HIGH-SPATIAL-RESOLUTION ANALYSIS OF GE LAYERS IN SI

This paper describes the results of preliminary experiments to characterize the focused-probe properties of a new 200 kV field-emission TEM/STEM. Probe currents are measured using a Faraday stage. Probe size is measured by high-angle annular-dark-field STEM line scans across a Ge monolayer embedded coherently in single-crystal silicon. These measurements show that the instrument is capable of producing probes with a full-width at half-maximum of order 3 nm and less with at least a few tenths of a nanoampere of current. This is sufficient to execute X-ray microanalysis measurements with good signal-to-noise at nanometer length scales. As part of the same set of experiments, this work shows experimentally that the HAADF scattering from pure amorphous silicon is stronger than that from pure crystalline silicon, possibly due to the increased Debye-Waller factor and the absence of channeling effects in the amorphous structure.