RHEED intensity oscillation of C₆₀ layer epitaxial growth

Intensity oscillations of reflection high-energy electron diffraction are observed during a C₆₀ layer epitaxial growth on GaAs (1 1 1)B, (1 1 4)A and (1 1 4)B substrates. Frequencies of the oscillations coincide well with growth rates of C₆₀ layers, suggesting that C₆₀ layers grow by layer-by-layer growth mode as with GaAs and other semiconductor materials. Anomalous oscillations are observed in the initial stage of a C₆₀ layer growth on GaAs (1 1 1)B surface with (2×2) reconstruction. These oscillations indicate that the C₆₀ first-layer growth is completed at approximately half monolayer coverage. This phenomenon is explained by a model that C₆₀ adsorption sites are limited due to As-trimers adsorbed on GaAs surface. Clear oscillations are observed during a C₆₀ layer growth on GaAs (1 1 4)A substrate, and X-ray diffraction peaks of the layer are sharp. In contrast, no oscillation is detected during the growth on the (1 1 4)B substrate, and these layers exhibit poor X-ray diffraction characteristics. Thus, the C₆₀ epitaxial layer growth on GaAs substrates is strongly affected by the GaAs surface reconstruction and polarity.