Atomic Bridging and Barrier-Type AC Surface Photovoltage Measurements on Iron- and Copper-Contaminated Silicon Surfaces

Abstract

The rise time of the alternating current (ac) surface photovoltage (SPV) of n-type silicon (Si) contaminated by Fe and/or Cu aqueous solutions was investigated. After a rinse time of about 1000 min in Fe contaminated water, three monolayers (0.59 nm) of oxide were formed, with a resulting incorporation of Fe. The variation of ac SPV signals indicated the appearance of a negative charge corresponding to the increasing concentration of Fe on surface of the Si wafer. This negative charge can be accounted for by postulating a bridging mechanism between trivalent Fe ions, and quadrivalent Si ions, forming an network in the native oxide. In contrast to Fe, Cu was deposited at the beginning of the rinsing on partially hydrophobic n-type Si surfaces as an Cu atomic layer or Cu particles (maximum Cu concentration: around resulting in a Cu-Si contact. Because the reduction potential of is larger than that of Si, the process was accomplished through electron capture. It is postulated that the Cu-Si contact may have formed a Schottky barrier between the Cu and n-type Si, resulting in the occurrence a so-called barrier-type ac SPV. This may prove to be a promising method for fabricating atomic layer Schottky devices. © 2003 The Electrochemical Society. All rights reserved.