利用掃描穿隧顯微術對Si (100)- 2×1: H表面熱脫附現象的研究

Abstract

在成長燐與矽的薄膜時常使用PH3、Si2H6氣體，成長過程中大量的氫原子會吸附在Si(100)表面影響成長模式。本文利用變溫式掃描穿隧顯微術觀察Si (100)-2×1:H結構，在不同溫度氫原子形成氫氣自表面脫附的影像。根據升溫的時間，配合以直接計數的方式由影像上得到表面的氫原子脫附比例，得到585-668K的溫度範圍內氫原子從表面脫附的速率遵守脫附動力學一次式。由氫原子在611、622、633、644和668Ｋ的數據，可以推得知氫原子從表面脫附所需的動能Ed = 1.9 eV，而pre-exponential 因子νd= 2.0×1012 s-1。另外，再以PH3、Si2H6兩種氣體作為成長源，在611K的溫度下成長成一維鏈狀結構在Si(100)表面，比較表面上所成長的一維鏈狀結構上和在Si (100) 表面上Si (100)-2×1:H結構上的氫原子脫附情形有何差異，由鏈上的脫附情形看出氫原子脫附後留下的具有斷鍵的雙體之間相互排斥。

Under the procedure of P and Si growth on Si (100) by chemical vapor deposition from phosphine and disilane, the hydrogen of adsorbed on Si (100) impedes the growth. We investigated, using real-time variable-temperature scanning tunneling microscopy, the image of hydrogen desorption from Si (100)-2×1: H at several temperature. According to the annealing time and hydrogen desorption coverage by directly counting the site on image, then desorption rate of hydrogen from surface in 585-668K temperature range has known to obeys the first-order kinetics. The data of isothermal desorption at temperature 611, 622, 633, 644 and 668K give us the kinetic parameter activity energy Ed = 1.9 eV and pre-exponential factor νd= 2.0×1012 S-1. In addition, the disilane and phosphine grow to 1D line structure on Si (100) surface at 611K. Then we compare the difference of hydrogen desorption from Si (100) surface and 1D line structure, the 1D line structure dimers that hydrogen has desorbed repel each other.