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With electron nuclear double resonance (ENDOR) the superhyperfine interactions of Fe3+ impurities with five shells of Li neighbours were measured in a congruent LiTaO3 crystal. From the analysis of the ENDOR spectra it is found that Fe3+ is on a substitutional Li+ site on the threefold symmetry axis of the crystal. From the shape of the ENDOR spectrum it is concluded that most Fe3+ impurities are on very perturbed sites.

EPR studies on ultraviolet-irradiated crystals of AgC1:Pd have confirmed earlier results on AgCl:Cu for the existence of an energy barrier in the self-trapping of the photohole. The height of this barrier is near 1.8 meV. Migration of the self-trapped hole was found to be athermal for temperatures below 30 K; above 35 K the self-trapped hole hops, with a diffusivity given by D =7&(10 exp( -. 61 meV/kT) cm /sec. This suggests that the value of the electron transfer integral is about 1% of the energy of the phonons involved, that the bandwidth for the self-trapped hole is of the order of 2 meV, and that the binding energy of the hole is approximately 0.1 eV. The dependence on temperature of the efficiency of photoproduction of various trapped-carrier palladium centers was determined, and was correlated with the migration of the self-trapped hole. The presence of a small amount of Fe + "tracer" served to indicate those decay processes that were due to thermal release of trapped holes.

Investigation of polycrystalline diamond films by electron paramagnetic resonance at 9.5 and 35 GHZ has revealed the presence of forbidden transitions resulting from a simultaneous microwave induced flipping of unpaired electron spins and environmental nuclear spins. The spacing of the resonance lines identifies hydrogen as the atom neighboring the paramagnetic active site.

Hole trapping at cation vacancies in doped, irradiated silver halides is studied by means of electron paramagnetic resonance (EPR). From detailed studies of the behavior of the EPR spectra upon thermal annealing and of the effects of the concentrations of various divalent cations, it is demonstrated that in AgCl the positive hole can indeed be bound to the negative cation vacancy.The resulting two types of paramagnetic centers, which survive up to 70 and 110 K, respectively, are identified as perturbed self-trapped hole centers with a cation vacancy in either the nextnearest-neighbor or nearest-neighbor position in the equatorial plane, respectively. In addition, the perturbing cation vacancy is determined to be an isolated vacancy, free from any nearby divalent cation. In AgBr, however, no corresponding EPR effects due to the interaction between the hole and the cation vacancy have been observed.

It has long been believed that the electron paramagnetic resonance (EPR) signal identified as the E~ center is due to fixed positive charge generated by ionizing radiation in SiQ. This hypothesis has been studied in the past, with results consistent with this idea. However, the possibility that the generic E' center is related to neutral electron traps, which are also created with ionizing radiation, has not been examined since the earlier studies did not involve electron injection, and large neutral electron traps were not widely known to exist when the initial correlation was made. The present study examines this possibility, utilizing two different radiation dose levels, where the ratios of the densities of fixed positive charge and neutral electron traps are different, to differentiate the two possibilities. It involves correlations between actual insulated gate field effect transistors, whose oxides were irradiated the same as blanket oxides, used for EPR studies. By comparing the density of E~ centers with the densities of fixed positive charge and neutral electron traps, measured by a two-step electron injection sequence, as well as examining the ratios between the two radiation levels, two independent measures of the nature of the E~ center are obtained. It was found that the density of the E~ centers matches the density of the fixed positive charge, and that the ratio of the densities between the two different dose levels also follows the behavior of the fixed positive charge. The density of fixed positive charge plateaus at high radiation dose as does the EPR signal attributed to fixed positive charge. Conversely, the densities of neutral electron traps do not track the change in EPR signal as radiation level changes. Thus, we conclude that E4 centers are indeed fixed positive charge, and not neutral electron traps.It has long been suggested (1-6) that fixed positive charge created by ionizing radiation and the E~ center, detected with EPR, are one and the same. The presence of fixed positive charge is deduced from studies on either capacitors or insulated gate field effect transistors (IGFETs) where either flatband or threshold lowering, respectively, is observed following exposure to ionizing radiation. The EPR resonance which has been correlated to fixed positive charge has been observed on blanket SiO2 grown on silicon substrates. This correlation was made on the basis that fixed positive charge was detected in devices and the E~ resonance was observed in blanket oxides after exposure to ionizing radiation. At that time it was not widely known that large neutral electron traps (7, 8) are also created during exposure of SiO~ to ionizing radiation. Since the studies involving EPR had not been correlated with actual electron injectio n studies of devices, correlations of the E~ center with fixed positive charge were made without taking into account the presence of uncharged large neutral electron traps also created by ionizing radiation, and not detectable by either flatband or threshold voltage shifts...

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