Electron Field Emission of Geometrically Modulated Monolayer Semiconductors

Abstract

Electron field emission, electrons emitted from solid surfaces under high electric field, offers significant scientific interests in materials sciences and potential optoelectronics applications. 2D atomic layers, such as MoS2, exhibit fascinating properties for diverse applications in next‐generation nanodevices and rich physical phenomena for fundamental research. However, the study on field emission of semiconducting monolayers is lacking owing to its low efficiency and stability of electron emission. Here, electron field emission of the geometrically modulated monolayer semiconductors suspended with 1D nanoarrays is demonstrated. Chemical vapor deposition synthesis of two prototype monolayers of transition metal dichalcogenides (TMD), MoS2 and MoSe2, is presented and their diverse band structures offer an ideal platform to explore the fundamental process of the electron emission in the TMD. Geometrical modulation and charge transfer of the semiconducting monolayers can be significantly tuned with the structural suspension with the 1D ZnO nanoarrays. Possible mechanisms on the enhanced electron emission of the 2D monolayers are discussed. With geometrical control of the monolayers, a highly efficient and stable electron emission of TMD monolayers is achieved in low turn‐on electric fields, enabling applications on electrons sources and opening a new avenue toward geometrically tuned atomic layers.

Highly Stable Field Emission from a Tungsten Diselenide Monolayer on Zinc Oxide Nanowire by Geometrically Modulating Hot Electrons

“…From the high‐magnification scanning electron microscopy (SEM) images in the inset of Figure d, we see that some of the NWs have a tent‐like structure. This has been reported in other 2D–1D structures, but the others were bent or even fallen after the WSe 2 transfer. Since this tent‐like structure is believed to be responsible for the field emission, we focus on it in this work.…”

Transition-Metal Substitution-Induced Lattice Strain and Electrical Polarity Reversal in Monolayer WS2

“…HAADF imaging has been demonstrated to be an effective way for atom-by-atom chemical analysis in monolayer materials while the atomic intensity is directly used to distinguish different atomic species such as MoSe 2x S 2(1−x) 9 and W x Mo 1−x Se 2y S 2(1−y) . 10 In this study, the large Z 2 value difference between the heavy atom W (Z 2 = 5476) and the lighter atom Nb (Z 2 = 1681) makes them easy to be identified. Because of the heavy atomic weight of the W atom, it exhibits a brighter HAADF contrast than the Nb atom.…”

“…Figure a shows a low-magnification bright field STEM (BF-STEM) image exhibiting a large area of monolayer ternary alloy. HAADF imaging has been demonstrated to be an effective way for atom-by-atom chemical analysis in monolayer materials while the atomic intensity is directly used to distinguish different atomic species such as MoSe 2 x S 2(1– x ) and W x Mo 1– x Se 2 y S 2(1– y ) . In this study, the large Z 2 value difference between the heavy atom W ( Z 2 = 5476) and the lighter atom Nb ( Z 2 = 1681) makes them easy to be identified.…”

Extreme nonlinear strong-field photoemission from carbon nanotubes

“…The sharpness of the bending, referred to as the K of the I–F curve, should be proportional to the bandgap. The behavior has been observed in static-field emission from semiconductors 35 , which is expected to be observed in OFE in principle.

Fig. 1Operation principle of extreme nonlinear OFE.

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