Kelvin Probe Microscopy and Cathodoluminescence Microanalysis of the Irradiation Induced Modification of Insulating Mate
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Kelvin Probe Microscopy and Cathodoluminescence Microanalysis of the Irradiation Induced Modification of Insulating Materials. Marion A. Stevens-Kalceff School of Physics and Electron Microscope Unit, University of New South Wales, Sydney, 2052, NSW, AUSTRALIA ABSTRACT A combination of Kelvin Probe Microscopy (KPM) and Cathodoluminescence (CL) microanalysis has been used to characterize ultra pure silicon dioxide (SiO2) exposed to electron irradiation in a Scanning Electron Microscope. Charged beam irradiation of poorly conducting materials results in the trapping of charge at pre-existing or irradiation induced defects thereby inducing a localized electric field within the irradiated micro-volume of specimen. The residual surface potentials associated with the localized electric field have been mapped using KPM. Evidence of electro-diffusion and defect micro-segregation in charged beam irradiated SiO2 is observed. The associated mobile defect species are identified using CL microanalysis techniques. The high correlation between KPM and CL images confirms the significant influence of localized potentials on the microstructure of technologically important SiO2. INTRODUCTION Scanning electron and scanning probe microscopies are analytical techniques that are commonly used to characterize materials at high spatial resolution. It is necessary to assess and characterize the perturbing influences of these experimental probes on the specimens under investigation. In this work, the significant influence of electron beam irradiation on poorly conducting materials has been assessed by a combination of Cathodoluminescence Microanalysis (spectroscopy and microscopy) and Kelvin Probe Microscopy. Cathodoluminescence is the nonincandescent emission of light resulting from the electron irradiation. CL microscopy and spectroscopy in a Scanning Electron Microscope (SEM) enables high spatial resolution and high sensitivity detection of defects in poorly conducting materials. Local variations in the distribution of defects can be non-destructively characterized with high spatial (lateral and depth) resolution by adjusting electron beam parameters to select the specimen micro-volume of interest [1]. Kelvin Probe Microscopy (KPM) is a Scanning Probe Microscopy technique in which longrange Coulomb forces between a conductive atomic force probe and the specimen enable the surface potential to be characterized with high spatial resolution [2]. EXPERIMENTAL DETAILS Homogeneous ultra-pure synthetic single crystals of c-cut α-quartz (SiO2) have been investigated [3]. Technologically important SiO2 is a poor electrical conductor, and is often incorporated into devices that operate in irradiation environments. The SiO2 specimens have been continuous irradiated with a stationary 30keV electron beam of radial symmetry and 4µm diameter at normal incidence. Electron irradiation induces reproducible characteristic permanent changes in the surface topography of SiO2 enabling the implanted regions to be unambiguously located for investigation [
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