EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Two-dimensional material-based field effect transistors have received significant attention due to the materials’ interesting properties. However, graphene based electronic devices are limited by the zero bandgap of single layer graphene. Alternatively, molybdenum disulfide (MoS2), has been considered a promising candidate for electronic device applications, owing to the thickness dependent tunable bandgap, where the bandgap changes from direct (~1.8 eV) to indirect (~0.9 eV), from mono-layer to multi-layer, respectively. Laser direct writing techniques, such as Laser Induced Forward Transfer (LIFT), could offer an alternative to the more conventional photolithographic processes, for the possibility of mass production and working at room temperature to form functional electronic devices. LIFT has been widely investigated, as it is a time efficient and environmentally friendly technique, and has been applied to print a wide range of materials.
In this study, the reliability of a commercially available MoS2 ink (solid content: 3.0-3.85%, viscosity: 4-11 mPa.s) deposited via LIFT printing is reported. LIFT process parameters have been examined (i.e. laser fluence) to define the optimum process for reproducible transfer of MoS2 on silicon dioxide receiver substrates. Measured diameters of the printed droplets range from 50 to 100 μm. Next, a side-view imaging setup was coupled to the LIFT setup for the complete visualization of the ejection process with one laser pulse on the donor. The experimental data from the captured videos were analyzed to determine the transferred droplet velocity and morphological aspects like the volume of the printed droplets. Measured volume values range from 2.55 pL to 18.06 pL. In addition, the printed MoS2 was examined using RAMAN spectroscopy. Preliminary results showed the two characteristic Raman peaks (E12g and A1g) of MoS2. Finally, the resulting information, is used for the uniform and reproducible formation of droplets on top of source/drain electrodes of FET substrates.