Tungsten ditelluride(WTe_(2))is a layered transition metal dichalcogenide(TMD)that has attracted increasing research inter-est in recent years.WTe_(2) has demonstrated large non-saturating magnetoresistance,potential ...Tungsten ditelluride(WTe_(2))is a layered transition metal dichalcogenide(TMD)that has attracted increasing research inter-est in recent years.WTe_(2) has demonstrated large non-saturating magnetoresistance,potential for spintronic applications and promise as a type-II Weyl semimetal.The majority of works on WTe_(2) have relied on mechanically exfoliated flakes from chemical vapour transport(CVT)-grown crystals for their investigations.While producing high-quality samples,this method is hindered by several disadvantages including long synthesis time,high-temperature annealing and an inherent lack of scalability.In this work,a synthesis method is demonstrated that allows the production of large-area polycrystalline films of WTe_(2).This is achieved by the reaction of pre-deposited films of W and Te at a relatively low temperature of 550℃.Sputter X-ray photoelectron spectroscopy reveals the rapid but self-limiting nature of the oxidation of these WTe_(2) films in ambient conditions.The WTe_(2) films are composed of areas of micrometre-sized nanobelts that can be isolated and offer potential as an alternative to CVT-grown samples.These nanobelts are highly crystalline with low defect densities indicated by transmission electron microscopy and show promising initial electrical results.展开更多
Atomic force microscopy(AFM)and scanning probe lithography can be used for the mechanical treatment of various surfaces,including polymers,metals,and semiconductors.The technique of nanoshaving,in which materials are ...Atomic force microscopy(AFM)and scanning probe lithography can be used for the mechanical treatment of various surfaces,including polymers,metals,and semiconductors.The technique of nanoshaving,in which materials are removed using the AFM tip,is employed in this work to produce nanopatterns of self-assembled monolayers(SAMs)on two-dimensional(2D)materials.The materials used are monolayers of transition metal dichalcogenides(TMDs),namely,MoS_(2)and WS_(2),which are noncovalently functionalized with perylene diimide(PDI),a perylene derivative.The approach involves rastering an AFM probe across the surface at a controlled increased load in ambient conditions.As a result of the strong bond between PDI SAM and TMD,loads in excess of 1|1N are required to pattern the monolayer.Various predefined patterns,including a grating pattern with feature sizes below 250 nm,are demonstrated.Results indicate the high precision of nanoshaving as an accurate and nondestructive lithographic technique for 2D materials.The work functions of shaved heterostructures are also examined using Kelvin probe force microscopy.展开更多
基金This work was financially supported by Science Foundation Ireland(SFI,grant numbers:15/SIRG/3329,12/RC/2278_P2,PI_15/IA/3131)the Irish Research Council(Project 204486,Award 13653)+2 种基金Science Foundation Ireland and the Royal Society Fellowship(URF/RI/191637)The SEM and(S)TEM imaging for this project was carried out at the Advanced Microscopy Laboratory(AML),Trinity College Dublin,Ireland.The AML is an SFI supported imaging and analysis centre,part of the CRANN Institute and affiliated to the AMBER centre.G.S.D and T S-L acknowledge the European Commission under the project Graphene Flagship(Grant No.881603)the German Ministry of Education and Research(BMBF)under ACDC(Grant No.13N15100).
文摘Tungsten ditelluride(WTe_(2))is a layered transition metal dichalcogenide(TMD)that has attracted increasing research inter-est in recent years.WTe_(2) has demonstrated large non-saturating magnetoresistance,potential for spintronic applications and promise as a type-II Weyl semimetal.The majority of works on WTe_(2) have relied on mechanically exfoliated flakes from chemical vapour transport(CVT)-grown crystals for their investigations.While producing high-quality samples,this method is hindered by several disadvantages including long synthesis time,high-temperature annealing and an inherent lack of scalability.In this work,a synthesis method is demonstrated that allows the production of large-area polycrystalline films of WTe_(2).This is achieved by the reaction of pre-deposited films of W and Te at a relatively low temperature of 550℃.Sputter X-ray photoelectron spectroscopy reveals the rapid but self-limiting nature of the oxidation of these WTe_(2) films in ambient conditions.The WTe_(2) films are composed of areas of micrometre-sized nanobelts that can be isolated and offer potential as an alternative to CVT-grown samples.These nanobelts are highly crystalline with low defect densities indicated by transmission electron microscopy and show promising initial electrical results.
基金Science Foundation Ireland,PI_15/IA/3131,Georg Stefan Duesberg。
文摘Atomic force microscopy(AFM)and scanning probe lithography can be used for the mechanical treatment of various surfaces,including polymers,metals,and semiconductors.The technique of nanoshaving,in which materials are removed using the AFM tip,is employed in this work to produce nanopatterns of self-assembled monolayers(SAMs)on two-dimensional(2D)materials.The materials used are monolayers of transition metal dichalcogenides(TMDs),namely,MoS_(2)and WS_(2),which are noncovalently functionalized with perylene diimide(PDI),a perylene derivative.The approach involves rastering an AFM probe across the surface at a controlled increased load in ambient conditions.As a result of the strong bond between PDI SAM and TMD,loads in excess of 1|1N are required to pattern the monolayer.Various predefined patterns,including a grating pattern with feature sizes below 250 nm,are demonstrated.Results indicate the high precision of nanoshaving as an accurate and nondestructive lithographic technique for 2D materials.The work functions of shaved heterostructures are also examined using Kelvin probe force microscopy.
