應用超快雷射技術於新穎量子物質和太陽能電池薄膜物理特性之研究

Abstract

在本三年計晝中，我們將延續前面幾年有關利用超快光譜技術量測高溫超導體、龐 磁阻、多鐵等材料物理特性的經驗，繼續研究新穎量子物質-石墨烯與拓樸絕緣體的的 超快動力行為；同時也將投入超快光譜技術在太陽能電池薄膜的研究，並且將利用飛秒 級脈衝雷射蒸鍍這些材料的薄膜和探討超快雷射對這些材料進行退火處理與造型後，其 物理特性和轉換效率的改變。本計晝擬使用的系統，包含非共軸光學參量放大器超連續 白光輸出時間解析光激發-光檢測系統、時間解析光波長可調光激發-光檢測系統、時間 解析光激發-中紅外波檢測系統、兆赫波時域光譜量測系統、時間解析光激發-兆赫波檢 測系統和超快雷射鍍膜與退火處理系統等。

利用上述激發-探測實驗，將量測不同摻雜的石墨烯與拓樸絕緣體的載子與聲子的 弛緩與載子復合等動力行為、導電率動力行為、同調聲子機制、電子能帶結構等。利用 兆赫波時域光譜量測系統，將研究這些材料的兆赫電磁特性，包含複數折射率、導電率、 介電常數、化學位勢和載子射散率與遷移率等。這些研究，將有助於瞭解這些材料的基 礎物理特性，尤其是不同摻雜對這些材料的載子、聲子與導電率等在迪拉克點附近的動 力學的影響；並開發這些新穎量子物質在製作新型超高速/高頻/高效率電子和光電應用 元件、兆赫波應用元件、磁電耦合元件、自旋量子元件和非線性光學元件等的應用。在 拓樸絕緣體方面，我們亦將探討調變元素比例(Bi2-xSbxTe3-ySey)及磁性/非磁性元素摻雜 (Cu, Mn doped BisSe〗)的單晶和薄膜樣品，對物理特性的影響以及誘發超導性或磁性的 物理機制。

我們亦將利用超快光電技術來研究薄膜太陽能電池材料銅銦鎵硒與銅鋅錫硫/硒，其 中包含以超連續白光激發-光探測光譜量測該材料的超快載子動力學，如載子冷卻、載 子復合與缺陷分析等，以期透過不同時間尺度的量測能取得一些重要的物理參數及協助 釐清該材料目前遇到的製程瓶頸，有助於將來突破效率理論值的技術研發。此外，我們 也將利用超短脈衝雷射蒸鍍銅銦鎵硒與銅鋅錫硫/硒薄膜，並首度完成其相關的元件製 作，進而幫助探討其電性；並利用超快雷射對銅銦鎵硒與銅鋅錫硫/硒進行退火處理、造 型和微加工等處理，研究其對太陽能電池薄膜品質和轉換效率影響的物理機制。

In this three-year project, we will extend our previous experience in studying the high Tc superconductor, colossal magnetoresistive material and multiferroics by using the ultrafast techniques to investigate the ultrafast dynamics of novel quantum matters such as graphene and topological insulators. We will also study the characteristics of solar cell thin films by ultrafast spectroscopy. Besides, we are going to prepare the samples by ultrafast laser deposition and study the changes of physical properties and transfer efficiency after ultrafast laser annealing and patterning. The ultrafast laser systems used in this project include a time-resolved optical pump-optical (NOPA supercontinuous white spectrum/ 800 nm) probe system (OPOP) , time-resolved optical(400 nm/800 nm) pump- MIR/THz probe systems (OPMP and OPTP), a THz time domain spectroscopy (THz-TDS) system, and ultrafast laser deposition, annealing and patterning systems.

We will use the OPOP, OPMP and OPTP measurements to study the carrier and phonon dynamics, carrier combination, optical conductivity dynamics, the mechanism of the coherent phonon, and the electronic band structure of graphene and topological insulators with various dopant atoms. A THz-TDS system will be used to study the THz characteristics of these materials, such as complex refractive index, optical conductivity, dielectric constant, chemical potential, carrier scattering rate and mobility. The study of the ultrafast dynamics of these novel quantum matters by the ultrafast techniques will help us to understand the fundamental physical properties, especially the effect of various dopings on the carrier, phonon, and optical conductivity dynamics near Dirac point, and to develop the potentially revolutionary applications for high-speed/high-frequency/high-efficiency electronic and optoelectronic devices, terahertz -based devices, magneto-electric coupling devices, quantum spintronic devices and nonlinear optical elements. Besides, we will study the modulation of physical properties induced by controlling the chemical composition (Bi2-xSbxTe3-ySey) or magnetic/nonmagnetic doping (Cu, Mn doped BkSe3 single crystals or thin films) in topological insulators and investigate the possible mechanisms for the superconductivity and magnetism in these materials.

We will also investigate the ultrafast carrier dynamics of CuIni-xGaxSe2/Cu2ZnSn(S,Se)4 (CIGS/CZTSe) solar cell thin films by using ultrafast laser techniques. The NOPA supercontinuous white spectrum pump-probe measurement will be used to study the ultrafast carrier dynamics, include carrier cooling process, carrier recombination, and defect-analysis. We expect to obtain important physical parameters from the carrier dynamics in femtosecond and picosecond timescales, and find the solution to break through the bottleneck of the development of these materials. Additionally, we will prepare the CIGS/CZTSe thin films by ultrafast pulsed laser deposition, develop the device and measure its electrical performances. We will also use the ultrafast laser annealing and patterning processes to improve the quality and transfer efficiency of these films.