Scanning Electron Microscope
Depth-Resolved Micro-Cathodoluminescence Spectroscopy
Extensive and unique facilities already exist at Ohio State that will enable completion of the proposed research tasks. State-of-the-art facilities are available to perform electron – excited cathodoluminescence spectroscopy (CLS) on a nanometer scale, either depth – wise or in – plane. A normal incidence, 0.5 – 25 keV JEOL 7800F UHV scanning electron microscope (SEM) is equipped with a < 5 nm minimum probe size for high spatial resolution laterally and a cold cathode Schottky field emitter for high energy (0.05%) resolution.This system has capabilities for acquiring spectral data for electronic defect, band gap, and temperature measurements, depth profile, line profile, secondary electron imaging, Auger chemical mapping, electron beam induced current (EBIC) and work function mapping of spectral features and morphology. EBIC stages also permit in-situ operation of high power electronics. It is equipped with high performance CLS optics and detection, i.e., 70% collection efficiency and 0.5 nm spectral resolution (2.4 mV or 20 cm-1 at 500 nm). The SEM chamber is equipped with an Oxford liquid He cold stage for temperature control ranging from 8 – 323 K for achieving high spectral resolution and high detection efficiency optical studies. The cold stage also has special cryoshrouding to minimize any surface contamination over and above the 0.8 x 10-11 Torr base vacuum pressure. The Oxford cold stage is designed to minimize drift rate during spectral acquisition. A CCD detector is now in place to further increase the speed of data acquisition, particularly for imaging quantum – scale structures and, despite beam blooming, preferentially exciting cathodoluminescence within such structures. A hemispherical energy analyzer (HSA) and variable energy, charge-neutralized Ar+ ion sputtering attachment permits high resolution AES spectra and depth profiling from the same spatial volumes probed by CLS. This quantum-scale UHV SEM is also interlocked with a process chamber for UHV cleaving, metallization, chemical processing and surface science analysis.