Ph.D. Tezi Görüntüleme | |||||||||||||||||||||
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| Summary: In this study, the effect of the cold substrate temperature on the CdS thin films, which are used as optical window in solar cells, have been investigated. Also the effect of the cold substrate temperature on Cu/CdS/SnO_2 Schottky diode structure has been investigated. CdS thin films were prepared on glass substrate by vacuum evaporation in quasi-closed volume. The substrate temperatures were selected as 300, 250, 200, 150 and 100 K. The structural, electrical and optical properties of these thin films were investigated. For preparation of Schottky diode structure on SnO_2 coated glass substrate the CdS thin films were produced at substrate temperature 300 K and 200 K. CdS thin films have hexagonal crystal structure. Miller indices corresponding to the peaks in the pattern were determined as (100), (002) and (004). Reflection from (002) plane was the most intense for all samples. Although the thickness for the samples prepared at relatively low temperature (1.6 µm) is higher than that of the sample prepared at 300 K (1.0 µm) the former had approximately 10 % smaller particle size. It is determined that lattice parameter c increased from 6.662 Å to 6.711 Å with decreasing substrate temperature. Also it is observed that band gaps of samples increased from 2.40 eV to 2.42 eV as the substrate temperature was decreased. The carrier concentration (~ 5×10^(17) cm^(-3)) of the sample prepared at 300 K is found to be larger than that of the one prepared at cold substrate (~ 5×10^(15) cm^(-3)). Tunnelling mechanism was found to be the dominant conduction mechanism above 250 K for the sample prepared at 300 K. However, thermionic emission mechanism was the dominant conduction mechanism above 250 K for samples prepared at cold substrates (200 K, 100 K).The Schottky diode, Cu/CdS/SnO_2, produced at a substrate temperature of 200 K had a larger barrier height (0.64 eV) than that of the Schottky diode (0.57 eV) produced at 300 K. All diodes have larger ideality (5.4 for 300 K, 3.1 for 200 K) factor than 1. Tunnelling was the dominant conduction mechanism for these diodes. Keywords : CdS, Cold Substrate, Schottky Diode, Current Transport Mechanism | |||||||||||||||||||||