What effect on dislocation density if thin film grown by sputtering rather than mbe?
Answers
Answer:
Renewable energy sources offer a viable green energy solution to the increasing global energy demands, and the photovoltaics offers a means of tapping into the abundance of the solar energy. Molybdenum (Mo) thin film has been used as a back-contact electrode in high-efficiency solar cells mainly due to its ohmic nature with the absorber material (especially with chalcopyrites and kesterites), low resistivity, adequate reflectance, and porosity to alkali materials. Mo thin films used in solar cells are deposited by direct current (DC) sputtering under argon ion atmosphere. The present work deals with the effects of the sputtering deposition conditions (i.e., working pressure and power) on the electrical properties of Mo thin films deposited on soda-lime glass using DC magnetron sputtering at different working pressures (5–20 mTorr) and deposition powers (100–800 W). Optimized deposition power and sputtering pressure were used to deposit a Mo bilayer thin film intended for solar cells application. X-ray diffractometric studies showed the (110) plane corresponding to the body-centered cubic structure of the Mo material. Calculated values were used to estimate other parameters of the deposited films (e.g., stress, dislocation density), as these properties affect the potential diffusion of sodium (Na) through the soda-lime glass into the absorber layer that is important as the moderate inclusion of Na improves the cell efficiency. The cross-section of the deposited film was analyzed using a field-emission scanning electron microscopy, to confirm the successful deposition of the bilayer. The surface of the films plays a vital role in the Mo interface with the absorber layer. Atomic force microscopy was used to acquire the topographical information from the sputtered bilayer film. The resistivity, as measured using a four-point probe, of the Mo films deposited at different conditions was in the order of 10−6 Ω m while the resistivity of the bilayer was 0.60 × 10−6 Ω m.
Explanation:
Generally speaking you have much greater control in the overall quality of the samples grown by MBE as compared with the sputtering technique, which that also applies to lower dislocation density for MBE grown samples. In fact MBE technique allows control at the single atomic layer, something that one may not achieve using sputtering technique.