鍍鎳(111)單晶鑽石基板上之同質磊晶鑽石薄膜成長與結構分析

Abstract

本論文使用微波電漿化學氣相沉積製程(Microwave plasma chemical vapor deposition, MPCVD)成功地在有鍍鎳層之單晶鑽石基板上製備出高品質的(111)同質磊晶鑽石薄膜，並使用光學顯微鏡(Optical microscopy, OM)、電子顯微鏡(Electron microscopy, EM)、拉曼光譜(Raman spectroscopy)與X光繞射(X-ray diffraction, XRD)等儀器觀察與分析鎳層在微波電漿處理過程中的變化與其對鑽石薄膜的影響，並透過實驗與分析結果探討鎳層與鑽石薄膜的表面形貌、結晶品質、殘留應力與磊晶關係等特性，了解鎳層對同質磊晶鑽石薄膜厚度增加的影響。主要結果如下列所示： 1. 單晶鑽石基板上之鎳層在經過氫電漿熱處理後會轉變為數百奈米尺寸的鎳單晶顆粒，並分佈在鑽石(111)表面上。 2. 鎳晶粒形成後，在接續的鑽石以側向磊晶成長(Epitaxial lateral overgrowth )覆蓋鎳晶粒而聚合成一連續膜。高解析度穿透式電子顯微鏡的觀察，並未發現鎳晶粒與鑽石界面處有任何中間層。 3. 在具有20 nm鎳塗層的鑽石基板上可以MPCVD成長出膜厚超過5 μm、結晶品質佳且未脆裂之(111)同質磊晶鑽石薄膜，當鎳層厚度增至50 nm，則鑽石膜厚可增加至15 μm而未出現裂痕。拉曼光譜與XRD分析發現主要因鑲埋鎳晶粒降低鑽石薄膜之張應力，進而減緩(111)鑽石薄膜的脆裂行為。 4. 在膜厚為5 μm之(111)同質磊晶鑽石薄膜的穿透式電子顯微鏡橫截面影像中可觀察到在鑽石薄膜內部出現的差排大多數皆在鑽石薄膜內部形成，跟鎳晶粒無明顯之關係，並不影響鑽石薄膜的結晶品質。

此外更進一步探討鑲埋於鑽石薄膜內部的鎳、金顆粒之應變與應力。

The homo-epitaxial diamond films with superior quality were successfully grown on nickel-coated single crystal (111) diamond substrates by microwave plasma chemical vapor deposition (MPCVD). The effects of nickel layers on the surface morphologies, crystal qualities, and epitaxial relationships of over-grown diamond films were characterized by using optical microscopy, electron microscopy, Raman spectroscopy, and X-ray diffraction (XRD). The results are shown as the following: 1. Ni islands with a dimension of several hundred nanometers formed from the nickel layers after the thermal treatment in the hydrogen plasma are epitaxially oriented on (111) diamond surface. 2. Transmission electron microscopy observations show that further MPCVD-grown diamond can fully encapsulate the Ni islands in epitaxial lateral overgrowth. With coalescence, a continuous homopeitaxial diamoond film forms on the substrate. 3. A crack-free homo-epitaxial (111) diamond film with a thickness about 5 μm was achieved on single crystal (111) diamond substrate coated with 20 nm nickel. For 50 nm Ni coating, the diamond film thickness can be increased to 15 μm eithout cracks. Stress analyses with Raman spectroscopy and XRD show a reduced tensile stress in the grown diamond film with the embedded nickel islands which can retard the formation of cracks. 4. The Ni islands have a negligible effect on defect formation in the homoepitaxial diamond film as TEM analyses reveal that most of dislocations are rarely generated from the Ni islands and the diamond film.

The strain and stress state of the nickel islands and the gold islands in the homoepitaxial dimaond are further discussed.