以過濾式陰極真空電弧電漿系統合成碳化鉻薄膜製程與特性之研究

Processing and properties of chromium carbide thin films synthesized by a filtered cathodic vacuum arc plasma system

林君純(Chun-Chun Lin)

指導教授 ： 施漢章

國立清華大學/工學院/材料科學工程學系/博士(2007年)

https://doi.org/10.6843/NTHU.2007.00152

摘要

本研究主要是使用過濾式陰極電弧電漿沉積法在鋼材上合成碳化鉻薄膜，藉由控制製程參數，如沉積溫度、基板偏壓及反應氣體流量 (C2H2/Ar)沉積出結晶與非晶質之碳化鉻薄膜，並探討其微結構變化、機械性質、腐蝕行為及光學性質。
研究結果顯示，使用過濾式陰極電弧電漿系統在沉積溫度500℃下能成功合成出均勻且緻密的碳化鉻薄膜，且在此溫度下，施加不同基材偏壓(-50—-550V)能有效使碳化鉻薄膜由非晶質相轉變成結晶相(cryst-CrC)，為Cr3C2且含有似纖維結構之Cr23C6相。結晶化碳化鉻薄膜相較於非晶質化碳化鉻薄膜具有較佳之機械強度及附著性，也因本身結構緊密且無微粒(micro-particles)存在，故在氯鹽環境下具有極佳抗腐蝕能力。
針對披覆結晶(cryst-Cr3C2)與非晶質(a-CrC)之碳化鉻的鋼材之腐蝕行為做更進一步探討，使用等效電路模擬EIS量測之結果互相比較，以了解cryst-Cr3C2/steel 與a-CrC/steel腐蝕機制的影響。 結果顯示cryst-Cr3C2/steel的腐蝕阻抗較a-CrC/steel佳。
本論文的另一重點是利用陰極發光技術分析非晶質碳膜摻雜鉻原子與碳化鉻薄膜的光學性質，結果指出兩者之光學性質相似，發出2.10、2.03和1.99 eV的光譜，主要是由π鍵基態至π鍵激發態能階的跳躍、外來元素的摻雜與缺陷能階所造成。

關鍵字

filtered cathodic vacuum arc plasma system ； chromium carbide

並列摘要

In this thesis, the 90o-bend filtered cathodic vacuum arc (FCVA) technology was employed to deposit the chromium carbide films on the steel (AISI D2). This investigation was to compare various conditions which including the deposition temperature, the substrate bias voltage and the C2H2/Ar flow. The micro-structures, mechanical properties, corrosion behavior and optical properties of the chromium carbide film are thoroughly discussed.
The uniform and dense of the chromium carbide films have been successfully synthesized using our FCVA system. The chromium carbide is transformed from amorphous to crystallized phase, as the negative substrate bias voltage increases from -50 to -550 V at 500 ℃.Moreover, the crystallized Cr23C6 phase appears as the negative substrate bias voltage further increases. A compact and dense Cr3C2 film with the fibrous structure of Cr23C6 was successfully prepared.
The Cr3C2 coated steel has a relatively high nanohardness and excellent adhesion compare with the amorphous chromium carbide. The corrosion resistance of the Cr3C2 coated steel is owing to the establishment of a defects-free microstructure. No pitting corrosion was observed on the Cr3C2 coated steel.
The corrosion behaviors of cryst-Cr3C2/steel and a-CrC/steel were investigated further. All samples was measured and the results obtained from electrochemical impedance spectroscopy (EIS) simulated by the equivalent circuit to interpret the corrosion mechanism of the cryst-Cr3C2/steel and a-CrC/steel were compared. The results indicated that the cryst-Cr3C2/steel more effectively isolates the defects than dose a-C:Cr/steel in saline environment.
The cathodoluminescence spectra of the DLC:Cr films are evident in the visible region, thereby shifting the red emission to 1.99 eV. The orange emission at 2.03 eV also appears due to transitions between chromium-related electron levels and σ* states. Additionally, the peak at 2.10 eV likely results from the defective structures in the DLC:Cr films. The effect of Cr doping changed DLC band structure and its consequent cathodoluminescence property.

參考文獻

2. M. M. M. Bilek, W. I. Milne, “Electronic properties and impurity levels in filtered cathodic vacuum arc (FCVA) amorphous silicon”, Thin Solid Films 308-309 (1997) 79.

3. M. Hakovirta, K. C. Walter, B. P. Wood, M. Nastasi, “Graphite macroparticle filtering efficiency of three different magnetic filter designs used in the filtered cathodic vacuum arc deposition of tetrahedral amorphous carbon films” J. Vac. Sci. Technol. A 17(5) (1999) 3077.

5. H. Holleck, “Material selection for hard coatings”, J. Vat., Sci. Technol., A 4(6) (1986) 2661.

6. A. Kagawa, Y. Ohta, “Wear resistance of laser clad chromium carbide surface layers”, Mater. Sci. Technol. 11 (1995) 515.

7. H. O. Pierson, Handbook of Refractory Carbides and Nitrides, (1996) 101.