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Thin (<5 nm) air-oxidized Cr layers are deposited on the alumina output windows of radio-frequency klystron tubes to prevent electron multipactor by reducing the secondary electron emission yield of the alumina surface. The top several nanometers of these layers appear to be Cr2O3. To compare the measured surface properties of these layers with those of clean stoichiometric Cr2O3, quasibulk Cr2O3 layers were produced by wet-H2-firing magnetron-deposited Cr films on Cu substrates and characterized by x-ray photoelectron-, Auger electron-, and electron energy loss spectra and secondary electron emission yield measurements. Other properties measured were x-ray diffraction structure, sheet resistance, and optical reflectivity. In particular, the peak of the secondary electron yield was found to be ∼1.7, which is considerably higher than the <1 yield value reported earlier in the literature. The Cr2O3 Cr 2p x-ray photoelectron core level spectrum was curve-fit using Doniach–Sunjic line shapes and statistical fitting methods. It is shown that each 2p level is composed of three multiplet-split peaks 1.1 eV apart. In addition, the three 2p1/2 peaks are folded with a 2p3/2 3d satellite.

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