Two-dimensional (2D) layered materials including transition metal dichalcogenides (TMDCs) have recently been at the heart of the quantum materials and information sciences research due to unusual properties associated with their firmly defined dimensionalities. Many efforts have focused on developing new methods for the accelerated growth and discovery of 2D materials, including physical and chemical vapor deposition techniques. However, the synthesis of these multi-component crystals in the gas phase has been extremely challenging due to complex and uncontrolled gas-phase reactions and flow dynamics. Here, we demonstrate a novel laser-assisted synthesis technique (LAST), which significantly reduces the existing growth complexities and notably accelerates the growth of 2D materials. This approach facilitates the growth of various 2D materials directly from stoichiometric powders by laser vaporization process. We show that directed laser heating allows pressure-independent decoupling of the growth and evaporation kinetics enabling the use of stoichiometric powder as precursors for the growth of high-quality 2D materials including MoS 2 , MoSe 2 , WSe 2 , and WS 2 . A comprehensive experimental study was conducted to identify the system behavior, including the evaporation and growth parameters as well as the processproperty relationships. This method presents a general yet simple approach for accelerating the discovery of emerging quantum materials.

Direct growth and patterning of atomically thin two-dimensional (2D) materials on various substrates are essential steps towards enabling their potential for use in the next generation of electronic and optoelectronic devices. The conventional gas-phase growth techniques, however, are not compatible with direct patterning processes. Similarly, the condensed-phase methods, based on metal oxide deposition and chalcogenization processes, require lengthy processing times and high temperatures. Here, a novel self-limiting laser crystallization process for direct crystallization and patterning of 2D materials is demonstrated. It takes advantage of significant differences between the optical properties of the amorphous and crystalline phases. Pulsed laser deposition is used to deposit a thin layer of stoichiometric amorphous molybdenum disulfide (MoS 2 ) film (∼3 nm) onto the fused silica substrates. A tunable nanosecond infrared (IR) laser (1064 nm) is then employed to couple a precise amount of power and number of pulses into the amorphous materials for controlled crystallization and direct writing processes. The IR laser interaction with the amorphous layer results in fast heating, crystallization, and/or evaporation of the materials within a narrow processing window. However, reduction of the midgap and defect states in the as crystallized layers decreases the laser coupling efficiency leading to higher tolerance to process parameters. The deliberate design of such laser 2D material interactions allows the selflimiting crystallization phenomena to occur with increased quality and a much broader processing window. This unique laser processing approach allows high-quality crystallization, direct writing, patterning, and the integration of various 2D materials into future functional devices.

Recently, two-dimensional (2D) quantum materials and particularly transition metal dichalcogenides have emerged as an exciting class of atomically thin materials that possess extraordinary optoelectronic and photonic properties. The strong light interactions with these materials not only govern their fascinating behavior but can also be used as versatile synthesis and processing tools to precisely tailor their structures and properties. This review highlights the recent progress in laser-based approaches for synthesis and processing of 2D materials that are often challenging via conventional methods. In the synthesis section, the review covers the pulsed laser deposition as the main growth method due to its ability to form and deliver atoms, clusters, or nanoparticles for the growth of 2D materials and thin films with controlled stoichiometry, number of layers, crystallite size, and growth location. It is also shown that the tunable kinetic energy of the atoms in the laser plume is essential for healing defects and doping of 2D layers. In the processing section, the review highlights the application of lasers in crystallization, sintering, direct writing, thinning, doping, and conversion of 2D materials. The spatial and temporal tunability, controlled energy, and power densities of laser beams enable a broad spectrum of applications in the synthesis and processing of 2D quantum materials that are not accessible by other means.

No abstract

No abstract