脈衝雷射沈積技術(pulsed laser deposition, PLD) 是一種多樣性的方法，可用來長成不同組成成份以及結構的薄膜。其強大的功能係源自於它可將靶材上的材料未達熱平衡時，即完全一致地轉移到基板上。此外，在 PLD 系統也可以簡易地加入其它設備以控制長膜各項參數，如加入反應氣體，單靶、雙靶甚至多靶系統，而超短脈衝雷射沈積技術(ultra-short pulsed laser deposition, uPLD)則對於電漿中離子的游離態和動能提供了更高的可調性。另外，由於PLD技術可以容忍相當高的反應氣體壓力，這在需要反應氣體的高溫超導釔鋇銅氧(Yttrium barium copper oxide , YBa2Cu3O7-δ, YBCO)薄膜成長上是一大優勢。本實驗以超短脈衝雷射沈積技術成長YBCO超導薄膜，改變雷射脈衝能量、雷射波長、基板溫度、氧氣濃度等參數，尋找最適當的薄膜生長條件，用以成長出YBCO單晶薄膜。而後以雷射掃描共焦顯微鏡來量測此YBCO超導薄膜在不同溫度下其反射光強度的二維分佈的變化，以得到YBCO超導薄膜的臨界溫度二維分佈。By using a home-made ultrashort pulsed laser deposition system, super-conducting yttrium barium copper oxide (YBCO) thin films are fabricated. Several parameters such as pump laser energy, wavelength, substrate temperature, and oxygen density are adjusted to fine the optimal condition for the growing process. The structure and crystal orientation of the thin films are characterized by using the x-ray diffraction method, showing that polycrystalline structure is obtained. The surface quality is characterized by using a surface profiler and an optical microscopy, revealing that it is spread with micrometer-size islands. Finally, by using a laser scanning confocal microscopy to measure the reflection from the YBCO thin film, the two dimensional distribution of its critical temperature is obtained. This distribution is varied in a micrometer length scale, which consists with the results of its polycrystalline structure and surface quality.
