Precise measurements of diamond lattice constant using Bond method

Precise lattice constant measurements based on the Bond method for various types of diamond were performed with a recently reported compensation technique. For the measurements, a calibrated Si single crystal was used as a reference; it was placed in a chamber whose temperature was carefully controlled below the standard deviations of +/- 0.1 degrees C, including thermo-couple fluctuation of +/- 0.06 degrees C for +/- o , X-ray wavelength calibration was performed using the monochromator temperature. A calibration was also carried out for the instrumental value depending on the Bragg angle and it was applied to the 004 diffraction peak of diamond. The lattice constant of high quality insulating undoped IIa type diamond was 3.567095 +/- 0.000017 angstrom (+/- 2 sigma), which was larger than the previous data derived without above mentioned calibrations. The measurements were carried out for various types of diamond including high pressure high temperature (HPHT) grown crystals as well as crystals grown by the chemical vapor deposition (CVD) method. (C) 2018 The Japan Society of Applied Physics