Developments of the Raman microprobe—Instrumentation and applications

Abstract

The development of the molecular optical laser examiner (MOLE) Raman microprobe during the 70s (M. Delhaye and P. Dhamelincourt, J. Raman Spectrosc., 1975, 3, 33 ; G. J. Rosasco, E. S. Etz, and W. A. Cassatt, Appl. Spectrosc., 1975, 29, 396 ; P. Dhamelincourt, Ph.D. thesis, L'Universite des Sciences et Techniques de Lille, 1978; G. J. Rosasco, in Advances in Infrared and Raman Spectroscopy, Vol. 7, Heyden, London, 1980 ) has provided the ability to acquire analytical quality Raman spectra with 1-μm spatial resolution. In addition to applications in the fields of organic contaminant analysis, differentiation of crystallographic phase, orientation of polymer fibers, corrosion scale analysis, and in situ stress measurements in films, results in several newer areas of research are presented. MOLE Raman microprobe examination of diamond-like carbon films has effectively monitored the presence of genuine crystalline diamond as opposed to amorphous hexagonal carbon phases which also occur in these films. In addition, the technique can quantify the magnitude of stress in these films due to mismatch of the thermal expansion coefficient with the substrate. For a variety of reasons that are discussed, the microprobe provides spectra of many fluorescing samples that cannot be recorded with standard macro-sampling geometry ( F. Adar, in Microbeam Analysis 1981, San Francisco Press, 1981 ). The development of multichannel instruments with integrated software control is demonstrating reduction of spectra collection time by a factor of approximately 10. After linearizing and merging of spectra acquired on these instruments, the data can be compared to any classically acquired Raman spectra.