以電化學法在乙二醇溶液中沉積Bi-Sb-Te薄膜及奈米線之研究

Abstract

本研究首先利用循環伏安法探討Bi-Te、(Bi,Sb)2-xTe3+x在含有TeCl4，SbCl3以及Bi(NO3)3˙5H2O乙二醇溶液中的沉積行為。乙二醇溶液是除水之外可作為溶劑的另一種選擇，且乙二醇溶液具有可以在較負的電位下進行電沉積而不產生溶劑還原反應的優點。實驗結果發現當施加電位介於0.4V~-0.2V vs Ag/AgCl之範圍時，主要為Te金屬形成，而BiSbTe三元化合物則是出現在-0.2V~-0.6V的區間，此外沉積薄膜的組成主要是受乙二醇溶液中離子濃度的影響，其次才是沉積電位。為降低離子濃度對薄膜組成之影響，本論文採用脈衝電鍍方式來調控沉積物的組成比例，可以將沉積物中之(Bi+Sb)/Te比例調整至理想之2/3。另外，在本研究中亦採電化學沉積法嘗試於陽極氧化鋁板內製造不同成份的奈米線材，實驗中發現所製得的奈米線為非晶型，且受反應動力、質傳控制的相互作用使得奈米線成份趨向於Te-rich。

In this study, Bi-Te and (Bi,Sb)2-xTe3+x depositions from the ethylene glycol solution containing TeCl4, SbCl3 and Bi(NO3)3˙5H2O were investigated by means of cyclic voltammetry. Ethylene glycol could be an alternative electrolyte to water and used for electrodeposition without reduction of the solvent in more negative potentials. Experimental results show that Te was synthesized in the potential range between 0.4 V and -0.2 V vs. Ag/AgCl, and BiSbTe deposits were obtained in the potential range between -0.2 V and -0.6 V vs. Ag/AgCl; moreover, the film composition is more dependent on ion concentrations in the ethylene glycol solution than on the deposition potential. In order to decrease the influence of the ion concentration on the film composition, the pulse plating was used to accommodate the deposit composition. The (Bi+Sb)/Te ratio of the deposit could approximate the perfect stoichiometric ratio, 2/3. Furthermore, this work makes an attempt to fabricate nanowires with various compositions in the porous anodic alumina template using electrochemical deposition. The nanowire produced in this work has the amorphous structure and the composition tends to Te-rich due to the interaction of the reaction kinetics and mass transfer.