Gary A. Glass

Structure and magnetic properties of pure and Gd-doped HfO2 thin films

Pure HfO2 and Gd-doped HfO2 thin films have been grown on different single crystal substrates (silicon, R-Al2O3, and LaAlO3) by pulsed laser deposition. X-ray diffraction (XRD) patterns show that the pure HfO2 thin films are of single monoclinic phase. Gd-doped HfO2 films have the same XRD pattern except that their diffraction peaks have a shift toward lower angles, which indicates that Gd dissolves in HfO2. Transmission electron microscopy images show a columnar growth of the films. Very weak ferromagnetism is observed in pure and Gd-doped HfO2 films on different substrates at 300 and 5K, which is attributed to either impure target materials or signals from the substrates. The magnetic properties do not change significantly with postdeposition annealing of the HfO2 films. In addition to the films, HfO2 powders were annealed in pure hydrogen flow, and a ferromagnetic signal was not observed.

An overview of the facilities, activities, and developments at the University of North Texas Ion Beam Modification and Analysis Laboratory (IBMAL)

The Ion Beam Modification and Analysis Laboratory (IBMAL) at the University of North Texas includes several accelerator facilities with capabilities of producing a variety of ion beams from tens of keV to several MeV in energy. The four accelerators are used for research, graduate and undergraduate education, and industrial applications. The NEC 3MV Pelletron tandem accelerator has three ion sources for negative ions: He Alphatross and two different SNICS-type sputter ion sources. Presently, the tandem accelerator has four high-energy beam transport lines and one low-energy beam transport line directly taken from the negative ion sources for different research experiments. For the low-energy beam line, the ion energy can be varied from ∼20 to 80 keV for ion implantation/modification of materials. The four post-acceleration beam lines include a heavy-ion nuclear microprobe; multi-purpose PIXE, RBS, ERD, NRA, and broad-beam single-event upset; high-energy ion implantation line; and trace-element accelerator...

Report on the Acadiana Research Laboratory nuclear microprobe system

The Acadiana Research Laboratory of the University of Louisiana at Lafayette provides high energy ion beams for materials research. Major components of the ion beam systems include a National Electrostatics Corporation (NEC) 1.7 MV tandem Pelletron accelerator system with both SNICS and RF ion sources and a Varian CF-4 200 kV implanter. The NEC Pelletron has three operational beamlines that provide a wide range of capabilities for materials modification and analysis, including such techniques as PIXE, PIGE, RBS, RFS, TOF-ERDA and ion implantation. An Oxford Microbeams Ltd. microprobe system was recently declared operational with the attainment of a 1.5 μm×2.0 μm beam spot size. Microprobe techniques presently available include μPIXE, μRBS and scanning transmission ion microscopy (STIM).

Electrochemical passivity of titanium implanted with 1 MeV gold ions

Abstract Titanium samples implanted with 1 MeV gold ions at doses of 8.8 × 1014ions/cm2 to 1.5 × 1016ions/cm2 were allowed to corrode freely in 20 wt% sulfuric acid solution at 40 °C while continuously measuring the open circuit potential (OCP). Inductively Coupled Plasma (ICP), was used to calculate the corrosion rates from the corrosive solutions. The time required for the OCP to drop to a value characteristic of pure titanium in this solution ( − 718 mVSCE), was related to the implant dose. Implantation of gold produced a passivating effect but the observed trend towards passivity persisted beyond the depth of implanted gold. Rutherford Backscattering (RBS) and Nuclear Resonance Scattering (NRS) spectra revealed the presence of oxygen atoms recoil-implanted slightly deeper than the gold. Scanning Tunneling Microscopy (STM) was used to study the differences in surface roughness before and after ion implantation.

Magnetic quadrupole doublet focusing system for high energy ions

A high energy focused ion beam microprobe using a doublet arrangement of short magnetic quadrupole lenses was used to focus 1-3 MeV protons to spot sizes of 1x1 microm2 and 1-4.5 MeV carbon and silicon ion beams to spot sizes of 1.5x1.5 microm2. The results presented clearly demonstrate that this simple doublet configuration can provide high energy microbeams for microanalysis and microfabrication applications.

Maskless micromachining with high-energy focused ion beams

High Energy Focused Ion Beam (HEFIB) direct writing is proving to be an attractive and powerful maskless lithography technique for production of high aspect ratio 3-D microstructures in polymer resists and semiconductors. HEFIB with Proton beam (P-beam writing) offers several unique advantages for microfabrication applications: (a) the focused beam is scanned directly across the sample (no mask), (b) the range of the beam in the sample is well defined with minimal lateral straggling than any other techniques, (c) use of different energies allows different exposure depths, (d) complex shapes are possible and (e) patterns can be made within short exposure time. These characteristics allow P-beam writing to be applied in several areas of microfabrication including (a) rapid (and cheaper) prototyping of 3-D microstructures, (b) custom built structures for basic research, (c) mask production and (d) stamp and mold manufacturing. Recently we have implemented high energy P-beam direct writing with a nuclear microprobe at the Louisiana Accelerator Center (LAC). We are presenting some of the modular structures illustrating the capabilities of this maskless micromachining technique and possible application into Micro-Electro-Mechanical Systems (MEMS) devices.

Direct etching of SiO2 and Al2O3 by 900-keV gold ions

We report the direct etching of Al 2 O 3 and SiO 2 using 900-keV Au + ions. 2000-mesh Cu grids were employed as masks using two different configurations: (1) the Cu mesh was placed on top of each insulator separately and independent irradiations were performed, and (2) the Al 2 O 3 and SiO 2 substrates were positioned in an edge-to-edge configuration with a single Cu grid providing a common mask to both insulators. Scanning electron microscopy (SEM) analysis revealed quite different patterns resulting from the two irradiation configurations. While the irradiation using individual masks resulted in mirror-image patterns of the Cu mask in the substrates, the use of a common mask led to single line structures approximately normal to the edges of the substrates. The role of charge buildup and sputtering in relation to relative dielectric properties of the substrates and close proximity of the samples during irradiation is discussed.

Results from the nuclear microprobe PIXE analysis of selected rare earth fluor compounds

Most previous research measures fluorescence properties over the macroscopic regime. Properties of individual microscopic grains could be significantly different than those measured over the macroscopic scale. Until recently, it was difficult to measure properties of individual fluor grains. Existing characterization techniques like scanning electron microscopy are not practical, since the resulting fluorescence masks the electron surface profile. Starting in September 2000, a research program was initiated at the Acadiana Research Laboratory to determine microscopic fluorescence properties for selected inorganic rare earth compounds. The initial phase of this program utilized microscopic proton induced X-ray emission (μPIXE) to characterize the elemental composition of individual fluor grains. Results show that both individual grains and small clusters of grains could be seen using μPIXE. Maps of this type can be used to estimate grain dimensions for the selected rare earth fluor. This technique is a new and innovative method to characterize a fluor material.

Mercury sensitivity measurements in Southern Magnolia wood using nuclear microprobe PIXE

Abstract Thick-target PIXE has been extensively used to determine trace element concentrations in tree rings. However, the concentrations of mercury and other heavy metal elements are commonly less than one part-per-million (ppm), which are below the typical sensitivity limits for traditional PIXE. In this research, a Southern Magnolia (magnolia grandiflora) tree sample with a known concentration of mercury was PIXE analyzed using a 2 MeV proton microbeam with a 100×100 μm 2 scan area. A second analysis was completed using a stationary macrobeam of 3 MeV protons with a cross-sectional area of 1×1 mm 2 . The minimum detection limit for mercury in Southern Magnolia wood was found to be approximately 1 ppm, which was based on X-ray yield, sample geometry, and detector efficiency.

Surface oxygen implanted in titanium by recoil collisions with 1 MeV gold ions

Abstract Oxygen is known to be an important factor in reducing the corrosion rate of titanium, yet small amounts of oxygen on the titanium surface are practically undetectable by standard Rutherford Backscattering Spectrometry (RBS) analysis. The 3.05 MeV nuclear scattering resonance for 4 He + on oxygen was used in this study to show that surface oxygen is recoil-implanted by collisions with 1 MeV gold ions and produces a noticeable effect on corrosion test results.