Interface specific reflection-absorption infrared spectroscopy of layered solid-state materials.

摘要

Numerous advancing technologies require a thorough knowledge and precise control over factors that effect bonding between the layers of dissimilar materials. Corrosion barriers, lubricated surfaces, sensors, and integrated circuits represent an important group of layered systems, composed of dielectric materials deposited adjacent to metal surfaces.; The "interfacial" region between metal and dielectric represent a very small fraction of the total thickness of a complete layered system. In order to observe and characterize the interface bonding in its native environment, it is necessary to choose a technique that recovers information specifically related to the bonding and non-bonding interactions between the metal and dielectric. It is then necessary to develop a means to selectively filter out and remove the spectral components peripheral to the interface with minimal corruption of the signal originating from the interfacial region.; Methods are described to systematically collect and parse RAIRS data from layered metal dielectric systems in a manner that facilitates separation of spectral contributions from bulk and interface regions. An SP/FTIR spectrometer is introduced which can be used in multiple configurations to enhance the interface specificity of RAIRS. Energy coupled into the metal/dielectric interface as a surface plasmon polariton (SPP) is used as a secondary source of modulation for double modulation FTIR. In addition, the resonance coupling can provide specific information about the interface, which is complimentary to the FTIR spectrum. This complimentary information is used to extract interface specific spectral information from data sets using multivariate analysis.; Two full spectrum multivariate methods, Classical Least Squared (CLS) and Partial Least Squared (PLS) are used to model RAIR spectral information from polyimide thin films on noble metals. Methods are presented that enable classification of the layered systems based on interfacial spectral information, and extraction of information relating to the composition of the bulk phase. A method of experimental design is introduced which minimizes the problem of correlations brought on by a two dimensional (2-D) surface (or interface). Recovery of pure and interaction (interface) spectral components from an imide thiol adhesion promoter layer is demonstrated using the above methods.