Local investigation of the electrical properties of grain boundaries

Abstract

Abstract We present the recent development of three related techniques for the local investigation of grain boundaries (GBs): grain boundary electron-beam-induced current (GB EBIC), grain boundary light-beam-induced current (GB LBIC) and local grain boundary photoconductance spectroscopy (GB PCS). Two grains which are separated by a common GB are ohmically connected to a current amplifier. In GB EBIC a focused electron beam and in GB LBIC a focused light beam of above band gap energy is scanned across the GB. At GBs with a two-dimensional coherent potential barrier a characteristic dark-bright signal is observed which is directly related to the recombination current through the boundary. By applying a small bias, the local attenuation of the potential barrier height as a function of the injection level can be determined. In GB PCS a beam of monochromatic subband gap light is used. By applying a bias, the change in the GB barrier height due to the excitation of carriers into the GB trap states can be detected by the change in the over-barrier current. By varying the light energy, a section of the local distribution of states in the gap can be determined.