超空間解析飛秒激發偵測顯微鏡與飛秒瞬態吸收顯微鏡技術研究

想要突破以飛秒雷射為光源之瞬時吸收顯微術的光學解析度上的限制，過程中必定會面臨許多的挑戰和困難。而本論文將會詳述我們所面臨到的挑戰，以及如何突破光學限制的方法和巧思來完成此一新型態顯微術。此一新想法有別於一般的瞬時吸收顯微術之處在於我們使用了三道超快雷射光源。第一道為雷射模態為TEM00之激發雷射，第二道為雷射模態為TEM01*的激發光源，其相位與第一道雷射模態為TEM00之激發雷射的相位相差180度，而第三道光源為雷射模態為TEM00之探測光源。我們將三道雷射光在時間及空間上重合後，藉由偵測第三道探測光源受到激發光源影響後之探測光源強度的變化情形。而我們利用此一新型顯微術可以觀測到光學解析度為36 nm之ZnO奈米粒子，突破了繞射極限的限制(<100 nm)。我們將此新型顯微術將應用在研究MAPbI3 中的超快電荷動力學上，並探討目前仍具爭議的晶界與晶粒內部在電荷萃取中所扮演的角色。為此，我們利用此瞬態吸收顯微鏡（TAM）研究在MAPbI3樣品中的不同地方觀察電荷傳遞隨時間的變化情形。這裡的主要挑戰是，這種雷射掃描系統相較於掃描式電子顯微鏡(SEM)來說，其光學解析度非常差，並且不能從光學圖像本身推斷出晶粒尺寸或形態。而掃描式電子顯微鏡具有極佳的光學解析度，但無法做大範圍的掃描。因此，如果可以同時重疊兩個影像，則在某些區域的形態和動力學之間的相關性就能被分析。在這個系統中，我們使用高強度雷射，在膜上蝕刻了一些標記，以用作TAM和SEM圖像的對齊的標準。最後，我們發現在晶界處的鬆弛現象較慢，這可以相對應在晶粒邊緣處有較高的捕陷濃度。據推測，晶界充當電荷蓄積中心，這可能降低電荷萃取效率。

關鍵字

空間解析；飛秒激發；顯微鏡；飛秒瞬態吸收顯微鏡

並列摘要

This dissertation was aimed to bring a brief introduction in various microscopy routine and provide a practical pathway to setup a highly modular and multi-purpose microscope. Building a pump-probe microscope based on a femtosecond laser source cannot be achieved in high sensitivity without facing multiple challenges and difficulties. Here, the effort has been put to address the challenges, difficulties and guidelines and provide solution, workarounds and practical information for a complete setup. After setting up a microscope, we improve the setup by bringing something new to the field in terms of enhancing the resolving power. In the first attempt, the layout was set up to enhance the optical resolution and be able to visualized nanoparticles below the diffraction limit. The main idea was to find a work around that can offer fast acquisition speed and higher resolving power when it comes to nanoparticles place close to each other within the point spread function of a confocal microscope. It was shown that by means of the second pump beam in TEM01* at an anti-phase channel the ZnO nanoparticles in order of 36 nm can be visualized well below the diffraction limit (<100). For another application, the main goal was to develop a system to study the charge dynamics in MAPbI3 spatially and elaborate on the ongoing debate of grain boundary versus the grain interior role in charge extraction. To do so, the system was developed for a transient absorption microscopy (TAM) to observe the temporal profile spatially. The challenge here is, the resolution of such a laser scanning system is very poor and from the optical image itself, one cannot infer the grain size or morphology. However, scanning electron microscope (SEM) is the right tool for imaging thin film with nm resolution. Consequently, if one can overlay both images, the correlation between the morphology and the dynamics for certain region is made possible. In this system, with high intensity laser some markings were etched on the film to be used as an alignment guideline for TAM and SEM images. By mapping the TAM and SEM images of high efficiency MAPbI3 film, it was found that relaxation at the boundaries are slower which corresponds to higher trap state densities at the grain edges. The results show that, the grain boundaries act as charge retards the recombination which might have a positive impact in charge extraction mechanism in contact with a hole or electron transfer layer.