An absolute measurement of the lattice parameter of germanium using multiple-beam X-ray diffractometry

The d spacing of the 355 reflexion in silicon has been compared with the d spacing of the 800 reflexion in germanium using pseudo non-dispersive multiple-beam X-ray diffractometry with Mo Ka₁ radiation. This technique gives the ratio of the two lattice parameters without the need for a precise knowledge of the X-ray wavelength. Symmetric transmission geometry was used to eliminate the refractive index correction. The results were: = 1.0002348 (± 0.0000006) at 22.5 °C and = 1.0002458 ( ± 0-0000016) at 25 °C. By using the known lattice parameter of silicon obtained by X-ray and optical interferometry it was found that the lattice parameter of germanium at 25 °C is 5.6579060 ± 0.0000092 Å.