一維奈米線之電子傳輸特性與奈米線之分子反應檢測器

Abstract

由材料組成的一維奈米線具有潛力成為下個世代的電子元件。一方面，由一維奈米線組成的元件展現出具有極好的傳輸現象，其可以介觀物理學來解釋，而非以傳統普遍常見的歐姆定律來解釋。在另一方面，一維半導體奈米線也是理想的電荷感應器，因為他們具有非常大的表面積。在本論文中，分別討論一維氮化銦奈米線的傳輸現象與矽奈米線於分子感應器的應用。 由於表面積對體積比值較大的條件下，氮化銦奈米線的傳輸特性幾乎由圍繞著表面電子來決定。因為相對低密度，電子與電子之間的交互作用是顯而易見的。這些表面電荷的移動可以由介觀物理學來解釋，其中包含：電子本身顯著的波動與不可忽略的長程電子關連性。在我們研究的氮化銦元件中，在低溫的電子傳輸行為變化多半取決於電極-奈米線接觸及缺陷結構。氮化銦奈米線伴隨著雜質/缺陷分佈，表現出磁致電阻擾動現象；在高接觸電阻下，奈米線中電子的強侷限效應造成了庫侖阻斷發生，另外也量測到穿隧接觸型態的超導現象。較完整且詳細的結果，將在下列幾章節中討論。 在感應器應用上，我們利用在奈米線的表面修飾具有反應末端基的分子，藉由在待測的矽奈米線導電度的變化，來偵測分子中電荷的改變。在我們的研究中，矽奈米線被使用作為研究其表面分子形成極化的特性行為，並用來檢測互補的單股-去氧核醣核酸分子的雜交。進一步的，我們發現在外加電場下，極化的表面修飾分子會規則排列，分子規則的程度可以由在分子下方的矽奈米線測得。 一維奈米線是個極有趣的題材，不僅因為他具有多方面的傳輸現象可以成為最佳的介觀物理學研究對象，而且，高靈敏度的特性，可用來偵測分子級的反應。由於它的高電荷-靈敏度，將一維奈米線合併入現代的半導體積體電路電子元件中，將有希望出現嶄新的電子元件紀元。

One-dimensional (1D) nanowires fabricated from different materials are potential candidates for the next generation of electronic devices. On the one hand, devices based on 1D nanowires exhibit fascinating transport phenomena which can be described in the context of mesoscopic physics rather than the well-known Ohm’s law. On the other hand, 1D semiconductor wires are ideal charge sensors due to their relatively large surface area. In this thesis, electron transport properties in 1D InN nanowires and sensor application using Si-nanowires are investigated. Owing to the large surface-to-volume ratio, the transport characteristics of InN nanowires are generally governed by the surface charges. Because of relatively low density, the electron-electron interaction is noticeable. The motion of these surface charges can be described by mesoscopic physics in which, electron wave nature is notable and long-range electron correlation cannot be overlooked. In the 1D nanowire devices that we studied, the low temperature transport behaviors were depending on the lead-wire contacts and the wire defects. For devices with low contact resistances, the wires exhibited magnetoresistance fluctuations associated with weak disorder system, and for devices with high contact resistances, Coulomb blockade behaviors due to strong localization of electrons in the wires were generally observed. Furthermore, we also found superconductivity in an individual InN nanowire. When the 1D nanowire is fabricated into a sensor, its surface is modified with an active target molecular layer, and the variation in the molecular charge is reflected by a change in the wire conductance. In our study, silicon nanowires are employed to characterize the polarization of surface molecules and to detect the hybridization between complimentary single-stranded DNA molecules. Furthermore, we showed it is possible to order the surface molecules by an external electric field, and the degree of ordering can be detected by the underneath nanowire. 1D nanowire is an interesting subject to investigate not only because of its rich transport phenomena that provide a good playground for studying mesoscopic physics, but also the high-sensitivity that allows detection of reactions at molecular levels. With its high charge-sensitivity, the incorporation of 1D nanowire with current CMOS electronic devices may results in an innovative era for future semiconductor electronics.