The effects of a change in the chemical environment of an atom in a surface region are manifested in several subtle ways on the measured Auger electron spectra. The first, a shift in the energies of the Auger electrons, is the result of charge transfer and is a measure of the valence state of an atom. Examples of this effect are the oxidation results on refractory metals presented here. It is found that measurable changes are found even for submonolayer coverages of oxygen on an otherwise clean surface. The second main effect is a change in the shape of a complex spectrum, which occurs when some of the electrons involved in this Auger process are valence electrons. The best example of this behavior is that of carbon, and it is found that these complex spectra serve as a fingerprint for the identification of the form of the carbon at a surface. Problems and opportunities for the exploitation of both these effects are discussed, the data included here being illustrative of the usefulness of this type of measurement.

Gallium oxide (Ga₂O₃) thin films were made by sputter deposition employing a Ga₂O₃ ceramic target for sputtering. The depositions were made over a wide range of substrate temperatures (T_s), from 25 to 600 °C. The effect of T_s on the chemical bonding, surface morphological characteristics, optical constants, and electrical properties of the grown films was evaluated using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and four-point probe measurements. XPS analyses indicate the binding energies (BE) of the Ga 2p doublet, i.e., the Ga 2p_3/2 and Ga 2p_1/2 peaks, are located at 1118.0 and 1145.0 eV, respectively, characterizing gallium in its highest chemical oxidation state (Ga³⁺) in the grown films. The core level XPS spectra of O 1s indicate that the peak is centered at a BE ∼ 531 eV, which is also characteristic of Ga-O bonds in the Ga₂O₃ phase. The granular morphology of the nanocrystalline Ga₂O₃ films was evident from AFM measurements, which also indicate that the surface roughness of the films increases from 0.5 nm to 3.0 nm with increasing T_s. The SE analyses indicate that the index of refraction (n) of Ga₂O₃ films increases with increasing T_s due to improved structural quality and packing density of the films. The n(λ) of all the Ga₂O₃ films follows the Cauchy's dispersion relation. The room temperature electrical resistivity was high (∼200 Ω-cm) for amorphous Ga₂O₃ films grown at T_s = RT-300 °C and decreased to ∼1 Ω-cm for nanocrystalline Ga₂O₃ films grown at T_s ≥ 500–600 °C. A correlation between growth conditions, microstructure, optical constants, and electrical properties of Ga₂O₃ films is derived.