Showing papers by "Bruce E. Gnade published in 1989"

The University of North Texas Ion Beam Modification and Analysis Laboratory

Abstract: The University of North Texas Ion Beam Modification and Analysis Laboratory consists of three accelerators. These are: a 200 kV, 10 MA Cockcroft-Walton, a 2.5 MV single-ended Van de Graaff machine and a newly installed National Electrostatics Corporation Model 9-SDH-2, 3 MV tandem. The tandem accelerator was received in November of 1987 and acceptance tests were completed in December of 1987. The tandem — and the 2.5 MV Van de Graaff — are now both installed in a new 7000 ft 2 laboratory in the physics building. The tandem which will be used for many of the activities in the laboratory was purchased with a rf charge exchange (Alphatross) source and a SNICS-type cesium ion sputter source. Each of these sources injects through a 30° magnet into a 90° analysis magnet and then into the tandem accelerator. This configuration gives the high mass resolution which is needed for the AMS system. A table will be shown that overviews the analyzed beams that have been obtained to date with the tandem accelerator. A summary of the beam lines that are being constructed for all the activities of the laboratory will also be given. These include: accelerator mass spectrometry (AMS), nuclear reaction analysis (NRA), Rutherford backscattering and channeling (RBS&C), particle-induced X-ray emission (PIXE), high-energy ion implantation (HEII) and atomic collision physics.

Study of the low‐pressure chemical‐vapor‐deposited tungsten‐silicon interface: Interfacial fluorine

Abstract: Single‐crystal silicon 〈100〉 substrates uniformly doped at ≳12 Ω cm with boron were deposited with ∼800 A of low‐pressure chemically vapor deposited W in a hot‐quartz‐walled (Anicon) system at a deposition temperature of 300 °C. The samples studied include an as‐deposited sample and two others which were post‐deposition annealed at 600 °C in Ar for 15 min each. X‐ray photoelectron spectroscopy (XPS) coupled with an Ar+ ion sputter profiling technique was employed to investigate these structures as a function of depth. Particular emphasis was placed on the depth distribution, content, and chemical state of the fluorine present. Rutherford backscattering spectrometry and x‐ray diffraction were used to corroborate the XPS data. Results show that, for the as‐deposited and 600 °C annealed sample, the maximum concentration of fluorine (0.6–0.8 at. %) is observed, not at the W/Si interface, but rather at the W (H2 reduction)/W (Si displacement) interface. For the sample annealed at 850 °C, WSi2 is formed in the ...