Pulsed Laser Annealing for synthesis and tuning of TMD nanomaterials

Sputtering has attracted significant attention among physical vapor deposition (PVD) techniques for the synthesis of layered transition metal dichalcogenide (TMD) films. Its simplicity, combined with high reliability, uniform large-area coverage, and excellent repeatability, makes it a promising approach for next-generation nanoelectronics, optoelectronics, catalysis, photovoltaics, and energy applications. However, achieving high crystalline quality while maintaining uniformity and tunable properties often requires post-deposition thermal treatments. These treatments are generally incompatible with silicon CMOS integration due to the strict back-end-of-line (BEOL) thermal budget limit of 770 K. Previous studies have shown that stoichiometric MoS₂ thin films sputtered at room temperature can be crystallized via nanosecond ultraviolet (248 nm) pulsed laser annealing (PLA) on Si/SiO₂ substrates. This ultra-rapid thermal processing, using 22 ns laser pulses, enables localized and controlled heating confined to the film surface without significantly affecting the substrate. In this work, a systematic study of sputtered MoS₂ films is presented, focusing on the crystalline structure resulting from the two-step synthesis process and on how the number of crystalline layers influences material properties. Films with thicknesses between 2 and 16 nm were successfully crystallized without post-sulfurization, using tailored laser energy densities and pulse counts on different substrates, including Si, SiO₂-on-Si, and glass. The resulting films exhibited a nanocrystalline structure with preferential (002) orientation. Comprehensive characterization was performed by Raman spectroscopy, X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), atomic force microscopy (AFM), and field-effect transistor (FET) measurements, supported by heat flow simulations of the laser annealing process. An AFM-based analysis method was developed to quantify grain size and grain boundaries through a rapid and reliable segmentation procedure. The results show that reducing the initial amorphous MoS₂ thickness down to 2 nm provides insight into the crystallization mechanism and its dependence on film thickness, which is critical for achieving few-layer and monolayer devices. Finally, PLA was also applied to ALD-grown MoS₂ and CVD-grown MoSe₂, demonstrating that this approach can be extended to tune the properties of already crystalline materials. Overall, the results confirm the viability of sputtering deposition combined with PLA for fabricating high-quality few-layer MoS₂ films, showing notable improvements in crystalline quality and grain size. Moreover, this method offers promising opportunities for selective crystallization and doping, paving the way for scalable integration of large-area 2D materials with Si-based technologies.