Surface Infrared Spectroscopy during Low Temperature Growth of Supported Pt Nanoparticles by Atomic Layer Deposition

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• 作者：Roger H. E. C. Bosch ; Frank L. Bloksma ; Jochem M. M. Huijs ; Marcel A. Verheijen ; Wilhelmus M. M. Kessels
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：January 14, 2016
• 年：2016
• 卷：120
• 期：1
• 页码：750-755
• 全文大小：362K
• ISSN：1932-7455

文摘

The growth of supported Pt nanoparticles at room temperature employing a three-step atomic layer deposition (ALD) process, involving exposures to MeCpPtMe₃, O₂ plasma, and H₂ plasma, has been investigated. From spectroscopic ellipsometry and transmission electron microscopy measurements it has been established that up to 300 cycles of ALD nanoparticles are formed by island formation and island growth. In situ infrared spectroscopy has been used to obtain more insight into the surface chemistry by determining which species are present at the surface during the different stages of nucleation as well as within one ALD cycle. After precursor exposure the surface is covered with a carbonaceous layer, originating from the precursor ligands or (de)hydrogenated fragments thereof. Also adsorbed CO is present, which is already formed in the preceding H₂ plasma step. The O₂ plasma removes both the carbonaceous layer and the CO. Furthermore, the surface region of the nanoparticle is oxidized by the O₂ plasma; i.e., PtO_x and Pt–OH are formed at the surface. The subsequent H₂ plasma converts the PtO_x back into Pt and removes the Pt–OH. The oxidizing and reducing properties of the O₂ and H₂ plasma have also been observed through changes in free-carrier absorption. Overall, the experiments resulted in a refined understanding of the reaction mechanism of Pt nanoparticles grown by ALD at room temperature.