Surface structure of hexagonal SiC surfaces: key to crystal growth and interface formation?

The atomic structure of the SiC(0001) surface was analysed using low-energy electron diffraction (LEED), scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES). Dependent on the preparation procedure, the s urface assumes different complex reconstruction phases. Using an ex situ hy drogen etching procedure, the sample surfaces can be passivated and are cov ered by a silicon oxide monolayer on top of the SiC bulk. In this state, th e surface could serve as a seed to grow epitaxial oxide films for MOS devic e applications. Subsequent preparation in ultra high vacuum (UHV) by anneal ing under simultaneous silicon deposition results in a complex (3 x 3) reco nstruction which proves to be almost free of dangling bonds. This surface s tructure favours the homoepitaxial single polytype growth by enabling incom ing particles to diffuse to steps, thus, allowing for an efficient step flo w growth mechanism. By further annealing, this phase can be transformed int o a (root 3 x root 3)R30 degrees phase, which is characterized by a Si adat om geometry. Variation of the preparation procedure for this structure allo ws the controlled switch of the surface stacking sequence from hexagonal to cubic stacking, which might be useful as a starting point to grow heterost ructures of different SiC polytypes. (C) 2000 Elsevier Science B.V. All rig hts reserved.