Suppression of carbon contamination in tungsten oxide by oxygen-plasma-assisted electron beam-induced deposition

Electron beam-induced deposition (EBID) is a direct-writing technique that utilizes a focused electron beam and a precursor gas to fabricate materials with arbitrary shapes. One of the challenges of EBID is the incorporation of residual carbon, primarily originating from organometallic precursors, which hampers the formation of high-purity deposits. In this study, we present a plasma-assisted EBID method in which externally generated oxygen plasma is introduced into the deposition chamber during growth to mitigate carbon contamination. Using tungsten oxide as a model system, thin films were deposited from tungsten hexacarbonyl in different plasma environments. The tungsten oxide fabricated under oxygen plasma showed a significant reduction in carbon content, as confirmed by scanning transmission electron microscopy and electron energy loss spectroscopy. Furthermore, the tungsten oxide deposited under the oxygen plasma condition was found to have an oxygen-rich composition, and an increase in conductivity was also observed. These findings highlight the critical role of the oxygen plasma in enhancing the chemical and electrical properties of oxide films fabricated by EBID.