以電子束微影術製作氧化鋅核/碲化鋅殼奈米線元件

Fabrication of ZnO/ZnTe Core/Shell Nanowire Device by Electron Beam Lithography

尤聖涵(Sheng-Han Yu)

指導教授 ： 張顏暉

國立臺灣大學/理學院/物理研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.02865

摘要

本篇論文主要探討的是氧化鋅奈米線及氧化鋅/碲化鋅-核/殼奈米線元件的製程及在光性電性運用的研究。
本論文中我們使用兩種不同的奈米線：氧化鋅奈米線及氧化鋅/碲化鋅-核/殼奈米線這兩個奈米結構，第一種材料是目前學術界常用的氣體、光的感測器，但其表面易與空氣中的水氣與氧氣等有作用，使在其上的電子載子受困，形成無法利用的空乏區，且在量測時表面與空氣的作用會驟增，並隨著量測時間的延長而有作用程度的不等，因此有不可排除的干擾，有些數據無法有重複性(除非再放置多日或抽真空)。
有鑑於此，在其表面作鈍化變成此元件研究的大方向，有許多發表的論文都致力於此。我們在氧化鋅奈米線表面鍍上了碲化鋅奈米薄膜，形成化鋅/碲化鋅-核/殼的奈米線，不僅鈍化了表面，更可探討電子在此第二型接面(type Ⅱ)的傳遞模式。

關鍵字

氧化鋅 ； 氧化鋅/碲化鋅 ； 奈米線 ； 核/殼奈米結構

並列摘要

One-dimensional ZnO nanowires have attracted much attention for their potential applications in making electronic and opto-eletronic devices. As the nanowires have large surface to volume ratio, the surface effect, especially the effect of surface defects on the performance of ZnO-nanowire-based device cannot be overlooked. For example, it is well-known that chemisorption of ambient gases, primarily oxygen, has a strong effect on the electrical properties of ZnO nanowire. In order to improve the stability of the performance of the ZnO-nanowire-based devices it is desirable to passivate the surface of the ZnO nanowire. In this paper we report the growth and characterization of ZnO-ZnTe core-shell nanowires and their electrical and opto-electronical properties. In this structure the ZnTe layer not only serve the purpose of passivating the ZnO surface, it also forms a type -II semiconductor heterosructure with the ZnO core layer . The separation of electron and hole in the type-II heterostructure is expected to enhance the light induced photo-conductivity for the core-shell nanowire.

A two-step synthesis was used to fabricate ZnO/ZnTe core/shell nanowire. In the first step, the ZnO nanowires were grown for 40 minutes at T= 930 °C in a furnace by chemical vapor deposition with a gold thin film as catalyst. After the sample was cooled down, it was then transferred to the MOCVD chamber for the deposition of ZnTe shell on ZnO core for 300 sec at T= 550 °C. The morphology and size distribution of the ZnO/ZnTe core/shell nanowire arrays were studied by scanning electron microscopy and it was found that the surfaces of the well-aligned ZnO nanowires became rougher after the growth of ZnTe layer and the diameter of the nanowire increase from 70-100 nm to 150-300 nm. The x-ray diffraction and transmission electron microscope measurements show that the ZnO core has wurtzite structure, the ZnTe shell has zinc-blende structure and both materials have good crystalline quality.

The nanowire was then placed on top of a 300 nm SiO2 layer which in term was on top of a n-type Si substrate to form a field effect transistor with the heavily doped silicon substrate served as a metal gate. Metallic electrodes consisting of Ti /Au were then deposited on the two ends of the nanowire by an electron beam evaporator and defined as source and drain electrodes by a photolithography and lift-off process. Wavelength-dependent photoconductivity of the nanowire was then studied by dispersing the light emitted from a Xe lamp with a monchromator. It was found that the ZnO-ZnTe core-shell narrowire show improved device performance over ZnO nanowire both as a field effect transistor and as a photo-detector.

並列關鍵字

ZnO ； ZnO/ZnTe ； nanowire ； core-shell

參考文獻

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