| AVS 64th International Symposium & Exhibition | |
| 2D Materials Focus Topic | Tuesday Sessions |
| Session 2D+BI+MN+SS-TuA |
| Session: | Surface Chemistry, Functionalization, Bio and Sensor Applications |
| Presenter: | Adam Friedman, Naval Research Laboratory |
| Authors: | A.L. Friedman, Naval Research Laboratory A.T. Hanbicki, Naval Research Laboratory F.K. Perkins, Naval Research Laboratory G.G. Jernigan, Naval Research Laboratory J.C. Culbertson, Naval Research Laboratory P.M. Campbell, Naval Research Laboratory |
| Correspondent: | Click to Email |
Transition metal dichalcogenides (TMDs) show remarkable potential for use in chemical vapor sensor devices. They are inexpensive, inherently flexible, low-power, can be grown in large areas, and have shown high sensitivity and selectivity to electron donor analyte molecules. However, for most devices the conductance response is dominated by Schottky contacts, to the detriment of the sensitivity and obscuring the intrinsic sensing capability of the devices. We use contact engineering to transition the contacts in a MoS2 FET-based chemical vapor sensor to the 1T conducting phase, leaving the channel in the 2H semiconducting state, thus providing functional Ohmic contacts to the device. We show that the resultant sensors have greatly improved electrical characteristics, are more selective, and recover fully after chemical vapor exposure—all major improvements to previous MoS2 sensor devices. We study the dynamics of the sensing reactions identifying two possible models for the chemical sensing reaction with physisorption likely dominant. Additionally, we present both conductance and optical evidence that the phase transition can be induced in MoX2 films by a saturating dose of strong electron donor vapor. We find that the conductance response to strong electron donors in both monolayer MoS2 and MoSe2 FET devices ceases after moderate exposure, with final value of the conductance being on order of that expected for the 1T phase. We also examine chemically exposed TMD films intermittently interrogated with Raman and photoluminescence spectroscopy. We observe the appearance of weak characteristic 1T phase Raman features for MoS2 and we observed a quenching of the photoluminescence of both TMD films that is recoverable with annealing. The data cannot by explained solely by doping mechanisms. Our results suggest a mechanism for a new type of passive chemical vapor sensor.
[1] F.K. Perkins, A.L. Friedman, et al., Nano Lett. 13, 668-673 (2013).
[2] A.L. Friedman, F.K. Perkins, et al., Sol. St. Elec. 101, 2-7 (2014).
[3] A.L. Friedman, F.K. Perkins, et al., Nanoscale8, 11445 (2016).