Optical absorption edge shifts in electrodeposited ZnO thin films

Poduska, Kristin M. and Ren, Tingting and Baker, Holly R. (2007) Optical absorption edge shifts in electrodeposited ZnO thin films. Thin Solid Films, 515 (20-21). pp. 7976-7983. ISSN 0040-6090

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Abstract

Electrodeposited wurtzite ZnO thin films exhibit shifts in their optical absorption edges with changes in thickness (0.2 – 2 μm), deposition potential (-0.80 V to -1.50 V), and aging time (days to months under ambient conditions). Increases in absorption edge energy are consistent with H+ incorporation as a shallow donor (Burstein-Moss effect) due to deposition in the presence of electrochemically evolved hydrogen. Diffuse reflectance spectroscopic data and Raman spectroscopic data show both potential- and thickness-dependent changes in defect levels and absorption edges, which suggests that H+ can be trapped in secondary defects. Such defects also increase the diffusion time for H+ and lead to the observed decay in absorption edge energy with aging.

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