| AVS 62nd International Symposium & Exhibition | |
| 2D Materials Focus Topic | Monday Sessions |
| Session 2D+EM+MC+MS+NS-MoA |
| Session: | 2D Materials: Devices and Applications |
| Presenter: | Joshua Wood, Northwestern University |
| Authors: | J.D. Wood, Northwestern University S. Wells, Northwestern University D. Jariwala, Northwestern University K.-S. Chen, Northwestern University X. Liu, Northwestern University V. Sangwan, Northwestern University E. Cho, Northwestern University L. Lauhon, Northwestern University T.J. Marks, Northwestern University M.C. Hersam, Northwestern University |
| Correspondent: | Click to Email |
Exfoliated black phosphorus (BP) is an elemental, two-dimensional (2D) nanomaterial with high carrier mobility (~100 cm2V-1s-1), a layer-dependent band gap (~0.3 to 2.0 eV), and in-plane anisotropy. Further, 2D BP is air sensitive, culminating in undesirable surface reactions that degrade device performance. We find that unencapsulated, exfoliated BP flakes form oxidized derivatives following ambient exposure, as ascertained by X-ray photoelectron spectroscopy, atomic force microscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, and electrostatic force microscopy measurements. BP ambient oxidation is driven by oxygen-saturated H2O, as we observe two-fold faster degradation for BP on hydrophobic substrates versus hydrophilic ones. After 48 hours of ambient oxidation, unencapsulated BP field-effect transistors (FETs) decline in mobility and current on/off ratio by factors of over 1000. In contrast, alumina (i.e., AlOx) passivated BP flakes and FETs are robust and unoxidized for over seven months in ambient conditions. Alumina-passivated BP FETs possess mobilities of ~100 cm2V-1s-1, on/off ratios of 1000, and ambipolar transport, even following extensive ambient exposure [1]. This understanding of BP ambient oxidation—and how to prevent it—is also impacting ongoing work in solution-phase BP separation [2], BP chemical modification, and high-performance BP optoelectronic applications.
[1] J. D. Wood et al., Nano Lett. 14, 6964 (2014); [2] J. Kang et al., ACS Nano 9, 3596 (2015).