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利用AAO模板MBE外延生長Ge納米點(diǎn)和薄膜
-浙江大學(xué)葉輝教授又一篇論文發(fā)表于Nanotechnology
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利用超薄AAO模板，首先轉(zhuǎn)移到Si上，然后在Si表面刻蝕形成納米坑陣列。高密度的Ge納米點(diǎn)陣列可以通過Si納米坑道結(jié)構(gòu)的限制作用獲得。高質(zhì)量的Ge膜也能夠通過SiO2窗口層實(shí)現(xiàn)。所謂SiO2窗口層是指將AAO模板轉(zhuǎn)移到SiO2/Si表面，然后刻蝕在SiO2 表面形成孔陣列。比如80nm和60nm孔徑的超薄AAO模板轉(zhuǎn)移到SiO2/Si表面，刻蝕可以形成70, 50和20 nm孔徑的窗口。通過70nm和50nm的窗口層，沒有發(fā)現(xiàn)“threading dislocations”，主要原因是降低了晶格失配。20nm窗口層是通過一種創(chuàng)新的“陰影刻蝕”技術(shù)實(shí)現(xiàn)的。截面透射電鏡結(jié)果表明，在20nm窗口層的輔助下，選擇性外延生長的Ge膜沒有缺陷，主要的原因是“threading dislocations”和Ge-Si之間的互擴(kuò)散。
這篇論文中的所使用的AAO模板，主要是孔徑80和60nm，孔深只有200-500nm（可控），是上木科技和浙江大學(xué)合作完成。
具體內(nèi)容可以參考剛剛online的原文：http://iopscience.iop.org/0957-4484/24/18/185302/
Heteroepitaxy of Ge on Si(001) with pits and windows transferred from
free-standing porous alumina mask
Yourui Huangfu, Wenbo Zhan, Xia Hong, Xu Fang, Guqiao Ding
and Hui Ye*
E-mail: [email protected]
Abstract
This paper reports the use of ultrathin free-standing porous alumina membrane (PAM) in pattern transferring for selective epitaxial growth (SEG) of Ge dots and films on Si. PAM, as a large-scale, controllable and lithography-free mask, can transfer nanopatterns onto Si without introducing any contaminants. High-density Ge dots are achievable with Ge adatoms confined in Si pits transferred from PAM. High-quality Ge films can also be grown on Si substrates through SiO2 nano-windows. In this work, 80 and 60 nm pore sizes of PAM were transferred to 70, 50 and 20 nm windows for comparison. For the former two sizes, over-etching of Si beneath every SiO2 window forms epi-seeds to improve intermixing of Ge–Si. No threading dislocations can be observed emanating from the epi-seeds due to the decreased lattice mismatch. An innovative shadow-etching technique utilizing the aspect ratio of PAM further decreased the lateral dimension of patterns from 60 to 20 nm. Cross-sectional transmission electron microscopy images show that the selective epitaxial Ge films grown from a 20 nm-width interface are defect free, which is attributed to the exponential decay of strain energy as well as Ge–Si intermixing.
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