Anodic oxidation of chemically hydrogenated Si(100)

The first oxidation stages of HF-etched Si surfaces were studied at potentials lower than 10 V by using conventional electrochemical techniques. The use of the droplet cell allows defining areas of less than 10 −3 cm 2 and a great number of measurements can be carried out in a relative short period of time. In this way, the first layer transformation may be studied before the surface becomes oxidised by the air humidity, assuring a better reproducibility. Potentiodynamic measurements of surface capacity give evidence of the formation of surface states generated by an adsorption process at the beginning of oxidation. As a consequence of an increasing OH − coverage, the potential drop is gradually displaced from the semiconductor space charge layer to the Helmholtz layer with increasing pH. A model for the oxidation of the H-terminal bonds based on a charge transfer via the conduction band was proposed.