期刊
SURFACE SCIENCE
卷 606, 期 21-22, 页码 1649-1669出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.susc.2012.07.004
关键词
STM; Growth dynamics; Silicides; Si surfaces; Wires
资金
- NUS [R-144-000-159-112]
- IMRE
The growth of cobalt silicide nanostructures on clean Si(001) was studied using scanning tunnelling microscopy and transmission electron microscopy. Two types of CoSi2 nanostructures, flat and ridge-type islands, were formed when 0.1 ML Co was deposited onto clean Si(001) between 500 degrees C and 800 degrees C These islands form elongated islands along [110] directions and grow into the Si-substrate within the temperature range. The formation of the two types of islands arises primarily due to the type of CoSi2{111}-Si{111} interface formed between the island and the substrate. Flat islands are bound by CoSi2{111}-Si{111} Type-A interfaces such that CoSi2(001)//Si(001) and CoSi2[001]//Si[001]. Ridge islands, on the other hand, are bound by a twinned CoSi2{111}-Si{111} Type-B interface such that CoSi2(221)//Si(001) and CoSi2[1 (1) over bar0]//Si[1 (1) over bar0]. This leads to the formation of three less energetically-favourable interfaces: CoSi2((111) over bar)-Si(11 (5) over bar), CoSi2((112) over bar)-Si(11 (2) over bar), and CoSi2((115) over bar)-Si(11 (1) over bar). Analysis of the interfacial energies through dangling bond counting per interfacial area for each interface shows that the formation of the Type-B interface is energetically more favourable compared to the rest of the interfaces. As a result, the island elongates preferentially along the Type B interface leading to the formation of long nanowires with large length-width aspect ratio of 20:1. However, this formation is only achieved at high growth temperatures due to the presence of corner-barriers constraining the growth at low temperatures. Conversely, flat islands are slightly elongated at low growth temperatures with aspect ratio reaching 7:1 at 650 degrees C. As temperature increases towards 760 degrees C, they are brought closer to equilibrium and hence become less elongated with aspect ratio reduced to 1.6:1. (C) 2012 Elsevier B.V. All rights reserved.
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