Topic Review: Application of Raman Spectroscopy Characterization in Micro/Nano-Machining

Abstract

The defects and subsurface damages induced by crystal growth and micro/nano-machining have a significant impact on the functional performance of machined products. Raman spectroscopy is an efficient, powerful, and non-destructive testing method to characterize these defects and subsurface damages. This paper aims to review the fundamentals and applications of Raman spectroscopy on the characterization of defects and subsurface damages in micro/nano-machining. Firstly, the principle and several critical parameters (such as penetration depth, laser spot size, and so on) involved in the Raman characterization are introduced. Then, the mechanism of Raman spectroscopy for detection of defects and subsurface damages is discussed. The Raman spectroscopy characterization of semiconductor materials’ stacking faults, phase transformation, and residual stress in micro/nano-machining is discussed in detail. Identification and characterization of phase transformation and stacking faults for Si and SiC is feasible using the information of new Raman bands. Based on the Raman band position shift and Raman intensity ratio, Raman spectroscopy can be used to quantitatively calculate the residual stress and the thickness of the subsurface damage layer of semiconductor materials. The Tip-Enhanced Raman Spectroscopy (TERS) technique is helpful to dramatically enhance the Raman scattering signal at weak damages and it is considered as a promising research field.

Raman Characterization of Carrier Concentrations of Al-implanted 4H-SiC with Low Carrier Concentration by Photo-Generated Carrier Effect

“…The absorption depth of the exciting line at 325 nm in SiC is approximately 4 μm, which has been confirmed by Xu et al and Derst et al [34,35]. With such laser, the LOPCsub peak could not have been found in any Raman spectrum of the investigated epi sample, because the epi layer thickness of the tested samples is larger than 5 μm, which supports the above conclusion that the LOPCsub peak shown in Figure 5 is originating from the substrate only.…”

X-ray Laue Microdiffraction and Raman Spectroscopic Investigation of Natural Silicon and Moissanite

“…The penetration depth of a laser is dependent on the material absorption coefficient, α, which is wavelength-and temperature-dependent, but for a constant α, intensity decays exponentially with depth, according to the Beer-Lambert Law. For a 532 nm laser the penetration depth in Si is ~0.7 μm [67]. The lowest intensities are from just outside where…”

Оптические свойства гибридных гетероструктур GaN/SiC/por-Si/Si(111)

“…При этом в рамановском спектре наблюдается отдельная неперекрывающаяся мода, локализованная около 792 см −1 , представляющая собой поперечный оптический фонон TO SiC , запрещенный в выбранной геометрии съемки. Появление этой фононной моды в рамановском спектре вызвано возникновением дефектов упаковки в слое SiC [35].…”