量子點在目前的應用上，已有包括量子電腦、量子點雷射、量子 點太陽能燃料電池等方面的應用。量子點在應用上遇到的問題主要是 在空間和尺寸分布上的控制問題，由於其尺寸分布會對應其相對的螢 光光譜而位置控制也和應用上息息相關，故目前也有眾多方法如電子 束蝕刻、離子束打洞和光學蝕刻等方式研究此問題。 故此篇在探討用雷射光控制矽鍺量子點的方法是否可行，此方法 主要是先利用長脈衝雷射對基板做照射使基板產生週期性的結構，之 後再將矽鍺量子點利用雷射脈衝沉積的方式在此表面結構上沉積，希 望此基板前置處理產生出的表面空間分布，使得量子點的產生侷限在 週期性結構的谷底，進而達到矽鍺量子點在空間上和尺寸分布上的控 制。 本論文內容展示了如何在基板上產生雷射光激發表面週期性結 構，以及其週期和理論運算的對應關係，接著也參考過去論文資料實 際使用雷射脈衝沉積來做矽鍺量子點的成長，最後將兩者過程結合希 望利用基板表面的週期性結構使量子點的成長受到侷限，但最後發現 無論在週期性結構的谷底以及無週期性結構的部分都沒有發現量子點 的存在，或許是因為在基板清潔等部分仍有問題造成量子點的成長不 穩定，此部分的原因目前還有待釐清。 The quantum dots have been widely applied on several region like quantum computer, quantum dots laser, and quantum dot solar cell etc..The most important property of quantum dots for application is that his photoluminescence spectrum is discret and the emission wavelength is corresponded to the quantum dots size.To achieve the control of the size distribution and the position, many methods have been used and investigated like electron beam lithography, ion beam patterning and optical lithography etc..
Here we study the feasibility of the control of the size distribution of quantum dots by laser pre-processing of substrate.In the beginning we use long pulse laser to produce laser-induced periodic surface structure with long pulsed laser.And then the self-assembled Ge/Si quantum dots was grown with pulsed laser deposition on this kind of laser-induced periodic surface structure to achieve the control of the size distribution of Ge/Si quantum dots.For our prediction the Ge/Si quantum dots should be located in the valley of laser-induced periodic surface structure.
In this thesis we show how to produce the laser-induced surface structure on the silicon substrate and also have some comparison of the theoretical calculation and experimental data.The next we grew the Ge/Si quantum dots with pulsed laser deposition with the parameter refered to the past papers.Finally, we combined these two process hope to produced location-confined Ge/Si quantum dots on the laser pre-processing substrate. But we couldn't find any Ge/Si quantum dots whether in laser-induced periodic surface structure or not.Maybe the reason for this phenomenon is that the unclean silicon substrate caused the unstability of the growth of Ge/Si quantum dots.The actual reason will be claritied in the future.
