Optoelectronics from 2D Semiconductors

Two-dimensional (2-D) materials research done in the Escarra lab is a multidisciplinary effort to create large scale technologies from atomically flat materials.  Since the discovery of graphene in 2004, 2-D materials have experienced a boom in research and development that has led to the discovery of a many new 2-D materials and characteristics1,2.  These two-dimensional materials are stable, flexible, strong, and possess a wealth of qualities that could enable electronics to be made smaller and better than previously thought possible.  For example, graphene can conduct electrons with great efficiency and has unparalleled strength.  Molybdenum disulfide is a 2-dimensionsal direct-gap semiconductor that can be used to fabricate detectors, light emitters, and solar cells3.  These materials have already shown great promise, and many more remain to be discovered; the race is on to synthesize these materials with high quality and large quantity.

The Escarra lab particularly focuses on the synthesis of 2-dimensional semiconductors and their development into optoelectronic technologies.  We synthesize MoS2 and other 2D materials using thermal vapor sulfurization (TVS), which is a type of chemical vapor deposition (CVD) well-suited for large-area (cm-scale) growth with good thickness control in the few-layer range.  Grown monolayer MoS2 and WS2 possess direct bandgaps in the visible light spectrum, making them leading candidates for 2D optoelectronic devices.  In addition to these materials, the Escarra lab also develops new materials with desirable physical, electronic, and optical qualities.  For example, the ternary chalcogenide family of materials are 2-D layered structures that provide a range of tunable bandgaps.  Several techniques, including CVD and TVS, are being explored as synthesis mechanisms for ternary materials and various other semiconductor materials.  Finally, as these materials are made, they are tested for quality using a suite of experimental techniques and ultimately developed into devices such as light emitters, detectors, and photovoltaics.

Elements of materials science, electrical engineering, chemistry and physics are combined to improve our understanding of these materials.  The wealth of new information yet to be discovered makes 2-D materials an exciting frontier of science.

(1) Novoselov, K. S.; Geim, A. K.; Morozov, S. V.; Jiang, D.; Zhang, Y.; Dubonos, S. V.; Grigorieva, I. V.; Firsov, A. A. Electric Field Effect in Atomically Thin Carbon Films. Science (80-. ). 2004, 306 (5696), 666–669.

(2) Mak, K. F.; Lee, C.; Hone, J.; Shan, J.; Heinz, T. F. Atomically Thin MoS2: A New Direct-Gap Semiconductor. Phys. Rev. Lett. 2010, 105 (13), 2–5.

(3) Bernardi, M.; Palummo, M.; Grossman, J. C. Extraordinary Sunlight Absorption and One Nanometer Thick Photovoltaics Using Two-Dimensional Monolayer Materials. Nano Lett. 2013, 13 (8), 3664–3670.

The wealth of new information about these 2-D materials yet to be discovered makes this research area an exciting scientific frontier to explore.”