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Determining the sub-surface damage of CdTe single crystals after lapping

Publication at Faculty of Mathematics and Physics |


We introduce an affordable and easy-to-implement method of determining the thickness of a mechanically damaged layer on the surface of a cadmium telluride single crystal after mechanical lapping. This method is based on This method is based on different usage of already known defect-revealing etchants: the side projection of the lapped surface.

A comparison of developed etch pit patterns in the vicinity of the lapped side etched by the Everson solution, Nakagawa solution, Hahnert and Schenk solution, Saucedo solution, Inoue E-Ag II solution and FeCl3 is provided. The most commonly used defect-revealing etchants the Nakagawa and Everson solutions-did not show any trend of etch pit formation towards a mechanically damaged surface.

On the other hand, the Saucedo, FeCl3 and E-Ag II etches were successful and achieved similar results. These etchants revealed three distinctive regions of sub-surface damage: (i) a severely polycrystalline 50 mu m deep damaged region with micro cracks.

This region was best revealed by the FeCl3 etch. (ii) A region of plastic deformations that is 180 mu m deep. This region was best revealed by the E-Ag etch. (iii) A region free from mechanical damage.

High-resolution X-ray diffraction (HRXRD) further confirmed the results obtained by chemical methods. Full-width at half maximum of the rocking curves decreased from the value of 1000 arcsec on the lapped surface to the value lower than 30 arcsec after the removal of 200 mu m of the surface.

From HRXRD analysis, the region (i) can be further divided into an approx. 10 mu m thin nearly amorphous region, followed by a microcrystalline region. The region (ii) showed mosaic structure consisted of large crystallic blocks, with low angle misorientation from the main diffraction peak.

The results showed that the thickness of the mechanically damaged layer is ten times higher than the size of the abrasive used.