Discipline: Technology and Engineering
Subcategory: Electrical Engineering
Louis Paul Romero - Hartnell College
Co-Author(s): Houk Jang, Harvard School of Engineering and Applied Sciences, Cambridge, Massachusetts ; Donhee Ham, Harvard School of Engineering and Applied Sciences, Cambridge, Massachusetts
The physical and intrinsic properties of transition-metal dichalcogenides (TMDCs) have made them a subject of intensive investigation. Various atomically thin, two-dimensional (2D) TMDCs, exhibit properties that have flexible electronic and optoelectronic device applications.
The development of new devices with low contact resistance (Rc) has been inhibited due to the inability of controlling doping concentration in thin-film transistors (TFTs) with a 2D TMDC semiconducting layer. Doping a 2D TMDC by physical implantation and chemically has resulted in damage and defects, and instability due to unstable physisorption, respectively.
The addition of gate electrodes at the contact region of a TFT enables electrostatic doping and may permit controllable carrier density and show a decrease in Rc. Using monolayer metal-organic chemical vapor deposition molybdenum disulfide as a semiconducting layer we have fabricated TFTs and by the addition of two gate electrodes we have enabled electrostatic doping. The carrier density in each device is modulated by applying voltage at the gate electrodes. By the transmission-line method, Rc, sheet resistance, transfer length and contact resistivity is determined, to compare the difference in Rc between our non-dopable and dopable devices. Our research indicates electrostatically doping a TFT significantly decreases Rc. Our electrostatically dopable TFT, with negligible Rc, has potential to advance electronics and innovate current state of the art technologies, which can lead to a higher quality of life ultimately benefiting mankind.
Funder Acknowledgement(s): NSF EFMA-1542807 ; NSF EFRI 2-DARE: Quantum Optoelectronics, Magnetoelectronics and Plasmonics in 2-Dimensional Materials Heterostructures ; EFRI-2DARE, Research Experience and Mentoring Supplement
Faculty Advisor: Donhee Ham, PhD, donhee@seas.harvard.edu
Role: I contributed to my mentor's research by testing his non-dopable and electrostatically dopable transistors. This required testing our transistors using a probestation at various stages of development. Also, I processed most of that data generated; I achieved this by using Python. In addition, I assisted with fabricating a gate to remove channel resistance on all the dopable devices. That fabrication step required writing a pattern, developing it, deposition and lift-off. Once completed with that fabrication step, I tested those devices and also processed some of that data too.