In situ x-ray topography of silicon carbide during crystal growth by sublimation method

We have developed an instrument for real-time observation of silicon carbide (SiC) crystal during the sublimation growth process by x-ray topography. It is constructed by combining an x-ray goniometer and a crystal-growth chamber. The vertical goniometer consists of three circles, an α circle for the x-ray source, a β circle for the detector, and a φ circle for the azimuthal rotation of the sample. The growing crystal boule is set at the center of the goniometer glued on a crucible lid. Transmission topographs are taken using an asymmetric (1011) reflection with the scattering angle 2 θ_B - β - α from the (0001)-oriented boule. A rotating-anode 18 kW generator with a molybdenum target is employed as the x-ray source. Topographs are observed by a direct imaging system using a charge-coupled device camera. Incident and scattered x-ray beams pass through beryllium windows mounted on the bottom and top flanges of the crystal-growth chamber, respectively. The crucibles are also designed for in situ measurements so that the x-ray beam path is separated from the source materials. The in situ topographs demonstrated the movement of micropipes and other defects during the crystal growth.