A molecular simulation study of an organosilane self-assembled monolayer/SiO2 substrate interface.
A molecular simulation study of an organosilane self-assembled monolayer/SiO2 substrate interface.
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DOI：
10.1063/1.2895052
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发表时间：
2008-04
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影响因子：
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通讯作者：
Hideaki Yamamoto;Takanobu Watanabe;I. Ohdomari
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文献类型：
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作者：
Hideaki Yamamoto;Takanobu Watanabe;I. Ohdomari
用正则蒙特卡罗方法研究了烷基硅烷自组装单层（SAM）SiO2/衬底界面的键合网络.采用大都会MC方法对具有不同界面键结拓扑的SAMSiO（2）体系进行了采样，并采用新开发的有机硅参数的AMBER势得到了具有给定键结拓扑的优化结构。下面的衬底被建模为羟基封端的（100）或（111）方石英。SAMSiO（2）界面的特征是聚硅氧烷键合网络，它包括锚定键和交联键，即分子-基底和分子-分子Si-O-Si键。我们表明，在热平衡时，锚定键的数量的比例，交联键的总Si-O-Si键密度的增加而减少，尽管如此，锚定键的数量总是占主导地位的交联键。此外，我们表明，总的Si-O-Si键密度强烈地影响烷基硅烷分子的横向有序性，并且Si-O-Si键密度的增加会扰乱分子堆积。我们的研究结果表明，在实验制备的自组装膜的实验室到实验室的变化可以归因于不同的Si-O-Si键密度在SAMSiO（2）界面。
The bonding network of an alkylsilane self-assembled monolayer (SAM)SiO(2) substrate interface is investigated by means of canonical Monte Carlo (MC) simulations. SAMSiO(2) systems with different interfacial bonding topologies are sampled by the Metropolis MC method, and the AMBER potential with a newly developed organosilicon parameters are used to obtain an optimized structure with a given bonding topology. The underlying substrates are modeled as hydroxy-terminated (100) or (111) cristobalites. The SAMSiO(2) interface is characterized by a polysiloxane bonding network which comprises anchoring bonds and cross-linking bonds, namely, molecule-substrate and molecule-molecule Si-O-Si bonds, respectively. We show that at thermal equilibrium, the ratio of the number of anchoring bonds to cross-linking bonds decreases as a total Si-O-Si bond density increases, and that nevertheless, number of anchoring bonds always dominate over that of cross-linking bonds. Moreover we show that the total Si-O-Si bond density strongly affects the lateral ordering of the alkylsilane molecules, and that increase in the Si-O-Si bond density disorders the molecular packing. Our results imply that a lab-to-lab variation in the experimentally prepared SAMs can be attributed to different Si-O-Si bond densities at the SAMSiO(2) interface.