Film Thickness and Surface Plasmon Tune the Contribution of SFG Signals from Buried Interface and Air Surface  

埋层界面和空气表面和频光谱信号贡献的调控

作　　者：Liang Zhang Junjun Tan Quanbing Pei Shuji Ye 张良;谈军军;裴权炳;叶树集(中国科学技术大学化学物理系,合肥微尺度物质科学国家研究中心,合肥230026;中国科学技术大学,量子信息和量子物理协同创新中心,合肥230026)

机构地区：[1]Hefei National Laboratory for Physical Sciences at the Microscale,and Department of Chemical Physics,University of Science and Technology of China,Hefei 230026,China [2]Synergetic Innovation Center of Quantum Information Quantum Physics,University of Science and Technology of China,Hefei 230026,China

出　　处：《Chinese Journal of Chemical Physics》2020年第5期532-539,I0078,共9页化学物理学报（英文）

基　　金：supported by the National Key Research and Development Program of China(No.2018YFA0208700 and No.2017YFA0303500);the National Natural Science Foundation of China(No.21925302,No.21633007,and No.21873090);Anhui Initiative in Quantum Information Technologies(AHY090000)。

摘　　要：Sum frequency generation vibrational spectroscopy(SFG-VS)is a powerful technique for determining molecular structures at both buried interface and air surface.Distinguishing the contribution of SFG signals from buried interface and air surface is crucial to the applications in devices such as microelectronics and bio-tips.Here we demonstrate that the SFG spectra from buried interface and air surface can be differentiated by controlling the film thickness and employment of surface-plasmon enhancement.Using substrate-supported PMMA(poly(methyl methacrylate))films as a model,we have visualized the variations in the contribution of SFG signals from buried interface and air surface.By monitoring carbonyl and C-H stretching groups,we found that SFG signals are dominated by the moieties(-CH2,-CH3,-OCH3 and C=O)segregated at the PMMA/air surface for the thin films while they are mainly contributed by the groups(-OCH3 and C=O)at the substrate/PMMA buried interface for the thick films.At the buried interface,the tilt angle of C=O decreases from65°to 43°as the film preparation concentration increases;in contrast,the angles at the air surface fall in the range from 38°to 21°.Surface plasmon generated by gold nanorods can largely enhance SFG signals,particularly the signals from the buried interface.

关 键 词：Sum frequency generation Surface structure Buried interface Poly(methyl methacrylate) Surface plasmon 

分 类 号：TB383.2[一般工业技术—材料科学与工程]