Investigation of annealing effects on the laser-induced damage threshold of amorphous Ta2O5 films

Ta2O5 films were deposited using the conventional electron beam evaporation method and then annealed at temperatures in the range 373-673 K. Chemical composition, scattering and absorption were examined by X-ray photoelectron spectroscopy (XPS), total integrated scattering (TIS) measurement and the surface thermal lensing (m) technique, respectively. The laser-induced damage threshold (LIDT) was assessed using the output from an Nd:YAG laser with a pulse length of 12 ns. The results showed that the improvement of the LIDT after annealing was due to the reduced substoichiometric and structural defects present in the film. The LIDT increased slightly below 573K and then increased significantly with increase in annealing temperature, which could be attributed to different dominant defects. Moreover, the root mean square (RMS) roughness and scattering had little effect on the LIDT, while the absorption and the LIDT were in accord with a general relation. (c) 2008 Elsevier Ltd. All rights reserved.

Influence of substoichiometer on the laser-induced damage characters of HfO2 thin films

HfO2 is one of the most important high refractive index materials for depositing high power optical mirrors. In this research, HfO2 thin films were prepared by dual-ion beam reactive sputtering method, and the laser-induced damage thresholds (LIDT) of the sample were measured in 1-on-1 mode for laser with 1064 nm wavelength. The results indicate that the LIDT of the as-grown sample is only 3.96 J/cm(2), but it is increased to 8.98 J/cm(2) after annealing under temperature of 200 degrees C in atmosphere. By measuring the laser weak absorption and SIMS of the samples, we deduced that substoichiometer is the main reason for the low LIDT of the as-grown sample, and the experiment results were well explained with the theory of electronic-avalanche ionization. (C) 2008 Elsevier B.V. All rights reserved.

Trawl-induced Damage to Sponges Observed From a Research Submersible

Three experimental trawl paths subjected to a single pass with the trawl in 1996 in about 200 m of water on the eastern Gulf of Alaska continental shelf were revisited in July 1997, 1 year post-trawl. Many large, erect sponges, the taxa impacted most significantly, had been removed or damaged by the trawl. Sponges in the cold, deep water of the Gulf of Alaska were slow to recover from trawling effects. These findings contrast with recovery times for shallow, warmwater sponges and may have fishery management implications for cold-water regions.

Characterization of impact induced damage modes in single lap joints of woven GFRP composites

Single lap joints of woven GFRP composites have been investigated for impact induced damage modes using C-scan, X-ray micro tomography, imaging and finite element (FE) modelling. This has allowed for damage modes to be observed in 3D from macro to micro level-resulting in much better understanding of damage mechanisms and realistic FE modelling.

Friction-induced vibration: Model development and comparison with large-scale experimental tests

This paper presents a comparison between theoretical predictions and experimental results from a pin-on-disc test rig exploring friction-induced vibration. The model is based on a linear stability analysis of two systems coupled by sliding contact at a single point. Predictions are compared with a large volume of measured squeal initiations that have been post-processed to extract growth rates and frequencies at the onset of squeal. Initial tests reveal the importance of including both finite contact stiffness and a velocity-dependent dynamic model for friction, giving predictions that accounted for nearly all major clusters of squeal initiations from 0 to 5 kHz. However, a large number of initiations occurred at disc mode frequencies that were not predicted with the same parameters. These frequencies proved remarkably difficult to destabilise, requiring an implausibly high coefficient of friction. An attempt has been made to estimate the dynamic friction behaviour directly from the squeal initiation data, revealing complex-valued frequency-dependent parameters for a new model of linearised dynamic friction. These new parameters readily destabilised the disc modes and provided a consistent model that could account for virtually all initiations from 0 to 15 kHz. The results suggest that instability thresholds for a wide range of squeal-type behaviour can be predicted, but they highlight the central importance of a correct understanding and accurate description of dynamic friction at the sliding interface. © 2013 Elsevier Ltd. All rights reserved.

Dependence of implantation-induced damage with photoluminescence intensity in GaN : Er

Erbium was implanted with energies 200 or 400 keV into epitaxial (0 0 0 1) GaN grown on (0 0 0 1) Al2O3 substrate at room temperature (RT) and 400degreesC. Both random (10degrees tilt from c-axis) and channeled (along c-axis) implantations were studied. RBS/Channeling technique was used to study the dependences of the radiation damage with ion implantation energy, direction and temperature. It was found that the channeling implantation or elevating temperature implantation both resulted in the decrease of the damage. Moreover, the Photoluminscence (PL) properties of Er-implanted GaN thin filius were also studied. The experimental results indicate that the PL intensity can be enhanced by raising implantation energy or implanting along channeling direction. (C) 2004 Elsevier B.V. All rights reserved.

Effect of ion-induced damage on GaNAs/GaAs quantum wells grown by plasma-assisted molecular beam epitaxy

The effect of ion-induced damage on GaNAs/GaAs quantum wells (QWs) grown by molecular beam epitaxy employing a DC plasma as the N source was investigated. Ion-induced damage results in: (i) an observed disappearance of pendellosung fringes in the X-ray diffraction pattern of the sample; (ii) a drastic decrease in intensity and a broadening in the full-width at half-maximum of photoluminescence spectra. It was shown that ion-induced damage strongly affected the bandedge potential fluctuations of the QWs. The bandedge potential fluctuations for the samples grown with and without ion removal magnets (IRMs) are 44 and 63 meV, respectively. It was found that the N-As atomic interdiffusion at the interfaces of the QWs was enhanced by the ion damage-induced defects. The estimated activation energies of the N-As atomic interdiffusion for the samples grown with and without IRMs are 3.34 and 1.78 eV, respectively. (C) 2001 Elsevier Science B.V. All rights reserved.

Plasma induced damage in GaN-based light emitting diodes - art. no. 68410X

The effects of plasma induced damage in different conditions of ICP and PECVD processes on LEDs were presented. For ICP mesa etch, in an effort to confirm the effects of dry etch damage on the optical properties of p-type GaN, a photoluminescence (PL) measurement was investigated with different rf chuck power. It was founded the PL intensity of the peak decreased with increasing DC bias and the intensity of sample etched at a higher DC bias of -400V is less by two orders of magnitude than that of the as-grown sample. Meanwhile, In the IN curve for the etched samples with different DC biases, the reverse leakage current of higher DC bias sample was obviously degraded than the lower one. In addition, plasma induced damage was also inevitable during the deposition of etch masks and surface passivation films by PECVD. The PL intensity of samples deposited with different powers sharply decreased when the power was excessive. The PL spectra of samples deposited under the fixed condition with the different processing time were measured, indicating the intensity of sample deposited with a lower power did not obviously vary after a long time deposition. A two-layer film was made in order to improve the compactness of sparse dielectric film deposited with a lower power.