Structural and Property Engineering of 2D Titanium Carbides (mxene) Thin Films Using Ion Irradiation

MXenes are a large family of two-dimensional transition metal carbides and/or nitrides combining hydrophilicity with metallic conductivity, thereby leading to a plethora of potential applications. This study expands the current possibilities for the structural engineering of MXenes by demonstrating medium energy range ion irradiation as a controllable and flexible strategy to deeply modify Ti3C2Tz thin films. By adjusting the fluence of a 180 kV He+ ion beam, we evidence the gradual modification of the different structural elements of typical MXene multilayers, inducing well-defined impacts on properties. Low fluences allow modifying the interlayer spacing, inhibiting the long-term rehydration capacity of the thin films with expected major benefits on MXene aging issues. In addition to this, irradiation allows affecting the layers functionalization with major impact on the normalized optical transmission profile, suppressing the absorption valley at IR-visible limit and expanding their transparency in the UV. These effects, combined with improved electrical contact between the Ti3C2Tz layers, are highly desirable for transparent conductive electrodes applications. Finally, higher fluence irradiations induce preferential sputtering of titanium atoms. Transition metal vacancies being known to be highly relevant to deeply modify properties beyond those investigated here, these results show the large benefits of ion irradiation for MXene design.