超高真空樣品經乾燥曝氣之熱釋氣研究

The study of thermal outgassing on ultra high vacuum system with venting extremely dry nitrogen

鄭宇尊(Yu-Tsun Cheng)

指導教授 ： 陳俊榮

國立清華大學/原子科學院/生醫工程與環境科學系/碩士(2009年)

https://doi.org/10.6843/NTHU.2009.00032

摘要

本論文主要為探討鋁合金與鈦之真空腔，經各種乾燥氮氣曝氣後之釋氣率情形。為了有效阻絕環境之水氣而得到較低的釋氣率，實驗中比較了多種乾燥曝氣實驗條件，並且探討真空表面之相關狀況。本實驗也採用紅外光表面分析，探討熱氮氣與冷氮氣對於樣品表面已吸附之水氣的吹離效果，以及利用表面覆蓋模型計算得到各參數進行比對。由各種不同曝氣之結果顯示，以手套箱保護之曝氣過程(曝氣溼度1.3ppb)具有最低之釋氣率，鋁合金真空腔於該情況下抽氣1小時後之釋氣率q1為1.1x10^(-11)mbar.L/s.cm2，於10小時後之釋氣率q10為1.6x10^(-12)mbar.L/s.cm2，這些值比一般條件曝氣(空氣)所得之q1及q10小約100倍及80倍，顯示極乾燥曝氣之效果。而鈦真空腔於相同之手套箱保護曝氣，釋氣率為鋁合金3.4倍，殘餘氣體水氣訊號為鋁合金之3.3倍，顯示乾燥曝氣對鋁合金有較佳之效果。由表面覆蓋模型計算結果顯示，各曝氣實驗之覆蓋度約在10^12~10^15 molecules/cm2之間，黏滯係數約在10^(-5)級數。而在極乾燥曝氣實驗或空白實驗中，鋁合金與鈦釋氣率曲線發現存在和時間平方成反比(t^(-2))之成分，表示極乾燥處理後，表面狀況異於一般曝氣之表面。而由紅外光光譜分析實驗中，證實利用乾燥氮氣氣流能將已吸附於樣品表面之水氣吹離，但是，冷氮氣與熱氮氣兩者無顯著差異。

關鍵字

真空 ； 熱釋氣 ； 表面覆蓋 ； 黏滯係數

並列摘要

Thermal outgassing rates of aluminum and titanium chambers, which were vented to dry nitrogen atmospheres with different conditions, were measured. The vacuum surface states were compared with different venting conditions in order to obtain lower outgassing rates. Both hot and cold nitrogen gas purging dried water vapor, which was adsorbed on surface, were compared by FT-IR. The surface coverage model was also discussed.
The results showed that vented by dry nitrogen (1.3 ppb humidity) and protected the vacuum chamber from atmosphere environment by glove box, had the lowest outgassing rate. The outgassing rates of aluminum chamber at the 1st and 10th hour were showed as q1=1.1x10^(-11) mbar.L/s.cm2 and q10=1.6x10^(-12) mbar.L/s.cm2, which were 100 and 80 times relatively lower than general venting to air. In the same condition, outgassing rate and H2O residual gas signal of titanium chamber were 3.4 and 3.3 times relatively higher than aluminum chamber. It indicated that, aluminum chamber had a better result, when venting to dry nitrogen. In surface model calculating, the surface coverage was from 10^12 to 10^15 molecules/cm2, and the sticking coefficient was in the order of 10^(-5). The outgassing rate was inversed proportional to the square of time (t^(-2)) by venting with extremely dry nitrogen gas, the results showed that the surface state was much different from regular. In FT-IR experiment, both hot and cold nitrogen gases had the same ability of blowing the water vapor which was adsorbed on the surface.

並列關鍵字

vacuum ； thermal outgassing ； surface coverage ； sticking coefficient

參考文獻

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