高透光度與高靈敏性氧化鋅薄膜電晶體之奈米金粒子共軛光檢測器

Abstract

在本論文中，我們利用簡易、低溫製程與無毒氧化鋅半導體材料，成功製作出可在低電壓操作下的薄膜電晶體，並結合金奈米粒，使其光檢測範圍延伸至可見光波段。 本研究之薄膜電晶體元件在非工作區間時有較小的漏電流，在工作區間時有相對較大的飽和電流，顯示出此元件具有良好的開關特性；電晶體的通道層材料決定了其電性表現的優劣，此元件選用了氧化鋅半導體材料，因其無毒性、高透光度且具有良好載子遷移率；於製備上，沉積氧化鋅薄膜之製程也選用可在常溫常壓下完成的旋轉塗佈法；本研究欲將薄膜電晶體作為具光感測功能的光檢測薄膜電晶體，然而氧化鋅通道層能隙為3.3 eV，只能檢測紫外光波段，無法偵測可見光波段，所以我們在通道層及介電層間結合了金奈米粒，因金奈米粒子具有表面電漿共振之效應，藉由控制金奈米粒之尺寸大小，即可與可見光波段起反應，來達成延伸偵測可見光波段的目的。 本研究分別探討了薄膜電晶體結合金奈米粒子後，元件本身電特性上的改變，以及探討在紫外光與可見光波段下作為光感測器的偵測能力，最後將其結構轉製於高透光度的Fluorine tin oxide (FTO)玻璃基板上。本研究主要以元件的臨限電壓(Threshold voltage, Vth)漂移量的大小，來判斷其特性上的改變以及光偵測的能力；在元件本身電特性的改善上，結合高濃度金奈米粒，臨限電壓可漂移至-14 V，大大增加薄膜電晶體之工作區域；在可見光檢測靈敏度上，臨限電壓漂移量可達至6 V，且其施加的汲極電壓只需0.5 V；於FTO基板上的光電晶體元件，照光前後，臨限電壓漂移量也有0.8 V。 本研究希望提供一個利用低成本、無毒、常溫常壓下的製程，即可製造出可應用於透明玻璃基板上的光感測器，並應用於工業上與生活上的諸多電子元件之中。

In this thesis, we fabricated a non-toxic zinc oxide (ZnO) material as the semiconducting channel layer for thin-film transistor (TFT) by using simple and low-temperature processing method. The thin-film transistors can be operated at low voltage, and it can be a photo-detector for sensing the visible light. The thin-film transistors exhibited good electrical switching characteristics which have very low leakage current in the non-working region, in contrast, they have relatively higher saturation drain current in the working region. In this study, we used the ZnO material as the channel layer, because it is not only non-toxic and abundant but also possesses highly transparent and excellent electrical characteristics. Moreover, we can deposit the ZnO channel layer by spin-coating processing which can be carried out at the room temperature and atmosphere. We made the photo-transistors with ZnO channel layer only sensing the UV light band and not detecting the visible band, so we linked the gold nanoparticles (AuNPs) between the channel and dielectric layer. The AuNPs can react with visible light through the surface plasmon resonance (SPR) effect. Consequently, the TFTs with AuNPs can be the photo-detector for sensing UV and visible light. In this work, we investigated the electrical performance before and after linking AuNPs. And then investigated the ability of photo-detecting of the phototransistors with AuNPs under the various conditions of illumination. Finally, fabricated the phototransistors on fluorine tin oxide (FTO) glass substrate, and found there is still the photosensing ability. In this work, the electrical characteristics of threshold voltage (Vth) shift represent the improvement of electrical performance and the ability of photo-sensing. The Vth could shift to -14 V when the TFT with more AuNPs. In the photo-sensing, the ZnO-based TFT with AuNPs Vth shift was 6 V after being illuminated. And the operation voltage of drain voltage was only 0.5 V. Finally, the device was fabricated on the FTO glass substrate, the Vth shift could be 0.8 V after being illuminated. We hope to utilize low-cost, non-toxic process which can be carried out at the room temperature and atmosphere and fabricate the photodetector on FTO glass substrate. The devices on FTO glass substrate can be applied in various electronic products for industry and life.