- 學位論文
發展先進脈衝雷射沉積技術並應用於製作功能性材料
Development of Advanced Pulsed-Laser Deposition and application to Functional Materials
摘要
在本論文中，經由控制雷射靶材交互作用與電漿環境氣體交互作用，我們開發了脈衝雷射沉積技術應用於製作功能性材料的潛力，例如利用超短脈衝雷射製做了高指向性且熱不穩定性的FeCO3薄膜、利用基質輔助脈衝雷射蒸發(MAPLE)蒸鍍有機分子（melanin, YD2-o-C8 跟N3）與利用奈秒雷射製作過渡金屬氧化物。最後，也發明了簡易與快速的化學浸泡法沉積鐵鎳氧化物，作為太陽能輔助電解水的催化劑。 能夠成功成長高指向性FeCO3薄膜的關鍵是利用超短脈衝雷射而非使用較常見的奈秒雷射，飛秒雷射誘發電漿的機制不像奈秒雷射是經由吸收、加熱與氣化的過程而是光場游離，所以靶材分子並不會因為被雷射加熱而分解。然後飛秒雷射誘發的電漿也帶有較高的動能，在電漿分子落在基板之後，動能會轉化為熱能，幫助分子有效移動，由於此加熱的過程非常短暫，所以基板的FeCO3 分子也不致於會受加熱分解。實驗結果顯示薄膜的晶相與平整度受到沉積速率的影響很大，當沉積速率低於0.03 nm/pulse，薄膜是單一指向的且平整度小於50 nm。 為了在成長有機分子的時候，有機分子不至於被光分解，人們從脈衝雷射沉積技術發展出基質輔助脈衝雷射沉積技術。有限的有機分子鍍膜技術，如：浸泡法(immersion method)、浸塗法(dip coating)跟旋轉塗布法(spin coating)，皆有無法製作大面積樣品的問題。為了解決此問題，我們證明了利用基質輔助脈衝雷射沉積技術沉積有機染料的可行性。為了證明此方法的可行性，我們將傳統染料敏化太陽能電池製程中的染料沉積技術由浸泡法改為使用基質輔助脈衝雷射蒸發。結果發現，實驗組的染料敏化太陽能電池校率達到1.47%，與對照組的2.55%相去不遠。 最後一個工作中，我們發明了新的且快速的化學浸泡法製作鎳鐵氧化物作為催化劑，搭配脈衝雷射沉積技術製作的氧化鐵電極，成功製作出低啟動電位的氧化鐵光電極。在脈衝雷射沉積的製程中，利用填充氧氣與氮氣的混和氣體調整氧化鐵的氧空缺進而增加載子濃度。在化學浸泡的製程中，利用調整前驅物中的鐵鎳比與浸泡時間，最佳化電極表面的費米能階與催化劑層的厚度，達到光電極擁有最低的啟動電位與最高的光電流密度。
並列摘要
In this thesis, potential of pulsed laser deposition PLD) to grow functional materials, such as crystalline hermal-unstable material (FeCO3), organic dyes (melanin, YD2-o-C8 and N3) and transitional metal oxide (Fe2O3-x) have been demonstrated by controlling laser-matter interaction and plasma-ambience interaction precisely. Furthermore, characteristics of electrocatalyst (NixFe1-xOy) was investigated as function of composition and the film thickness by using a new and facile chemical bath deposition (CBD). The Key for growing strongly textured FeCO3 thin films on substrates is to take advantage of the transient high temperature provided from plasma plume generated by ultrafast-pulsed laser. The thin film morphology and crystallinity are found to be significantly affected together by deposition rate. The results show that, when the peak deposition flux is lower than 0.03 nm/pulse, single-oriented crystallinity experiment can be achieved with roughness smaller than 50 nm. Matrix-assisted pulsed laser evaporation (MAPLE) is a popular form of PLD for deposition of organic materials. However because organic materials may decomposed under light, water vapour and heat. There exist few workable methods for growing organic thin films. Methods, such as dip coating and spin coating, may not be suitable for preparing large-area samples. To solve the problem, the possibility of using MAPLE as a deposition method of organic materials was studied. By comparing experiments on melanin, YD2-o-C8 and N3, the dye-sensitized solar cell (DSSC) using YD2-o-C8 shows energy conversion efficiency of 1.47% which is comparable to traditional method. A new and facile chemical bath deposition (CBD) of NixFe1-xOy electrocatalyst and application to PLD-prepared Fe2O3-x (hematite) photoanode for solar hydrogen production are presented. The optimization of photoelectrochemical efficiency is achieved via integration of PLD and CBD. At the PLD stage, the oxygen deficiency in hametite was controlled by using backfilled oxygen. At the CBD stage, the Ni-to-Fe ratio and electrolyte layer thickness are optimized. The dependence of the electrochemical and photoelectrochemical characteristics of the photoanode on the composition and the film thickness of the electrocatalyst was studied systematically and explained based on energy level diagrams and kinetics.