Laser-Induced Crystallization and Oxidation Phase Diagrams for High-Throughput Evaluation of MoS2/MoOx Optical Thin Films

Abstract

The development of thin film materials for optoelectronic and meta-optic applications requires the discovery of novel materials and reliable control over their optical constants during the growth process. In this work, localized laser oxidation and crystallization are used to tailor the optical constants of an amorphous MoS₂ precursor thin film. By scanning focused laser light across multiple films with varying intensity and speed in a controlled oxygen environment, the transient heating associated with this technique is used to control the localized oxidation of each film. Characterization of the laser-processed regions results in synthesis phase diagrams indicating the laser conditions at which each oxide phase is formed. The optical constants of each phase are also measured, showing changes in refractive index Δn and extinction coefficient Δk as large as Δn = 0.43 and Δk = 0.35 for MoS₂, Δn = 1.7 and Δk = 1.6 for MoO₃, and Δn = 1.7 and Δk= 1.3 for MoO₂. These changes are attributed to oxygen dopants, strain, improved crystallinity for MoS₂, and oxygen vacancies and sulfur dopants for the oxide phases. These findings demonstrate the versatility of the laser processing approach for the highly controlled tailoring of thin film optical properties for high-throughput materials discovery.