利用穿透式電子顯微鏡觀測多層奈米碳管的三電極特性

Abstract

Understanding the electrical properties of an individual carbon nanotube will have an essential impact on its application. In this thesis, the electrical properties of multiwall carbon nanotubes (MWCNTs) have been investigated by ultra-high vacuum (UHV) transmission electron microscope (TEM) equipped with a three-electrode setup. In situ tuning of a multiwall carbon nanotube field-effect transistor (CNFET) was performed. Furthermore, electric current distribution of a MWCNT has been studied. The three-electrode setup has been fabricated inside a UHV-TEM. The triangular cantilever of an AFM chip is shaped into two electrodes by focused ion beam, and an electrochemically etched gold tip is used as the third electrode. By use of the three-electrode setup inside TEM, the electrical properties of a MWCNT can be investigated with concurrent high-resolution TEM images. Ultra-clean and hysteresis-free multiwall CNFETs have been fabricated inside the TEM equipped with the movable gold tip as a local gate. The electronic characteristics of a MWCNT can be tuned by tailoring the tube structure as well as varying the applied drain-source voltage (Vds). The Schottky barrier of a multiwall CNFET was found generated within the tube, and the barrier height was estimated. The current distribution in a side-bonded MWCNT was studied by using the gold tip as a potentiometric probe. The current on the outermost shell of a MWCNT is measured by probing the gold tip along the tube. We have quantitatively derived that the current on the outermost shell depends on the applied current and the shell diameter. The current is mainly on the outer two shells of a side-bonded MWCNT.