Effects of external stress on defect complexes in semiconductors
Crystal field gradients that exist at lattice sites in solids depend on the symmetry of charge distribution around atomic sites. The charge symmetry could be broken either by the presence of impurity complexes in the host matrix or by external stress on the samples, which leads to an observable magnitude of electric field gradients (EFGs). The perturbed γ–γ angular correlation (PAC) method is employed here to investigate the effect of uniaxial stress on 111Cd sites in crystalline doped semiconductors.
Pairing of acceptors with interstitial donors in silicon and germanium
Abstract The interaction of acceptor atoms with the interstitial impurity atoms hydrogen and lithium in the semiconductors silicon and germanium has been studied with help of the perturbed γγ angular correlation technique at the radioactive acceptor 111 In. The formed acceptor-donor pairs, as characterized by their electric field gradients, show some striking differences in silicon and germanium. In particular, besides the thermal stability of the pairs, the number of formed InLi and InH complexes is different in silicon and germanium. The behaviour of the formed complexes as a function of the carrier concentration will be discussed.
5.63 and 5.80 MeV levels of Ne20; de-excitation branching
Abstract The ratio Г γ /Г for the 5.63 and 5.80 MeV levels of Ne 20 has been determined to be 0.077 (±0.008) and −4 , respectively, by using the C 12 (C 12 , α)Ne 20 reaction and determining the fraction of the events in which the alpha-particle and the Ne 20 recoil are present in coincidence at the kinematically correct angles. In both cases these results in themselves are shown to imply radiative E1 transition (5.63→1.63 and 5.80→0, respectively) probabilities ⪡5 × 10 −5 Weisskopf units. When taken together with the life-time for the 5.63 MeV level measured by Evans et al . values of Г( E1 ) ≲ 5 × 10 −6 and Г α ≈ 6% of the particle estimate are obtained for this state.