Formation mechanisms of nano and microcones by laser radiation on surfaces of Si, Ge, and SiGe crystals

Abstract

In this work we study the mechanisms of laser radiation interaction with elementary semiconductors such as Si and Ge and their solid solution SiGe. As a result of this investigation, the mechanisms of nanocones and microcones formation on a surface of semiconductor were proposed. We have shown the possibility to control the size and the shape of cones both by the laser. The main reason for the formation of nanocones is the mechanical compressive stresses due to the atoms’ redistribution caused by the gradient of temperature induced by strongly absorbed laser radiation. According to our investigation, the nanocone formation mechanism in semiconductors is characterized by two stages. The first stage is characterized by formation of a p-n junction for elementary semiconductors or of a Ge/Si heterojunction for SiGe solid solution. The generation and redistribution of intrinsic point defects in elementary semiconductors and Ge atoms concentration on the irradiated surface of SiGe solid solution in temperature gradient field take place at this stage due to the thermogradient effect which is caused by strongly absorbed laser radiation. The second stage is characterized by formation of nanocones due to mechanical plastic deformation of the compressed Ge layer on Si. Moreover, a new 1D-graded band gap structure in elementary semiconductors due to quantum confinement effect was formed. For the formation of microcones Ni/Si structure was used. The mechanism of the formation of microcones is characterized by two stages as well. The first stage is the melting of Ni film after irradiation by laser beam and formation of Ni islands due to surface tension force. The second step is the melting of Ni and subsequent manifestations of Marangoni effect with the growth of microcones.

Negative Magnetoresistance in Si Nanograting Layers

“…Various phenomena related to G‐doping were already reported for several other systems. In disordered nanostructures obtained by wet etching of p‐Si, as well as in nearly periodic nanostructures made by laser radiation interaction with surfaces of Si, Ge, and SiGe crystals . Additionally, it was found in mesoporous p‐Si where pore dimensions are close to the de Broglie wavelength like it is in our NGs …”

Pulsed laser ablation of Germanium under vacuum and hydrogen environments at various fluences

“…Medvid et al [15] observed the growth of nano and micro-cones on Ge, Si and SiGe after laser irradiation. The mechanism of nanocones is explained on the basis of mechanical compressive stresses induced by the absorption of laser radiation.…”

Laser Surface Hardening of Gun Metal Alloys

“…The presence of a small number of scratches in the micrograph was due to the polishing of the gun metal surface. Laser produced structure formation was observed [31,32] when the gun metal was irradiated with a laser from 100–500 laser shots. Figure 6b shows the re-solidification of the melt surface, due to which some oblong structures and cone formations were observed.…”