No abstract

AFM-generated surface modifications are used to fabricate free-standing Si nanostructures. We employ the local electric field of a metal-coated AFM tip which is operated in air to selectively oxidize regions of a H-passivated Si surface. The resulting oxide, ∼ 1-2 nm thick, is used as a mask for deep selective etches of the unoxidized regions of Si. The etched structures reside on a buried oxide layer which is removed to produce free-standing Si wires and cantilevers. Due to the uniformity of the exposure and self-limiting etch processes, these structures are extremely uniform, which is a critical feature for nanometer-scale device applications.

A recent experiment by Takemura et al (2005 Proc. Joint 20th AIRAPT-43rd EHPRG (Karlsruhe, June-July)) on the pressure-induced hexagonal-closepacked phase of mercury, at pressures between 0.5 and 2 Mbar, has produced reliable data on lattice parameters, axial ratio and the equation of state. We have carried out first-principles calculations at 0 K of the structure parameters as functions of pressure by minimization of the Gibbs free energy. The agreement of the calculated lattice parameters and axial ratio with experiment is in the range of 1% for the lattice parameters and 2% for the axial ratio; the corresponding agreement for the equation of state is between 2 and 3%.