Thermal-vibrational amplitudes of silicon determined by channeling-radiation measurements

We have observed radiation emitted by electrons channeled along the (110) and (100) planes of silicon for four different beam energies ranging from 16.9 to 54.5 MeV. Taking advantage of the great sensitivity of the positions of some of the spectral peaks to the vibrations of the Si nuclei, we have determined the vibrational amplitude at room temperature to be 0.08130.0009 for the (110) plane and 0.07890.0007 for the (100) plane. The values obtained from channeling-radiation measurements differ substantially from the value of 0.075 obtained from x-ray-diffraction measurements, which fail to distinguish between vibrational amplitudes for different planes. For many crystals, electron-channeling-radiation measurements of thermal-vibrational amplitudes may prove to be more accurate than x-ray measurements. © 1991 The American Physical Society.