Energy band effects in Si L ELS edges of Si and SiC

Abstract

Interpretation of near-edge core shell fine structure in electron energy loss spectra (ELS) can aid in the phase identification of small areas of sample in an analytical transmission electron microscope. Previously we performed extended Hückel molecular orbital (EHMO) calculations on a series of tetrahedral Si clusters. The resulting energies and wavefunctions were used to calculate 1st Born inelastic scattering cross sections for discrete transitions to molecular states. We have extended this work to include the effects of translational symmetry in crystalline materials - energy band effects.Si and α-SiC samples were prepared by crushing, chemical dissolution, or grinding followed by ion beam thinning. A cryogenic stage (80K) was used to eliminate specimen contamination. ELS spectra were acquired with a 100keV converged electron probe (100Å diameter at specimen, 13mrad convergence angle) from single scattering regions (<500Å thick). Samples were tilted into kinematic diffracting conditions, with the Si near the [111] and SiC near the [0001] zone axes.