Metal-semiconductor diodes constructed from two-dimensional(2D)van der Waals heterostructures show excellent gate electrostatics and a large built-in electric field at the tunnel junction,which can be exploited to mak...Metal-semiconductor diodes constructed from two-dimensional(2D)van der Waals heterostructures show excellent gate electrostatics and a large built-in electric field at the tunnel junction,which can be exploited to make highly sensitive photodetector.Here we demonstrate a metal-semiconductor photodiode constructed by the monolayer graphene(Gr)on a few-layer black phosphorus(BP).Due to the presence of a built-in potential barrier(~0.09±0.03 eV)at the Gr-BP interface,the photoresponsivity of the Gr-BP device is enhanced by a factor of 672%,and the external quantum efficiency(EQE)increases to648%from 84%of the bare BP.Electrostatic gating allows the BP channel to be switched between p-type and n-type conduction.We further demonstrate that excitation laser power can be used to control the current polarity of the Gr-BP device due to photon-induced doping.The versatility of the Gr-BP junctions in terms of electrostatic bias-induced or light-induced switching of current polarity is potentially useful for making dynamically reconfigurable digital circuits.展开更多
Metallizing 2D semiconductors is a crucial research area with significant applications,such as reducing the contact resistance at metal/2D semiconductor interfaces.This is a key challenge in the realization of next-ge...Metallizing 2D semiconductors is a crucial research area with significant applications,such as reducing the contact resistance at metal/2D semiconductor interfaces.This is a key challenge in the realization of next-generation lowpower and high-performance devices.While various methods exist for metallizing Mo-and W-based 2D semiconductors like MoS_(2) and WSe_(2),effective approaches for Pt-based ones have been lacking.This study demonstrates that platinum dichalcogenides(PtX_(2),X=Se or Te)undergo a semiconductorto-metal transition when grown on niobium dichalcogenides(NbX_(2),X=Se or Te).PtX_(2)/NbX_(2) heterostructures were fabricated using molecular beam epitaxy(MBE)and characterized by Raman spectra,scanning transmission electron microscopy(STEM)and scanning tunneling microscopy/spectroscopy(STM/STS).Raman spectra and STEM confirm the growth of 1T-phase PtX_(2) and 1H-phase NbX_(2).Both 2D STS mapping and layer-dependent STS show that regardless of their layer numbers,both pristine semiconducting PtSe_(2) and PtTe_(2) are converted to metallic forms when interfacing with NbSe_(2) or NbTe_(2).Density functional theory(DFT)calculations suggest that the metallization of PtSe_(2) on NbX_(2) and PtTe_(2) on NbTe_(2) results from interfacial orbital hybridization,while for PtTe_(2) on NbSe_(2),it is due to the strong p-doping effect caused by interfacial charge transfer.Our work provides an effective method for metallizing PtX_(2) semiconductors,which may lead to significant applications such as reducing the contact resistance at metal electrode/2D semiconductor interfaces and developing devices like rectifiers,rectenna,and photodetectors based on 2D Schottky diodes.展开更多
Two-dimensional(2D)van der Waals transition metal dichalcogenides(TMDs)are a new class of electronic materials offering tremendous opportunities for advanced technologies and fundamental studies.Similar to conventiona...Two-dimensional(2D)van der Waals transition metal dichalcogenides(TMDs)are a new class of electronic materials offering tremendous opportunities for advanced technologies and fundamental studies.Similar to conventional semiconductors,substitutional doping is key to tailoring their electronic properties and enabling their device applications.Here,we review recent progress in doping methods and understanding of doping effects in group 6 TMDs(MX2,M=Mo,W;X=S,Se,Te),which are the most widely studied model 2D semiconductor system.Experimental and theoretical studies have shown that a number of different elements can substitute either M or X atoms in these materials and act as n-or p-type dopants.This review will survey the impact of substitutional doping on the electrical and optical properties of these materials,discuss open questions,and provide an outlook for further studies.展开更多
We report a systematic study of the etching of MoSs crystals by using XeF2 as a gaseous reactant. By controlling the etching process, monolayer MoS2 with uniform morphology can be obtained. The Raman and photoluminesc...We report a systematic study of the etching of MoSs crystals by using XeF2 as a gaseous reactant. By controlling the etching process, monolayer MoS2 with uniform morphology can be obtained. The Raman and photoluminescence spectra of the resulting material were similar to those of exfoliated MoS2. Utilizing this strategy, different patterns such as a Hall bar structure and a hexagonal array can be realized. Furthermore, the etching mechanism was studied by introducing graphene as an etching mask. We believe our technique opens an easy and controllable way of etching MoS2, which can be used to fabricate complex nanostructures, such as nanoribbons, quantum dots, and transistor structures. This etching process using XeF2 can also be extended to other interesting two-dimensional crystals.展开更多
We demonstrate a facile and effective approach to significantly improve the photoluminescence of bulk MoS2 via laser thinning followed by gold particle decoration. Upon laser thinning of exfoliated bulk MoSz photolumi...We demonstrate a facile and effective approach to significantly improve the photoluminescence of bulk MoS2 via laser thinning followed by gold particle decoration. Upon laser thinning of exfoliated bulk MoSz photoluminescence emerges from the laser-thinned region. After further treatment with an AuCl3 solution, gold particles self-assemble on the laser-thinned region and thick edges, further increasing the fluorescence of bulk MoS2 28 times and the Raman response 3 times. Such fluorescence enhancement can be attributed to both surface plasmon resonance and p-type doping induced by gold particles. The combination of laser thinning and AuCl3 treatment enables the functionalization of bulk MoS2 for optoelectronic applications. It can also provide a viable strategy for mask-free and area-selective p-type doping on single MoS2 flakes.展开更多
基金the financial support provided by the Fundamental Research Funds for the Central Universities(Nos.NS2020008,NC2018001,NJ2020003,NZ2020001)the Program for Innovative Talents and Entrepreneur in Jiangsu,Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures(Nos.MCMS-I-0419G02,MCMS-I-0421K01)+2 种基金National Key Research and Development Program of China(No.2019YFA0705400)Australian Research Council Future Fellowship(No.FT160100205)DECRA Fellowship(No.DE200101622)。
文摘Metal-semiconductor diodes constructed from two-dimensional(2D)van der Waals heterostructures show excellent gate electrostatics and a large built-in electric field at the tunnel junction,which can be exploited to make highly sensitive photodetector.Here we demonstrate a metal-semiconductor photodiode constructed by the monolayer graphene(Gr)on a few-layer black phosphorus(BP).Due to the presence of a built-in potential barrier(~0.09±0.03 eV)at the Gr-BP interface,the photoresponsivity of the Gr-BP device is enhanced by a factor of 672%,and the external quantum efficiency(EQE)increases to648%from 84%of the bare BP.Electrostatic gating allows the BP channel to be switched between p-type and n-type conduction.We further demonstrate that excitation laser power can be used to control the current polarity of the Gr-BP device due to photon-induced doping.The versatility of the Gr-BP junctions in terms of electrostatic bias-induced or light-induced switching of current polarity is potentially useful for making dynamically reconfigurable digital circuits.
基金Ministry of Education Singapore,Grant/Award Number:MOET2EP50122-0020。
文摘Metallizing 2D semiconductors is a crucial research area with significant applications,such as reducing the contact resistance at metal/2D semiconductor interfaces.This is a key challenge in the realization of next-generation lowpower and high-performance devices.While various methods exist for metallizing Mo-and W-based 2D semiconductors like MoS_(2) and WSe_(2),effective approaches for Pt-based ones have been lacking.This study demonstrates that platinum dichalcogenides(PtX_(2),X=Se or Te)undergo a semiconductorto-metal transition when grown on niobium dichalcogenides(NbX_(2),X=Se or Te).PtX_(2)/NbX_(2) heterostructures were fabricated using molecular beam epitaxy(MBE)and characterized by Raman spectra,scanning transmission electron microscopy(STEM)and scanning tunneling microscopy/spectroscopy(STM/STS).Raman spectra and STEM confirm the growth of 1T-phase PtX_(2) and 1H-phase NbX_(2).Both 2D STS mapping and layer-dependent STS show that regardless of their layer numbers,both pristine semiconducting PtSe_(2) and PtTe_(2) are converted to metallic forms when interfacing with NbSe_(2) or NbTe_(2).Density functional theory(DFT)calculations suggest that the metallization of PtSe_(2) on NbX_(2) and PtTe_(2) on NbTe_(2) results from interfacial orbital hybridization,while for PtTe_(2) on NbSe_(2),it is due to the strong p-doping effect caused by interfacial charge transfer.Our work provides an effective method for metallizing PtX_(2) semiconductors,which may lead to significant applications such as reducing the contact resistance at metal electrode/2D semiconductor interfaces and developing devices like rectifiers,rectenna,and photodetectors based on 2D Schottky diodes.
基金the Ministry of Education(MOE),Singapore,under AcRF Tier 3(MOE2018-T3-1-005)the Singapore National Research Foundation for funding the research under medium-sized centre programme.M.B.acknowledges support from MOE’s AcRF Tier 1(R-284-000-179-133).
文摘Two-dimensional(2D)van der Waals transition metal dichalcogenides(TMDs)are a new class of electronic materials offering tremendous opportunities for advanced technologies and fundamental studies.Similar to conventional semiconductors,substitutional doping is key to tailoring their electronic properties and enabling their device applications.Here,we review recent progress in doping methods and understanding of doping effects in group 6 TMDs(MX2,M=Mo,W;X=S,Se,Te),which are the most widely studied model 2D semiconductor system.Experimental and theoretical studies have shown that a number of different elements can substitute either M or X atoms in these materials and act as n-or p-type dopants.This review will survey the impact of substitutional doping on the electrical and optical properties of these materials,discuss open questions,and provide an outlook for further studies.
文摘We report a systematic study of the etching of MoSs crystals by using XeF2 as a gaseous reactant. By controlling the etching process, monolayer MoS2 with uniform morphology can be obtained. The Raman and photoluminescence spectra of the resulting material were similar to those of exfoliated MoS2. Utilizing this strategy, different patterns such as a Hall bar structure and a hexagonal array can be realized. Furthermore, the etching mechanism was studied by introducing graphene as an etching mask. We believe our technique opens an easy and controllable way of etching MoS2, which can be used to fabricate complex nanostructures, such as nanoribbons, quantum dots, and transistor structures. This etching process using XeF2 can also be extended to other interesting two-dimensional crystals.
文摘We demonstrate a facile and effective approach to significantly improve the photoluminescence of bulk MoS2 via laser thinning followed by gold particle decoration. Upon laser thinning of exfoliated bulk MoSz photoluminescence emerges from the laser-thinned region. After further treatment with an AuCl3 solution, gold particles self-assemble on the laser-thinned region and thick edges, further increasing the fluorescence of bulk MoS2 28 times and the Raman response 3 times. Such fluorescence enhancement can be attributed to both surface plasmon resonance and p-type doping induced by gold particles. The combination of laser thinning and AuCl3 treatment enables the functionalization of bulk MoS2 for optoelectronic applications. It can also provide a viable strategy for mask-free and area-selective p-type doping on single MoS2 flakes.
