Substrate-Controlled Photothermal Properties of Femtosecond Laser-Fabricated Zirconium Nitride Periodic Structures

Zirconium nitride (ZrN), a typical refractory transition metal nitride, is characterized by excellent plasmonic properties, high-temperature stability and mechanical properties. It has been demonstrated to have tremendous application potential in fields such as photothermal conversion and solar energy utilization. However, limitations including poor structural consistency and low processing efficiency are encountered in its application. Moreover, the synergistic regulation mechanism of micro-nano structures and substrate materials toward photothermal performance remains unclear. A method for preparing high-performance ZrN photothermal thin films through femtosecond laser substrate regulation is proposed in this paper, and the fabrication of ZrN thin films with laser-induced periodic surface structures (LIPSS) is achieved with high efficiency and high uniformity. The regulation laws of the aspect ratio of LIPSS and the parallel and perpendicular polarizations of light sources on photothermal conversion capability are systematically investigated using the finite-difference time-domain (FDTD) method, and it is revealed that a high aspect ratio can significantly enhance the photothermal capability under all polarization conditions. Comparative photothermal experiments are carried out on ZrN thin films on silicon (Si) and titanium (Ti) substrates with LIPSS, and the enhancement effect of a high aspect ratio on photothermal capability was verified. Excellent linear relationships between temperature rise magnitude and light intensity are observed for ZrN thin films on Si and Ti substrates with LIPSS, with correlation coefficients of 0.996 and 0.984, respectively. Meanwhile, outstanding photothermal stability is demonstrated for both samples during multiple thermal cycles within 600 s, and ZrN thin films on Si substrates with LIPSS can be rapidly heated to 50 ℃ within 60 s under 2.5 Sun irradiation. Furthermore, the analysis of heat transfer mechanisms in different substrates verifies that materials with high thermal conductivity can better exert the photothermal capability of ZrN thin films. The photothermal conversion mechanism of periodic ZrN structures and the regulation law of substrate thermal conductivity on temperature field distribution are revealed in this work. The intrinsic mechanism of improving ZrN photothermal performances through femtosecond laser substrate regulation is clarified, and a theoretical basis is provided for the structural design and material selection of ZrN photothermal devices.