Raman Piezospectroscopy of Phonons in Bulk 6H-SiC

Grodecki, K.; Wysmołek, A.; Stępniewski, R.; Baranowski, J. M.; Hofman, W.; Tymicki, E.; Grasza, K.

doi:10.12693/aphyspola.116.947

Cited by 6 publications

(4 citation statements)

References 11 publications

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“…The spectrum was deconvoluted using a custom MATLAB script to accurately track the positions of overlapping vibrational modes. The first transverse optical (FTO) mode at 788 cm −1 is used for the stress analysis as is common in the literature due to the intensity of this mode and its relative sensitivity to stress 19,26 . The literature value of 0.167 GPa/cm −1 for the Raman piezospectroscopic coefficient is used to translate the shift in this peak to stress 27 …”

Section: Methodsmentioning

confidence: 99%

Microstructural and thermal stress effects on mechanical properties of boron carbide particle‐reinforced silicon carbide

Shoulders,

Guziewski,

Swab

2023

J Am Ceram Soc.

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Ceramic composites consisting of a silicon carbide matrix and boron carbide particles of various sizes and weight percentages were produced, characterized, and mechanically tested to elucidate the effect of microstructure on the mechanical response. All samples were observed to have flexural strength values lower than either of the constituent phases; however, blends with finer B4C particles (<10 μm) exhibited improved fracture toughness. Residual stresses from the mismatch in thermal expansion of the materials are found to be fundamental to these variations in mechanical response, resulting in either microcracking during processing or producing an initial stress state within the composite prior to testing. Microcracks were observed in samples with larger B4C particles (∼77 μm), causing a significant reduction in mechanical properties, while the finer B4C particles were found to be microcrack free. Residual stress measurements via X‐ray diffraction and Raman spectroscopy show increasing compressive stresses within the SiC matrix as the weight percentage of boron carbide increases, however both flexural strength and fracture toughness are found to decrease, indicating that the boron carbide particles that are in a tensile stress state are an important strength‐limiting feature. This is corroborated by fracture analysis. The results of both characterization and mechanical testing compare well with those predicted by micromechanics models.

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Section: Methodsmentioning

confidence: 99%

Microstructural and thermal stress effects on mechanical properties of boron carbide particle‐reinforced silicon carbide

Shoulders,

Guziewski,

Swab

2023

J Am Ceram Soc.

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“…However, these experiments have been done mostly on the cubic, 3C, polytype [12,[22][23][24][25][26][27][28] because of its importance and wide usage in the power electronics field. Only a few papers [5,6,29] discuss the use of Raman for stress analysis in 6H-SiC. In the current study we have focused on the equations developed by Liu and Vohra [5,6] for analysis of data as these are widely accepted for use on 6H silicon carbide.…”

Section: Raman Spectroscopymentioning

confidence: 99%

Relating residual stresses to machining and finishing in silicon carbide

Groth

Langan

Haber

et al. 2016

Ceramics International

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Machining and surface finishing is essential in the processing of many ceramics, however, it can be detrimental to subsequent performance as it introduces residual stresses and structural defects. Using micro-Raman spectroscopy the residual stress and crystallinity of hotpressed SiC tiles was examined after finishing with several different methods. 514 nm and 633 nm lasers in both conventional and confocal settings enabled stress as a function of depth to be assessed. Single crystal, electronics grade SiC was used for comparison. Compressive residual stresses were present at the surface and in the sub-surface region in all the samples, but the surface with lowest roughness and a mirror-like finish had the highest residual stress. Crystallinity in SiC is reduced by defects and stacking faults produced during machining and finishing. The finer surface finishes had higher residual stresses, but were actually found to have better crystallinity than the rough surfaces. The dependence of residual stress and crystallinity on surface roughness is attributed to a change in the mode of ceramic removal from energetic and brittle for rough finishes to ductile for the shallow cuts of smooth finishes. The dependence of stress and crystallinity on roughness means a balance must be struck between smoothness, crystallinity and stresses in choosing the best finish for a given application.

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“…The coefficient a is the phonon deformation potential. The value of a is 0.41 cm -1 /GPa [11]. Using Eq.…”

Section: Contributedmentioning

confidence: 99%

Circular polariscopic measurement of a semi‐insulating SiC wafer for evaluating strains and its relation with Raman spectra: Superiority to monochromatic Lang X‐ray topography

Takeuchi

2011

Phys. Status Solidi C

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We have explored the effectiveness of applying the circular polariscopic measurement to the mapping of the strains in a semi‐insulating 6H‐SiC wafer. Initially, monochromatic Lang X‐ray topography, which is regarded as a fundamental evaluation technique for wafers, is applied. In the monochromatic Lang X‐ray topograph, the disappearance of the images is found in various areas, which suggests that the monochromatic Lang X‐ray topographic measurement is not almighty. Next, we apply the circular polariscopic measurement, which is sensitive to strains through the photoelastic effect. The brightness of the circular polariscopic wafer map reveals that the inhomogeneous distribution of the strains. The observed phenomenon indicates that the magnitude of the crystal‐plane distortion is too strong to apply monochromatic Lang X‐ray topography. The presence of the relatively large strains is confirmed from the fact that the forbidden reflection lines are observed in the θ ‐2θ X‐ray diffraction pattern. We also measure the Raman spectra of the several region of the wafer to evaluate the stress from the phonon frequency shift. The maximum stress is estimated to be ∼490 MPa. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Raman Piezospectroscopy of Phonons in Bulk 6H-SiC

Cited by 6 publications

References 11 publications

Microstructural and thermal stress effects on mechanical properties of boron carbide particle‐reinforced silicon carbide

Microstructural and thermal stress effects on mechanical properties of boron carbide particle‐reinforced silicon carbide

Relating residual stresses to machining and finishing in silicon carbide

Circular polariscopic measurement of a semi‐insulating SiC wafer for evaluating strains and its relation with Raman spectra: Superiority to monochromatic Lang X‐ray topography

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