2.2 eV.

Structural and optical properties of sulfur-annealed CuInS 2 thin films

CuInS 2 thin films were deposited by single source vacuum thermal evaporation method on substrates submitted to longitudinal thermal gradient. Some of these films were annealed in sulfur atmosphere and converted into CuInS 2 homogenous layers. Both of the as-deposited and sulfurated films were characterized by X-ray diffraction, optical transmission and reflection measurements. The optical band gap of films after sulfurization was 1.50 eV which is near the optimum value for photovoltaic energy conversion.