Download or read book Plasma-enhanced Chemical Film Conversion (PECFC) written by Tianqi Liu and published by . This book was released on 2019 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thin films of crystalline materials are typically synthesized by thermally decomposing vapor precursors on a catalytic substrate. Plasmas enable the process temperature to be lowered by assisting in decomposition of the precursor molecule through gas-phase excitation as in the case of plasma-enhanced chemical vapor deposition (PECVD) and plasma-enhanced atomic layer deposition (PEALD). In this work, we develop another plasma-assisted approach to synthesizing thin films which we term plasma-enhanced chemical film conversion (PECFC). Molecular precursors are first prepared as a thin film on a substrate by solution methods, and subsequently converted by a combination of heating and plasma treatment. In comparison to other thin film growth techniques, our approach circumvents the adsorption step to promote nucleation and reduce substrate interactions, allowing direct growth on metal-free substrates which eliminates the need for transfer. Additionally, the approach is additive, reducing materials wastage and producing materials at the point-of-need including patterned structures. Two examples of thin film materials will be presented that demonstrate the capabilities of this synthesis approach: hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS2), both of which are layered materials and can be produced atomically thin. To synthesize h-BN, a single-molecular precursor, ammonia borane, is initially prepared as a thin film by spray deposition, spin coating, or ink jet printing, and subsequently converted in a cold-wall reactor with a planar, atmospheric-pressure dielectric barrier discharge. We show that h-BN synthesized by this process can be integrated in two-dimensional (2D)-based field effect transistor (FET) devices and improve the mobility by up to 4 times over silicon dioxide. To synthesize MoS2, a similar approach of converting its corresponding single-molecule precursor, ammonium tetrathiomolybdate with a plasma has been studied. In this case, a single-step conversion leads to a rough, nanostructured film. Adding a second thermal annealing step produces a very smooth (RMS