Increased cathodoluminescence signal intensity from surfaces prepared using xenon vs gallium focused ion beam

Cathodoluminescence (CL) is a powerful technique for the analysis of optoelectronic materials and devices. When used with Scanning Electron Microscopy (SEM) or Scanning Transmission Electron Microscopy (STEM), it provides bandgap and defect analysis with high spatial resolution. When used with STEM, it is capable of mapping with nanometer resolution. The technique has important applications in the analysis of solar cells, light-emitting diodes, and lasers. Sample preparation is carried out using a focused ion beam (FIB) to produce a cross section or bevel for SEM or a thin lamella for STEM. A gallium FIB is commonly used for sample preparation, although the recent development of a xenon plasma FIB is now an alternative. Maximizing the CL signal intensity is key to obtaining high CL spectral resolution and high spatial resolution mapping. Using single-crystal CdTe, we show that the use of Xe+ ion milling results in more than a factor of two increase in the CL signal strength. The improvement in signal is attributed to the reduced depth of damage caused by xenon compared to gallium ion milling at the same beam energy. The higher signal intensity provided by the use of xenon ion milling results in higher CL signal intensity, improved image contrast, and signal to noise.