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RISS 인기검색어
- 검색키워드
- 저자 : Puretzky, Alexander A. (검색결과 2 건)
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Edge-Controlled Growth and Etching of Two-Dimensional GaSe Monolayers
Li, Xufan,Dong, Jichen,Idrobo, Juan C.,Puretzky, Alexander A.,Rouleau, Christopher M.,Geohegan, David B.,Ding, Feng,Xiao, Kai American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.1
<P>Understanding the atomistic mechanisms governing the growth of two-dimensional (2D) materials is of great importance in guiding the synthesis of wafer-sized, single-crystalline, high-quality 2D crystals and heterostructures. Etching, in many cases regarded as the reverse process of material growth, has been used to study the growth kinetics of graphene. In this work, we explore a growth-etching-regrowth process of monolayer GaSe crystals, including single-crystalline triangles and irregularly shaped domains formed by merged triangles. We show that the etching begins at a slow rate, creating triangular, truncated triangular, or hexagonally shaped holes that eventually evolve to exclusively triangles that are rotated 60 degrees with respect to the crystalline orientation of the monolayer triangular crystals. The regrowth occurs much faster than etching, reversibly filling the etched holes and then enlarging the size of the monolayer crystals. A theoretical model developed based on kinetic Wulff construction (KWC) theory and density functional theory (DFT) calculations accurately describe the observed morphology evolution of the monolayer GaSe crystals and etched holes during the growth and etching processes, showing that they are governed by the probability of atom attachment/detachment to/from different types of edges with different formation energies of nucleus/dents mediated by chemical potential difference Ait between Ga and Se. Our growth-etching-regrowth study provides not only guidance to understand the growth mechanisms of 2D binary crystals but also a potential method for the synthesis of large, shape-controllable, high-quality single-crystalline 2D crystals and their lateral heterostructures.</P>
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Mahjouri-Samani, Masoud,Liang, Liangbo,Oyedele, Akinola,Kim, Yong-Sung,Tian, Mengkun,Cross, Nicholas,Wang, Kai,Lin, Ming-Wei,Boulesbaa, Abdelaziz,Rouleau, Christopher M.,Puretzky, Alexander A.,Xiao, K American Chemical Society 2016 Nano letters Vol.16 No.8
<P>Defect engineering has been a critical step in controlling the transport characteristics of electronic devices, and the ability to create, tune, and annihilate defects is essential to enable the range of next-generation devices. Whereas defect formation has been well-demonstrated in three-dimensional semiconductors, similar exploration of the heterogeneity in atomically thin two-dimensional semiconductors and the link between their atomic structures, defects, and properties has not yet been extensively studied. Here, we demonstrate the growth of MoSe2-x single crystals with selenium (Se) vacancies far beyond intrinsic levels, up to similar to 20%, that exhibit a remarkable transition in electrical transport properties from n- to p-type character with increasing Se vacancy concentration. A new defect-activated phonon band at similar to 250 cm(-1) appears, and the A(1g) Raman characteristic mode at 240 cm(-1) softens toward similar to 230 cm(-1) which serves as a fingerprint of vacancy concentration in the crystals. We show that post-selenization using pulsed laser evaporated Se atoms can repair Se-vacant sites to nearly recover the (p)roperties of the pristine crystals. First-principles calculations reveal the underlying mechanisms for the corresponding vacancy induced electrical and optical transitions.</P>
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