# Nickel-Assisted Laser Oxidation of WSe2 Layered Films for Spatially Controlled WO3 Patterning Process toward Resistive Memory and Molecular Sensing

## TL;DR

A new laser process using nickel helps convert WSe2 into WO3 patterns for memory devices and sensing applications.

## Contribution

A novel Ni-assisted laser oxidation method enables spatially controlled WO3 patterning from WSe2 films.

## Key findings

- RRAM devices using Ni-assisted laser-oxidized WO3 show clear resistive switching behavior.
- The WO3 structure exhibits strong SERS signals for crystal violet and methylene blue at low concentrations.

## Abstract

A novel approach to convert a 2D WSe2 film
into a WO
x
film by the laser-induced oxidation
process
using a nickel (Ni) adsorption layer, namely Ni-assisted laser oxidation
process, was demonstrated. A layer of Ni metal was deposited to absorb
the heat of the laser and oxidize the top WSe2 layer, for
which an aluminum oxide (Al2O3) layer is then
deposited as a barrier layer. A continuous wave laser with a wavelength
of 808 nm is selected as the laser source, as it is not absorbed by
the WSe2 layer. By introducing a patterned Ni layer, the
selective oxidation process on WSe2 into WO3 can be achieved owing to the photothermal effects caused by the
Ni layer with O2 gas. The successful oxidation parameters,
including laser powers and irradiation durations with a fixed Al2O3 barrier layer thickness of 50 nm, were investigated.
Resistive random-access memory (RRAM) devices fabricated using the
Ni-assisted laser-oxidized WO3 structure exhibit clear
resistive switching behavior compared to the structure without the
laser oxidation process. In addition, the Ni-assisted laser-oxidized
WO3 structure showed obvious surface enhanced Raman spectroscopy
(SERS) signals of crystal violet (CV) and methylene blue (MB) with
the lowest concentration of 10–6 M.