Complete and incomplete wetting of krypton and oxygen on graphite: Reentrant type-2 growth on a scale of substrate strength

Abstract

Reflection high-energy electron-diffraction (RHEED) studies of krypton and oxygen films on basal-plane graphite show that the low-temperature mode of growth of Kr is type 1 (complete wetting) whereas that of ${\mathrm{O}}_{2}$ is type 2 (incomplete wetting). The present results extend earlier RHEED measurements on other gases, and indicate the existence of two distinct regimes of incomplete wetting growth separated by a narrow region of complete-wetting growth. These results, together with published work on other films, are analyzed on an improved scale of relative interaction parameters. Arguments are presented to suggest that the mechanisms for incomplete wetting are different in the weak and strong substrate regimes. The present study also shows certain distinct structural relationships between crystallites and layered film in the incomplete wetting growth regime.