超高真空熱蒸鍍碲化鎘薄膜及其表面分析之研究

Abstract

在超高真空環境下, 以p型矽晶片(111), p 型矽晶片(100),以及玻璃為 基板來蒸鍍碲化鎘薄膜. 蒸鍍後之碲化鎘薄膜以 X 射線繞射分析儀研究 其晶格結構, 以歐傑電子光譜,X 射線光電子光譜研究其表面特性. 由歐 傑電子光譜,X 射線光電子光譜分析顯示, 長在矽晶片上的碲化鎘薄比長 在玻璃上的碲化鎘薄膜品質佳. 在薄膜厚度大於 256A 時 X 射線繞射分 析儀可以顯示繞射尖峰. 由歐傑電子光譜知薄膜顆粒大小平均小於 256A,SEM 照相分析無法清析顯示顆粒大小, 因為其解析度的限制. 由歐 傑電子光譜知碲比鎘之比例是 2:1.超量之碲可能由以下原因所引起. 當 CdTe 鍵斷裂而與週圍的氧鍵結形成,CdO 及 TeO2. 因 CdO 較不穩定, 導 致 Te 的超量.CdTe 被氧化可能以另一種形式 - 氧從基板滲透到 CdTe 薄膜. 此外 CdTe 塊材在空氣中被氧化也可能導致 Te 的超量. Three kinds of substrates-Si(p-type,[1,0,0]),Si (p- type,[1,1,1]) and glass were used deposit the CdTe thin films by thermal evaporation method under ultra-high vacuum condition. X ray diffraction, Auger electron spectroscopy and X-ray photoelectron spectroscopy were employed to investigate the crystal structure and surface properties of CdTe thin film. XPS and AES studies showed that the CdTe thin films grown on Si substrate can easily obtain better crystalline than glass. Our results showed only for a thicker film(>265A),the XRD can yield the peaks.AES depth profile showed that the grain sizes of our films should be smaller than 265A in average. The SEM photographs can not show the grain sizes of our films clearly due to the limitation of resolution. The ratio Cd:Te bonds and the formation of Te-O and Cd-O bonds at the surface of CdTe due to oxidation in ambient atmosphere subsequently. Since CdO was less stable than TeO2 therefore,can be vaporized firstly and make the oxide layer rich in Te. CdTe was probably oxidized in another way which the oxide diffuses from the substrate and incorporate the CdTe films. This cause the excess of Te in the CdTe thin films . In addition, CdTe bulk maybe oxidized when it was in atmosphere. The film deposited by such bulk may also result in the excess of Te.