MXenes are a young family of two-dimensional transition metals carbides, nitrides, and carbonitrides with highly controllable structure, composition, and surface chemistry to adjust for target applications. Here, we demonstrate the modifications of two-dimensional MXenes by low-energy ion implantation, leading to the incorporation of Mn ions in Ti3C2Tx thin films.Damages and structural defects caused by the implantation process are characterized at different depths by XPS on Ti2p core-level spectra, ToF-SIMS and with electron energy loss spectroscopy analyses. Results show that the ion-induced alteration of the damage tolerant Ti3C2Tx layer is due to defects formation in both Ti and C sites, thereby promoting the functionalization of these sites with oxygen groups. This work contributes to the inspiring approach of tailoring 2D MXenes structure and properties through doping and defects formation by low-energy ion implantation to expand their practical applications.
For applications in energy harvesting, environmentally friendly cooling, and as power sources in remote or portable applications, it is desired to enhance the efficiency of thermoelectric materials. One strategy consists of reducing the thermal conductivity while increasing or retaining the thermoelectric power factor. An approach to achieve this is doping to enhance the Seebeck coefficient and electrical conductivity, while simultaneously introducing defects in the materials to increase phonon scattering. Here, we use Mg ion implantation to induce defects in epitaxial ScN (111) films. The films were implanted with Mg + ions with different concentration profiles along the thickness of the film, incorporating 0.35 to 2.2 at.% of Mg in ScN. Implantation at high temperature (600 ˚C), with few defects due to the temperature, does not substantially affect the thermal conductivity compared to a reference ScN. Samples implanted at room temperature, in contrast, exhibited a reduction of the thermal conductivity by a factor of three. The sample doped with 2.2 at.% Mg also showed an increased power factor after implantation. This study thus shows the effect of ion-induced defects on thermal conductivity of ScN films. High-temperature implantation allows the defects to be annealed out during implantation, while the defects are retained for room-temperature implanted samples, allowing for a drastic reduction in thermal conductivity.
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