Surface characterization of Hg0.7Cd0.3Te native oxides

Abstract

Ultraviolet photoelectron spectroscopy (UPS), x-ray photoelectron spectroscopy (XPS), and electron energy loss spectroscopy (ELS) were used to characterize the surfaces of Hg0.7Cd0.3Te native oxide films grown by air exposure, ozone treatment, oxygen plasma, and electrochemical anodization. The surfaces of the air-grown, plasma-grown, and anodically grown native oxides were found to all be relatively rich in Cd, while the ozone oxide was rich in Hg. Two ELS absorption edges were detected at ∼2.1 and ∼3.6 eV and are attributed to an oxide trap state and the fundamental band gap of the oxide, respectively. Changes in the ELS and XPS spectra following prolonged electron beam exposure resulted from a loss of Hg from the oxide and incomplete bonding of Te in the oxide. The electron beam induced changes were much more dramatic in the ozone oxide spectrum than for any of the other samples studied. XPS analysis of the interface of an air-grown native oxide which was subsequently covered with a thin layer of photochemical SiO2 demonstrated that the air-grown native oxide was partially, but not completely, reduced by chemical reaction with SiH4 during the deposition of SiO2. A generic energy band diagram of the native oxide Hg0.7Cd0.3Te interface is constructed and discussed in terms of its implications for the passivation of Hg1−xCdxTe surfaces.