Study of Cryogenic Unmasked Etching of "Black Silicon" with Ar Gas Additives.

The influence of Ar gas additives on ≪black silicon≫ formation is shown in this work. The way to achieve the conical shape of Si texture using low Ar dilution is demonstrated. Also, a possibility of silicon nanowire width reduction keeping a high density of array is shown. No damage to the Si structure caused by Ar plasma was detected. The introduction of Ar into the plasma also does not affect electrical properties. The lifetime value after cryogenic etching with 5 sccm Ar flow remains at the same level of 0.7 ms. The resulting black silicon has a low total reflectance of 1 ± 0.5% in the range of 450-1000 nm in the overall 100 mm Si wafer surface.

Friction of -bead macromolecules in solution: effects of the bead-solvent interaction.

The role of the bead-solvent interaction has been studied for its influence on the dynamics of an N-bead macromolecule which is immersed into a solution. Using a Fokker-Planck equation for the phase-space distribution function of the macromolecule, we show that all the effects of the solution can be treated entirely in terms of the friction tensors which are assigned to each pair of interacting beads in the chain. For the high-density as well as for the critical solvent, the properties of these tensors are discussed in detail and are calculated by using several (realistic) choices of the bead-solvent potential. From the friction tensors, moreover, an expression for the center-of-mass friction coefficient of a (N-bead) chain macromolecule is derived. Numerical data for this coefficient for "truncated" Lennard-Jones bead-solvent potential are compared with results from molecular dynamic simulations and from the phenomenological theoretical data as found in the literature.

Effects of the bead-bead potential on the restricted rotational diffusion of nonrigid macromolecules.

The influence of the bead-bead interaction on the rotational dynamics of macromolecules which are immersed into a solution has been investigated by starting from the microscopic theory of the macromolecular motion, i.e., from a Fokker-Planck equation for the phase-space distribution function. From this equation, we then derived an explicit expression for the configuration-space distribution function of a nonrigid molecule which is immobilized on a surface. This function contains all the information about the interaction among the beads as well as the effects from the surrounding solvent particles and from the surface. For the restricted rotational motion, the dynamics of the macromolecules can now be characterized in terms of a rotational diffusion coefficient as well as a radial distribution functions. Detailed computations for the rotational diffusion coefficient and the distribution functions have been carried out for HOOKEAN, finitely extensible nonlinear elastic, and a DNA type bead-bead interaction.