Studies On The Properties And Devices Of Heterostructures Based On Carbon Nanotube And 2D Materials

In the recent years,carbon nanotubes?CNTs?and 2D materials are the representive nano-materials in the research field of nanotechnology.CNT has attracted much attentions for it's 1D structure and great electrical,mechanical properties.Van der Waals heterostructures based on 2D materials expand device functions on the vertical dimension within ultrasmall size of the atomic layer structures,showing great potential in both academic research and industry application.However,the in-plane size of the heterostructures are micrometer scale.In this dissertation,the advantages of both 1D carbon nanotubes and 2D materials are ultilzed to construct the mixed-dimensional heterostructures.The in-plane size of the mixed-dimensional heterostructures can be scaled down to nanometer scale.The physical properties and device application of these heterostructures were further studied.The first point of this dissertation focus on the growth of horizontally aligned single-walled carbon nanotube?SWCNT?array on quartz substrate and the CNT field effect transistor?FET?.The single CNT junction deivces have been studied via controlling the density of as-grown SWCNTs.In addition,we studied the FETs with different 2D material channels,such as graphene,molybnum disulfide,tungsten diselenide and black phosphrous,which facilitate the exploration of mixed-dimensional heterostructures.As the in-plane size of the heterostructures based on 2D materials are in micrometer scale and CNT is an ideal 1D material and metallic CNT can be 1D conductor with diameter of 1nm,we constructed the SWCNT-MoS₂-SWCNT vertical point heterostructures?VPHs?having the effective heterostructure area of¹ nm².The VPH can be used as a light detector with high spatial resolution due to the nanoscaled heterostructure area,which has been verified by scanning photocurrent mapping.It can also be a high-performance FET with high on/off ratio?10⁶?.Further we built a complementary invertor based on VPHs.So the VPHs have shown the potential application in both logic circuit and light detector.Considering asymmetric contacts have been widely used in devices,the CNT-confined vertical heterostructures?CCVHs?has been fabricated by sandwiching 2D structures with SWCNT and metal.The 2D structures can be MoS₂,WSe₂,WSe₂/MoS₂and so on.WSe₂ CCVH showed different transfer characteristics at positive and negative bias.Furthermore,complementary invertor based on CCVHs and vertical pn junction have been built.The reconfigurable properties of the asymmetric heterostructures arise from that the fermi level of SWCNT can be modulated by gate electrode.