ABSTRACT
In nanoarchitectonics, the advanced technology of directional etching is highly demanded for the fabrication of modern electronic device with high anisotropy ratio of structures. To facilitate the manufacturing processes, in this study we focus on establishing a phase-field model with a directional source term to simulate the dynamics of morphological formation and profile evolution in a crystalline substrate. Additionally, the influences of the etching rate, the degree of etching directionality, and the oblique angle on the structural characteristics are also taken into consideration to offer a broad perspective on the directional etching technologies. In the numerical analyses, the featured morphologies are elucidated by the dominant factors based on the mechanism of the profile evolution. The etched surface tends to be roughened with the crystallographic characters, while the kinetics of directional etching plays a prevailing role in the morphological formation. As the surface diffusion of substrate becomes a controlling factor, a flattened profile of the etched surface would be formed even in a condition of high directionality or high oblique angle. The featured surface morphologies, including the pyramid, ripple, mounds and etch pits, are reproduced numerically, and these simulation results correspond well with the observations of directional etching experiments. This study provides the fundamental knowledge and detailed information for the advanced application of the directional etching technology.
ABSTRACT
The technique of the anisotropic wet chemical etching had turned into one of the widely used processes for manufacturing the functional materials in microelectromechanical systems. To better understand the issues of growth mechanisms for the characteristic surface morphologies during an anisotropic chemical etching, in this study the formation and evolution of surface structures were investigated by numerical simulation methods. A chemical etching model was established on the basis of chemical reaction and atomic diffusion. Affecting by the anisotropy of the crystalline structure and etching rate, various featured surface morphologies, including the rippling surface, cusp-like hillock, and nano-pyramid, were numerically developed in accordance with the etching conditions. These characteristic structures were also in well agreements with the corresponding experiments. From the theoretical point of view, the surface morphologies were critically influenced by the kinetic factors of the anisotropic etching rate and the atomic diffusion. With the enhancement of theoretical work in the formation mechanism for the anisotropic chemical etching, the practical technique would possess a more competitive advantage for the wide applications in the fields of the functional materials fabrication.
ABSTRACT
The faceted nanoparticle synthesized by ion implantation, such as Zn, Cu or Ag nanoparticles, is one of the promising materials for the next generation of optical devices. To understand and better control the manufacturing processes of ion implantation, a theoretical model is applied to investigate the formation and evolution of faceted nanoparticles under various experimental conditions of implantation processing. In this study, the mechanisms of the anisotropic interfacial energy and kinetics with different ion distributions are taken into consideration to demonstrate the role of the crystallographic symmetry, ion energy and temperature on the faceted nanoparticles formation in a crystalline matrix. As presented in the numerical results, the morphological shape of the nanoparticles is mainly affected by the crystallographic symmetry, while the distribution of the precipitates is principally determined by the ion energy. For the condition of high-temperature implantation, a high mobility of ions causes the characteristic length of nanostructures to increase and creates a coarsening morphology of nanoparticles. It is attributed to a longer diffusion distance during the nucleation and growth processes. This model can be widely used for the predictions of the nanostructures formation with various ion implantation processes.
Subject(s)
Models, Chemical , Nanoparticles/chemistry , Ions/chemistryABSTRACT
High-energy ion irradiation of InSb results in the formation of bimodal surface structures, namely microscale hillock-like structures fully composed of nanoscale fibers. Analysis of the surface structures by a wide range of electron microscopy techniques reveals correlations between the irradiation conditions, such as the ion energy and fluence, and changes in the surface morphology. Sputtering effects play a key role in the integrity of the surface layer with increasing ion fluence. Possible mechanisms responsible for the morphological transformation are discussed, including both irradiation-induced and mechanical effects.
