以溶膠凝膠法製備0.0~1.0at.%鈦及2.0at.%鎵共摻之氧化鋅膜並研究其光電特性

Ti (0.0 ~1.0 at.%), Ga (2.0 at.%) co-doped ZnO Thin Films Prepared by Sol-gel Method and Their Optoelectronic Properties

本研究利用溶膠-凝膠法並搭配旋轉塗佈技術，製備鈦（0 ~ 1 at.%）鎵（2 at.%）共摻氧化鋅（Ti, Ga co-doped zinc oxides，TGZO）薄膜，進而研究薄膜之微結構、光學與電學特性，並以三極式電化學系統於0.5 M Na2SO4溶液中量測其光電化學電流。氧化鋅摻雜鈦、鎵主要目的在調整半導體的能隙值與載子濃度，以便利用於TFT元件和光電化學元件。研究結果顯示：XRD得知TGZO薄膜皆屬於多晶之六方晶系纖維鋅礦結構，在C軸（002）具有優選方向，其晶粒尺寸隨摻鈦量由0.0增高至1.0 at.%時，由16 nm下降至13 nm，稍有細化現象；於光學上，測試透光率（UV-vis spectra），均在85%以上，依據透光性估計此薄膜之光學能隙（band gap）約為3.32 ~ 3.27 eV。由蕭特基式接觸及光電化學電池之電流-電壓量測可知，當鈦含量為1 at.%時得到最佳之光電流值，主因在於價帶中的載子容易吸收光而激發至導帶，而增加薄膜的光電轉換效率。

Ti (0~1 at.%), Ga (2 at.%) co-doped ZnO (TGZO) thin films prepared on glass substrates by sol-gel method combined with spin-coating and their microstructure, optical, electrical and photoelectrochemical properties were investigated. Photo-electrochemical experiments were conducted in a standard three-electrode cell filled with 0.5 M Na2SO4 solution. Co-doping of Ti and Ga in ZnO thin films was dedicated to modulate the energy gap and carrier concentration for their demand of application in TFT devices and photo electrochemical devices. XRD results showed that all the films belonged to polycrystalline hexagonal wurtzite structure with a preferred orientation along the c-axis, (002), perpendicular to the substrate. With increasing the concentration of Ti-dopant from 0.0 to 1.0 at.%, the films inclined to slight refinement in grain size from 16 to 13 nm. The optical transmittance of the films was excellent (i.e. over 85%) and their band gaps were evaluated to be in the range from 3.32 to 3.27 eV. According to the measurements resultant from I-V (current-voltage) diagrams of Schottky contact and photo electrochemical cell, the film co-doped with 1.0 at. % revealed the highest photo electrochemical current because of the carriers were facilitated to excitation from the valence band to the conduction band.