A new class of graphene materials is developed where graphene are self-assembled (SA) on boron nitride nanotubes (BNNTs) without the use of metallic catalyst. These SA graphene/BNNTs are found to conduct current in a nonlinear manner at room temperature, which is unexpected from the metallic nature of graphene. This transport property was revealed by using four-probe scanning tunneling microscopy (4-probe STM) [1] under real time scanning electron microscopy (SEM) imaging on individual SA Graphene/BNNTs. Merely no current (~10-11 A) was detected at low bias voltages. Current was increased nonlinearly with the increase of bias voltages up to ~10-7 A. This result suggests that SA Graphene/BNNTs are new graphene-based materials applicable for electronic devices with a switching ratio of 104. 

Graphene is known for its high electron mobility and metallic nature.[2, 3] These have enabling their application in high-frequency analogue devices but preventing them from use in digital switches. [4] In contrast, the structurally analogous h-BN sheets and BN nanotubes (BNNTs) are insulators. [5, 6] The h-BN under layer is known to enhance electron mobility of graphene.[7,8] More recently, in-plane graphene/h-BN heterojunctions were also demonstrated due to their small lattice mismatch. [9-11] However, graphene digital switches have not being demonstrated by these graphene/h-BN heterostructures. Here we show that SA graphene/BNNTs are functional as current rectifiers with a switching ratio of 104. 

Our SA Graphene/BNNTs are prepared by growing BNNTs by chemical vapor deposition (CVD).[12, 13] As shown in Figure 1a and b, patchy graphene shells are coated on the surfaces of BNNTs. With refined procedures, thin and uniform graphene (Figure 1c and d) can be coated on the surfaces of BNNTs. These uniformly coated SA graphene/BNNTs are then characterized by 4-probe STM for their transport properties (Figure 1e and f). Comprehensive data based on SEM, Raman spectroscopy, UV-Vis spectroscopy, Fourier Transform IR spectroscopy, High Resolution Transmission electron microscopy (HRTEM), Electron Energy Loss Spectroscopy (EELS), Energy Filtered Transmission Electron Microscopy (EFTEM), and 4-probe STEM has led to the understanding of the growth model and transport model of these SA graphene/BNNTs. All these will be discussed in the meeting. 

A new class of graphene materials is developed where graphene are self-assembled (SA) on boron nitride nanotubes (BNNTs) without the use of metallic catalyst. These SA graphene/BNNTs are found to conduct current in a nonlinear manner at room temperature, which is unexpected from the metallic nature of graphene. This transport property was revealed by using four-probe scanning tunneling microscopy (4-probe STM) [1] under real time scanning electron microscopy (SEM) imaging on individual SA Graphene/BNNTs. Merely no current (~10-11 A) was detected at low bias voltages. Current was increased nonlinearly with the increase of bias voltages up to ~10-7 A. This result suggests that SA Graphene/BNNTs are new graphene-based materials applicable for electronic devices with a switching ratio of 104. 

Graphene is known for its high electron mobility and metallic nature.[2, 3] These have enabling their application in high-frequency analogue devices but preventing them from use in digital switches. [4] In contrast, the structurally analogous h-BN sheets and BN nanotubes (BNNTs) are insulators. [5, 6] The h-BN under layer is known to enhance electron mobility of graphene.[7,8] More recently, in-plane graphene/h-BN heterojunctions were also demonstrated due to their small lattice mismatch. [9-11] However, graphene digital switches have not being demonstrated by these graphene/h-BN heterostructures. Here we show that SA graphene/BNNTs are functional as current rectifiers with a switching ratio of 104. 

Our SA Graphene/BNNTs are prepared by growing BNNTs by chemical vapor deposition (CVD).[12, 13] As shown in Figure 1a and b, patchy graphene shells are coated on the surfaces of BNNTs. With refined procedures, thin and uniform graphene (Figure 1c and d) can be coated on the surfaces of BNNTs. These uniformly coated SA graphene/BNNTs are then characterized by 4-probe STM for their transport properties (Figure 1e and f). Comprehensive data based on SEM, Raman spectroscopy, UV-Vis spectroscopy, Fourier Transform IR spectroscopy, High Resolution Transmission electron microscopy (HRTEM), Electron Energy Loss Spectroscopy (EELS), Energy Filtered Transmission Electron Microscopy (EFTEM), and 4-probe STEM has led to the understanding of the growth model and transport model of these SA graphene/BNNTs. All these will be discussed in the meeting.