Influence of surface and interface properties on the electrical conductivity of silicon nanomembranes

We investigate the electronic transport properties of silicon nanomembranes (SiNMs) on oxide by the van der Pauw method. SiNMs, thin sheets of single-crystal Si, feature an extreme sensitivity of electronic transport properties to surface and interface condition, because of the large surface-to-volume ratio. Removing the top oxide with HF reduces the sheet resistance four orders of magnitude for the thinnest NMs ($\sim $20nm) [1], a value much greater than can be accounted for by simply reducing interface traps. We compare SiNMs prepared with HF to H terminations prepared via CVD, to identify which factors control this change in conductivity. We also perform a forming gas (5{\%} H$_{2}$ in N$_{2})$ anneal on oxidized NMs. The sheet resistance drops relative to unannealed NMs, demonstrating the influence of states at Si/SiO$_{2}$ interfaces. A qualitative model that includes these several factors influencing the sheet resistance is described. \\[4pt] [1] Scott S. \textit{et al}, ACS Nano 3 (2009) 1683.