Radical-Driven Silicon Surface Passivation by Benzoquinone– and Hydroquinone–Methanol and Photoinitiators
This work confirms that radical intermediates are the reactive species in quinhydrone/methanol (QHY/ME) passivation on silicon surfaces. The two constituent parts, p-benzoquinone (BQ) and hydroquinone (HQ), have been studied separately. BQ abstracts the hydrogen atom from methanol to become semiquin...
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Published in | Journal of physical chemistry. C Vol. 121; no. 39; pp. 21364 - 21373 |
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Main Authors | , , , , |
Format | Journal Article |
Language | English |
Published |
American Chemical Society
05.10.2017
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Online Access | Get full text |
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Summary: | This work confirms that radical intermediates are the reactive species in quinhydrone/methanol (QHY/ME) passivation on silicon surfaces. The two constituent parts, p-benzoquinone (BQ) and hydroquinone (HQ), have been studied separately. BQ abstracts the hydrogen atom from methanol to become semiquinone radicals (QH*). Both QH* and the resulting methanol radical are responsible for the large, instantaneous increase in minority carrier lifetime in BQ/ME, obtaining the lowest surface recombination velocity of 1.6 cm/s. HQ releases a hydrogen atom to become QH*. The quinone derivatives containing a lower electronegativity group (Cl or O) on the benzene ring form radicals more easily, and give better passivation results. This radical-driven passivation mechanism is also valid on other radical sources. X-ray photoelectron spectroscopy (XPS) supports the radical mechanism in the observation of dominating BQ bonding after 1 h of BQ/ME treatment, and increasing methanol bonding with increasing immersion time, reaching a roughly 21% SiOSi, 13% ME, and 6% BQ monolayer coverage in 24 h for BQ/ME passivated silicon. Density functional theory (DFT) further confirms the thermodynamic possibility of radical bonding and proves that the “edge-on” single-bonded configuration is more energetically favorable than the “face-on” double-bonded configuration. |
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ISSN: | 1932-7447 1932-7455 |
DOI: | 10.1021/acs.jpcc.7b05686 |