以矽為介層之燒結碳化鎢基材沉積之鑽石膜特性

Abstract

本實驗先在燒結碳化鎢基材上利用E-gun沉積Si介層然後採用熱燈絲 化學氣相沉積法, 以CH4和H2為反應氣體在介層上沉積鑽石薄膜, 藉以探 討矽介層, 基材前處理和基材含鈷量對鑽石薄膜成核成長、附著性和磨潤 性之影響。沉積條件為:CH4/H2 = 0.6％; 流量, 100sccm; 系統壓力, 40 torr;燈絲溫度, 2250∼2300℃; 底材溫度, 680∼720℃。沉積膜以 SEM, Raman,壓痕測試, 磨潤測試和切削測試分析其性質。實驗結果顯 示, 基材面上之鈷會吸收碳使得鑽石孕核所需時間加長並有催化鑽石成為 石墨的作用, 易於形成非晶質團狀結構。表面鈷含量過高 ,鑽石膜甚至會 造成剝落,這可能是因鈷在沉積溫度下吸收大量的碳, 在冷卻過程中再以 石墨形態釋出, 使得介層與底材之間, 鍵結力弱而破裂。在燒結碳化鎢基 材上沉積矽介層對於鑽石膜沉積有下列影響： (1)使鑽石成核速率略降, 因為碳之擴散係數在矽晶中比在WC晶中為高。 (2)有抑制鈷元素對鑽石成 長之負面影響, 使得鑽石膜中非鑽石結構的數量降低, 提高膜之附著性 。 (3)在已使用的條件中, Si介層厚度在5000A時; 鑽石膜殘於內應力最 小, 摩擦係數最小, 抗裂強度最好, 切削性能最佳。 (4)矽介層之表面粗 糙度在某一範圍內, 鑽石膜具最佳附著性。 Silicon interlayers were deposited on cemented tungasten carbids sybstrates by an E-beam evaporator. The diamond films source gases by suing a hot filament assisted chemical vapor deposition sustem. Effects of the Si interlayer and the nucleation, growth, adhesion and frication behaviour of diamond film were investigated. For cemented Tungasten carbide substrates, effects of Si interlayer on diamond deposition can be summarized as follows: (1) The diffusion coefficient of carbon in Si interlayer is greater than that in WC grains. It is believed to be responsible for a slightly lower diamond nucleation rate on Si interlayer than on the substrate. (2) Silicon interlayer can act as a diffusion barrier to suppress the negative effect of Co on diamond nucleation, resulting in a decrease in the quantity of non-diamond structures, and so an increase in adhesionof the films. (3) At the present deposition conditions, it was found that diamond film with a Si interlayer thickness of 5000A possesses a lower residual internal stress and frication coeffient, resulting in a higher cracking resistance and a better cutting perpormance. (4) There exists an approprite range of the interlayer roughness valves as well as the substrate roughness values for an optmium adhesion strength of the film.