Modulation of lattice constants by changing the composition and strain in incommensurate Nowotny chimney-ladder phase FeGeγ epitaxially grown on Si

SURFACE SCIENCE

卷:690

Article

Terada, Tsukasa¹  Ishibe, Takafumi¹  Nakamura, Yoshiaki¹ 

[1] Osaka Univ, Grad Sch Engn Sci, 1-3 Machikaneyama Cho, Toyonaka, Osaka 5608531, Japan

关键词: Epitaxial growth;    Nanostructure;    Strain relaxation;    Nowotny chimney-ladder;    Nanocrystal;    Silicon;   

DOI  :  10.1016/j.susc.2019.121470

来源: Elsevier

【 摘 要 】

The single phase FeGe gamma nanocrystals (NCs) with incommensurate Nowotny chimney-ladder structure were epitaxially grown on Si substrates by reaction between deposited Fe atoms and Ge nanostructured layers on Si. The Ge nanostructured layers worked as blocking layers of the Fe diffusion to Si substrates. We used the two kinds of the Ge nanostructured layers: Ge wetting layers formed by direct Ge deposition on Si and Ge NCs formed by Ge deposition on ultrathin SiO2 films with ultrasmall nanowindows on Si. In the case of Ge wetting layers, the FeGe gamma NCs were directly formed on Si, where there was a-axis strain due to the 2.9% lattice mismatch between FeGe gamma and Si. On the other hand, in the case of Ge NCs, formed FeGe gamma NCs were elastically-strain-relaxed due to the small contact with Si substrates through nanowindows in the ultrathin SiO2 films. Furthermore, the c-axis lattice constant in the epitaxial FeGe gamma NCs changed due to the variation of the Fe-Ge composition. These results demonstrated that a-axis lattice constant was modulated by strain control of FeGe gamma NCs due to the change of contact area with Si substrate and that c-axis lattice constant of FeGe gamma NCs with incommensurate Nowotny chimney-ladder structure was modulated by manipulating Fe-Ge composition. These modulation of lattice constants will open a road for manipulating phonon group velocity related to the lattice constant and managing the waste heat in various devices implemented on Si substrates.

【 授权许可】

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