2D Single Crystals Research Articles

Electrical conductivity in silicon nanomembranes

Silicon nanomembranes (SiNMs) are very thin, large, free-standing or free-floating two-dimensional (2D) single crystals that can variously be flat, rolled into tubes, or made into any number of odd shapes, cut into millions of identical wires, used as conformal sheets, or chopped into tiny pieces. Because SiNMs are mostly surface or interface and little bulk, they have very interesting properties. We describe electrical conductivity in SiNMs. Because of trap states at the Si/SiO2 interface, bulk dopants become irrelevant to electronic transport when the membrane is thin enough. Replacing the oxide at one interface with the clean-Si surface reconstruction dramatically increases the nanomembrane conductivity. We provide a model for this behaviour. The dimer reconstruction surface states provide a means of ‘surface doping’. Other materials with proper highest-occupied molecular orbital (HOMO) or lowest-unoccupied molecular orbital (LUMO) bands, when deposited on the Si surface, should produce the same conductivity effect, affording a broad opportunity for membrane-based sensors.

Morphology and chemical composition microanalysis of 2D and 3D ordered structures on porous InP

AbstractPorous InP proves to be promising for use in nanotechnologies due to the possibility to fabricate ordered structures like two‐dimensional (2D) single crystals of nanopores. The main goal of this paper is to demonstrate that, along with 2D structures, one can fabricate 3D ordered porous structures on InP using alternative anodic current superimposed to a constant current or by pulsing the current. The dependence of the efficiency of pore diameter modulation upon the current frequency was explored. The stoichiometric composition of 2D and 3D porous InP structures was evidenced by chemical composition microanalysis. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)