Formation of nanostructures during laser-induced melting of solid surfaces

Abstract

In recent years, nanostructures in solids have begun to receive more attention from researchers as important objects having very promising applications in various fields of science and technology. Ordered and disordered ensembles of nanoparticles represent new artificial materials with a broad range of applications due to their unique properties. The nanostructured surfaces improve the electrical, thermal, and electron-emission properties of materials and lead to better compatibility of tissues with implants used in orthopedics and dentistry. They also find application in selective nanocatalysis, microelectronics, nanophotonics, spectroscopy, and high-power optics; ensure superhigh data recording density; and are used in developing light-emitting silicon-base devices. This implies a need for developing the physical foundations of new effective methods for the formation of two- and three-dimensional structures with characteristic sizes less than one micrometer both at the surface and in the bulk of solids and for studying the mechanisms of nanostructure formation, which can be of various natures. In this study, the possibility of forming nanostructures at solid surfaces by laser pulses leading to the melting of the material surface is evaluated. The action of a laser pulse with a certain energy density and duration on a solid surface can lead to the melting of the surface layer. Let us consider the process of its solidification due to subsequent heat removal in the depth of the solid phase. In this case, the liquid turns out to be in the supercooled state and a considerable temperature difference across the liquid‐solid interface is established. Depending on the degree of supercooling, the subsequent nucleation of the crystal phase can have either a fluctuational [1] or a spontaneous [2] character (Fig. 1). The variation of the thermodynamic potential during the formation of a new phase center (nucleus) consisting of n atoms can be described as follows: