二维有机分子吸附层对过渡金属硫化物纳米薄片超低波拉曼光谱的影响（英文）
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摘要
在二维材料下表面与衬底之间的受限空间中,物理吸附物如水分子和有机分子等可形成二维吸附层.然而,这类吸附层如何影响其上层二维材料的性能尚未被探究.本文中,我们结合原子力显微镜、开尔文力显微镜以及超低波拉曼光谱仪来探究有机分子吸附层对其上的少层二硫化钼及二硒化钨纳米薄片性质的影响.随吸附层厚度增加,纳米薄片的超低波呼吸模式拉曼峰发生红移、红移和蓝移共存以及仅有蓝移的现象.此外,纳米薄片的掺杂程度也逐渐增强.理解有机分子吸附层与二维材料下表面之间的相互作用,有望对二维材料性质的调节提供帮助.
Recently, it has been reported that physisorbed adsorbates can be trapped between the bottom surface of twodimensional(2D) materials and supported substrate to form2 D confined films. However, the influence of such 2D confined adsorbates on the properties of 2D materials is rarely explored. Herein, we combined atomic force microscopy(AFM), Kelvin probe force microscopy(KPFM) and Raman spectroscopy especially the ultralow frequency(ULF) Raman spectroscopy to explore the influence of 2D confined organic adlayer thickness on the ULF breathing modes of few-layer MoS2 and WSe2nanosheets. As the thickness of organic adlayers increased, red shift, coexistence of blue and red shifts as well as blue shift of ULF breathing mode was observed. KPFM measurement confirmed the enhanced n-doping and p-doping behaviors of organic adlayers as their thickness increased,respectively. Our results will provide new insights into the interaction between 2D confined adsorbates and bottom surface of 2D nanosheets, which could be useful for modulating properties of 2D materials.
Recently, it has been reported that physisorbed adsorbates can be trapped between the bottom surface of twodimensional(2D) materials and supported substrate to form2 D confined films. However, the influence of such 2D confined adsorbates on the properties of 2D materials is rarely explored. Herein, we combined atomic force microscopy(AFM), Kelvin probe force microscopy(KPFM) and Raman spectroscopy especially the ultralow frequency(ULF) Raman spectroscopy to explore the influence of 2D confined organic adlayer thickness on the ULF breathing modes of few-layer MoS2 and WSe2nanosheets. As the thickness of organic adlayers increased, red shift, coexistence of blue and red shifts as well as blue shift of ULF breathing mode was observed. KPFM measurement confirmed the enhanced n-doping and p-doping behaviors of organic adlayers as their thickness increased,respectively. Our results will provide new insights into the interaction between 2D confined adsorbates and bottom surface of 2D nanosheets, which could be useful for modulating properties of 2D materials.
引文
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2 Kozlov SM,Vi?es F,G?rling A.Bandgap engineering of graphene by physisorbed adsorbates.Adv Mater,2011,23:2638-2643
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4 Fang H,Chuang S,Chang TC,et al.High-performance single layered WSe2p-FETs with chemically doped contacts.Nano Lett,2012,12:3788-3792
5 Fang H,Tosun M,Seol G,et al.Degenerate n-doping of few-layer transition metal dichalcogenides by potassium.Nano Lett,2013,13:1991-1995
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14 Jing Y,Tang Q,He P,et al.Small molecules make big differences:molecular doping effects on electronic and optical properties of phosphorene.Nanotechnology,2015,26:095201
15 Cai Y,Zhou H,Zhang G,et al.Modulating carrier density and transport properties of MoS2by organic molecular doping and defect engineering.Chem Mater,2016,28:8611-8621
16 Choi J,Zhang H,Du H,et al.Understanding solvent effects on the properties of two-dimensional transition metal dichalcogenides.ACS Appl Mater Interfaces,2016,8:8864-8869
17 Singh D,Gupta SK,Sonvane Y,et al.Modulating the electronic and optical properties of monolayer arsenene phases by organic molecular doping.Nanotechnology,2017,28:495202
18 Li L,Pi LJ,Li HQ,et al.Photodetectors based on two-dimensional semiconductors:Progress,opportunity and challenge.Chin Sci Bull,2017,62:3134-3153
19 Huang Y,Zhuge F,Hou J,et al.Van der Waals coupled organic molecules with monolayer MoS2for fast response photodetectors with gate-tunable responsivity.ACS Nano,2018,12:4062-4073
20 Kufer D,Konstantatos G.Highly sensitive,encapsulated MoS2photodetector with gate controllable gain and speed.Nano Lett,2015,15:7307-7313
21 Zhang W,Huang JK,Chen CH,et al.High-gain phototransistors based on a CVD MoS2monolayer.Adv Mater,2013,25:3456-3461
22 Lin JD,Han C,Wang F,et al.Electron-doping-enhanced trion formation in monolayer molybdenum disulfide functionalized with cesium carbonate.ACS Nano,2014,8:5323-5329
23 Xu K,Cao P,Heath JR.Graphene visualizes the first water adlayers on mica at ambient conditions.Science,2010,329:1188-1191
24 Cao P,Xu K,Varghese JO,et al.Atomic force microscopy characterization of room-temperature adlayers of small organic molecules through graphene templating.J Am Chem Soc,2011,133:2334-2337
25 Komurasaki H,Tsukamoto T,Yamazaki K,et al.Layered structures of interfacial water and their effects on Raman spectra in graphene-on-sapphire systems.J Phys Chem C,2012,116:10084-10089
26 Lee MJ,Choi JS,Kim JS,et al.Characteristics and effects of diffused water between graphene and a SiO2substrate.Nano Res,2012,5:710-717
27 Shim J,Lui CH,Ko TY,et al.Water-gated charge doping of graphene induced by mica substrates.Nano Lett,2012,12:648-654
28 Chen S,Li H,Cao P,et al.Understanding liquid-solid-like behavior of tetrahydrofuran adlayers at room temperature between graphene and mica:a Born-Oppenheimer molecular dynamics study.J Phys Chem C,2013,117:21894-21900
29 Varghese JO,Agbo P,Sutherland AM,et al.The influence of water on the optical properties of single-layer molybdenum disulfide.Adv Mater,2015,27:2734-2740
30 Lee DE,Ahn G,Ryu S.Two-dimensional water diffusion at a graphene-silica interface.J Am Chem Soc,2014,136:6634-6642
31 Zhang Q,Peng B,Chan PKL,et al.A pentacene monolayer trapped between graphene and a substrate.Nanoscale,2015,7:14663-14668
32 Bampoulis P,Witteveen JP,Kooij ES,et al.Structure and dynamics of confined alcohol-water mixtures.ACS Nano,2016,10:6762-6768
33 Vo?tchovsky K,GiofrèD,JoséSegura J,et al.Thermally-nucleated self-assembly of water and alcohol into stable structures at hydrophobic interfaces.Nat Commun,2016,7:13064
34 Mak KF,He K,Lee C,et al.Tightly bound trions in monolayer MoS2.Nat Mater,2012,12:207-211
35 Guo W,Cheng C,Wu Y,et al.Bio-inspired two-dimensional nanofluidic generators based on a layered graphene hydrogel membrane.Adv Mater,2013,25:6064-6068
36 Guo W,Jiang L.Two-dimensional ion channel based soft-matter piezoelectricity.Sci China Mater,2014,57:2-6
37 Gao J,Feng Y,Guo W,et al.Nanofluidics in two-dimensional layered materials:inspirations from nature.Chem Soc Rev,2017,46:5400-5424
38 Ji J,Kang Q,Zhou Y,et al.Osmotic power generation with positively and negatively charged 2D nanofluidic membrane pairs.Adv Funct Mater,2016,27:1603623
39 Cheng H,Zhou Y,Feng Y,et al.Electrokinetic energy conversion in self-assembled 2D nanofluidic channels with janus nanobuilding blocks.Adv Mater,2017,29:1700177
40 Wang L,Feng Y,Zhou Y,et al.Photo-switchable two-dimensional nanofluidic ionic diodes.Chem Sci,2017,8:4381-4386
41 Feng Y,Zhang K,Li H,et al.In situ visualization and detection of surface potential variation of mono and multilayer MoS2under different humidities using Kelvin probe force microscopy.Nanotechnology,2017,28:295705
42 Li Y,Xu CY,Hu PA,et al.Carrier control of MoS2nanoflakes by functional self-assembled monolayers.ACS Nano,2013,7:7795-7804
43 Rice C,Young RJ,Zan R,et al.Raman-scattering measurements and first-principles calculations of strain-induced phonon shifts in monolayer MoS2.Phys Rev B,2013,87:081307
44 Lin H,Schilo A,Kamoka AR,et al.Insight into the wetting of a graphene-mica slit pore with a monolayer of water.Phys Rev B,2017,95:195414
45 Buscema M,Steele GA,van der Zant HSJ,et al.The effect of the substrate on the Raman and photoluminescence emission of single-layer MoS2.Nano Res,2014,7:561-571
46 Yu Y,Yu Y,Xu C,et al.Engineering substrate interactions for high luminescence efficiency of transition-metal dichalcogenide monolayers.Adv Funct Mater,2016,26:4733-4739
47 Li H,Wu JB,Ran F,et al.Interfacial interactions in van der Waals heterostructures of MoS2and graphene.ACS Nano,2017,11:11714-11723
2 Kozlov SM,Vi?es F,G?rling A.Bandgap engineering of graphene by physisorbed adsorbates.Adv Mater,2011,23:2638-2643
3 Cao P,Varghese JO,Xu K,et al.Visualizing local doping effects of individual water clusters on gold(111)-supported graphene.Nano Lett,2012,12:1459-1463
4 Fang H,Chuang S,Chang TC,et al.High-performance single layered WSe2p-FETs with chemically doped contacts.Nano Lett,2012,12:3788-3792
5 Fang H,Tosun M,Seol G,et al.Degenerate n-doping of few-layer transition metal dichalcogenides by potassium.Nano Lett,2013,13:1991-1995
6 Goncher SJ,Zhao L,Pasupathy AN,et al.Substrate level control of the local doping in graphene.Nano Lett,2013,13:1386-1392
7 Mouri S,Miyauchi Y,Matsuda K.Tunable photoluminescence of monolayer MoS2via chemical doping.Nano Lett,2013,13:5944-5948
8 Tongay S,Zhou J,Ataca C,et al.Broad-range modulation of light emission in two-dimensional semiconductors by molecular physisorption gating.Nano Lett,2013,13:2831-2836
9 Dhakal KP,Duong DL,Lee J,et al.Confocal absorption spectral imaging of MoS2:optical transitions depending on the atomic thickness of intrinsic and chemically doped MoS2.Nanoscale,2014,6:13028-13035
10 Kiriya D,Tosun M,Zhao P,et al.Air-stable surface charge transfer doping of MoS2by benzyl viologen.J Am Chem Soc,2014,136:7853-7856
11 Yang L,Majumdar K,Liu H,et al.Chloride molecular doping technique on 2D materials:WS2and MoS2.Nano Lett,2014,14:6275-6280
12 Zhao P,Kiriya D,Azcatl A,et al.Air stable p-doping of WSe2by covalent functionalization.ACS Nano,2014,8:10808-10814
13 Andleeb S,Kumar Singh A,Eom J.Chemical doping of MoS2multilayer by p-toluene sulfonic acid.Sci Tech Adv Mater,2015,16:035009
14 Jing Y,Tang Q,He P,et al.Small molecules make big differences:molecular doping effects on electronic and optical properties of phosphorene.Nanotechnology,2015,26:095201
15 Cai Y,Zhou H,Zhang G,et al.Modulating carrier density and transport properties of MoS2by organic molecular doping and defect engineering.Chem Mater,2016,28:8611-8621
16 Choi J,Zhang H,Du H,et al.Understanding solvent effects on the properties of two-dimensional transition metal dichalcogenides.ACS Appl Mater Interfaces,2016,8:8864-8869
17 Singh D,Gupta SK,Sonvane Y,et al.Modulating the electronic and optical properties of monolayer arsenene phases by organic molecular doping.Nanotechnology,2017,28:495202
18 Li L,Pi LJ,Li HQ,et al.Photodetectors based on two-dimensional semiconductors:Progress,opportunity and challenge.Chin Sci Bull,2017,62:3134-3153
19 Huang Y,Zhuge F,Hou J,et al.Van der Waals coupled organic molecules with monolayer MoS2for fast response photodetectors with gate-tunable responsivity.ACS Nano,2018,12:4062-4073
20 Kufer D,Konstantatos G.Highly sensitive,encapsulated MoS2photodetector with gate controllable gain and speed.Nano Lett,2015,15:7307-7313
21 Zhang W,Huang JK,Chen CH,et al.High-gain phototransistors based on a CVD MoS2monolayer.Adv Mater,2013,25:3456-3461
22 Lin JD,Han C,Wang F,et al.Electron-doping-enhanced trion formation in monolayer molybdenum disulfide functionalized with cesium carbonate.ACS Nano,2014,8:5323-5329
23 Xu K,Cao P,Heath JR.Graphene visualizes the first water adlayers on mica at ambient conditions.Science,2010,329:1188-1191
24 Cao P,Xu K,Varghese JO,et al.Atomic force microscopy characterization of room-temperature adlayers of small organic molecules through graphene templating.J Am Chem Soc,2011,133:2334-2337
25 Komurasaki H,Tsukamoto T,Yamazaki K,et al.Layered structures of interfacial water and their effects on Raman spectra in graphene-on-sapphire systems.J Phys Chem C,2012,116:10084-10089
26 Lee MJ,Choi JS,Kim JS,et al.Characteristics and effects of diffused water between graphene and a SiO2substrate.Nano Res,2012,5:710-717
27 Shim J,Lui CH,Ko TY,et al.Water-gated charge doping of graphene induced by mica substrates.Nano Lett,2012,12:648-654
28 Chen S,Li H,Cao P,et al.Understanding liquid-solid-like behavior of tetrahydrofuran adlayers at room temperature between graphene and mica:a Born-Oppenheimer molecular dynamics study.J Phys Chem C,2013,117:21894-21900
29 Varghese JO,Agbo P,Sutherland AM,et al.The influence of water on the optical properties of single-layer molybdenum disulfide.Adv Mater,2015,27:2734-2740
30 Lee DE,Ahn G,Ryu S.Two-dimensional water diffusion at a graphene-silica interface.J Am Chem Soc,2014,136:6634-6642
31 Zhang Q,Peng B,Chan PKL,et al.A pentacene monolayer trapped between graphene and a substrate.Nanoscale,2015,7:14663-14668
32 Bampoulis P,Witteveen JP,Kooij ES,et al.Structure and dynamics of confined alcohol-water mixtures.ACS Nano,2016,10:6762-6768
33 Vo?tchovsky K,GiofrèD,JoséSegura J,et al.Thermally-nucleated self-assembly of water and alcohol into stable structures at hydrophobic interfaces.Nat Commun,2016,7:13064
34 Mak KF,He K,Lee C,et al.Tightly bound trions in monolayer MoS2.Nat Mater,2012,12:207-211
35 Guo W,Cheng C,Wu Y,et al.Bio-inspired two-dimensional nanofluidic generators based on a layered graphene hydrogel membrane.Adv Mater,2013,25:6064-6068
36 Guo W,Jiang L.Two-dimensional ion channel based soft-matter piezoelectricity.Sci China Mater,2014,57:2-6
37 Gao J,Feng Y,Guo W,et al.Nanofluidics in two-dimensional layered materials:inspirations from nature.Chem Soc Rev,2017,46:5400-5424
38 Ji J,Kang Q,Zhou Y,et al.Osmotic power generation with positively and negatively charged 2D nanofluidic membrane pairs.Adv Funct Mater,2016,27:1603623
39 Cheng H,Zhou Y,Feng Y,et al.Electrokinetic energy conversion in self-assembled 2D nanofluidic channels with janus nanobuilding blocks.Adv Mater,2017,29:1700177
40 Wang L,Feng Y,Zhou Y,et al.Photo-switchable two-dimensional nanofluidic ionic diodes.Chem Sci,2017,8:4381-4386
41 Feng Y,Zhang K,Li H,et al.In situ visualization and detection of surface potential variation of mono and multilayer MoS2under different humidities using Kelvin probe force microscopy.Nanotechnology,2017,28:295705
42 Li Y,Xu CY,Hu PA,et al.Carrier control of MoS2nanoflakes by functional self-assembled monolayers.ACS Nano,2013,7:7795-7804
43 Rice C,Young RJ,Zan R,et al.Raman-scattering measurements and first-principles calculations of strain-induced phonon shifts in monolayer MoS2.Phys Rev B,2013,87:081307
44 Lin H,Schilo A,Kamoka AR,et al.Insight into the wetting of a graphene-mica slit pore with a monolayer of water.Phys Rev B,2017,95:195414
45 Buscema M,Steele GA,van der Zant HSJ,et al.The effect of the substrate on the Raman and photoluminescence emission of single-layer MoS2.Nano Res,2014,7:561-571
46 Yu Y,Yu Y,Xu C,et al.Engineering substrate interactions for high luminescence efficiency of transition-metal dichalcogenide monolayers.Adv Funct Mater,2016,26:4733-4739
47 Li H,Wu JB,Ran F,et al.Interfacial interactions in van der Waals heterostructures of MoS2and graphene.ACS Nano,2017,11:11714-11723