Effect Of Surface Damage Research Articles

Gate formation in GaAs MESFET's using ion-beam etching technology

The use of ion-beam etching for the controllable formation of very thin active channel layers in GaAs MESFET's is investigated and compared with chemical and plasma etching techniques. The Schottky gate diodes associated with ion-beam etched surfaces show significant surface damage, a substantial part of which can be removed by annealing. Typical annealed diodes exhibit a barrier height of 0.53 eV and an ideality factor of 1.22. A modified Schottky theory is presented which includes the effects of surface damage and a thin interfacial layer between the metal and semiconductor. This model appears to account for most of the observed behavior. Capacitance-voltage-and current-voltage characteristics are presented for both large-area diodes on ion-beam etched surfaces and for MESFET's with gate lengths of 3 and 0.15 µm.

Effect of surface damage on the IR optical performance of Ge

Effect of surface damage on the IR optical performance of Ge

Rotating ring-disc electrode studies of the grain-boundary and surface damage effects on the stabilization of n-Si photoanode

We have investigated the grain-boundary and surface damage effects on the stabilization of n-Si photoelectrode using the rotating ring-disc electrode technique. The effect of surface damage is to lower the stabilization efficiency. We conclude that the defective surfaces lead to changes in the overall competition between the oxidation of the stabilizing agent and the oxidation of the electrode surface atoms. In addition, we have shown that the stabilization efficiency of polycrystalline n-Si is comparable to that of the surface-damage-free single crystal n-Si if its electronically active grain boundaries are not exposed to the electrolyte.

The effects of surface damage and oxide films on the optical properties of cuprite

SummarySpectral ellipsometry in the range 240 nm to 540 nm has been used to investigate the influence of surface damage induced by mechanical polishing and surface films of CuO on the optical properties of pure synthetic cuprite. Comparison is made between bulk CuO and thin film CuO produced by low-temperature oxidation of cuprite. The effects of strain and disorder are discussed in relation to the suppression of excitonic transitions. Recently developed techniques have been used to simplify the analysis and take full advantage of the spectral data.

Temperature dependence of Pt(111) surface relaxation

A careful investigation of the Pt(111) surface has been carried out, using the MeV heliumscattering technique. The anomalously large surface relaxation effect reported previously has been identified as an experimental artifact resulting from an unexpectedly large surface damage effect at low temperature. Optimum conditions have been established for minimizing the main experimental sources of error: background subtraction, radiation damage, and deviations from the Rutherford scattering law. Using these optimum conditions, a series of scattering measurements has been made over the temperature range 40–300 K. At all temperatures, we observe a significant anisotropy in the 〈111〉 angular scans, indicating an outward relaxation of the Pt(111) surface plane. By comparing this observed anisotropy with a set of Monte Carlo simulations, a value of 0.03 ∓ 0.01 Å (i.e. 1.3 ∓ 0.4%) is obtained for the surface relaxation. The temperature dependence of the surface peak also indicates that the enhanced vibrational amplitude of the surface atoms is not nearly as large as had been derived previously from high-temperature LEED studies.

Surface damage and the optical reflectance of single-crystal silicon

The reflectance of silicon measured at 4.3 eV can be used to determine the surface quality of silicon. Crystallographic damage, which occurs with abrasive polishing, and texture, which occurs with epitaxial film growth, can be detected. The effect of surface damage on the optical reflectance of silicon measured at 4.3 eV is reported. The reflectance measurement is nondestructive, simple, fast (on the order of seconds), and sensitive. The technique is readily adaptable to quality control inspection in silicon device manufacturing facilities.

Surface damage and thermal effects from transient thermonuclear radiation in inertial confinement fusion reactors

A general model for transient deposition of thermonuclear radiation has been developed and applied to calculate the response of copper to a reference spectrum typical of laser fusion reactors. At 7 m from a 100 MJ pellet, temperature excursions of approximately 700°C above the ambient temperature are noted for both photons and ions, occurring 0.02 and 2 μs after the thermonuclear burn, respectively. Total displacement rates approach 100 dpa/s at the surface and 500 dpa/s at 1 μm into the copper. Filling the chamber with Ne at 0.5 Torr was found to be sufficient to reduce the temperature excursion in copper by 50% and the dpa rate at the front surface by 25%. The combination of surface temperature transients and ion bombardment was found to increase the sputtering yield by a factor of 4 over ambient temperature values indicating that previous calculations may have seriously underestimated the sputtering damage in laser fusion first walls.

The effect of tilt and surface damage on practical capacitance displacement transducers (interferometric technique)

The effects of non-parallelism and surface roughness on the linearity of a guard-ring, three-terminal capacitance displacement transducer have been observed using a Michelson interferometer technique. The results are referred to an established theoretical model, modified slightly to account for the particular geometry of the transducer. For small electrode separations the effect of non-parallelism could lead to calibration errors in capacitance transducers but the surface roughness of the electrodes is unlikely to present great practical problems.

An investigation of the effect of surface damage on the intensity of diffracted neutrons

The possible effect of surface damage on the intensity of diffracted neutrons has been investigated by a series of measurements for a plate-shaped crystal of SrF2 with the large faces alternatively polished and roughened to various degrees. No significant effects were observed until the crystal thickness was reduced to about 1.7 mm and it is concluded that inhomogeneity of the extinction properties within the volume of the crystal is likely to be a far more important effect for normal neutron diffraction experiments.

Gauge length and surface damage effects on the strength distributions of silicon carbide and sapphire filaments : Kotchick, D. M., Hink, R. C. and Tressler, R. E. Journal of Composite Materials, Vol 9 (Oct 1975) pp 327–336

Gauge length and surface damage effects on the strength distributions of silicon carbide and sapphire filaments : Kotchick, D. M., Hink, R. C. and Tressler, R. E. Journal of Composite Materials, Vol 9 (Oct 1975) pp 327–336

Gauge Length and Surface Damage Effects on the Strength Distributions of Silicon Carbide and Sapphire Filaments

The assumption of the constancy of the Weibull distribution parameters with variations in gauge length was tested for SiC-on-carbon and sapphire filaments. Surface damage was superimposed on the gauge length variations to investigate the effect of the additional flaw spectrum on the gauge length conclusions. The results have demonstrated that, even when failure is due to a single flaw spectrum, the Weibull m parameter is not constant over a gauge length range of 40 times the shortest length. When failure is due to overlapping flaw distributions the possibility of extrapolations assuming constant Weibull parameters is even more remote. The constant gauge length data was used in a modified form of the Poisson distribution proposed by Phoenix to compare to the extrapolative ability of the Weibull distribution. Very little difference in accuracy was found with the former approach being marginally better.

Surface damage and environmental effects on the strain-rate sensitivity of the strength of sapphire and silicon carbide filaments

c-axis sapphire and silicon carbide-on-carbon filaments with pristine and damaged surfaces were tensile tested in water and dry toluene at various strain rates. There was no evidence of slow crack growth during the testing of the silicon carbide filaments. However, the surface damaged sapphire filaments exhibited slow crack growth in the water environment. The slope of the stress intensity factor versus crack velocity curve in region I of the characteristic curve was found to be 28 in excellent agreement with previous results from slow crack growth studies in which the stress corrosion phenomenon is adequately explained by the Hillig-Charles mechanism. The corresponding tests in dry toluene produced no evidence of slow crack growth. The sapphire filaments with virgin surfaces exhibited slow crack growth in both water and toluene which is apparently not related to the moisture assisted growth observed in the abraded filaments.

Surface damage effects on allowed and forbidden phonon raman scattering in cuprous oxide

Ten laser frequencies near the blue and violet excitons in Cu 2O were used to study the resonance Raman intensities of the Raman-allowed phonon, Γ + 25, and of two Raman-forbidden phonons, Γ - 15 and Γ - 12. Cu 2O samples with chemically etched surfaces show Raman cross section enhancements from 10 3−10 4 and considerable structure whereas unetched crystals show much less enhancement and little structure.

The effect of surface damage on the intensity of X-rays diffracted by ground spherical single crystals

Integrated intensities from ground spherical single crystals of silicon, zinc sulphide, and calcium fluoride before and after etching are compared. The surface damage of the unetched crystals, apparent on scanning electron micrographs, is shown to give rise to a very appreciable enhancement of the X-ray Bragg intensities. A possible explanation for physically unrealistic phenomenological extinction parameters reported in the literature is suggested.

Mechanism of Dry Friction : Part 1, Effect of Surface Damage on Friction between Soft Cone and Hard Plane Surface

Mechanism of Dry Friction : Part 1, Effect of Surface Damage on Friction between Soft Cone and Hard Plane Surface

Effect of Surface Damage on the Strength of Al2O3 Ceramics with Compressive Surface Stresses

In fully dense fine‐grained Al2O3 ceramics, fracture originates at surface flaws. The severity of these flaws depends on the methods used to form the surface and any subsequent damage that may have occurred. It is desirable to find ways to minimize the severity of these flaws. Both untreated and quenched Al2O3 rods were scratched by rotating them under a diamond point with various loads. The strengths of the quenched rods decreased less than those of the untreated rods. Microscopic examination showed that the compressive surface stresses induced by quenching reduced the penetration of surface damage.

Effect of surface damage on the strength of c-axis sapphire filaments : Crane, R. L. and Tressler, R. E. Journal of Composite Materials, Vol 5, p 537 (October 1971)

Effect of surface damage on the strength of c-axis sapphire filaments : Crane, R. L. and Tressler, R. E. Journal of Composite Materials, Vol 5, p 537 (October 1971)

Effect of Surface Damage on the Strength of C-Axis Sapphire Filaments

Effect of Surface Damage on the Strength of C-Axis Sapphire Filaments

Reflectivity Enhancement of Semiconductors by Q-Switched Ruby Lasers

Reflectivity enhancement of single-crystal silicon, germanium, gallium arsenide, and indium antimonide and polycrystalline boron and cadmium selenide was observed. The reflectivity variations were produced by irradiating the semiconductor with the output of a Q-switched ruby laser (6943 Å) with pulses of 30 and 10 nsec. The reflectivity variations were monitored with a pulsed argon-ion laser (mainly 4880 and 5145 Å). The effect of surface damage at high power levels produced an irreversible reflectivity decrease. Polished samples of molybdenum and tungsten, when irradiated by the Q-switched ruby-laser light, exhibited irreversible decreases in reflectivity due to surface damage and reversible variations, which were attributed to elastic deformation. Reflectivity enhancement of semiconductors was attributed to the formation on the semiconductor surface of a liquid film with metallic properties.

The relation between surface damage and film strengthening effects

The strengthening effects produced by various metallic coatings on copper single crystals were studied. There was no relation between the magnitude of the strengthening produced and the mechanical strength of the various coatings. On this basis, a mechanism involving the operation of the coating as a simple barrier to dislocation egress from the crystal was considered inappropriate. Likewise, there was no relation between the relative shear moduli of coating and substrate and the strengthening produced. Thus, the elastic repulsion of dislocations from the coating-substrate interface was also considered to be unimportant as a mechanism. None of the results suggested that the suppression of surface Frank-Read sources or coating-substrate incompatibility made an important contribution to the strengthening effect. Significant film strengthening effects were always accompanied by cracking of the coating either prior to or during deformation. Associated with film cracking was an increase in dislocation density at the substrate surface. This surface damage which resulted from residual stresses in the coating is believed to be the critical factor in producing the film strengthening effects which were observed.