Silicon Isotope Shifts of the 648-cm~(-1) Infrared Absorption Line of Oxygen in Silicon

摘要

Infrared absorption measurements for the silicon crystals with very high oxygen concentrations have clarified that the 648.1-cm~(-1) line due to ~(28)Si-~(16)O(-28)Si centers is accompanied by the silicon isotope lines at 643.2 cm~(-1) and 638.5 cm~(-1) due to ~(29)Si-~(16)O~(-28)Si and ~(30)Si-~(16)O~(-28)Si, respectively. Presence of the silicon isotope lines (shifts) supports the previous explanation for the origin of the 648.1-cm~(-1) line: the combination of the A_(1g) local mode and the low-energy anharmonic excitation of the oxygen. The silicon isotope shifts, 4.9 and 9.6 cm~(-1), well agreed with the previously calculated silicon isotope shifts of the A_(1g) local mode frequency, confirming the above explanation for the origin of the 648.1-cm~(-1) line. These measured silicon isotope shifts have also confirmed our previous explanation for the origin of the 1748.6-cm~(-1) line: the combination transition involving one A_(2u) local phonon and one A_(1g) local phonon.