Unlike other thin film deposition techniques, close spaced sublimation (CSS) requires a short source-substrate distance. The kind of source used in this technique strongly affects the control of the deposition parameters, especially the deposition rate. When depositing CdTe thin films by CSS, the most common CdTe sources are: single-crystal or polycrystalline wafers, powders, pellets or pieces, a thick CdTe film deposited onto glass or molybdenum substrate (CdTe source-plate) and a sintered CdTe powder. In this work, CdTe thin films were deposited by CSS technique from different CdTe sources: particles, powder, compact powder, a paste made of CdTe and propylene glycol and source-plates (CdTe/Mo and CdTe/glass). The largest deposition rate was achieved when a paste made of CdTe and propylene glycol was used as the source. CdTe source-plates led to lower rates, probably due to the poor heat transmission, caused by the introduction of the plate substrate. The results also showed that compacting the powder the deposition rate increases due to the better thermal contact between powder particles
CdTe thin films are used as absorber layer in CdS/CdTe solar cells. The microstructure of this absorber layer plays a fundamental role in photovoltaic conversion and can be controlled by the deposition parameters used during the film growth. In this work, CdTe thin films were deposited by the CSS method onto glass substrates previously covered with In 2 O 3 :Sn. The effects of pressure, source temperature and substrate temperature on the microstructural properties of the films were studied. The properties were mainly influenced by the pressure, the presence of oxygen in the reaction chamber, and the substrate temperature. For films deposited under an argon atmosphere, an increase in grain size and a reduction of the texture were observed as the pressure and substrate temperature were increased. The introduction of oxygen in the atmosphere led to a decrease in the deposition rate and affected the microstructure and composition of the film. Films deposited under an argon-oxygen atmosphere have smaller grains than those deposited under argon and are richer in Te. The addition of oxygen to the atmosphere apparently did not result in the formation of oxides.
ZnO thin films were produced by argon plasma assisted electron beam vacuum evaporation and d.c. magnetron sputtering deposition techniques. ZnO films are used in solar cells as transparent contact in heterojunction cells, and can be deposited on a variety of substrates by different techniques, including electron beam deposition and sputtering and laser ablation. ZnO thin films were prepared for photovoltaic applications and the structural properties were studied. The results showed that the sputtering and the vacuum evaporation techniques resulted, respectively, in a textured ZnO and ZnO plus Zn mixed phases. The annealing of the vacuum evaporation ZnO films resulted in films with high crystallinity.
Undoped zinc oxide thin films were grown at room temperature using two techniques: plasma deposition (PD) and electron beam evaporation in an argon atmosphere. PD offers some advantages, such as low ion damage and low deposition temperature. The optical transmittance of the films deposited by both methods was higher than 80% in the near UV-VIS range; the energy band gap and index of refraction agree with values reported in the literature. The resistivity of films grown by PD was 3.1 Â 10 À2 V cm, lower than the value of 1.2 Â 10 À1 V cm found for plasma assisted e-beam evaporated films.
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