臺灣博碩士論文加值系統

鹼金族原子吸附在矽半導體表面這個系統有電子與觸媒工業的應用價值。過去的研究以鹼金族原子吸附在Si(100)-(2×1)表面居多，鹼土族原子則很少見，而鹼金、鹼土原子團的直接吸附似乎未見過，本篇論文針對Si(111)表面。我們先由代表一個表面單位晶格的矽氫原子團簇開始，增加至四個unit cells，原因是矽氫原子團簇太小時最佳化下來，週邊的矽原子因為較自由，所以會發生不合理的位移。當矽氫原子團簇加大時，這樣的情形可以逐漸獲得改善，原則上能讓我們把越大的金屬團簇和各種吸附物放在愈大的矽氫原子團簇的中間，就愈接近表面在低覆蓋率的真實情況，但計算時間也大量增加。基本上我們的結果顯示吸附之後，至少有一個金屬之間的鍵長比自由時短很多。鹼土族原子若形成分子，σns*將被填滿，所以鍵結薄弱。吸附之後反鍵結軌域的電子流入矽的dangling bonds，因此鍵結增強，Mg 分子靠近氧之後鍵長縮短也是這個原因。

Most studies in this area focus on the alkali atom Si(001)-2×1 surface. Work on the alkali or alkaline earth clusters, has not been seen. We have used some small Si-H clusters to represent the nuit cells of a reconstructed ideal Si(111) surface. Adsoprtion of some Mg clusters will be reported here. We used the softwares and GAUSSIAN 03 package at the NCHC of structure imization on the B3LYP/6-31G* level. For adsorptions on the Si-H cluster of one surface unit cell, peripheral Si atoms are much more free to make unreasonable moving, This problem can be gradually improved by increasing the number of unit cells. Our current result shows that upon adsorption, at least one of the metal-metal bond is shorten compared to that an isolated molecule. When two alkaline atoms bond, theirσns* filled. Thus, the bonding is actually very weak. When the metal molecule comes onto Si surface, part of the anti-bonding density flows into surface dangling bonds and then strengthens the metal- metal bond. Mg clusters having their bond distances shorten upon O2 adsorbed at neighbor sites is due to the same reason.

謝 誌…………………………………………………Ⅲ
圖目錄…………………………………………………IV
表目錄…………………………………………………Ⅵ
能量圖…………………………………………………Ⅷ
摘 要…………………………………………………1
英文摘要………………………………………………2
第一章 Mg、Mg2、Mg3分子吸附在第四族元素Si(100)
1.1研究背景介紹………………………………………3
1.2研究目的……………………………………………7
1.3軟體與硬體…………………………………………8
第二章 計算方法
2.1首先必須用繪圖軟體大致畫出基座和吸附物的相關位置…………………………………………………9
2.2我們可以先用繪圖軟體中的一些最佳化的功能，先畫出圖形的大概………………………………………10
2.3將所畫出來的圖形save as為gjc檔，用notepad
轉成文字檔……………………………………………11
2.4進入工作站………………………………………..12
2.5建立運算檔案……………………………………..13
2.6寫入運算的指令………………………………..…14
2.7運算完成，產生output……………………………16
2.8 查看output……………………………………….17
2.9 虛數頻率………………………………………….18
2.10 最佳化的座標和能量…………………………...19
2.11 查看其能量……………………………………...21
結果與討論……………………………………………22
結論……………………………………………………59
參考文獻………………………………………………60

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