Structural and electrical characterisation of semiconductor materials using a nuclear microprobe

High-resolution imaging techniques (submicron) have not traditionally been the domain of MeV ions. Instead, this domain is occupied by a vast array of techniques that utilise scanned low-energy ion beams (keV ion microprobe), electrons (transmission or scanning electron microscopy), light (near field microscopy) or all variants of scanning probe microscopies. Techniques that utilise focused X-rays are also developing. Now, with a nuclear microprobe, high-energy ion beams have begun to enter this domain, bringing a range of unique techniques for making images. With a MeV ion beam focused to a probe smaller than 1 mu m, conventional techniques like Rutherford (and non-Rutherford) backscattering spectrometry and particle induced X-ray emission may be used to image and analyse the composition and structure of microscopic regions of inhomogeneous specimens. New ion beam analysis techniques have been developed specifically for use with microbeams. These include ion beam induced charge for imaging charge transport characteristics in materials to ion microtomography for making non-destructive 3-D maps of mass density and elemental composition. Another novel technique is ionoluminescence, which may be used to map various electronic properties of the material. Presented here are some examples of these imaging techniques in a wide variety of semiconductor materials including diamond, HgCdTe, polycrystalline silicon and a mineral semiconductor crystal: pyrite. In all these examples, the specimens display structural inhomogeneities on the scale of 10 mu m, making it essential to employ a focused beam. Present limitations to taking imaging with focused MeV ions into the nanometre resolution domain are also discussed. (C) 1998 Elsevier Science B.V.