Transferring high-quality exfoliated graphene flakes onto different substrates while keeping the graphene free of polymer residues is of great importance, but at the same time very challenging. Currently, the only fea...Transferring high-quality exfoliated graphene flakes onto different substrates while keeping the graphene free of polymer residues is of great importance, but at the same time very challenging. Currently, the only feasible way is the so-called all-dry "pick-and-lift" method, in which a hexagonal boron nitride(hBN) flake is employed to serve as a stamp to pick up graphene from one substrate and to lift it down onto another substrate. The transferred graphene samples, however,are always covered or encapsulated by hBN flakes, which leads to difficulties in further characterizations. Here, we report an improved "pick-and-lift" method, which allows ultra-clean graphene flakes to be transferred onto a variety of substrates without hBN coverage. Basically, by exploiting the superlubricity at the graphene/hBN stack interface, we are able to remove the top-layer hBN stamp by applying a tangential force and expose the underneath graphene.展开更多
Single-walled carbon nanotubes(SWCNTs),due to their outstanding electrical and optical properties,are expected to have extensive applications,such as in transparent conductive fims and ultra-small field-effect transis...Single-walled carbon nanotubes(SWCNTs),due to their outstanding electrical and optical properties,are expected to have extensive applications,such as in transparent conductive fims and ultra-small field-effect transistors(FETs).However,those applications can only be best realized with pure metallic or pure semiconducting SWCNTs.Hence,identifying and separating metallic from semiconducting SWCNTs in as-grown samples are crucial.In addition,knowledge of the type of an SWCNT is also important for further exploring its new properties in fundamental science.Here we report employing scanning near-field optical microscopy(SNOM)as a direct and simple method to identify metallic and semiconducting SWCNTs on SiO2/Si substrates.Metallic and semiconducting SWCNTs show distinct near-field optical responses because the metallic tubes support plasmons whereas the semiconducting tubes do not.The reliability of this method is verified using FET testing and Rayleigh scattering spectroscopy.Our result demonstrates that the SNOM technique provides a reliable,simple,noninvasive and in situ method to distinguish between metallic and semiconducting SWCNTs.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0302001)the National Natural Science Foundation of China(Grant Nos.11574204 and 11774224)
文摘Transferring high-quality exfoliated graphene flakes onto different substrates while keeping the graphene free of polymer residues is of great importance, but at the same time very challenging. Currently, the only feasible way is the so-called all-dry "pick-and-lift" method, in which a hexagonal boron nitride(hBN) flake is employed to serve as a stamp to pick up graphene from one substrate and to lift it down onto another substrate. The transferred graphene samples, however,are always covered or encapsulated by hBN flakes, which leads to difficulties in further characterizations. Here, we report an improved "pick-and-lift" method, which allows ultra-clean graphene flakes to be transferred onto a variety of substrates without hBN coverage. Basically, by exploiting the superlubricity at the graphene/hBN stack interface, we are able to remove the top-layer hBN stamp by applying a tangential force and expose the underneath graphene.
基金the National Natural Science Foundation of China under Grant Nos.11574204 and 11774224the National Key Research and Development Program of China(2016YFA0302001)+1 种基金Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learningadditional support from a Shanghai talent program。
文摘Single-walled carbon nanotubes(SWCNTs),due to their outstanding electrical and optical properties,are expected to have extensive applications,such as in transparent conductive fims and ultra-small field-effect transistors(FETs).However,those applications can only be best realized with pure metallic or pure semiconducting SWCNTs.Hence,identifying and separating metallic from semiconducting SWCNTs in as-grown samples are crucial.In addition,knowledge of the type of an SWCNT is also important for further exploring its new properties in fundamental science.Here we report employing scanning near-field optical microscopy(SNOM)as a direct and simple method to identify metallic and semiconducting SWCNTs on SiO2/Si substrates.Metallic and semiconducting SWCNTs show distinct near-field optical responses because the metallic tubes support plasmons whereas the semiconducting tubes do not.The reliability of this method is verified using FET testing and Rayleigh scattering spectroscopy.Our result demonstrates that the SNOM technique provides a reliable,simple,noninvasive and in situ method to distinguish between metallic and semiconducting SWCNTs.
