Strain-induced polymorph conversation in gallium oxide via focused ion beam irradiation

Monoclinic 𝛽-Ga2O3 is chemically and thermally the most stable compound
compared to its other polymorphs. It is a promising semiconductor
material for power electronics, optoelectronics, and batteries.
However, controlling the metastable polymorph phases is challenging,
and the fabrication technology at the nanoscale is immature. Our goal
is to understand and control the polymorph conversion, so we can establish
new fabrication methods of single-phase polymorph coatings,
buried layers, multilayers, and different nanostructures in gallium oxide.

Under ion beam irradiation, most semiconductors show transformation
from crystalline to amorphous structure due to ion beam induced
damage. However, it is observed that, this transformation is
suppressed in gallium oxide, and a polymorph conversion is observed
instead. Here, we use Gallium and Neon focused ion beams (FIB) from
different sources (GFIS, LMIS) to create local strain and induce the
polymorph transition. After irradiation, characterization of the exposed
areas was conducted by electron backscatter diffraction (EBSD)
and atomic force microscopy (AFM). First results indicate that the
strain created by the FIB irradiation leads to a local transformation
of beta gallium oxide to another polymorph.