Static and dynamic electron holography of electrically active grain boundaries i

2019-11-04 18:16:52

grain potential gB electron holography

责任者: Johnson, K.D.;Dravid, V.P. 单位: Dept. of Mater. Sci. & Eng., Northwestern Univ., Evanston, IL, USA 来源出处: Interface Science(Interface Sci. (Netherlands)),2000/08/,8(2-3):189-98 摘要: The dynamics of electrostatic potential barriers at grain boundaries (GBs) in Nb-doped SrTiO3 bicrystals is investigated using a unique combination of bulk and in-situ TEM electrical measurements across isolated GBs, coupled with electron holography under in-situ applied bias. The Nb bulk-doped bicrystals exhibit a positive GB potential that suppresses reversibly under applied bias greater than the nonlinearity threshold in the current-voltage curve. This suppression is interpreted as a breakdown of the potential barrier to current transport. The results on Nb bulk-doped bicrystals have been compared to those in which Mn has been added as a grain boundary specific dopant. This acceptor doping of the grain boundary causes an appreciable increase in the grain boundary resistance and extension of the nonlinear regime. A preliminary account of static electron holography shows a relatively flat potential profile across the GB, indicating probable compensation of donor states at the GB core with Mn-acceptors. Interestingly, the phase profile under applied bias in this case exhibits a reversible “dip” at the GB which is interpreted as an activation of GB trap states due to Mn-acceptor dopants trapping extra electrons (the majority charge carriers) at the GB core, inducing a negative GB potential, and diminishing current transport until the threshold bias is exceeded. The synergistic combination of nanoscale TEM measurements coupled with traditional macroscopic electrical measurements is emphasized 关键词: electron holography;grain boundaries;strontium compounds;transmission electron microscopy;electrically active grain boundaries;static electron holography;dynamic electron holography;electrostatic potential barriers;TEM;bulk-doped bicrystals;current-voltage curve;acceptor doping;threshold bias;SrTiO3