Surface dielectric tunnel barrier induced by Mn doping in SnO_2 micro- and nanostructures

Abstract

Electrical properties of undoped and Mn doped SnO2 microplates and rods are studied by electron beam induced current (EBIC) in a scanning electron microscope (SEM), and I-V curves acquired at room temperature. AFM measurements reveal the formation of numerous terraces at the (-101) surface of the analyzed Mn-doped SnO2 microplates, which also exhibit high carrier recombination processes at their central region, as confirmed by combined EBIC and cathodoluminescence (CL) measurements. A diffusion length for minority carriers about 205nm is obtained by EBIC measurements. Different electrical conduction mechanisms, such as Fowler-Nordheim, direct tunneling and Poole-Frenkel, are evaluated in the electrical analysis of the samples. Mn doped microplates show lower conductivity than the undoped microds. Moreover the height of the surface tunnel barrier is increased by Mn doping, as confirmed by the analysis of the I-V curves acquired under transversal configuration. A value of the relative dielectric constant E-r about 7.3 is estimated for the probed SnO2 microstructures.