The thermal stability of amorphous thin films deposited by molecular-beam deposition directly on (001) Si was investigated by high-resolution transmission electron microscopy (HRTEM), transmission infrared absorption spectroscopy (IRAS), and x-ray diffraction (XRD). IRAS indicated that the as-deposited films contained of at the interface between and silicon. XRD studies showed that the films remained amorphous after annealing in at , although HRTEM showed structural order on an length scale even in the as-deposited films. By , the had started to crystallize and formed a thick Sc-deficient interlayer between it and silicon.
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The nominal film thicknesses given were calculated from the fluxes of the molecular beams (measured by a quartz crystal microbalance), assuming that the amorphous films had the density of crystalline . The areal density of lanthanum and scandium in the films was confirmed by RBS. The thicknesses of the amorphous films were also measured by TEM and showed approximately three times the thicknesses determined assuming the density of crystalline . These differences will be discussed elsewhere.
