Synthesis of Carbon Nanotubes coated with Gate Insulator and its Application to Quantum Nanodevices

碳纳米管（CNTs）由于其独特的物理和化学性质，已成为未来纳米电子学的重要材料。例如，已经提出了场效应晶体管（FET），即以诸如库仑阻塞和弹道传导的量子现象为特征的量子纳米器件。由于每个CNT-FET需要独立驱动以操作作为集成电路的构建块的CNT-FET，因此，具有通过薄电介质与沟道分离的导电沟道上方的栅电极的顶栅结构是必不可少的。顶栅结构的CNT-FET的制备严重依赖于传统的纳米加工技术，本项目的目标是利用脉冲激光沉积（PLD）技术制备出具有顶栅结构的CNT-FET，并将其作为量子纳米器件的构建模块。值得特别提及的新发现如下。（1）使用PLD，用各种无机材料同轴涂覆CNT。对于氧化物材料，沉积物表现出均匀的层结构，其组成被精确控制。此外，不仅是一个单一的层，而且多层依次涂覆在碳纳米管上重复PLD。（2）将无机材料包覆的碳纳米管和利用碳纳米管模板合成的杂化无机纳米线应用于纳米器件，如扫描隧道显微镜的针尖和纳米机电系统（NEMS）的构建块。对于混合纳米线，该结构是一个碳纳米管模板夹在氧化铝和氧化钨，我们观察到热致纳米机械偏转。由于涂层的热膨胀系数不同，混合纳米线随着样品温度的升高而弯曲。这种机械偏转具有可重复性。

Carbon nanotubes (CNTs) have been the promising materials for future nanoelectronics due to their unique physical and chemical properties. For example, field-effect transistors (FETs), quantum nanodevices characterized by quantum phenomena such as Coulomb blockade and ballistic conduction have been proposed.Since independent drive of each CNT-FET is required to operate CNT-FETs as building blocks of the integrated circuit, the top gate structure with gate electrodes above the conduction channel separated from the channel by a thin dielectric is indispensable. The fabrication of CNT-FETs with the top gate structure strongly depends on the conventional nano-fabrication techniques.In this project, it is an aim to develop the high-throughput process for CNT-FETs with the top gate structure using gate insulator coated CNTs by pulsed laser deposition (PLD) as a building block for quantum nanodevices. The new findings worthy of special mention are as follows.(1)Using PLD, coaxial coating of CNTs with various inorganic materials has been performed. For oxide materials, the deposits exhibited a uniform layer structure the composition of which was precisely controlled. Moreover, not only a single layer but also multiple layers were sequentially coated on CNTs by repeating PLD.(2)CNTs coated with inorganic materials and hybrid inorganic nanowire synthesized using a CNT template were applied to the nanodevices such as tips of scanning tunneling microscopy and building blocks for nanoelectromechanical systems (NEMS). For the hybrid nanowire, the structure is a CNT template sandwiched by aluminum oxide and tungsten oxide, we observed thermally induced nanomechanical deflection. The hybrid nanowire was bent with increasing the specimen temperature due to the different coefficients of thermal expansion of the coated layers. This mechanical deflection exhibited repeatability.