We are professionals in the production of two-dimensional (2D) materials and will go to great lengths to ensure that our customers receive exceptional service. For our customers, Alfa Chemistry offers optical modification services to change the properties of 2D materials. Lasers are an effective tool we use for post-manufacturing modifications of 2D materials. We specialize in defect control, doping, surface passivation and modification, phase change, and strain modulation. Controlling the laser parameters makes these optical alteration techniques highly tunable. Below is a list of our specialized alteration capabilities. Please get in touch with us for the finest help!
Defect Introduction
Alfa Chemistry modifies the surface structure of 2D materials by introducing optical flaws using light energy. Sulfur vacancies in TMDs, hBN color centers, spin defects, and graphene point defects are examples of optically introduced 2D material defects. To increase device performance, offer novel device functionality, and contribute to the deterministic growth process, we use laser power, wavelength, irradiation time, and substrate selection to modify the concentration of point defects and vacancies.
Optical Doping
We employ optical doping to affect the properties of 2D materials, such as electrical and optical conductivity, and photoluminescence (PL). Because it introduces doping through surface alteration rather than subsurface effects induced during ion implantation, this approach is particularly advantageous for 2D materials. Optical doping also works by introducing optical defects and subsequently filling them with dopants from the precursor material or modulated doping induced by incandescent light. We can control the optical doping by laser power, irradiation time, and substrate type.
Fig 1. a) A schematic of the optical doping process for phosphorene-doped MoS2. b) PL map of a laser-doped MoS2 flake. (Kim E, et al. 2016)
Optical Reduction and Oxidation
Alfa Chemistry locally alters the electrical conductivity and chemical reactivity of 2D materials under environmental conditions through optical reduction and oxidation. Two-photon oxidation, thermally induced strain and oxygen binding, light-humidity interactions, and laser-driven sulfur element transfer have all been used to demonstrate optical oxidation of 2D materials. We can control these processes by laser wavelength, power, irradiation time, scanning speed, and environment. We can also use a mix of optical reduction and ablation, reduction and doping, holography, and laser interference patterning to create more complicated structures with added functionality.
Crystalline Phase Engineering
2D materials can exist in different crystalline phases with different properties, such as semiconductor 2H and metal 1T TMDs. We employ optical controlled phase engineering to develop 2D materials for optoelectronic applications. Photocontrolled phase engineering typically achieves local phase transitions by introducing a large number of defects and subsequently reconfirming the crystal structure. Although the process is usually irreversible, we can nevertheless have some influence over it by varying the laser wavelength, power, and irradiation period. Optical crystal phase change can also be used in conjunction with laser-induced thinning and LCVD.
Fig 2. Optical image of a thin MoTe2 flake with two areas of different reflection contrast. (Tan Y, et al. 2018)
Strain and Topographical Modification
Photostrain and its morphological modifications are our versatile methods for modifying 2D materials for use in quantum devices and sensing, and Alfa Chemistry can modify material properties by locally introducing photostrain into 2D materials. Photostrain can be used to design structures during and after material fabrication. In addition, photostrain can be used as an LDW method for shaping 3D patterns. The photostrain depends strongly on the pre-existing strain conditions of the material, but also on the substrate, laser power, wavelength, and irradiation time.
References
- Kim E, et al. (2016). "Site Selective Doping of Ultrathin Metal Dichalcogenides by Laser-Assisted Reaction." Adv. Mater. 28: 341-346.
- Tan Y, et al. (2018). "Controllable 2H-to-1T' Phase Transition in Few-Layer MoTe2." Nanoscale. 10: 19964-19971.
Please kindly note that our products are for research use only.
