| Abstract: | 本研究為了改善尖晶石ZnCo2O4薄膜的材料特性，利用外質摻雜方式提升半導體電學性質，研究摻雜效應所影響的晶體結構、微結構、光電特性以及抗菌特性，分別敘述如下:
分析研究Zn(Co1-xNix)2O4薄膜摻雜含量比由Nix=0增加至0.30，摻雜鎳於ZnCo2O4薄膜後均維持單一相尖晶石氧化物，並無生成鎳相關的二次相結構。鎳置換鈷元素會使得薄膜原子晶格排序的規則性下降，造成平均晶粒尺寸及表面的粗糙度減少。晶粒尺寸以及表面粗糙度皆會影響到薄膜半透明之光學性質，所有薄膜在波長550nm的透光率約為22%~38%，光子激發電子的特徵吸收峰約在波長400nm，較高的摻雜含量比Nix=0.20~0.30會使得吸收特徵峰逐漸消失。未摻雜ZnCo2O4薄膜直接能隙值為2.50eV，鎳摻雜於ZnCo2O4後改變能隙值的範圍為2.45~2.57eV。
所有薄膜均為P型半導體，正二價鎳可以置換正三價鈷促使載子濃度增加，造成Zn(Co1-xNix)2O4電阻率由312.5Ω-cm(Nix=0)下降至15.7Ω-cm(Nix=0.30)。大腸桿菌以及金黃色葡萄球菌無法在此薄膜上進行繁殖及生存，材料的抗菌率均可達99%以上，Ni-doped ZnCo2O4具有優異的應用潛力。
製備Zn(Co1-xCax)2O4薄膜摻雜含量比Cax=0.00 ~ 0.20，所有尖晶石結構薄膜中並無形成雜質相，細胞狀的表面微結構，摻雜鈣使得薄膜晶粒尺寸的減少，在較高的鈣摻雜含量(Cax=0.10~0.20)表面粗糙度逐漸提高。這些半透明ZnCo2O4薄膜在波長600nm具有約47% ~ 58%透光特性，因鈣摻雜含量比的增加會讓薄膜吸收藍光及紫外光的能力下降，並減少ZnCo2O4的特徵吸收特性。
Zn(Co1-xCax)2O4薄膜能隙由Cax=0.00的2.46eV增加至Cax=0.15的2.51eV，Ca+2置換Co+3使得導電率及載子濃度增加，最佳摻雜比Cax=0.07，薄膜電阻率由270.5Ω-cm (未摻雜)下降至15.4Ω-cm (Cax=0.07)，載子濃度由2.54×1015 (未摻雜)增加至6.25×1017cm-3(Cax=0.07)。在UV光照射以及在沒有任何光源的環境中薄膜均具有抗金黃色葡萄球菌以及大腸桿菌高達99%以上，P型的Zn(Co1-xCax)2O4薄膜可應用於抗菌以及電子元件之特性需求。
In this study, in order to improve the material properties of spinel ZnCo2O4 thin films, the electrical properties of semiconductors were enhanced by extrinsic doping. We studied the crystal structure, microstructure, photoelectric properties and antibacterial properties of doping effects on the ZnCo2O4.
The content ratio of Zn(Co1-xNix)2O4 doping increased from Nix=0 to 0.30, and nickel-doped ZnCo2O4 film maintained a single-phase spinel oxide, and no nickel-related secondary phase structure formed. The replacement of cobalt by nickel causes decreasing effect on the atomic lattice order, resulting in a decrease in the average grain size and a reduction in the roughness of the surface. Both grain size and surface roughness affect the transmittance of the film. The material has translucent optical properties. The transmittance of all films was about 22% ~ 38% at 550nm, and the characteristic peak of absorption was about 400nm. At a higher nickel doping content Nix=0.20 ~ 0.30, the absorption characteristic peak gradually disappears. The direct band gap of the un-doped ZnCo2O4 film was 2.50 eV, and the band gaps of the nickel-doped ZnCo2O4 were 2.45~2.57 eV. All films are p-type semiconductors, and positive divalent nickel can replace positive trivalent cobalt to increase the carrier concentration, resulting in a decrease in resistivity from 312.5 Ω-cm (Nix = 0) to 15.7 Ω-cm (Nix = 0.30). Escherichia coli and Staphylococcus aureus cannot breed and survive on the film, the antibacterial rate of the material can reach more than 99%, Ni-doped ZnCo2O4 has excellent application potential.
For Zn(Co1-xCax)2O4 films, the doping content ratios of Cax were from 0.00 to 0.20, no impurity phase formed in all spinel structure films. The surface had cell-like microstructure. Surface roughness values increased at higher calcium doping contents, and made the grain sizes decreasing. These translucent ZnCo2O4 films had light transmissions of 47% to 58% at wavelength of 600 nm. The absorption characteristics of blue and ultraviolet light of ZnCo2O4 were decreasing as increasing in calcium doping contentin the films. The band gaps of Zn(Co1-xCax)2O4 films increased from 2.46 eV (Cax= 0.00) to 2.51eV (Cax= 0.15), and Ca+2 replaces Co+3 to increase the conductivity and carrier concentration. The optimal doping ratio was Cax= 0.07. The resistivity decreased from 270.5 to 15.4 Ω-cm, and the carrier concentration increased from 2.54 × 1015 to 6.25 × 10 17 cm -3. The anti-S. aureus and E. coli abilities of the films had more than 99% in the UV light irradiation and in the absence of any light source. The p-type Zn(Co1-xCax)2O4 film can be applied to the antibacterial and electronic component. |
