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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.

To accurately determine the thickness of ultrathin SiO, films, the influence of roughness on ellipsometric measurements must be examined. Although ellipsometry has been applied to study roughness, quantitative relationship of Si surface roughness measured by ellipsometry and atomic force microscopy is not available. This leads to difficulties in estimating the influence of roughness on oxide thickness measurements. Here we first establish the correlation of roughness measured by these two techniques. Based on such a relationship, we can explain the discrepancy of oxide thickness measured by ellipsometry and surface sensitive techniques.

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