Electron beam evaporation of oriented Nb films onto GaAs crystals in ultrahigh vacuum

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Abstract
Thin layers of Nb, 100–400 Å thick, were grown by electron beam evaporation on (100)GaAs substrates in a molecular beam epitaxy system. The crystallographic relationship between deposit and substrate was monitored in situ by reflection high‐energy electron diffraction, and after deposition by transmission electron microscopy and grazing‐incidence x‐ray diffraction. In spite of the large lattice mismatch (17%) and the low deposition temperature (40–400 °C), a quite well oriented deposit with the orientation (100)Nb∥(100)GaAs and [001]Nb∥[011]GaAs was obtained for a substrate temperature of ∼170 °C. Changing the substrate temperature from the optimum value of ∼170 °C in either direction resulted in a gradual deterioration of the epitaxy.