Influence Of Strain On Morphology Evolution And Optical Properties Of Confined Ge/GeO₂ Nanoparticles

Ge nanoparticles embedded in a host matrix form core/shell Ge/GeO2 nanoparticles by the oxidation process. During the growth process, it is accompanied by strain which can tailor microstructure and morphology of nanoparticles, defects at the Ge-GeO2 interface, resulting in changing their optical properties. In this paper, it is studied systematacially to explore the mechanism of forming core/shell structure nanoparticles from confined semiconductor nanoparticles by oxidation process. Our researches are as follows:1.we have strudied the relationship of morphology and strain of core/shell structure nanoparticles via confined core/shell Ge/GeO2 nanoparticles.It is found that strain distributions of core/shell Ge/GeO2 nanoparticles at core and shell interface depend on strongly their morphology. It can be realized easily that tensile strain applied on core tranforms into compressive by adjusting the thickness of the shell. It indicates that strain gradients induced in the confined GeO2 shell during the oxidation process can facilitate the formation of the cracked GeO2. Strain of nanoparticles is designed by manipulating the morphology and their evolution, resulting in physical and chemical properties of core/shell structure nanoparticles.2.We prepared core/shell Ge/GeO2 nanoparticles with a crack shell and studied nonlinear optical properties. It has been found that two-photon absorption in Ge/GeO2core/shell nanoparticles is an instantaneous nonlinear process. The TPA effect is enhanced almost 2 times compared to that in pure Ge nanoparticles due to the suppressed strain-relaxing surface states at the heterostructure interface of the Ge core and the GeO2 shell by the formation of the cracked shell. It is demonstrated that strain effect has a potential application in manipulating the microstructure, morphology and optical properties of confined core/shell nanoparticles.