以CrN/Cr2N為中介層在不□鋼上沉積鑽石薄膜之研究

Abstract

鐵基材料(Ferrous metals)為目前工業上使用最廣的材料,假如能在 鐵基材料上被覆一層鑽石薄膜則更大大的提高了鐵基材料的用途。本研究 利用微波電漿化學氣相沉積法,在不□鋼上被覆一層或複層的CrN/Cr2N中 介層之後再沉積鑽石薄膜,以甲烷+氫氣及甲烷+二氧化碳作為反應氣體源, 研究在鐵基材料上預鍍CrN/Cr2N中介層再成長鑽石薄膜的附著性,並探討 這兩種不同的氣體源對沉積鑽石薄膜的附著性影響。 研究結果顯示, 在CH4/H2=0.4%,CH4/CO2=33.33%條件下可成長出晶面清晰的多晶鑽石膜, 膜厚分別為2.5e-6m及3e-6m,而根據拉曼光譜及陰極螢光光譜的分析結果 可以確定所得鑽石膜品質非常良好,由於甲烷+二氧化碳系氣體成長速率較 快所以在鑽石膜很容易有二次成核的結晶出現,惟甲烷+二氧化碳系氣體來 多了Cr7C3的化合物,很可能因此而加強了鑽石膜與中介層之間的附著性。 另外藉由中介層橫截面能量分散光譜儀(EDS)分析可以確定中介層可以完 全阻止鐵擴散到表面,避免在沉積鑽石時形成非晶質的碳而破壞了鑽石膜 與基材的附著性,而中介層的選擇以多層結構的複合層對阻止鐵擴散的情 形最好,CrN的效果又優於Cr2N。 最後由壓痕測試的結果可得知,加 以15Kg壓力的壓痕試驗於CH4/H2=0.4%,CH4/CO2=33.33%條件所沉積的鑽石 膜時,鑽石膜均有破裂的情形發生。甲烷+氫氣系氣體沉積的鑽石膜以CrN/ Cr2N、Cr2N/CrN中介層所得到的附著性較好,這可能是因為多層結構的複 合中介層有較好的防擴散效果。而甲烷+二氧化碳系氣體沉積的鑽石膜相 對於甲烷+氫氣系氣體不論在哪種中介層上都有較佳的附著性,這可能是因 為在甲烷+二氧化碳系氣體多了Cr7C3的緣故。 Ferrous metals are one of the popular materials in today's industry.If diamond films could be grown on them , there would be many applications usingjust the mechanical properties and chemical inertness of diamond.In this thesis,we use CrN/Cr2N as an interlayer to synthesize diamond films on stainless steelby means of microwave plasma chemical deposition (MPCVD) method.Two sets of gas mixtures were selected,i.e., CH4-CO2 and CH4-H2, to make a comparative study ofadhesion between diamond films and substrate. It was found that well defined facets diamond thin films can deposited onstainless steel substrate at CH4/H2=0.4% and CH4/CO2=33.33%.Because CH4-CO2 gas mixtures possess higher growth rate, few secondary nucleations were found.Butall these diamond thin films have good quality. From the results of X-ray diffraction,Cr2C was formed between diamond films and interlayer. There is another Cr7C3 compound formed on CH4-CO2 gas mixtures.These carbides enhanced the adhesion between diamond films and interlayer. Using interlayer cross-section EDS analysis , we can know that these interlayers can totally prevent iron diffudion to interlayer surface.Multi-layers structure is better than single-layer structure at the role of prevention iron diffusion and CrN is better than Cr2N. The toughness of the diamond films was evaluated by measuring the minimumload necessary to induce delamination with a cone-shaped diamond indentor.Allthe diamond films deposited at the condition of CH4/H2=0.4%, CH4/CO2=33.33% reveal pool adhesion. Delamination of diamond films were found at a normal loadof 15Kg.But the adhesion of multi-layers structure was better than single-layerstructure.The deposited diamond films using CH4-CO2 gas mixtures hae betteradhesion.This could be caused by Cr7C3 formed in CH4-CO2 gas mixtures.