Microwave absorption in the superconducting and normal phases of Y-Ba- Cu-O" (1987). Stephen Ducharme Publications. 25.

Four different metastable paramagnetic centers have been identified in the low-temperature, light-induced electron-spin resonance (ESR) spectrum of glassy As&S3. Two of the centers anneal at significantly lower temperatures than the other two, allowing the line shapes to be partially separated with isochronal annealing experiments. The two centers which anneal at lower temperatures, labeled type-I centers, constitute approximately 15% of the induced spins after long-time irradiation at high intensities ( 100 mW/crn~). These centers consist of a hole on a nonbonding 3p orbital of a sulfur atom (Si) and an electron on an s-p hybridized orbital of an arsenic atom (As&). Similar kinetic behavior suggests that the origin of these two centers is a single event, which may be the breaking of an arsenic-sulfur bond. The type-II centers, which are thermally more stable, represent -85%%uo of the induced spins and are concluded to be due to an electron in a nonbonding 4p wave function on a twofold-coordinated arsenic atom (As») and a hole on a nonbonding 3p orbital of a sulfur atom (Si&).The origin of these centers is suggested to be the breaking of As -As and S -S bonds. The densities of the different spins vary rapidly with the stoichiometry. Interpretation of the kinetic behavior of the type-I and type-II ESR signals suggests the existence of a third intermediate metastable state in addition to the ground state and the excited paramagnetic state. High-intensity () 100 mWcm ) light with energy above the band gap (A,~514.5 nm) creates new structural defects in the glass at densities which exceed 10' cm '. At high temperatures (T)250 K) the shift of the opticalabsorption edge to lower energies, which is known as the photodarkening effect, exhibits different kinetics from the electron-spin resonance. This fact suggests that there exists no one-to-one correlation between these two effects. There is, however, a close parallel at all temperatures between absorption well below the gap (midgap absorption) and the type-I ESR centers.

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Surface processing of microelectronic materials by bombardment with nanoparticles of condensed gases (i.e., clusters) in the form of an ion beam, makes possible etching and smoothing of those surfaces to very high figures of merit. As this is not possible with any conventional ion method, gas-cluster ion-beam systems have great potential in manufacturing. The formation of gas clusters and their collision with surfaces provides an interesting arena for novel physics and surface science. This paper outlines a physical model for the clusters and surface interactions, and provides examples of surface processing. In particular, the reduction of surface roughness while etching by cluster-ion bombardment is illustrated for various materials utilized in microelectronics.

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Comparative studies of red (633 nm) and infrared (IR) (1064 nm) light-induced electron spin resonance (LESR) have been performed on various samples of hydrogenated amorphous silicon. Redlight excitation always yields the well-known LESR spectra for that material which can be ascribed to a superposition of two resonances due to band-tail state carriers of both types in a 1:1 ratio. For the a-Si:H films examined in this study, which were all deposited on quartz substrates, IR excitation results in different LESR spectra with considerably less spin density in the broad line attributed to holes in the valence-band tail than in the narrow line attributed to electrons in the conduction-band tail. This asymmetry is not observed in a powdered sample, which points to interface states at the quartz surface of the films as the mechanism responsible for the excess spin density in the narrow line. The observed dependence on film thickness confirms this interpretation.Surprisingly, the number of these interface states is as large as 5 X 10' cm for a region which is assumed to be 1000 0 A thick near the a-Si:H/quartz interface. An increased density of dangling bonds in the interface region due to different growth conditions for the first few hundred angstroms of the filrn growth, which are doubly occupied because of band-bending effects, is one possibility to explain the results.

We present our recent results on Si thickness uniformity improvement in a SOI wafer. We improved the thickness uniformity by 50%. The effect of the correction process on the propagation loss and device uniformity is also presented.