In situ and ex situ structural characterization of β-FeSi2 films epitaxially grown on Si(111)

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Abstract
The structural properties of β‐FeSi2 films grown on Si(111) are studied by means of several techniques. The films were grown in ultrahigh vacuum by solid phase epitaxy. The as‐deposited Fe films were studied in situ by low energy electron diffraction (LEED) and Auger spectroscopy. Fe thicknesses were calibrated by Rutherford backscattering. The behavior of the FeMVV/SiLVV Auger peaks ratio intensity as a function of Fe thickness indicates a Stranski–Krastanov mode of growth. Annealing of the Fe layers at temperatures between 400 and 600 °C led to the β‐FeSi2 formation. Sharp LEED patterns typical of the β‐FeSi2 orthorhombic structure were obtained. X‐ray double‐crystal diffraction was carried out on a film about 200 Å thick in order to determine the lattice mismatch between the β‐FeSi2 and the Si(111) planes accurately. The measured value of (2.1±0.1)×10−2 unambiguously indicates that (101) epitaxy takes place only on Si(111). No elastic strain of the overlayer was evident. The full width at half maximum of the overlayer diffraction peak indicates a good crystalline quality. An upper limit for mosaic spread was determined to be about 0.05°.