Atomic and electronic structure of interfaces at sic studied by indirect super HRTEM and electron spectroscopyn imaging

摘要

Obtaining electronic and atomic structure of material simultaneously is very important for developing the nano-technology. In this paper, we demonstrate that atomic and electronic structure of an interface can be extracted with combination of Gerchberg-Saxton indirect microscopy and electron spectroscopy imaging (ESI) technique. Basically, Gerchberg-Saxton algorithm includes two projections. Projection in the real space is a maximum entropy (ME) de-convolution process and in reciprocal space is an amplitude substitution process. It has been shown that Gerchberg-Saxton algorithm can extend the structural resolution to near 0.1 nm. An application case of Gerchberg-Saxton algorithm to solve the atomic structure for 3C-polytypic SiC boundary is shown. ESI spectrum processed by FFT interpolation, maximum entropy de-convolution and wavelet transformation allow us to extract 2-dimensional map of the sp~2/sp~3 with a sub-nanometer resolution. Grain boundary and interface at SiC are good candidates for this study, since the bond distance of Si-C is slightly less than 0.1 nm which is not routinely resolvable using a FEG TEM and Si-L (99eV) and C-K-edges (283 eV) locate in a reasonable energy range. The resultant electronic structure can be compared with that calculated using WIEN97. An example of quantitative analysis on 2-dimensional sp~3/sp~2 map deduced from the C K-edge of ESI spectra acquired from 6H-SiC is given.