Mark G. Hollander

Formation of YBa2Cu3O7 superconducting films by ion implantation

We have fabricated superconducting thin films by ion implanting Y into a base material formed by the coevaporation of BaF2 and Cu. The implantations were carried out at 77 K and resulted in the formation of an amorphous Y‐Ba‐Cu‐F surface layer. Oxygen annealing with the addition of water vapor renders the base material insulating with a room‐temperature resistance of 105 Ω. An identical annealing treatment on the Y‐implanted material produces a superconductor with an onset temperature of 85 K.

In-situ capability of ion beam modification and characterization of materials at Los Alamos National Laboratory

Abstract The capability of in-situ ion beam modification and characterization of materials developed at Los Alamos National Laboratory is described. A beam-line from a 3 MV tandem accelerator and a beam-line from a 200 kV ion implanter are joined together in an in-situ target chamber. The chamber is equipped with a cold and hot sample stage with a temperature range from −100 to 500°C. The angular (sample spin and basal rotation) motions and translational motions of the sample stage are controlled by a multi-axis goniometer. This chamber provides a unique capability to conduct a temperature dependent experiment of ion irradiation and sequential backscattering and channeling analysis. The efficiency and reliability of in-situ ion beam techniques are demonstrated by two examples, irradiation damage in (100) MgAl 2 O 4 spinel crystals and ion-beam-induced densification of zirconia sol-gel thin films.

Formation of YBa/sub 2/Cu/sub 3/O/sub 7/ superconducting films by ion implantation

We have fabricated superconducting thin films by ion implanting Y into a base material formed by the coevaporation of BaF2 and Cu. The implantations were carried out at 77 K and resulted in the formation of an amorphous Y‐Ba‐Cu‐F surface layer. Oxygen annealing with the addition of water vapor renders the base material insulating with a room‐temperature resistance of 105 Ω. An identical annealing treatment on the Y‐implanted material produces a superconductor with an onset temperature of 85 K.

Optical absorption and thermoluminescence of MgAl2O4 spinel crystals implanted with Xe++ ions

Abstract We have studied changes in optical absorption of MgAl 2 O 4 spinel crystals implanted with 340 keV Xe ++ ions at about 120 K, to fluences ranging from 10 15 –10 21 ions/m 2 . With increasing ion fluence, we observe an increase in optical absorption, especially in the vicinity of two absorption bands: one centered at 5.3 eV, the other at 6.9 eV. The absorption band at 5.3 eV, caused by F-centers, saturates at a fluence between 1·10 18 and 1·10 19 ions/m 2 . This is the same dose range in which formation of a metastable phase of spinel has been reported previously. The band at 6.9 eV grows with increasing dose and saturates at 1·10 20 –3·10 20 ions/m 2 . Previous studies have shown that spinel is amorphized by Xe ion irradiation in this dose range. Annealing studies were also conducted on the Xe ion implanted spinel crystals. By optical absorption, F-centers were found to anneal at 500°C. Thermoluminescence measurements revealed a temperature dependence of luminescence that correlates well with the optical absorption.

In situ MeV ion beam analysis of ceramic surfaces modified by 100-400 keV ion irradiation

Abstract This paper describes the use of an in situ ion beam analysis facility developed at Los Alamos National Laboratory for the study of irradiation effects in ceramic materials. In this facility, an analytical beamline of 3 MV tandem accelerator and an irradiation beamline of 200 kV ion implanter are connected at 60° to a common target chamber. This facility provides a fast, efficient, and quantitative measurement tool to monitor changes of composition and crystallinity of materials irradiated by 100–400 keV ions through sequential measurement of backscattering events of MeV ions combined with ion channeling techniques. We will describe the details of the in situ ion beam analysis and ion irradiation and discuss some of the important issues and their solutions associated with the in situ experiment. These issues include (1) the selection of an axial ion channeling direction for the measurement of radiation damage; (2) sample surface charging and charge collection for data acquisition; (3) surface sputtering during ion irradiation; (4) the effects of MeV analytical beam on the materials; and (5) the sample heating effect on ion beam analysis.

Setup for in situ x-ray diffraction and ion-channeling studies of ion-implantation effects in thin films

A novel setup is introduced that combines energy-dispersive x-ray diffraction and ion-channeling capabilities for damage studies on single-crystalline thin films irradiated with 100–720 keV heavy ions. Channeling measurements using 2 MeV He ions provide depth-resolved information on the damage buildup. The x-ray diffraction tool is used to measure damage-related lattice strain, and can provide information on bombardment-induced disorder complementary to the channeling technique. Data obtained during the implantation of 360 keV Ar2+ ions into a zirconia thin film illustrate the potential of the instrument.

Tracing copper bell trade patterns in the greater Southwest using the Los Alamos nuclear microprobe

Abstract The Los Alamos nuclear microprobe has been used for trace-element analysis of cast copper crotals (bells) by proton induced X-ray emmission (PIXE). Small spot sizes were used because the copper bells have mineral inclusions and intercrystalline grain boundaries on the order of 40 μm. Information on the trace element metallurgy of copper bell castings is important for the establishment of early trade patterns. Results show that the PIXE technique has potential for tracking copper bell trade patterns using trace-elements at the 5 μg g level.