Formation of epitaxial SiC nanocrystals

Abstract

Epitaxial 3C–SiC grains are formed at 1190 °C in the top region of silicon, when Si wafers coated by SiO 2 are annealed in CO atmosphere. The formed SiC grains are 40–50 nm high and 100 nm wide in cross-section and contain only few defects. Main advantage of the method is that the final structure is free of voids. The above method is further developed for the generation of SiC nanocrystals, embedded in SiO 2 on Si, and aligned parallel with the interface. The nanometer-sized SiC grains were grown into SiO 2 close to the Si/SiO 2 interface by a two-step annealing of oxide covered Si: first in a CO, than in a pure O 2 atmosphere. The first (carbonization) step created epitaxial SiC crystallites grown into the Si surface, while the second (oxidation) step moved the interface beyond them. Conventional and high resolution cross-sectional electron microscopy showed pyramidal Si protrusions at the Si/SiO 2 interface under the grains. The size of the grains, as well as their distance from the Si/SiO 2 interface (peak of pyramids) can be controlled by the annealing process parameters. The process can be repeated and SiC nanocrystals (oriented in the same way) can be produced in a multilevel structure.