Epitaxial growth of Cu (001) on Si (001): Mechanisms of orientation development and defect morphology

We describe the evolution of microstructure during ultrahigh vacuum ion beam sputter deposition of Cu (001) at room temperature on hydrogen-terminated Si (001). In situ reflection high energy electron diffraction indicates growth of an epitaxial Cu (001) film on Si (001) with the intensity of the Bragg rods sharpening during 5–20 nm of Cu film growth. Post-growth x-ray diffraction indicates the Cu film has a mosaic spread of (001) textures of about ±2° and that a small fraction (0.001–0.01) is of (111) textures. High-resolution transmission electron microscopy shows an abrupt Cu/Si interface with no interfacial silicide, and reveals an evolution in texture with Cu thickness so as to reduce the mosaic spread about (001). Moiré contrast suggests a nearly periodic elastic strain field extending into the Cu and Si at the interface. Other aspects of film growth which are critical to epitaxy are also discussed

Strain modification in coherent Ge and SixGe1–x epitaxial films by ion-assisted molecular beam epitaxy

We have observed large changes in Ge and SixGe1–x layer strain during concurrent molecular beam epitaxial growth and low-energy bombardment. Layers are uniformly strained, coherent with the substrate, and contain no dislocations, suggesting that misfit strain is accommodated by free volume changes associated with injection of ion bombardment induced point defects. The dependence of layer strain on ion energy, ion-atom flux ratio, and temperature is consistent with the presence of a uniform dispersion of point defects at high concentration. Implications for distinguishing ion-surface interactions from ion-bulk interactions are discussed

Tests of microstrip dispersion formulas

A set of published formulas for the frequency dependence of the microstrip effective relative dielectric constant epsilon /sub re/(f) is tested relative to an assemblage of measured data values for this quantity chosen from the literature. The RMS deviation of the predicted data obtained from the measured values ranged from 2.3% to 4.1% of the seven formulas for epsilon /sub re/(f) tested. A formula due to M. Kirschning and R.H. Jansen (see Electron. Lett., vol.18, p.272-73, 1982) showed the lowest average deviation from measured values, although the differences between the predictions of their formula and others tested are of the order of the error limits of the comparison process. It is concluded that the results indicate the suitability of relatively simple analytical expressions for the computation for microstrip dispersion

Quantitative Determination of Enhanced and Suppressed Transmission through Subwavelength Slit Arrays in Silver Films

Measurement of the transmitted intensity from a coherent monomode light source through a series of subwavelength slit arrays in Ag films, with varying array pitch and number of slits, demonstrate enhancement (suppression) by as much as a factor of 6 (9) when normalized to that of an isolated slit. Pronounced minima in the transmitted intensity were observed at array pitches corresponding to lambda_SPP, 2lambda_SPP, and 3lambda_SPP where lambda_SPP is the wavelength of the surface plasmon polariton (SPP). Increasing the number of slits to more than four does not increase appreciably the per-slit transmission intensity. These results are consistent with a model for interference between SPPs and the incident wave that fits well the measured transmitted intensity profile.Comment: Figure 4 update

Alien Registration- Atwater, David H. (Canton, Oxford County)

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Microphotonic parabolic light directors fabricated by two-photon lithography

We have fabricated microphotonic parabolic light directors using two-photon lithography, thin-film processing, and aperture formation by focused ion beam lithography. Optical transmission measurements through upright parabolic directors 22 μm high and 10 μm in diameter exhibit strong beam directivity with a beam divergence of 5.6°, in reasonable agreement with ray-tracing and full-field electromagnetic simulations. The results indicate the suitability of microphotonic parabolic light directors for producing collimated beams for applications in advanced solar cell and light-emitting diode designs

Simulation of GaAs p-i-n diodes

GaAs p-i-n diodes have been modeled using numerical simulation, and the theoretical results have been compared to those of experiment. The simulations predict that with a lifetime of the carriers of 10^(-7)s, devices that have good i-layer modulation may be built. This is in agreement with currently available commercial devices

Size-dependent oxygen-related electronic states in silicon nanocrystals

Silicon nanocrystals embedded in SiO2 were isolated with a selective etching procedure, and the isolated nanocrystals' excitonic emission energy was studied during controlled oxidation. Nanocrystals having initial diameters, d(0), of similar to 2.9-3.4 nm showed a photoluminescence (PL) blueshift upon oxidatively induced size reduction, as expected from models of quantum confinement. Oxidation of smaller Si nanocrystals (d(0)similar to 2.5-2.8 nm) also initially resulted in a PL blueshift, but a redshift in the PL was then observed after growth of similar to 0.3 monolayers of native oxide. This decrease in excitonic emission energy during oxidation is consistent with the theoretically predicted formation of an oxygen-related excitonic recombination state