Thermal stability of LiF thin films on 6H-SiC(0001) surface

Abstract

The morphology and the temperature induced changes of LiF thin layers deposited on three different kinds of 6H-SiC(0001) surfaces have been investigated by the atomic force microscopy technique. As the substrates used were: a single crystal of Si-terminated on-axis oriented additionally hydrogen-etched, off oriented 3.5° from basal plane and with an epitaxial adlayer grown on the Si- or on the C-face surface. For all the systems investigated, independently of the substrate, the LiF grows uniformly at room temperature, and even for rather thick films (estimated to be about 5 nm), terraces are still visible. However, in each case the LiF layers are not temperature stable, and when the samples are heated (starting from ∼600 K), regular grains with radius up to 40 nm and with height up to 9 nm are formed (for initial layers thickness 2.5 nm). Subsequent sample heating procedures cause LiF desorption and consequently, a decrease of the dimensions of the islands.