In this work, w e first demonstrate the interface roughness as a function o f oxide thickness. For intentionally roughened samples, interface roughness always decreases as oxide thickness increases. O n the other hand, samples only treated with a regular preoxidation clean show a different quantitative trend. For such samples, the interface is initially roughened, and then becomes smooth as oxide thickness increases. This implies that the evolution o f interface roughness depends on h o w samples are pre ared Our results suggest that the most important factor dictating interface morphology is the oxide thickness, rather txan thermal history and growth ambient. Instead o f using simple statistical descriptions, such as root-mean-square roughness, w e also employ power spectral density o n atomic force microscopy image analysis. Our results suggest that the roughness components o f higher spatial frequencies are greatly reduced during thermal oxidation. ABSTRACT The photovoltage and the fill factor o f (indium-tin oxide (ITO)/silicon oxide/polycrystalline n-Si) junction solar cells are increased b y immersing S i i n a potassium cyanide solution before the deposition o f a n I T 0 film. Measurements o f the temperature dependence o f the dark current-voltage curves show that the mechanism o f the current flow through the S i depletion layer is changed from trap-assisted multistep tunneling t o thermionic-assisted tunneling b y the KCN treatment, indicating a decrease in the density o f the trap states i n the S i depletion layer. Measurements o f the electrode conductance also show that the trap density is greatly reduced b y the KCN treatment. The improvement o f the electrical characteristics is attributed t o the decrease i n the trap density and an increase i n the barrier height i n n-Si caused b y t h e inclusion o f cyanide ions at t h e oxide/Si interface and/or i n t h e silicon oxide layer.