基于温和等离子体技术的二硫化钨可控减薄
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摘要
二硫化钨(WS_2)作为二维过渡金属硫族化合物(TMDs)中的一员,具有独特的光学和电子性能,引起学术界和产业界的高度关注和广泛研究。当厚层WS_2转变为少层甚至单层WS_2时,其能带结构由间接带隙转为直接带隙,因此可用于光电探测器,和电致发光器件等。本文采用一种处于电容放电模式(E-mode)下的温和电感耦合等离子体对WS_2进行减薄。通过使用不同的RF功率密度,厚层WS_2可以被快速减薄,而少层WS_2可以被逐层减薄。拉曼和荧光表明,随着WS_2样品被减薄,其荧光显著增强。本研究为对二维材料的可控减薄提供了新途径。
In recent years,tungsten disulfide(WS_2),a member of two-dimensional transition metal chalcogenides(TMDs),has unique optical and electronic properties,which has aroused great attention and extensive research from academia and industry. When the thick layer WS_2 is transformed into fewlayer WS_2 or even monolayer WS_2,its band structure changes from an indirect band gap to a direct band gap. Therefore,it can be used for photodetectors and electroluminescent devices. In this paper,we adopted a soft inductively coupled plasma excited in capacitive discharge mode(E-mode) to thin WS_2.By using different RF power densities,thick WS_2 can be fastly thinned while few-layer WS_2 can be layerby-layer thinned. Raman spectra and Photoluminescence studies demonstrate that the Photoluminescence intesnity was greatly enhanced as WS_2 samples were thinned. This study provides a new approach to controllable thinning of two-dimensional materials.
In recent years,tungsten disulfide(WS_2),a member of two-dimensional transition metal chalcogenides(TMDs),has unique optical and electronic properties,which has aroused great attention and extensive research from academia and industry. When the thick layer WS_2 is transformed into fewlayer WS_2 or even monolayer WS_2,its band structure changes from an indirect band gap to a direct band gap. Therefore,it can be used for photodetectors and electroluminescent devices. In this paper,we adopted a soft inductively coupled plasma excited in capacitive discharge mode(E-mode) to thin WS_2.By using different RF power densities,thick WS_2 can be fastly thinned while few-layer WS_2 can be layerby-layer thinned. Raman spectra and Photoluminescence studies demonstrate that the Photoluminescence intesnity was greatly enhanced as WS_2 samples were thinned. This study provides a new approach to controllable thinning of two-dimensional materials.
引文
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[2]Novoselov K S,Geim A K,Morozov S V,et al.Electric Field Effect in Atomically Thin Carbon Films[J].Science,2004,306(5696):666-9.
[3]Radisavljevic B,Radenovic A,Brivio J,et al.Single-layer Mo S2transistors[J].Nature Nanotechnology,2011,6(3):147-150.
[4]Chen C,Qiao H,Xue Y,et al.Growth of large-area atomically thin Mo S2film via ambient pressure chemical vapor deposition[J].Photonics Research,2015,3(4):110.
[5]Liu J,Tse Wing Lo,Sun J,et al.A comprehensive comparison study of CVD-grown and mechanically exfoliated few-layered WS2:The vibrational and optical properties[J].Journal of Materials Chemistry C,2017,5(43):11239-11245.
[6]Chhowalla M,Shin H S,Eda G,et al.The chemistry of two-dimensional layered transition metal dichalcogenide nanosheets[J].Nature Chemistry.2013,5(4):263-275.
[7]Lan C,Li C,Yin Y.Correction:Large-area synthesis of monolayer WS2and its ambient-sensitive photo-detecting performance[J].Nanoscale,2015,7(14):5974-80.
[8]Wang Q H,Kalantarzadeh K,Kis A,et al.Electronics and optoelectronics of two-dimensional transition metal dichalcogenides[J].Nature Nanotechnology,2012,7(11):699-712.
[9]Mak K F,Lee C,Hone J,et al.Atomically thin Mo S2:a new direct-gap semiconductor[J].Physical Review Letters,2010,105(13):136805.
[10]Kuc A,Zibouche N,Heine T.Influence of quantum confinement on the electronic structure of the transition metal sulfide TS2[J].Phys.rev.b,2011,83(24):2237-2249.
[11]Splendiani A,Sun L,Zhang Y,et al.Emerging photoluminescence in monolayer Mo S2[J].Nano Letters,2010,10(4):1271-1275.
[12]Tonndorf P.Photoluminescence emission and Raman response of monolayer Mo S2,Mo Se2,and WSe2[J].Lasers and Electro-Optics.The Optical Society,2014:4908-16.
[13]Huang Y,Sutter E,Shi N N,et al.Reliable Exfoliation of Large-Area High-Quality Flakes of Graphene and Other Two-Dimensional Materials.[J].Acs Nano,2016,9(11):10612-10620.
[14]Berkdemir A,Gutiérrez H R,Botelloméndez A R,et al.Identification of individual and few layers of WS2using Raman Spectroscopy[J].Scientific Reports,2013,3(18):1755.
[15]Kuc A,Zibouche N,Heine T.Influence of quantum confinement on the electronic structure of the transition metal sulfide TS2[J].Phys.rev.b,2011,83(24):2237-2249.
[16]Coleman J N,Lotya M,O'Neill A,et al.Two-dimensional nanosheets produced by liquid exfoliation of layered materials[J].Cheminform,2011,42(18):568-571.
[17]Liu P,Luo T,Xing J,et al.Large-Area WS2Film with Big Single Domains Grown by Chemical Vapor Deposition[J].Nanoscale Research Letters,2017,12(1):558.
[18]Hong J,Hu Z,Probert M,et al.Exploring atomic defects in molybdenum disulphide monolayers[J].Nature Communications,2015,6:6293.
[19]Wu J,Li H,Yin Z,et al.Layer thinning and etching of mechanically exfoliated Mo S2nanosheets by thermal annealing in air[J].Small,2013,9(19):3314-9.
[20]Lu X,Utama M I,Zhang J,et al.Layer-by-layer thinning of Mo S2by thermal annealing[J].Nanoscale,2013,5(19):8904-8.
[21]Castellanosgomez A,Barkelid M,Goossens A M,et al.Laser-thinning of Mo S2:on demand generation of a single-layer semiconductor[J].Nano Letters,2012,12(6):3187.
[22]Xiao S,Peng X,Zhang X,et al.Atomic-layer soft plasma etching of Mo S2[J].Scientific Reports,2016,6:19945.
[23]Sha Y,Xiao S,Zhang X,et al.Layer-by-layer thinning of Mo Se2,by soft and reactive plasma etching[J].Applied Surface Science,2017,411.
[24]Lee C,Yan H,Brus L E,et al.Anomalous lattice vibrations of single-and few-layer Mo S2[J].Acs Nano,2010,4(5):2695-700.