Parts per Million Water in Gaseous Vapor Streams Dramatically Accelerates Porous Silicon Oxidation

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• 作者：Randi E. Deuro ; Joseph P. Richardson ; Justin M. Reynard ; Caley A. Caras ; Frank V. Bright
• 刊名：The Journal of Physical Chemistry C
• 出版年：2012
• 出版时间：November 1, 2012
• 年：2012
• 卷：116
• 期：43
• 页码：23168-23174
• 全文大小：457K
• 年卷期：v.116,no.43(November 1, 2012)
• ISSN：1932-7455

文摘

Substantial research has focused on exploiting and understanding porous silicon (pSi) photoluminescence (PL) for applications in areas ranging from chemical sensing to solid-state lighting. At ambient temperature, pure H₂O is well-known to slowly (over a time scale of hours to days) and irreversibly oxidize as-prepared pSi (ap-pSi) to form oxidized pSi (ox-pSi). In this paper, we report that the apparent ap-pSi to ox-pSi oxidation rates can be orders of magnitude faster in the presence of nonaqueous vapor streams that contain just ppm H₂O levels. When H₂O is removed from the nonaqueous vapor stream, ap-pSi oxidation ceases. The nonaqueous analyte vapors serve as a vehicle to transport H₂O directly into the hydrophobic, ap-pSi matrix where the H₂O then oxidizes the ap-pSi leading to ox-pSi, permanently changing the pSi PL and surface chemistry. The ap-pSi oxidation rate is much faster in the presence of nonaqueous vapors because H₂O transport into the pSi matrix is no longer limited by H₂O slowly percolating鈥搊xidizing鈥損ercolating through the ap-pSi matrix.