Electron beam induced current and scanning tunnelling spectroscopy correlative study of and CdTe crystals
A combined scanning electron microscope-scanning tunnelling microscope (SEM-STM) system has been used to characterize and CdTe crystals. The electron beam induced current (EBIC) mode of the SEM shows the existence of inhomogeneities in the electronic behaviour of the samples, mainly related to the presence of subgrain boundaries and precipitates. Current imaging tunnelling spectroscopy images and the related normalized differential conductance curves, obtained with the STM, reveal the electronic inhomogeneities at a finer scale. In particular, local variations of the band gap were shown by the conductance curves in regions with strong EBIC contrast. SEM- and STM-based techniques in a combined instrument appear to be complementary characterization techniques.