Tunneling states in neutron-disordered bulk silicon

Measurements of the variation of the low-temperature (LT) ultrasonic velocity and Raman scattering spectroscopy were performed on pure, bulk single-crystalline silicon, both unirradiated and irradiated with fast-neutron doses up to 1.7 and (Formula presented) This irradiation is found to transform the crystalline silicon structure into a partly disordered state. Previous LT studies on amorphous and partly disordered low-coordinated solids show the presence of low-energy excitations, which can be described as quantum mechanical tunneling states (TS’s). The possible “glassy” behavior of highly coordinated solids, is, however, still under discussion. Our observations indicate the presence of TS in neutron-irradiated bulk silicon. This result makes it possible to study TS in highly coordinated bulk solids.