Two-dimensional(2D)materials with reversible phase transformation are appealing for their rich physics and potential applications in information storage.However,up to now,reversible phase transitions in 2D materials t...Two-dimensional(2D)materials with reversible phase transformation are appealing for their rich physics and potential applications in information storage.However,up to now,reversible phase transitions in 2D materials that can be driven by facile nondestructive methods,such as temperature,are still rare.Here,we introduce ultrathin Cu_(9)S_(5)crystals grown by chemical vapor deposition(CVD)as an exemplary case.For the first time,their basic electrical properties were investigated based on Hall measurements,showing a record high hole carrier density of~1022 cm^(-3) among 2D semiconductors.Besides,an unusual and repeatable conductivity switching behavior at~250 K were readily observed in a wide thickness range of CVD-grown Cu_(9)S_(5)(down to 2 unit-cells).Confirmed by in-situ selected area electron diffraction,this unusual behavior can be ascribed to the reversible structural phase transition between the room-temperature hexagonalβphase and low-temperatureβ’phase with a superstructure.Our work provides new insights to understand the physical properties of ultrathin Cu_(9)S_(5)crystals,and brings new blood to the 2D materials family with reversible phase transitions.展开更多
Identifying air-stable two-dimensional(2D)ferromagnetism with high Curie temperature(T_(c))is highly desirable for its potential applications in next-generation spintronics.However,most of the work reported so far mai...Identifying air-stable two-dimensional(2D)ferromagnetism with high Curie temperature(T_(c))is highly desirable for its potential applications in next-generation spintronics.However,most of the work reported so far mainly focuses on promoting one specific key factor of 2D ferromagnetism(T_(c)or air stability),rather than comprehensive promotion of both of them.Herein,ultrathin Cr_(1-x)Te crystals grown by chemical vapor deposition(CVD)show thickness-dependent T_(c)up to 285 K.The out-of-plane ferromagnetic order is well preserved down to atomically thin limit(2.0 nm),as evidenced by anomalous Hall effect observed in non-encapsulated samples.Besides,the CVD-grown Cr_(1-x)Te nanosheets present excellent ambient stability,with no apparent change in surface roughness or electrical transport properties after exposure to air for months.Our work provides an alternative platform for investigation of intrinsic 2D ferromagnetism and development of innovative spintronic devices.展开更多
基金J.X.W.acknowledges financial support from the National Natural Science Foundation of China(NSFC)(No.92064005)Opening Project of State Key Laboratory of High Performance Ceramics and Superfine Microstructure(No.SKL202211SIC)+6 种基金H.T.Y.acknowledges the support from the NSFC(Nos.51861145201,52072168,and 21733001)the National Key Research and Development Program of China(No.2018YFA0306200)J.W.H.acknowledges the support from the National Key Research and Development Program of China(No.2021YFA1202901)X.W.F.acknowledges financial support from the NSFC at grant(Nos.11974191 and 2217830)the National Key Research and Development Program of China at grant(No.2020YFA0309300)the Natural Science Foundation of Tianjin at grant(Nos.20JCZDJC00560 and 20JCJQJC00210)the 111 Project(No.B23045).
文摘Two-dimensional(2D)materials with reversible phase transformation are appealing for their rich physics and potential applications in information storage.However,up to now,reversible phase transitions in 2D materials that can be driven by facile nondestructive methods,such as temperature,are still rare.Here,we introduce ultrathin Cu_(9)S_(5)crystals grown by chemical vapor deposition(CVD)as an exemplary case.For the first time,their basic electrical properties were investigated based on Hall measurements,showing a record high hole carrier density of~1022 cm^(-3) among 2D semiconductors.Besides,an unusual and repeatable conductivity switching behavior at~250 K were readily observed in a wide thickness range of CVD-grown Cu_(9)S_(5)(down to 2 unit-cells).Confirmed by in-situ selected area electron diffraction,this unusual behavior can be ascribed to the reversible structural phase transition between the room-temperature hexagonalβphase and low-temperatureβ’phase with a superstructure.Our work provides new insights to understand the physical properties of ultrathin Cu_(9)S_(5)crystals,and brings new blood to the 2D materials family with reversible phase transitions.
基金J.X.W.acknowledges financial support from the National Natural Science Foundation of China(No.92064005)Beijing National Laboratory for Molecular Sciences(No.BNLMS201914)+4 种基金thanks S.S.D.in Tianjin Key Laboratory of Molecular Optoelectronic Sciences for her instrumental assistance on PPMS(Dynacool-9T)H.T.Y.acknowledges the support from the National Natural Science Foundation of China(Nos.91750101,21733001,52072168,and 51861145201)the National Key Basic Research Program of China(No.2018YFA0306200)the Fundamental Research Funds for the Central Universities(Nos.021314380078,021314380104,and 021314380147)Jiangsu Key Laboratory of Artificial Functional Materials。
文摘Identifying air-stable two-dimensional(2D)ferromagnetism with high Curie temperature(T_(c))is highly desirable for its potential applications in next-generation spintronics.However,most of the work reported so far mainly focuses on promoting one specific key factor of 2D ferromagnetism(T_(c)or air stability),rather than comprehensive promotion of both of them.Herein,ultrathin Cr_(1-x)Te crystals grown by chemical vapor deposition(CVD)show thickness-dependent T_(c)up to 285 K.The out-of-plane ferromagnetic order is well preserved down to atomically thin limit(2.0 nm),as evidenced by anomalous Hall effect observed in non-encapsulated samples.Besides,the CVD-grown Cr_(1-x)Te nanosheets present excellent ambient stability,with no apparent change in surface roughness or electrical transport properties after exposure to air for months.Our work provides an alternative platform for investigation of intrinsic 2D ferromagnetism and development of innovative spintronic devices.
