Plasma immersion ion implantation (PIII) is an economical means to implant a high dose of hydrogen into silicon and when combined with ion cut, has been demonstrated to be a viable technique to fabricate silicon-on-insulator (SOI). However, its success in the industry hinges on the quality of the SOI wafers produced. One of the most important parameters is the thickness uniformity of the SOI film. We have observed that the thickness variation across a 150 mm wafer follows a pattern in which the transferred silicon film is thickest in the center and thinnest near the edge. Alpha step and SIMS measurements indicate that the lateral nonuniformity is caused by the different penetration depths of hydrogen across the wafer. The experimental results can be explained quantitatively by an oblique incidence model.

Vitamin K antagonists are currently recommended in patients with 'valvular' atrial fibrillation (AF), e. g. those having mitral stenosis or artificial heart valves. We compared thromboembolic risk in patients with 'non valvular' AF and in those with AF and biological valve replacement (valve bioprosthesis). Among 8962 AF patients seen between 2000 and 2010, a diagnosis of 'non-valvular AF' was found in 8053 (94 %). Among patients with 'valvular' AF, 549 (6 %) had a biological prosthesis. The patients with bioprosthesis were older and had a higher CHA2DS2-VASc score than those with non valvular AF. After a follow-up of 876 ± 1048 days (median 400 days, interquartile range 12-1483), the occurrence of thromboembolic events was similar in AF patients with bioprosthesis compared to those with 'non valvular' AF (hazard ratio [HR] 1.10 95 % confidence interval [CI] 0.83-1.45, p=0.52, adjusted HR 0.93, 95 %CI 0.68-1.25, p=0.61). Factors independently associated with increased risk of stroke/TE events were older age (HR 1.25, 95 %CI 1.16-1.34 per 10-year increase, p< 0.0001) and higher CHA2DS2-VASc score (HR 1.35, 95 %CI 1.24-1.46, p< 0.0001) whilst female gender (HR 0.75, 95 %CI 0.62-0.90, p=0.002), use of vitamin K antagonist (HR 0.83, 95 %CI 0.71-0.98, p=0.03) were independently associated with a lower risk of stroke/TE. Neither the presence of bioprosthesis nor the location of bioprosthesis was independent predictor for TE events. In conclusion, AF patients with bioprosthesis had a non-significantly higher risk of stroke/TE events compared to patients with non-valvular AF. Second, the CHA2DS2-VASc score was independently associated with an increased risk of TE events, and was a valuable determinant of TE risk both in AF patients with non-valvular AF as well as those with bioprosthesis, whether treated or not treated with OAC.

Summary form only given. The inner surface modification of many industrial components, such as dies, bushings, pipes, etc, using plasma immersion ion implantation (PIII) has grabbed the attention of physicists and materials scientists. One drawback of the PIII modification of inner surface is low ion impact energy. It has been shown that by inserting a zero potential conductive auxiliary electrode positioned at the axis of the implanted cylindrical bore, the average ion impact energy can be raised. Plasma immersion ion implantation (PIII) of the inner surface of a finite-length small cylindrical bore with a coaxial, grounded auxiliary electrode are calculated using a two-dimensional fluid model. Various ratios of bore diameters against bore lengths are simulated. It is found that the sheath structure resulting from the auxiliary electrode focuses ions from both inside and outside the bore onto the inner surface. If the bore length is long enough, the ions from outside the bore cannot be implanted into the deeper region of the inner surface. Therefore, we can simulate the implantation of the deeper region by a one-dimensional fluid model.

The ability to locate and characterize icy deposits and other hydrogenous materials on the Moon and Mars will help us understand the distribution of water and, therefore, possible habitats at Mars, and may help us locate primitive prebiotic compounds at the Moon's poles. We have developed a rover-borne neutron probe that localizes a near-surface icy deposit and provides information about its burial depth and abundance. We have also developed a borehole neutron probe to determine the stratigraphy of hydrogenous subsurface layers while operating within a drill string segment. In our field tests, we have used a neutron source to "illuminate" surrounding materials and gauge the instruments' efficacy, and we can simulate accurately the observed instrument responses using a Monte Carlo nuclear transport code (MCNPX). An active neutron source would not be needed for lunar or martian near-surface exploration: cosmic-ray interactions provide sufficient neutron flux to depths of several meters and yield better depth and abundance sensitivity than an active source. However, for deep drilling (>or=10 m depth), a source is required. We also present initial tests of a borehole gamma ray lithodensity tool and demonstrate its utility in determining soil or rock densities and composition.

The high voltage and electromagnetic field environment poses a big challenge to a control system for plasma immersion ion implantation (PIII). The automation process must be immune to electric field interference produced by the high voltage power supply, modulator, radio-frequency or microwave plasma generator, MEVVA plasma sources, and so on. We have recently designed and installed a distributed control system, PIIIDCS, to automate the operation of our PIII facility. Programmable logic controllers are used as the field control stations because of their good anti-interference ability and good real time response. A DH-485 network is used as the communication link between the field controllers and the management station in order to improve the robustness and reliability of the system. The newly developed interface is designed to work in a graphic mode in Microsoft Windows 95. Test runs have shown that the system is reliable, flexible, and easy to operate. The development of this novel control system will expedite the development of commercial PIII instrumentation.

Lanthanum oxide (La(2)O(3)) films with good hemocompatibility and antibacterial properties have been fabricated using dual plasma deposition. X-ray photoelectron spectroscopy (XPS) shows that La exists in the +3 oxidation state. The band gap of the materials is determined to be 3.6 eV. Activated partial thromboplastin time (APTT) and blood platelet adhesion tests were used to evaluate the blood compatibility. The bacteria, Staphylococcus aureus, were used in plate counting tests to determine the surface antibacterial properties. The APTT is a little longer than those of blood plasma and stainless steel (SS). Furthermore, the numbers of adhered, aggregated, and morphologically changed platelets are reduced compared with those on low-temperature isotropic carbon and SS. The antibacterial plate-counting test indicates that La(2)O(3) has good antibacterial activity against S. aureus. These unique hemocompatibility and antibacterial properties make La(2)O(3) useful in many biomedical applications.

A multiple-grid-particle-in-cell numerical method has been developed. This method uses grids of different cell sizes and details are needed in only one part of the simulation region and not others. Hence, there are fewer nodes in the simulation thereby reduced computational time without sacrificing details. In the multiple-grid system, a phenomenon is identified to arise at the interface between two grids and a half-cell weighting method is utilized to solve the weighting issue at the boundary. It is shown that the expression of the change of momentum has no weighting function. This method is employed to numerically simulate the plasma immersion ion implantation process into a nickel titanium rod measuring 50mm long and 4.8mm in diameter used in orthopaedic surgery. To conduct more uniform implantation, the NiTi rod is elevated on the sample stage by a metal rod. The nitrogen implantation fluences and depth profiles are simulated and compared to experimental values determined by x-ray photoelectron spectroscopy.

MIKHAIL, MARYANN MD; SCEPPA, JENNIFER MD; SMITH, BARRY L. MD; CHU, PAUL MD; MARGHOOB, ASHFAQ A. Author Information