Air-stable transport in graphene-contacted, fully encapsulated ultrathin black phosphorus-based field-effect transistors.

The presence of direct bandgap and high mobility in semiconductor few-layer black phosphorus offers an attractive prospect for using this material in future two-dimensional electronic devices. However, creation of barrier-free contacts which is necessary to achieve high performance in black phosphorus-based devices is challenging and currently limits their potential for applications. Here, we characterize fully encapsulated ultrathin (down to bilayer) black phosphorus field effect transistors fabricated under inert gas conditions by utilizing graphene as source-drain electrodes and boron nitride as an encapsulation layer. The observation of a linear ISD-VSD behavior with negligible temperature dependence shows that graphene electrodes lead to barrier-free contacts, solving the issue of Schottky barrier limited transport in the technologically relevant two-terminal field-effect transistor geometry. Such one-atom-thick conformal source-drain electrodes also enable the black phosphorus surface to be sealed, to avoid rapid degradation, with the inert boron nitride encapsulating layer. This architecture, generally applicable for other sensitive two-dimensional crystals, results in air-stable, hysteresis-free transport characteristics.

[1]  M. Demarteau,et al.  Tunable transport gap in phosphorene. , 2014, Nano letters.

[2]  Spin-orbit proximity effect in graphene. , 2014, Nature communications.

[3]  Z. Ong,et al.  Anisotropic charged impurity-limited carrier mobility in monolayer phosphorene , 2014, 1412.3211.

[4]  F. Xia,et al.  Rediscovering black phosphorus as an anisotropic layered material for optoelectronics and electronics. , 2014, Nature communications.

[5]  H. Wen,et al.  Control of Schottky barriers in single layer MoS2 transistors with ferromagnetic contacts. , 2013, Nano letters.

[6]  L. Lauhon,et al.  Emerging device applications for semiconducting two-dimensional transition metal dichalcogenides. , 2014, ACS nano.

[7]  Eric Pop,et al.  Improving contact resistance in MoS2 field effect transistors , 2014, 72nd Device Research Conference.

[8]  K. Novoselov,et al.  Micrometer-scale ballistic transport in encapsulated graphene at room temperature. , 2011, Nano letters.

[9]  A. Neto,et al.  Electronic transport in graphene-based heterostructures , 2014, 1406.2490.

[10]  Qing Hua Wang,et al.  Electronics and optoelectronics of two-dimensional transition metal dichalcogenides. , 2012, Nature nanotechnology.

[11]  Gautam Gupta,et al.  Phase-engineered low-resistance contacts for ultrathin MoS2 transistors. , 2014, Nature materials.

[12]  C. Hu,et al.  Field-effect transistors built from all two-dimensional material components. , 2014, ACS nano.

[13]  A. H. Castro Neto,et al.  Electric field effect in ultrathin black phosphorus , 2014 .

[14]  P. D. Ye,et al.  $\hbox{MoS}_{2}$ Dual-Gate MOSFET With Atomic-Layer-Deposited $\hbox{Al}_{2}\hbox{O}_{3}$ as Top-Gate Dielectric , 2011, IEEE Electron Device Letters.

[15]  J. Kwon,et al.  Influence of post-annealing on the off current of MoS2 field-effect transistors , 2015, Nanoscale Research Letters.

[16]  Xianfan Xu,et al.  Phosphorene: an unexplored 2D semiconductor with a high hole mobility. , 2014, ACS nano.

[17]  SUPARNA DUTTASINHA,et al.  Van der Waals heterostructures , 2013, Nature.

[18]  Xianfan Xu,et al.  Phosphorene: an unexplored 2D semiconductor with a high hole mobility. , 2014, ACS nano.

[19]  B. Radisavljevic,et al.  Mobility engineering and a metal-insulator transition in monolayer MoS₂. , 2013, Nature materials.

[20]  Kwang S. Kim,et al.  Tuning the graphene work function by electric field effect. , 2009, Nano letters.

[21]  Qiang Li,et al.  Toward intrinsic graphene surfaces: a systematic study on thermal annealing and wet-chemical treatment of SiO2-supported graphene devices. , 2011, Nano letters.

[22]  Engineering Schottky Barrier in Black Phosphorus field effect devices for spintronic applications , 2014, 1406.4476.

[23]  Jun Dai,et al.  Bilayer Phosphorene: Effect of Stacking Order on Bandgap and Its Potential Applications in Thin-Film Solar Cells. , 2014, The journal of physical chemistry letters.

[24]  Xiaolong Liu,et al.  In Situ Thermal Decomposition of Exfoliated Two-Dimensional Black Phosphorus. , 2015, The journal of physical chemistry letters.

[25]  Kenneth L. Shepard,et al.  Electron tunneling through atomically flat and ultrathin hexagonal boron nitride , 2011 .

[26]  G. Steele,et al.  Isolation and characterization of few-layer black phosphorus , 2014, 1403.0499.

[27]  Likai Li,et al.  Black phosphorus field-effect transistors. , 2014, Nature nanotechnology.

[28]  Mengwei Si,et al.  The Effect of Dielectric Capping on Few-Layer Phosphorene Transistors: Tuning the Schottky Barrier Heights , 2014, IEEE Electron Device Letters.

[29]  K. Shepard,et al.  Boron nitride substrates for high-quality graphene electronics. , 2010, Nature nanotechnology.

[30]  Wei Ji,et al.  High-mobility transport anisotropy and linear dichroism in few-layer black phosphorus , 2014, Nature communications.

[31]  Zhixian Zhou,et al.  High mobility WSe2 p- and n-type field-effect transistors contacted by highly doped graphene for low-resistance contacts. , 2014, Nano letters.

[32]  Daniele Chiappe,et al.  Hindering the Oxidation of Silicene with Non‐Reactive Encapsulation , 2013 .

[33]  G. Steele,et al.  Fast and broadband photoresponse of few-layer black phosphorus field-effect transistors. , 2014, Nano letters.

[34]  R. Soklaski,et al.  Layer-controlled band gap and anisotropic excitons in few-layer black phosphorus , 2014 .

[35]  Yida Li,et al.  Low resistance metal contacts to MoS2 devices with nickel-etched-graphene electrodes. , 2015, ACS nano.

[36]  Bin Liu,et al.  Hysteresis in single-layer MoS2 field effect transistors. , 2012, ACS nano.

[37]  A. Fazzio,et al.  Van der Waals heterostructure of phosphorene and graphene: tuning the Schottky barrier and doping by electrostatic gating. , 2015, Physical review letters.

[38]  Yihong Wu,et al.  Hysteresis of electronic transport in graphene transistors. , 2010, ACS nano.