Characterization of AgGa_0.5In_0.5Se₂thin films deposited by electron-beam technique

Abstract

AgGa0.5In0.5Se2 thin films were deposited onto a quartz substrate by the electron-beam technique. For the investigation of the annealing effect on structural, optical and electrical properties of deposited films, samples were annealed in the temperature range 300–775 °C. The composition analyses of the deposited films carried out by energy dispersive x-ray analysis measurements have shown that the deposited AgGa0.5In0.5Se2 films were indium- and gallium-rich but selenium- and slightly silver-deficient and there was a remarkable change in composition with annealing. As a result of x-ray diffraction measurements, the as-deposited films were found to have an amorphous structure and after annealing at 300 °C a polycrystalline structure with different phases was observed. However, subsequent annealing resulted in the formation of single phase AgGa0.5In0.5Se2 thin film at about 775 °C. The absorption coefficient of the films was determined from the transmission spectra and the band gap values were calculated and found to vary between 1.57 and 2.43 eV following annealing in the temperature range 300–775 °C. The refractive index (n) and extinction coefficient (k) of the films were evaluated by applying the envelope method to the transmission spectra. The spectral distributions of these quantities for both as-deposited and annealed films were determined in detail and it was observed that there has been a remarkable influence of annealing on these quantities. The electrical properties of AgGa0.5In0.5Se2 thin films were also investigated by means of temperature dependent conductivity measurements in the temperature range 100–460 K. The resistivity of the samples depending on the annealing temperature varied between 6.5 × 105 and 16 Ω cm. As a result of the hot-probe method it was observed that the as-deposited films have indicated an n-type behaviour, while all the annealed AgGa0.5In0.5Se2 thin films have shown p-type conduction.

Characterization of Co-evaporated Cu-Ag-In-Se Thin Films

“…Therefore, it is clear from the conductivity measurements that higher annealing Consequently, only for as-grown CAIS film, the variation of conductivity as a function of temperature showed a distinct semiconductor characteristic, and the observed different linear regions in this variation can be taken as the indication of existence of different conduction mechanism dominating in different temperature regions with different activation energies [26]. Since the deposited films were not intentionally doped, the variation in the conductivity mechanism was possibly due to the intrinsic defects [27]. There were three distinct slopes in the different temperature regimes: 100-230, 240-295, and 310-400 K. Therefore, it is possible to determine the dominant conduction mechanisms for these three distinct temperature regions by applying all possible conductivity mechanism models, calculating the slope of the conductivity versus temperature plot in the straight line region, and determining the maximum correlation coefficient (R 2 ) of the best fit [28,29].…”

Synthesis of Si Nanowires by Electroless Etching Technique and Their Integration Into I-III-VI2 Thin Films For Solar Cells

“…Following the fabrication of Si NWs , a p-type AGIS thin film was deposited on Si NWs to construct a p-n heterojunction solar cell. Deposition process of AgGa 0.5 In 0.5 Se 2 (AGIS) thin film by electron-beam (e-beam) technique has been reported elsewhere [1]. Indium (In) metallic top contacts to AGIS thin film layer were made by thermal evaporation using copper shadow masks.…”

“…In particular, chalcopyrite (I-III-VI 2 ) compound are promising candidates for the realization of highly-efficient solar cells based on the p-n heterojunction with II-VI semiconductors, which has similar crystal structure contributing to reduce the lattice miss-match in the structure. Cu-III-VI 2 and Ag-III-VI 2 compounds are wellknown groups of chalcopyrites which have considerably high absorption coefficient (10 5 cm -1 ) and optimum band gap energy, well matched to the optimum part of solar spectrum [1].…”

Optical properties of pulse electrodeposited ZnS films

“…Fig.3 shows the transmission spectra of the ZnS films deposited at different duty cycles. The spectra exhibit interference fringes and the value of the refractive index was estimated by the envelope method [18] as follows: n = [N + (N 2 -n s 2 )] 2 ………………………(3) N = (n s 2 + 1)/2 + 2 n s (T max -T min )/ T max T min …………………..(4) where n s is the refractive index of the substrate, T max and T min are the maximum and minimum transmittances at the same wavelength in the fitted envelope curve on a transmittance spectrum. The value of the refractive index at 450 nm, calculated from the above equations was in the range of 4.30 -3.00 for the samples deposited at different duty cycle.…”