Effects of substrate temperature and atmosphere on the electrical and optical properties of Ga-doped ZnO thin films deposited by rf magnetron sputtering were investigated. The electrical resistivity of Ga-doped ZnO (GZO) films decreases as the substrate temperature increases from room temperature to 300°C. A minimum resistivity of 3.3 x 10 -4 Ω cm is obtained at 300°C and then the resistivity increases with a further increase in the substrate temperature to 400°C. This change in resistivity with the substrate temperature is related to the crystallinity of the GZO film. The resistivity nearly does not change with the O 2 /Ar flow ratio, R for R < 0.25 but increases rapidly with R for R > 0.25. This change in resistivity with R is also related to crystallinity. The crystallinity is enhanced as R increases, but if the oxygen partial pressure is higher than a certain level (R = 0.25 ± 0.10) gallium oxides precipitate at grain boundaries, which decrease both carrier concentration and mobility. Optical transmittance increases as R increases for R < 0.75. This change in transmittance with R is related to changes in oxygen vacancy concentration and surface roughness with R.
The state-selective dissociation dynamics for anionic and excited neutral fragments of gaseous SiCl 4 following Cl 2p and Si 2p core-level excitations were characterized by combining measurements of the photoninduced anionic dissociation, x-ray absorption and UV/visible dispersed fluorescence. The transitions of core electrons to high Rydberg states/doubly excited states in the vicinity of both Si 2p and Cl 2p ionization thresholds of gaseous SiCl 4 lead to a remarkably enhanced production of anionic, Si − and Cl − , fragments and excited neutral atomic, Si * , fragments. This enhancement via core-level excitation near the ionization threshold of gaseous SiCl 4 is explained in terms of the contributions from the Auger decay of doubly excited states, shake-modified resonant Auger decay, or/and post-collision interaction. These complementary results provide insight into the state-selective anionic and excited neutral fragmentation of gaseous molecules via core-level excitation.
Al-doped ZnO (AZO), Ga-doped ZnO (GZO), and GZO/AZO thin films were deposited on polymer (PET) substrates with and without a ZnO buffer layer by using an r.f. magnetron sputtering technique and their structural, electrical, and optical properties were investigated to develop transparent conductors for flexible display applications. The transparent conducting oxide (TCO) films with a ZnO buffer layer showed better electrical and optical properties than those without a buffer layer. The crystal quality of the former was better than the latter, the electrical resistivity of the former is lower than the latter, and the transmittance of the former was also as high as that of the latter. The optimum buffer layer thickness with which the lowest resistivity of GZO/ AZO/ZnO films was obtained was found to be 150Jlm. On the other hand it was found that there was little difference in electrical, and optical properties between AZO, GZO and GZO/AZO films with a ZnO buffer layer.
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