Properties of nanocones formed on a surface of semiconductors by laser radiation: quantum confinement effect of electrons, phonons, and excitons

Abstract

On the basis of the analysis of experimental results, a two-stage mechanism of nanocones formation on the irradiated surface of semiconductors by Nd:YAG laser is proposed for elementary semiconductors and solid solutions, such as Si, Ge, SiGe, and CdZnTe. Properties observed are explained in the frame of quantum confinement effect. The first stage of the mechanism is characterized by the formation of a thin strained top layer, due to redistribution of point defects in temperature-gradient field induced by laser radiation. The second stage is characterized by mechanical plastic deformation of the stained top layer leading to arising of nanocones, due to selective laser absorption of the top layer. The nanocones formed on the irradiated surface of semiconductors by Nd:YAG laser possessing the properties of 1D graded bandgap have been found for Si, Ge, and SiGe as well, however QD structure in CdTe was observed. The model is confirmed by "blue shift" of bands in photoluminescence spectrum, "red shift" of longitudinal optical line in Raman back scattering spectrum of Ge crystal, appearance of Ge phase in SiGe solid solution after irradiation by the laser at intensity 20 MW/cm2, and non-monotonous dependence of Si crystal micro-hardness as function of the laser intensity.

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

“…Chen et al [41] also reported that Laser-induced periodic structures on the nanostructured surface of GaN are responsible for enhancing light extraction efficiency due a better spatial alignment of the electrons and holes. Photo thermo-deformed model [42] can be proposed for self-assembled LIPSS formation. According to this model, the conversion of light into heat and lateral deformation of the crystalline lattice takes place due to inhomogeneous absorption which leads to formation of LIPSS due to re-distribution of point defects (vacancy, interstitial defects).…”

Conductivity type conversion in p-CdZnTe under pulsed laser irradiation

“…Its origin may be caused by several reasons. Laser-induced modification of the surface in CdTe and CdZnTe was investigated in a number of studies using single and multiple irradiation of ruby and neodymium laser [2][3][4][5][6][7]. By using multiple irradiation, surface modification was carried out in the following order: emergence of excess tellurium, formation of dislocation networks and nanostructures [3,4].…”

“…The majority of the investigations of surface modification by using laser irradiation in these materials have concentrated on surface morphology and composition changes. Also, some physical properties were investigated in the irradiated CdZnTe [2][3][4][5][6][7]. The aim of this work is to study electrical and photoelectrical properties of barrier structures prepared on the lasermodified surface of Cd 0.9 ZnTe single crystals.…”

A Viable and Scalable Route for the Homogrowth of Si Nanocones and Si/C Nanostructures

“…Our approach appears more simple and effective in comparison with more complicated methodologies involving two-step processes. 25 The hypothesis for the building up of Si nanocones onto Nicoated Si substrates is that such Si nanostructures originate from a molten/recrystallizazion process driven by the selfbiasing of the substrate. The presence of Ni lowers the melting temperature of the crystalline Si substrate, due to the formation of a Si−Ni eutectic under both surface heating and activation via intense ion bombardment.…”