Influence of crystallinity of as-deposited Ge film on formation of quantum dot in carbon-mediated solid-phase epitaxy
Influence of crystallinity of as-deposited Ge film on formation of quantum dot in carbon-mediated solid-phase epitaxy
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DOI：
10.1016/j.mssp.2016.11.025
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发表时间：
2017-11
影响因子：
4.1
通讯作者：
Kaito Takeshima;Y. Itoh;T. Kawashima;K. Washio
中科院分区：
文献类型：
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作者：
Kaito Takeshima;Y. Itoh;T. Kawashima;K. Washio
研究了Ge薄膜的结晶性对碳介导固相外延生长Ge量子点的影响。样品采用固体源分子束外延（MBE）技术制备。在150-400 °C的沉积温度（TD）下通过C和Ge的顺序沉积形成Ge/C/Si结构，并在650 °C的MBE室中对其进行热处理。对于TD≤250 °C生长的非晶或非晶和纳米晶混合Ge薄膜，由于Ge层中C-Ge键的增加，量子点的密度随着TD的增加而增加。在TD=250 °C时，Ge量子点的最大密度为8.3× 1011 cm-2，直径为9.2±2.1 nm。相反，对于TD≥300 °C的多晶Ge膜，量子点密度略有下降。这是因为在SPE过程中，由于结晶的柱状晶粒，抑制了C掺入Ge层。这些结果表明，在非晶和纳米晶的混合状态下沉积的Ge膜适合于通过C介导的SPE形成小而致密的Ge量子点。
The influence of crystallinity of as-deposited Ge films on Ge quantum dot (QD) formation via carbon (C)-mediated solid-phase epitaxy (SPE) was investigated. The samples were fabricated by solid-source molecular beam epitaxy (MBE). Ge/C/Si structure was formed by sequential deposition of C and Ge at deposition temperature (TD) of 150–400 °C, and it was heat-treated in the MBE chamber at 650 °C. In the case of amorphous or a mixture of amorphous and nano-crystalline Ge film grown for TD≤250 °C, density of QDs increased with increasing TDdue to the increase of C-Ge bonds in Ge layer. Ge QDs with diameter of 9.2±2.1 nm were formed in the highest density of 8.3×1011cm−2for TD=250 °C. On the contrary, in the case of polycrystalline Ge film for TD≥300 °C, density of QDs decreased slightly. This is because C incorporation into Ge layer during SPE was suppressed due to the as-crystallized columnar grains. These results suggest that as-deposited Ge film in a mixture of amorphous and nano-crystalline state is suitable to form small and dense Ge QDs via C-mediated SPE.