In part I we looked at ‘what is Raman Spectroscopy’, its advantages and advanced techniques, now we look at the application of this technique in material science. Material science provides a varied and challenging range of samples for which this technique is ideal for studying as it is a very good characterization technique. Confocal Raman offers very good spatial resolution for depth analysis for analyzing polymer films and mapping for testing multi-component systems.
Let’s explore what Raman has to offer the material science community:
Superconductor and semiconductors
Raman measurements can be used for structural characterization for semiconductors and super conductors. It has been used to describe the shape, size and position of first order phonon bands in semiconductors. The Raman spectrum and map can also provide information about stress, crystal lattice disorder, phase separation of supersaturated solution and homogeneity. Raman spectroscopy was applied to characterize CVD synthesized MoS2 to give information about existence and quality for application in semiconductor technology.
Carbonaceous materials
Figure 1: Raman Spectra of diamond, graphite, glassy carbon and amorphus carbon (Cerium Labs)
Carbon allotropes have been differentiated using Raman spectroscopy through molecular morphology characterization due to C-C orientation and degree of crystallinity. Raman spectroscopy is often used to differentiate graphite, carbon nanotubes and fullerenes. This technique has become one of the prime methods for investigating carbon nanotubes by studying their vibrational, electronic and optical properties.
It allows for separating metallic and semi-conducting tubes. The Raman spectrum can be used to determine structural defects and disorder in the structures. figure 1 shows the differences between carbon structures using Raman spectroscopy.
Polymers
Raman spectroscopy is very often used to characterize the structure, environment and dynamics of polymeric materials. The chemical composition of the structure of polymers has been studied during online processing and development in factories. The technique has been used in forensics to identify traces of plastic explosives through molecular level detection. Confocal Raman microscopy has been very useful in studying immiscible polymers to analyze the structure of electrospun fibres.
Environmental materials
One very significant benefits of Raman spectroscopy is the analysis of aqueous samples, as a result it can be used to detect hazardous materials in trace amounts in water. Environmental contaminants such as uranium have been detected in water ways as a result. Raman spectroscopy has been used to monitor factory outputs, chemical plants, gas pipelines and for leakage of inflammable gases such as hydrogen, methane and nitrogen (cannot be detected with FTIR) with a portable device.
Crystalline studies
Micro-Raman spectroscopy has been used for assessing spatial variation of internal stress in synthetic diamond as it provides information about stress distribution around cracks. It has been used to investigate impurities such as Al2O3 in titanium oxide (TiO2). Cystallinity studies for materials have been conducted using Raman to determine changes due to high temperatures. Much work has also been done recently using this technique to study solid oxide fuel cells to verify their crystalline phase. Figure shows a spectrum of yttria-stabilized zirconia (YSZ), showing that it is a mixture of tetragonal and cubic phases.
Figure 2: Yttria-stabilized zirconia (YSZ)
Raman spectroscopy brings a whole host of resources to the world of material science by its versatility made possible by its advanced techniques, is easy to use, requires little to no sample preparation, samples can be solid or aqueous (no water effects), non-invasive and non-destructive.
References
Das, R.S. & Agrawal, Y. 2011 ‘Raman spectroscopy: Recent advancements, techniques and applications’ Vibrational Spectroscopy, Vol. 57(2), pp.163–176. Available: Elsevier/ScienceDirect/10.1016/j.vibspec.2011.08.003 , [5 Nov 2011]
Yusuke N, Yongjie Zhan, Sina Najmaei, Jun Lou, Applications of Raman Spectroscopy in Material Science: Material Characterization and Temperature Measurements, NanoJapan Program
Schamp T. ‘Materials Analysis with Raman Spectroscopy’, Cerium Labs, Technical Note
R. Kalish, A. Reznik, K.W. Nugent, S. Prawer, The nature of damage in ion-implanted and annealed diamond, Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 148, Issues 1–4, 2 January 1999, Pages 626-633, ISSN 0168-583X, 10.1016/S0168-583X(98)00857-X. (http://www.sciencedirect.com/science/article/pii/S0168583X9800857X)
Ian Lewis and Howell Edwards (ed.) (2001) Handbook of Raman Spectroscopy, Mercel Dekker, Inc., New York
Materials Science Research Group 