Influence of radiation defects on internal friction spectra of SiGe crystals

Influence of irradiation by 12 Mev energy electrons on structural-sensitive physical-mechanical properties of monocrystalline silicon and coarse-grained Si_0.98Ge_0.02 alloy is studied. The tendency to decrease of current carriers holes mobility is revealed in samples irradiated by ∼10¹³ cm^-2 fluence electrons. Relaxation maxima in temperature areas of 100 and 300℃ are revealed in internal friction temperature spectra of both crystals. Frequency factor of defects participating in relaxation is 10¹²-10¹³ s^-1, and the values of activation energy are 1.0 and 1.4 eV respectively for the relaxation processes revealed at 100 and 300℃ temperatures. Possible mechanisms of pointed relaxation processes are proposed: reverse motion of vacancy pairs in temperature area of 100℃ and reverse motion of vacancy-oxygen atom pairs in area of 300℃ in external periodic stress field. The increase of the values of critical strain amplitude are revealed on the curves of strain amplitude dependent internal friction and dynamic shear modulus. The obtained results reveal hardening of Si and Si_0.98Ge_0.02 alloy irradiated by high energy electrons under the impact of radiation defects. (author)