Deterministic Nanopatterning of Diamond Using Electron Beams.

Diamond is an ideal material for a broad range of current and emerging applications in tribology, quantum photonics, high-power electronics, and sensing. However, top-down processing is very challenging due to its extreme chemical and physical properties. Gas-mediated electron beam-induced etching (EBIE) has recently emerged as a minimally invasive, facile means to dry etch and pattern diamond at the nanoscale using oxidizing precursor gases such as O2 and H2O. Here we explain the roles of oxygen and hydrogen in the etch process and show that oxygen gives rise to rapid, isotropic etching, while the addition of hydrogen gives rise to anisotropic etching and the formation of topographic surface patterns. We identify the etch reaction pathways and show that the anisotropy is caused by preferential passivation of specific crystal planes. The anisotropy can be controlled by the partial pressure of hydrogen and by using a remote RF plasma source to radicalize the precursor gas. It can be used to manipulate the geometries of topographic surface patterns as well as nano- and microstructures fabricated by EBIE. Our findings constitute a comprehensive explanation of the anisotropic etch process and advance present understanding of electron-surface interactions.

The characteristic study and sonocatalytic performance of CdSe-graphene as catalyst in the degradation of azo dyes in aqueous solution under dark conditions.

The sonocatalytic degradation of azo dyes; methyl orange (MO) and rhodamine B (RhB) were studied catalyzed by cadmium selenide (CdSe)-graphene in dark ambiance. The CdSe-graphene composites were prepared by simple hydrothermal method. The characterizations of composites were studied by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), specific surface area (BET) and with energy dispersive X-ray (EDX). The UV-spectroscopic analysis of the dyes was done by measuring the change in absorbance. The degradation of the organic dyes was calculated based on the decrease in concentration of the dyes with respect to regular time intervals. The rate coefficients for the sonocatalytic process were successfully established and the reusability tests were done to test the stability of the used catalysts.