Critical assessment of birefringence imaging of dislocations in 6H silicon carbide

Synthesis of single crystals of V2AlC phase by high-temperature solution growth and slow cooling technique

“…5, right). In some unusual cases, the surface can even exhibit microscopic etch pits which might indicate the presence of threading dislocations, as observed for other materials with appropriate etchants [18]. Immersing crystals in concentrated HF (40%) for 5 days does not appreciably change their macroscopic appearance, but modifies their surface.…”

Birefringence Microscopy of Unit Dislocations in Diamond

“…To the best of our knowledge, and in spite of the many published studies on extended defects in diamond, there exists no published report on the detection of isolated unit dislocations in diamond by birefringence microscopy. Using the rotating polarizer method developed by Wood and Glaser 14 and a setup already described, 13 our present work aims at identifying unit dislocations in diamond by combining experimental and simulated patterns of dislocation-induced birefringence. We characterize the birefringence of HPHT substrates as well as that of CVD layers.…”

“…14 We use a green light source of wavelength λ = 546 nm and Zeiss Neofluar objectives with magnifications ranging from 2.5 to 100. The description of the experimental apparatus has already been discussed, 13 and the reader is referred to previous publications 13,18−20 for more detailed information. Due to the combination of a circular analyzer and a rotating polarizer, it is not necessary to discuss the orientation of the sample with respect to that of the analyzer and polarizer.…”

“…It is well-known that this residual stress component also determines the shape of the birefringence pattern, and its value can be precisely extracted from the background value of sin δ. 13,18 Then, the stress field is calculated in the crystal system x, y, z by an appropriate rotation. The stress field is connected to the optical retardance by piezo-optic coefficients which are fully known in the case of diamond.…”

“…It is highly desirable to assess if the birefringence technique permits detection of unit dislocations in diamond, as has been proven in the case of silicon carbide (SiC). 13 Although it is somewhat difficult to estimate the ultimate sensitivity of the technique, a rough estimation can be made by calculating the variation of the intensity of the birefringence pattern when the Burgers vector is varied from one to a few units, everything otherwise fixed, and to compare those patterns with experiment.…”