Abstract
Atomically thin transition metal dichalcogenides (TMDs) are currently receiving significant attention due to their promising opto-electronic properties. Tuning optical and electrical properties of mono and few-layer TMDs, such as tungsten diselenide (WSe2), by controlling the defects, is an intriguing opportunity to synthesize next generation two dimensional material opto-electronic devices. Here, we report the effects of focused helium ion beam irradiation on the structural, optical and electrical properties of few-layer WSe2, via high resolution scanning transmission electron microscopy, Raman spectroscopy, and electrical transport measurements. By controlling the ion irradiation dose, we selectively introduce precise defects in few-layer WSe2 thereby locally tuning the resistivity and transport properties of the material. Hole transport in the few layer WSe2 is degraded more severely relative to electron transport after helium ion irradiation. Furthermore, by selectively exposing material with the ion beam, we demonstrate a simple yet highly tunable method to create lateral homo-junctions in few layer WSe2 flakes, which constitutes an important advance towards two dimensional opto-electronic devices.
Highlights
Two-dimensional transition-metal dichalcogenides (TMDs) have recently garnered interest due to their novel electronic and optoelectronic properties and provide promise for generation device technologies
The p-n junction diodes are important because the built-in potential at the junction separates the photo-generated electron-hole pairs, which subsequently migrate to the respective electrodes, leading to higher photo-current at zero bias
The longitudinal acoustic (LA) mode at the M point of the Brillouin zone (LA(M)) is interesting as this peak is associated with defect generation and disorder within the lattice[19,20], analogous to the D band in graphene
Summary
Two-dimensional transition-metal dichalcogenides (TMDs) have recently garnered interest due to their novel electronic and optoelectronic properties and provide promise for generation device technologies. The p-n junction diodes are important because the built-in potential at the junction separates the photo-generated electron-hole pairs, which subsequently migrate to the respective electrodes, leading to higher photo-current at zero bias. Both vertical and lateral, homo- and hetero- p-n junctions have been realized in many TMDs by chemical doping[15,16], electrostatic doping[6,7,8], and material engineering[10,17,18]. We have demonstrated selective He+ irradiation within a few-layer WSe2 flake as a novel method to introduce an optically active homo-junction, similar to a conventional p-n junction
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