From Ion Beams to Superconducting Magnets and LEDs

by Dr Vladimir Matias (iBeam Materials Inc.)

Monday 10 Jul 2023, 14:00 → 15:00 US/Pacific

Speaker: Dr. Vladimir Matias (iBeam Materials, Inc.)

Host: Ian Pong

Zoom: https://lbnl.zoom.us/j/98491968734

Title: From Ion Beams to Superconducting Magnets and LEDs

Abstract: 

We review ion-beam induced crystalline alignment of thin films and the
significance of this process for industrial applications. In the Ion-beam
assisted deposition (IBAD) process an ion-beam impinges during
deposition of a film and induces in-plane and out-of-plane crystalline
alignment. The early research in this area was led by James Harper at IBM
Research Labs in the early 1980’s and the group was the first to show
texturing of thin films in IBAD. The next big step in the field was at Fujikura
Ltd. Labs in Japan in the early 1990’s in the research group led by
Yasuhiro Iijima. The researchers at Fujikura showed texturing of yttria-
stabilized zirconia that was sufficiently good to be used as a template for
epitaxial growth of cuprate superconductors with high critical currents. The
third development, with even better alignment, came out Stanford
University in the mid-1990’s led by Robert Hammond and it is now known
as IBAD-MgO or ITaN (Ion Texturing at Nucleation). We discuss what is
known for the phenomenology of these processes, focusing primarily on
Stanford’s and our work on IBAD-MgO.

We examined details of crystalline-texture evolution during IBAD of MgO
thin films. To perform these experiments, we developed a unique
experimental methodology based on linear combinatorics. This technique
allows us to fabricate film-thickness wedges that maximize data collection
and allow us to obtain texture evolution plots easily and systematically.
MgO <100> texture evolution can be separated into three different regions.
During initial ion beam assisted deposition an amorphous layer is formed
which is crucial for obtaining out-of-plane grain alignment. Onset of texture
appears in the first 1-2 nm of film deposit when MgO crystallizes. We
separate out-of-plane fiber texture that appears first, followed by in-plane
grain alignment along the ion-beam assist direction. Texture improves with
continued ion beam bombardment during deposition. Still further
improvement is seen with growth of a homoepitaxial overlayer. We have
studied texture evolution under different ion beam incidence angles and for
combinations of different angles. The best texture attained thus far in the
MgO template layer on polished metal tape has a FWHM of about 1°. For a
different set of materials we have obtained <111> oriented IBAD films.
These can be used to grow <111> cubic epitaxial layers or hexagonal
lattice materials such as wurtzite GaN. We discuss the use of these
artificially crystal-aligned films as templates for epitaxial growth of
functional layers such as superconductors for power applications and
semiconductors such as GaN.

This work was supported in part by the US DOE Office of Electricity and
DOE Advanced Research Planning Agency-Energy.