ChBE Seminar Series: James E. Maslar
Tuesday, October 4, 2016
Room 2108, Chemical and Nuclear Engineering Building
James E. Maslar
Chemical Sciences Division, NIST
Optimizing 2D Transition Metal Dichalcogenide Chemical Vapor Deposition Processes
Two dimensional (2D), layered transition-metal dichalcogenides (TMDCs), e.g., molybdenum disulfide, are of increasing interest for next-generation nanoelectronic and optoelectronic devices. For many applications, high volume manufacturing of devices based on TMDCs will require deposition techniques that are capable of reproducibly producing large-area, 2D TMDC films with monolayer control. To date, such a capability has not been widely demonstrated with typical TMDC deposition processes. This limitation has motivated this work, the goal of which is to assist in the development of high volume manufacturing processes for TMDC film deposition. Two approaches are being investigated to obtain monolayer thickness control: 1) employing self-limiting atomic layer deposition (ALD) and chemical vapor deposition (CVD) chemistries and 2) employing optical mass flow meters developed at NIST to precisely control precursor flux to the growth surface. The initial focus of this work is on molybdenum disulfide deposition and a range of potential ALD and CVD precursors are being investigated, including bis(tertbutylimido)bis(dimethylamido) molybdenum, (h5-ethylcyclopentadienyl) dicarbonylnitrosyl molybdenum, cycloheptatriene molybdenum tricarbonyl, bis(ethylenebenzene) molybdenum, elemental sulfur, 1-propanethiol, dipropyl sulfide, and diethyl disulfide. Screening such a variety of deposition chemistries requires the examination of a large number of potentially spatially-inhomogeneous samples, making spatially-resolved metrologies that require little sample preparation of particular interest. Hence, metrologies such as Raman and photoluminescence spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy are widely employed. A focus of this presentation will be on aspects of these ex situ metrologies and the in situ precursor flux measurements that are particularly useful for optimizing 2D TMDC film deposition processes.
More about the Speaker:
James Maslar is a Research Chemist in the Material Measurement Laboratory of the National Institute of Standards and Technology (NIST). He joined NIST as a postdoctoral research associateship after obtaining his Ph.D. in analytical chemistry at the University of Illinois at Urbana-Champaign. His research interests include developing and employing in situ optical diagnostics for understanding and optimizing vapor deposition processes, particularly precursor delivery and ultra-thin film thickness control.