氧化鋅奈米棒薄膜的製備與特性於記憶體和氣體感測器之應用

Fabrication and Characterization of ZnO Nanorods Thin Films in Memory and Gas Sensing Application

辛沛柔(Pragya Singh)

指導教授 ： 曾俊元

國立交通大學/電機學院/電機資訊國際學位學程/博士(2020年)

摘要

電阻式記憶體是未來非揮發性記憶體中最有前途的技術。在這篇論文中，我們報告了基於奈米顆粒的電阻元件在非揮發性記憶體和氣體感測應用中的發展。在基於氧化鋅奈米電阻的電阻式記憶體（RRAM）中，主要的挑戰之一為良好的耐久性能（記憶窗口、均勻性和切換週期）。本文提出了克服這些挑戰的新方法，重點為基於氧化鋅奈米棒的電阻式記憶體元件的製備和感測器應用，包括一氧化氮氣體的檢測。首先，討論了氧化鋅奈米棒中摻雜的影響以及透過缺陷和微結構調整提高之耐久性能，缺陷種類和結構方向都在開關特性中起到重要作用。觀察電阻層中各種濃度的鎵摻雜劑，透過調整這些因子，可以實現穩定的耐久性能。此外，進行電性和材料分析，以了解新方法中的現象。
其次，討論氧化鋅奈米棒薄膜的合成及其在室溫下對一氧化氮氣體檢測的感測特性。氧化鋅奈米棒透過水熱法在氧化鋅晶種層上生長薄膜，氧化鋅奈米棒氣體感測器對一氧化氮氣體高度敏感，檢測極限非常低，為100 ppb至10 ppb。該感測器具有良好的測量一氧化氮氣體濃度變化的能力，我們相信它可以用於製造低成本的高性能氣體感測器。在上一章中，我們研究了在各種氬氣–氧氣環境條件下沉積在不同氧化鋅晶種層上的氧化鋅奈米棒，以及影響其對一氧化氮氣體感應的晶種層的形態。我們討論了表面粗糙度、晶粒尺寸和晶種層缺陷濃度是造成這種現象的重要原因。在室溫下，可獲得出色的氣體感應特性（在1 ppm的一氧化氮氣體中為57.5％，在100 ppb的一氧化氮氣體中為7.1％），優於其他方法獲得之特性。這項研究不僅提出了用於高性能一氧化氮氣體感測器元件的氧化鋅奈米材料之潛力，還提供了一種簡單且低成本的方法來優化感應特性，而無需使用任何催化劑和其他處理方法。

關鍵字

開關記憶體 ； 非揮發性記憶體 ； 電阻元件 ； 氧化鋅 ； 奈米棒薄膜 ； 一氧化氮 ； 氣體感測器

並列摘要

Resistive memory is known to be the most promising technology for the future nonvolatile memory. In this thesis, we report the development of ZnO-nanorods based resistive devices for nonvolatile memory and gas sensing application. A decent endurance performance (memory window, uniformity and switching cycles) is one of the major challenges in ZnO-nanorods based resistive random access memory (RRAM). This thesis presents novel methods that have been developed and proposed to overcome the challenges. This thesis has separated into six chapters, which focus on the preparation of ZnO- nanorods based resistive memory devices and sensor application including the detection of Nitric Oxide gas. First, the effect of doping in ZnO nanorods and an enhanced endurance performance by defects and microstructures modulation is discussed. Both defects species and structural orientation play a significant role in the switching characteristics. Various concentration of gallium dopant in the resistive layer is employed to observe. Stable endurance performance can be achieved by adjusting these factors. Furthermore, electrical and materials analysis have been carefully analyzed to understand the phenomena in the proposed methods.
Secondly, the fabrication of ZnO nanorods thin film and their sensing characteristics with respect to nitric oxide (NO) gas detection at 26℃ (room temperature). ZnO nanorods thin film grown by hydrothermal process onto a ZnO seeding layer. ZnO nanorod thin film based gas sensor is very responsive towards NO gas with a very low detection range of 100 ppb to 10 ppb. The sensor has shown good performance to analysis the changes in the concentration of NO gas and we believe that it can be a good feature to fabricate high achievement gas sensor at low cost. In the last chapter, we investigated about the ZnO nanorods grown on distinct ZnO seed layers deposited at various Ar–O2 ambient conditions and the properties of the seed layers that influence their sensing response to nitric oxide (NO) gas. We discussed the effect of the surface roughness, grain stature, and defect concentration of the seed layer are important for this phenomenon. The gas sensing performance (57.5% at 1 ppm and 7.1% at 100 ppb of NO gas) is achieved at room temperature (26℃), higher to the response reported by other proposed methods. This research not only introduce the potential of ZnO-nanorods based thin film for high-performance NO gas sensor devices but also proposes a simple and low-cost technique to enhanced the response without using any catalyst and additional treatment.

並列關鍵字

switching memories ； nonvolatile memories ； resistive devices ； ZnO ； nanorods thin film ； nitric oxide ； gas sensor

參考文獻

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