Search

Study Design: Systematic review. Objectives: The objective of this study was to answer 5 key questions: What is the comparative effectiveness and safety of (1a) anticoagulant thromboprophylaxis compared to no prophylaxis, placebo, or another anticoagulant strategy for preventing deep vein thrombosis (DVT) and pulmonary embolism (PE) after acute spinal cord injury (SCI)? (1b) Mechanical prophylaxis strategies alone or in combination with other strategies for preventing DVT and PE after acute SCI? (1c) Prophylactic inferior vena cava filter insertion alone or in combination with other strategies for preventing DVT and PE after acute SCI? (2) What is the optimal timing to initiate and/or discontinue anticoagulant, mechanical, and/or prophylactic inferior vena cava filter following acute SCI? (3) What is the cost-effectiveness of these treatment options? Methods: A systematic literature search was conducted to identify studies published through February 28, 2015. We sought randomized controlled trials evaluating efficacy and safety of antithrombotic strategies. Strength of evidence was evaluated using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system. Results: Nine studies satisfied inclusion criteria. We found a trend toward lower risk of DVT in patients treated with enoxaparin. There were no significant differences in rates of DVT, PE, bleeding, and mortality between patients treated with different types of low-molecular-weight heparin or between low-molecular-weight heparin and unfractionated heparin. Combined anticoagulant and mechanical prophylaxis initiated within 72 hours of SCI resulted in lower risk of DVT than treatment commenced after 72 hours of injury. Conclusion: Prophylactic treatments can be used to lower the risk of venous thromboembolic events in patients with acute SCI, without significant increase in risk of bleeding and mortality and should be initiated within 72 hours.

In order to bring low-power epitaxy-based gallium antimonide (GaSb) electronics and electro-optics to market, high-quality GaSb substrates with smooth surfaces and no surface damage are required. Here, a novel final polishing technique, gas cluster ion beam (GCIB) processing, is shown to improve the surface finish of chemical–mechanical polished (CMP) 50 mm (1 0 0) GaSb wafers by etching and smoothing CMP surface atoms through the sub-surface damage. For the first time, a fluorine-based gas cluster ion beam is reported for GCIB surface etching and smoothing of GaSb material. For the selected processing sequence, the surface roughness of a high-quality, 0.70 nm RMS GaSb wafer was reduced to 0.18 nm RMS without any observed changes in the full-widths at half-maximum (FWHM) of the (4 0 0) and (1 1 1) X-ray peaks of 14 and 20 arcsec, respectively. Results indicate that the GCIB process did not contribute to wafer surface or sub-surface polish damage. In a second case, a GCIB etch removed 200 nm of material from a non-optimal CMP (1 0 0) GaSb surface and reduced the full-width at half-maximum (1 1 1) X-ray peak from 76 to 52 arcsec in conjunction with a surface roughness decrease from 0.70 to 0.35 nm RMS. The data suggests that GCIB processing appears to be promising as a final GaSb wafer polish with an etch rate compatible for large scale manufacturing.

Gas-cluster ion-beam (GCIB) processing of surfaces provides individual atoms within an accelerated gas cluster (∼1,500 atoms per cluster), an energy approximately equal to the individual bond energy of the target surface atoms. The gas-cluster beam is thus capable of providing smoothing and etching of the extreme surface of numerous semiconductors, metals, insulators, and magnetic materials. For semiconductor material systems, the gas-cluster processing effect on the surface and subsurface material is of critical interest for device and circuitry application integrity. In the case of III–V GaSb, chemo-mechanical or touch polishing is the final step in the semiconductor-wafer manufacturing process, often leaving scratches of various depths or damage on the polished surface. In this paper, we report the GCIB etching and smoothing of chemical-mechanical polished GaSb(100) wafers. Using a dual-energy, dual gas-cluster source process, ∼100 nm of material was removed from a GaSb(100) surface. Atomic-force microscopy (AFM) imaging and power spectral-density (PSD) analysis shows significant decrease in the post-GCIB root-mean-square (Rms) roughness and peak-to-valley measurements for the material systems. X-ray rocking-curve analysis has shown a 24-arcsec reduction in the full-width at half-maximum (FWHM) of the (111) x-ray diffraction peak of GaSb. High-resolution transmission-electron microscopy (HRTEM) shows the crystallinity of the subsurface of the pre- and post-GCIB surfaces to be consistent, following the 1 × 1016 ions/cm2 total-fluence processes, with dislocation density for both pre- and post-GCIB cases below the HRTEM resolution limit. X-ray photoelectron spectroscopy (XPS) indicates a strong Ga 3p electron binding-energy intensity for gallium-oxide formation on the GaSb surface with the use of an oxygen GCIB process. Analysis of the Ga 3p electron binding-energy peaks in the XPS data in conjunction with HRTEM indicates a higher Ga or GaSb content in the near-surface layer (less stoichiometric-oxide presence) with use of a CF4/O2 GCIB process. The same peak analysis indicates that the surface gallium-oxide state is nearly unchanged, except in thickness, with the use of an O2-GCIB second step. The material results suggest that GCIB provides a viable method of chemo-mechanical polish (CMP) damage removal on group III–V material for further device processing.

The reduction of roughness, without introducing damage, of thin-film surfaces in giant magnetoresistance (GMR) applications will be essential in the development of advanced devices. Tools and methods to accomplish this are limited at present. Gas-cluster ion beam (GCIB) technology shows promise as a dry, low-temperature process that can provide substantial improvement, and can be integrated into GMR-film deposition-and-etch tools. In this work, we describe recent GCIB technique developments and processes for tantalum, alumina, permalloy, and other relevant materials. With argon GCIB it is possible to reduce the roughness of many films to well below a nanometer (root-mean-square), with the roughness falling exponentially with cluster dose. Prototype magnetic films for evaluation were fabricated on GCIB-smoothed alumina gap layers. Transmission electron microscopy revealed changes in roughness and grain morphology that may be correlated with magnetic properties.

Materials processing with a gas cluster ion beam (GCIB) is an emerging technology that has been shown to produce novel material properties in the very near-surface (infusion. Its principal characteristic enables room temperature shallow processing with high concentration gradients and no sharp interfaces. Results are presented from an investigation of GCIB GeH4 infusion into Si(100) substrates for the purpose of producing a strained Si(1-x)Ge(x) layer relative to the Si substrate. The as-infused samples exhibit surface Ge concentrations up to 100%, with a steep concentration gradient over ∼40 nm. Specifically, a broad series of post-processing tube-furnace anneals was investigated over a temperature range of 400 °C to 1200 °C and the samples were analyzed by channeling/RBS to look at quality of recrystallization and for evidence of strain in the lattice. Some anneal schedules included a VLTA (very low temperature anneal) first step followed by subsequent HTA (high temperature anneal). Evidence is shown for improved results with no Ge loss using two-step anneals. Channeling analysis was performed along the and directions relative to the Si(100) substrate. Measurements of the min for both the Ge and Si were made to assess crystal quality and to determine the degree of epitaxial alignment with the Si lattice. High-resolution axial scans along were performed on selected samples to look for strain relative to the Si lattice. SIMS analysis of higher temperature anneals showed significant diffusion of Ge. Some samples were also examined by cross-sectional TEM. The best infusion samples show crystal quality comparable to a commercially available epi-grown Si75Ge25 control sample.

The surfaces of single-crystal wafers of sapphire and silicon carbide with microelectronic-grade high polish were exposed to a gas-cluster ion beam (GCIB) and significant reductions in roughness were observed. Atomic-force microscopy revealed that the typical initial surfaces consisted of a fine but small random roughness together with relatively large and sharp asperities. The latter were removed efficiently and GCIB smoothing process improvements are reported. The SiC wafers also have a high density of shallow scratch marks and these too were removed, with the average roughness Ra falling below 4 angstrom after the best process. Analysis of the SiC by Rutherford backscattering spectroscopy in channeling mode revealed that when the GCIB process was adjusted so that asperities and scratch marks were removed, there was no increase in near- and at-surface damage. In particular, no lattice damage was observed of the sort typically caused by ion implantation prior to annealing. Significantly, it was found that oxygen gas cluster ion beams provided superior results with SiC as compared with argon GCIB. Surface smoothing mechanisms are proposed to explain these results.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

With great attention now being given to the wide band gap materials for electronic and optoelectronic device applications, there is interest in using ion implantation to introduce dopants into selected regions of devices. Work on ion implantation into SiC and the III-V nitrides is reviewed, new device concepts are given, and recent results are presented. These include SiC implantations at elevated temperatures, a GaN sample implanted with Si having an electron mobility after annealing of 106 cm2/V-s, and a novel GaN np junction diode created by implantation.

Aluminum oxide films have been deposited by electron-beam evaporation on heated substrates under oxygen ion bombardment. Substrates were crystalline silicon, grafoil and glass. Both substrat temperature and ion current density were changed for each deposition The films deposited on silicon were examined by spectroscopie ellipsometry which showed that for substrate temperatures between 70°C and 250°C the index of refraction, and therefore the film density, first rose and then decreased with increasing ion current density. Ai 400°C the index reached a plateau under these conditions. Study by Rutherford backscattering of films deposited on grafoil showed no significant correlation between oxygen-aluminum stoichiometry and fi; density, suggesting that the decrease in density for large ion currei is not due to oxygen-ion incorporation, as has been suggested in the past. The films deposited on glass at 400°C showed some evidence of crystallization.

Significant improvements in the adhesion of several metals to polymers have been achieved through the ion beam assisted deposition (IBAD) technique. Films of silver, gold, and copper were deposited via IBAD onto poly(tetrafluoroethylene) (PTFE) substrates. These films are substantially more adherent than similar non-IBAD coatings. Film characterization was performed with conventional pull tests, selective abrasion tests, optical microscopy, ESCA, RBS, and static SIMS. Evidence is given for the “smearing” of the normally sharp metal/polymer interface by the ion beam recoil events. Further analysis, however, suggests that the improved adhesion may result from an increase in the shear strength of the PTFE surface layers due to the promotion of crosslinking.

Thin ceramic films (A12O3 ZrO2, Si3N4, and BN) have been prepared by ion beam assisted deposition (IBAD) and their mechanical properties examined. The films exhibit extreme ductility and adhesion, with the former property possibly attributed to the very fine grained, quasi-amorphous grain structure noted for low temperature IBAD coatings.

The method of Ion Beam Enhanced Deposition, (IBED), was used to produce hard films of i-BN, i-SixNy and i-TixNy. The friction, hardness, adhesion, and wear behavior of these nitride coatings were examined using a ball-ondisc friction/wear tester. The friction and wear results were sensitive to stoichiometry and the presence of impurities (e.g., hydrogen) in the film as well as the choice of ball material (400C stainless steel or silicon nitride).