量測奈米材料的局域溫度與電壓及相關的傳輸性質

Abstract

在這篇論文中，我提出一種實驗方法，去量測各種奈米線上不同位置的局部溫度與電壓，以及相關的傳輸性質。我將利用掃描式電子顯微鏡的電子束加熱方法證明其可行性。 在論文的第一部份，我會簡單介紹一下我做這個研究主題的背景與動機。 在論文的第二部分，我會介紹一些我在實驗上使用到的裝置和前置工作，包括使用的掃描式電子顯微鏡、鎖相放大器、儀器架設、如何測量元件的溫度係數；以及我們設計了一個裝置，可以週期性地加熱奈米線並減低其噪音，再用鎖相放大器偵測其訊號。 在論文的第三部分，我主要在探討如何量測奈米線上的局域溫度。我會先介紹我的實驗原理和方法。並得到矽奈米線、氮化矽微米桿、矽鍺奈米線和單壁奈米碳管的溫度與位置的關係。 在論文的第四部分，我從第三部分得到溫度的原理與方法衍生得到奈米線上的局部電壓，並同時得到奈米線的熱傳導與熱電性質。但是由於元件的短路，因此我無法在實驗上測得矽奈米線的熱電性質。 論文的第五部份，我將會總結我的工作，並且討論運用此方法，將發射源改成雷射光，而能夠得到雷射光加熱奈米線時的局域溫度。

In this thesis, I propose an experimental method to measure local temperature and voltage at different positions of various nanowires, and the associated transport properties. I demonstrate its feasibility by employing an electron beam heating method of a scanning electron microscope. In the first part of the thesis, I will briefly introduce the background and motivation of my research topic. In the second part of the thesis, I will introduce some of the equipment and preparations I have used in the experiment, including the scanning electron microscope, lock-in amplifiers, and how to measure temperature coefficients of our devices. In addition, I have designed a device that enables periodically heating a nanowire without introducing much noise. Then I have employed a lock-in amplifier to detect its signal. In the third part of the thesis, I will discuss how to measure the local temperature on the nanowire. I will first introduce my experimental principles and methods. Then I experimentally obtain the position-dependent temperatures and length-dependent thermal conductivities of silicon nanowires, silicon nitride microbeam, silicon germanium nanowires and single-walled carbon nanotubes. In the fourth part of the thesis, I further devise a method for obtaining local voltage on a nanowire from the principles and methods described in the third part. Unfortunately, experimentally obtaining thermoelectric properties of a Si nanowire has failed due to a short circuit of the device. In the fifth part of the thesis, I will summarize my works and discuss future experiments in applying this method to determine local temperatures of a nanomaterial under laser heating.