摘要
以光學顯微鏡與電子顯微鏡觀察脈衝雷射單一脈衝剝蝕多晶鈦靶，在靶材表面可得剝蝕坑與熱影響區，而其大小取決於雷射之能量密度與剝蝕過程所屬環境。 在不同剝蝕環境而相同雷射聚焦長度與功率密度下，剝蝕坑直徑變小而熱影響區寬度變大，其程度依序為水溶液、空氣與真空環境。在高功率雷射密度下剝蝕坑直徑變大於水溶液與空氣剝蝕環境，真空則維持不變，歸因於在此環境下具最小之雷射光寬化效應；熱影響區變大於真空與大氣剝蝕環境，水溶液則維持不變，則歸因於此環境下有效之熱消散效應。由電子繞射觀察於水溶液中雷射剝蝕鈦靶之橫截面，發現試片表面具較小之晶格間距，以Birch-Murnagham方程式計算其殘留應力達17 GPa。在掃描式與穿透式電子顯微鏡觀察熱影響區呈現凝固與再結晶之組織，且形成次微米之Ti6O與Ti3O顆粒，這是由於在動態雷射剝蝕過程中高溫氧化所造成。
關鍵詞: 脈衝雷射剝蝕、熱影響區、聚焦離子束、再結晶組織、Birch-Murnagham方程式、電漿引發壓力
Abstract
Polycrystalline a-Ti plates subjected to pulse laser ablation in a single pulse of specified energies showed crater and heat affected zone (HAZ) whose dimensions depend on the adopted power density and environment according to optical and electron microscopic observations. The crater diameter decreases, whereas HAZ width increases, in the order of water, air and vacuum environment under the same laser focal length and power density. A relatively high power density causes a significant increase of crater diameter for PLA in air and water but not vacuum with the least beam broadening effect. The increase of HAZ width with power density is significant for PLA in vacuum and air but not in water because of its effective heat dissipation. Electron diffraction of the cross sectioned a-Ti plates subjected to PLA in water showed smaller d-spacings in the upper level of the HAZ indicating a residual compressive stress up to ca. 17 GPa. The HAZ also showed solidified/recrystallized textures and submicron-sized Ti6O and Ti3O particles due to high temperature oxidation in the dynamic process.
Keywords: Pulsed Laser Ablation, Heat Affected Zone, Focused Ion Beam, Recrystallized Textures, Birch-Murnagham Equation, Plasma-induced Pressure