烷硫醇在砷化鎵表面上的吸附及熱解反應

Adsorption and Thermal Reactions of Alkanethiols on GaAs(100)

黃自平(Tzu-Ping Huang)

指導教授 ： 洪偉修

國立臺灣師範大學/理學院/化學系/碩士(2004年)

摘要

自組裝有機硫分子是目前熱門的研究話題之一，有機硫醇與有機硫化物擁有成為電子束微影光阻及可以修飾表面的物性及化性的前景。本篇主要是說明利用同步輻射為光源的光電子分析能譜及程溫脫附兩種技術來研究烷硫醇在砷化鎵的表面反應，實驗中的烷硫醇包括了甲硫醇、乙硫醇、丁硫醇及二甲基二硫等有機硫分子。由實驗的資料顯示，上述的有機硫分子皆會在115 K與砷化鎵表面生成吸附烷基硫和氫原子，經過加熱反應後，烷基硫會與表面上的氫原子重新鍵結產生烷硫醇及氫分子脫附，當溫度上升至570 K時，烷硫醇間的碳硫鍵會被破壞產生碳氫化合物，最後至770 K後表面留下硫原子鍵結在鎵原子上。甲基硫熱解會脫附甲基自由基而不是經氫化反應生成甲烷或偶合脫附乙烷；乙基硫與丁基硫熱反應經β-氫裂解產生烯化反應得到乙烯及丁烯；二甲基二硫則是在大曝露量下，主要的分解反應與甲硫醇一樣，少量的二甲基二硫在反應過程中會有甲基二硫的中間物與甲基反應熱脫附二甲基硫分子。本論文亦討論烷硫醇在砷化鎵表面的可能反應機制。

關鍵字

烷硫醇 ； 化學吸附 ； X 光光電子分析能譜 ； 程溫脫附 ； 砷化鎵

並列摘要

Organothiols and related organosulfur compounds hold promise for using as self-assembled ultra-thin electron beam resists and monolayer passivation layers. We report the results of temperature-programmed desorption (TPD) and X-ray photoemission spectroscopy (XPS) studies of the surface chemistry of alkanethiols (CH3SH, C2H5SH, C4H9SH and CH3SSCH3) on GaAs(100). Dissociation of sulfhydryl hydrogen (RS-H) of alkanethiol results in the formation of alkanethiolate at adsorption temperature 115 K. All of these alkanethiolates can decompose to evolve hydrocarbon via scission of the C-S bond, resulting in deposition of sulfur on Ga and As sites of surface. The dissociation of surface alkanethiolates is accompanied by the recombinative desorption of alkanethiol and hydrogen. The thermal reaction of methanethiolate appears to desorb methyl radical, while neither hydrogenation of CH4 nor coupling reaction of C2H6 undergo dissociative chemisorption. The surface of C2H5S and C4H9S undergo exclusively elimination of β-hydride to form C2H4 and C4H8 with desorption of H2. At a large coverage, most of dimethyl disulfides carry out the same passways as methanethiol reaction. The rests dissociate to form CH3SS of chemisorbed intermediates, and then react with segregation of methyl group to gaseous CH3SCH3. This paper discusses the surface reaction mechanisms of alkanethiols through products formed on GaAs(100).

並列關鍵字

alkanethiol ； chemisorption ； XPS ； TPD ； GaAs

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