Positron annihilation and electron spin resonance (ESR) have been used to study defects introduced by lMeV electron irradiation in n-type cubic silicon carbide (3C-SiC) epitaxially grown on Si by chemical vapor deposition. Positron annihilation measurements by using variable-energy positron beams indicated the narrowing of the Doppler-broadened energy spectrum of annihilation gamma-rays and the decrease in the effective diffusion length of positrons with increasing the electron fluence. These results show the formation of vacancy-type defects in 3C-SiC. An ESR spectrum labeled T1, which has an isotropie g-value of 2.0029±0.0001, was observed in electron irradiated 3C-SiC. The T1 spectrum is interpreted by hyperfine interactions of paramagnetic electrons with 13C at four carbon sites and 29Si at twelve silicon sites, leads that the Tl center results from a point defect at a silicon sublattice site. The production rate of the Tl center was in good agreement with the carrier removal rate, indicating that the Tl center captures an electron from the conduction band. All these results are accounted for by the introduction of negatively charged vacancies at silicon sublattice sites in 3C-SiC by the irradiation.

MOS device interfaces are investigated using carrier injection and monoenergetic positron beam experiments. Carrier injection reveals that the holes injected into gate S1O2 film seem to be the main cause of the interface state generation and the dielectric breakdown of thin-gate SiO2. Positron annihilation experiments show that the positron diffuse along the electric field in the Si and the gate SiO2 and are trapped in the interface region before annihilation. The obtained value of 5 at the SiO2/Si interface was 0.500 ±0.003. The behavior of holes in the SiO2 and SiO2/Si interface are simulated using the monoenergetic positron annihilation technique.

The topology of the Fermi surface in La2CuO4-σ is determined by two dimensional angular correlation measurements of annihilation radiations (2D-ACAR) at room temperature. The determined Fermi surface is two dimensional and has a slender electron pillar along ΓZ and two kinds of hole pillars along PX and along NN direction parallel to ΓZ, respectively, in the Bradley and Cracknell notation modified by Yu, Freeman and Xu. It is concluded that the Fermi surface is not a simple half filled one and this compound should be metallic at least at room temperature in the band picture.