Browsing by Author "Ferng, Shyh-Shin"

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Growth behaviour of Ge nano-islands on the nanosized Si{111} facets bordering on two {100} planes
(2006-10-28)
Ferng, Shyh-Shin
;
Yang, Tsung-Hsi
;
Luo, Guangli
;
Yang, Kai-Ming
;
Hsieh, Ming-Feng
Si( 100) substrates were used to fabricate various nanosized {111} facets between the ( 100) planes using photolithography and anisotropic wet chemical etching. Following simultaneous Ge chemical vapour deposition on the neighbouring ( 100) and {111} facets, the Ge nano-island formation and distribution was observed on both the ( 100) terraces and the {111} side walls using a dynamical atomic force microscope. The nano-island formation on the nanosized {111} strip facets was found to be strongly suppressed upon reducing the strip width due primarily to the interaction of adatoms on the neighbouring facets. Specifically, the difference in the effective chemical potential of Ge adatoms on the two neighbouring facets leads to the depletion of nano-islands on the {111} strip with width < 500 nm under the growth condition used in this study.
Mediation of chain reactions by propagating radicals during halogenation of H-masked Si(100): Implications for atomic-scale lithography and processing
(2009-04-28)
Ferng, Shyh-Shin
;
Wu, Shiao-Ting
;
Lin, Deng-Sung
;
Chiang, Tai C.
;
物理研究所
Scanning tunneling microscopy reveals a free radical-induced surface chain reaction in the chlorination of nanoscale patterns on an otherwise H-passivated (masked) Si (100). While scanning probe methods can be used to pattern active surface regions with single-bond precision, follow-up selective chemical vapor deposition with polyatomic molecules can produce various filling characteristics. On active surface regions, molecular Cl(2) undergoes an atom abstraction reaction in which a Si dangling bond abstracts one atom of the incident Cl(2) molecule while the complementary Cl atom is scattered away from the initial abstraction site either back into the vacuum or to be captured by a second dangling bond and adsorbed there, or to react with a nearby adsorbed H atom to form volatile HCl. In contrast, I(2) undergoes only dissociative adsorption on two immediately neighboring dangling bonds, whereby two I-Si bonds are formed simultaneously upon cleavage of the I(2) bond. The different chemisorption processes of the two model diatomic molecular gases place intrinsic limitations on atomic-scale lithography and processing: Adsorption of Cl(2) results in spillage over the prepatterned regions of active bonds. In contrast, adsorption of I(2) is a pair process and results in under-filling. (C) 2009 American Institute of Physics. [DOI: 10.1063/1.3122987]