Inhibition of Metal Induced Crystallization in the System Ag/ZnO/a-Si:H

A systematic investigation has been made on the barrier properties of ZnO layer between n-doped a-Si:H and Ag metallization films in the structures (001)Si/SiO2/Ag/ZnO/a-Si:H:P and (001)Si/SiO2/a-Si:H:P/ZnO/Ag. Plasma assisted CVD deposition was used to produce a-Si:H (2500Å thick) highly P-doped films over thermally oxidized Si-wafers at 190 and 270°C. Transparent conductive ZnO:Al layers, 1000Å and lum thickness, and Ag films (1000Å thick) were deposited by sputtering. The polycrystalline ZnO layers were textured along the <0001> axis in the as-deposited state. The structures were annealed in vacuum in the temperature range from 300 to 700°C for 1/4 to 16h. X-ray diffraction and transmission electron microscopy studies demonstrated the a-Si:H:P stability against crystallization under ZnO buffer protection up to 700°C (when free a-Si crystallizes itself). The (111) peak position of the Ag reflection was used to show that while the Ag was always strained, the strain was partially relaxed when in contact with the 0.1 µm ZnO film, it developed additional strain when in contact with the lµm ZnO film.