In this work, NbO layers with highly improved electrical properties respect to pristine material have been produced by ultrafast-laser powder bed fusion process. The conditions required for producing uniform and compact layers of NbO from powder material have been studied and optimized. It has been established that ultrafast-laser irradiation, performed in air at room temperature, leads to the formation of dense NbO layers with the high temperature monoclinic crystal structure (H-NbO) but oxygen deficient. The layers show a preferential crystal orientation with the short axis of the monoclinic structure lying in the structure plane. This preferential orientation can be controlled by the laser irradiation conditions. Anisotropic resistivity has been observed as a consequence of the induced microstructure, while the overall material resistivity is decreased by more than eight orders of magnitude due to the oxygen deficiency. These results indicate that it is feasible to use ultrafast laser processing to promote high-temperature non-stoichiometric niobium oxide phases in a few seconds and with low energy consumption. The highly improved electrical properties of the laser irradiated NbO layers are extremely interesting for different electronic and sensing applications.

The authors are grateful to the Comunidad de Madrid for support via the Project PR65/19-22464 (Proyectos de I+D para jóvenes doctores) and MCIN/AEI/10.13039/501100011033 for the financial support through grant PID2020-112770RB-C21. This work has also been funded by Complutense University of Madrid and Banco Santander via the project UCM-Santander 2019 (PR87/19-22613). B. Sotillo acknowledges financial support from Comunidad de Madrid (Ayudas del Programa de Atracción de Talento 2017-T2/IND-5465). We acknowledge the Technical Services of CENIM-CSIC for the XPS measurements.

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