| 摘要: | 本研究使用RF-DC濺鍍系統，分別以ZnO、Al(x)Sc合金(其中x=0, 0.4, 0.8, 1.7wt%) 雙靶 以及純ZnO、純鋁Al、純Sc等三靶，在STN(Super twisted nematic)玻璃上析鍍氧化鋅、摻鋁氧化鋅、鈧與鋁共摻雜之氧化鋅(Al, Sc co-doped zinc oxide)等透明導電薄膜。此薄膜經ICP分析得知: 由雙靶式所得薄膜之鈧含量(wt%)較低 (介於0 ~0.083)，而三靶式所得薄膜之鈧含量(wt%)較高(介於0.42 ~2.37)。薄膜組成的變化，影響其結構與性質甚大。 薄膜的結晶結構，經XRD分析得知：純ZnO薄膜屬於具(0002)優選之Wurtzite結晶，摻雜鋁後，結晶變形，共摻雜鋁、鈧後之薄膜，其結晶之[0002]優選方向，隨含鈧濃度增加而逐漸下降，當薄膜中含鈧量超過0.425%後，由[ 013]取代[0002]方向。由TEM觀察薄膜橫截面，顯示這些薄膜均由柱狀結晶構成，垂直於玻璃界面，晶徑接近界面處較小(約20nm)，隨遠離界面而增大(約65nm)。摻雜鈧使鍍膜晶粒細化，鈧摻雜量介於0.42~2.37 wt% 時，在HRTEM下，每一柱狀晶底部顯示出細小晶粒，大部份柱狀晶內則出現與疊差缺陷；部份柱狀晶內會出現垂直於界面方向之Moire fringe contrast缺陷。薄膜在氧氣氛下加熱400℃一小時，晶粒中之疊差缺陷密度明顯減少。 薄膜的物理性質均顯示：對可見光透光性良好，其電阻率則隨薄膜中鈧的摻雜量增加而大幅下降。在含氧氣氛中加熱400℃一小時，鋁、鈧共摻雜之氧化鋅薄膜，其電阻率僅增加數歐姆-厘米(Ω-cm)，較一般氧化鋅薄膜之電阻率低五次冪。薄膜經XPS檢測，模擬解析後，得知其中之氧成份，具有四種不同的化學態，分別對應不同之鍵結能：O(I) 鍵結能在530.00±0.15 eV屬於 Sc2O3 鍵結中之氧；O(II) 鍵結能在530.15 ± 0.15 eV，屬於纖維鋅礦結構中化學計量氧數量；O(III) 鍵結能在531.25 ± 0.20 eV ，與ZnO 薄膜中之缺氧有關；O(IV) 鍵結能在532.40 ± 0.15eV，屬於薄膜試片表面與氧氣之鍵結。 Transparent conductive films of Al, Sc co-doped zinc oxide were deposited on a super twisted nematic (STN) glass by using RF-DC sputtering on two targets (i.e., ZnO and Al-(x)Sc where x =0, 0.4, 0.8, 1.7wt%) and three targets (ZnO, Al and Sc) systems. Through inductively coupled plasma analysis, the films prepared from binary targets revealed less Sc-content (from 0 to 0.083 wt.%) than those (in the range 0.42 ~2.37 wt.%) from ternary targets. The crystal structure and characterization of the films were determined by the composition of the films. Analysis of x-ray diffraction (XRD) revealed that pure zinc oxide film belonging to wurtzite crystal textured on (0002). Doping of aluminum results in deformation of the zinc oxide and co doping of Sc shifts the crystal texture from (0002) to ( 013) as the concentration of Sc-dopant higher than 0.42 wt. %. Examination through transmission electron microscope (TEM) indicated that the oxide films consist of columnar crystals grown from the interface between the film and the glass. Smaller grains (around 20 nm) were found near the interface and greater ones (roughly 65 nm) with going away from the interface. Through examination by high resolution transmission electron microscope (HRTEM), the oxides containing Sc-codopant in the range from 0.42 to 2.37 wt.% lead to numerous fine grains on the bottom and a lot of stacking faults in the upper portion of the columnar crystals. In addition, some defects vertical to the film interface seemed to be Moire fringe contrasts in the colmns. The density of stacking faults in the films decreased prominently after heat treatment of the oxides at 400 ℃ for 1 h under ambient atmosphere. Physical properties such as optical transparency and electric resistivity were of interest. The optical transparency is higher than 80% for all the oxides. The electric resistivity of the Al, Sc co-doped oxide films is much lower than that of Al-doped ones. Annealing at 400 ℃ under ambient atmosphere for 1 h, the resistivity increases only a fewΩ-cm for the Al, Sc co-doped oxides but a huge increase (up to MΩ-cm) for the ordinary Al-doped oxides. X-ray photoelectron spectroscopy (XPS) indicated that the oxygen in the films could be classified as O(I), O(II), O(III) and O(IV) depending upon the binding energy (BE). O(I) with BE at530.00±0.15 eV belongs to the oxygen in Sc2O3, O(II) with BE at 530.15 ± 0.15 eV belongs to the stoichiometric oxygen in the ZnO wurtzite, O(III) with BE at 531.25 ± 0.20 eV belongs to deficient oxygen in ZnO, and O(IV) with BE at 532.40 ± 0.15eV belongs to gaseous oxygen bound to the free surface of the oxide. |
