Patterning Superatom Dopants on Transition Metal Dichalcogenides

Abstract

This study describes a new and simple approach to dope two-dimensional transition metal dichalcogenides (TMDCs) using the superatom Co6Se8(PEt3)6 as the electron dopant. Semiconducting TMDCs are wired into field-effect transistor devices and then immersed into a solution of these superatoms. The degree of doping is determined by the concentration of the superatoms in solution and by the length of time the films are immersed in the dopant solution. Using this chemical approach, we are able to turn mono- and few-layer MoS2 samples from moderately to heavily electron-doped states. The same approach applied on WSe2 films changes their characteristics from hole transporting to electron transporting. Moreover, we show that the superatom doping can be patterned on specific areas of TMDC films. To illustrate the power of this technique, we demonstrate the fabrication of a lateral p-n junction by selectively doping only a portion of the channel in a WSe2 device. Finally, encapsulation of the doped films with crystalline hydrocarbon layers stabilizes their properties in an ambient environment.

Progress on Electronic and Optoelectronic Devices of 2D Layered Semiconducting Materials

“…Remarkably, covering BP by Cs 2 CO 3 film with thickness of >10 nm or MoO 3 film (even particles, <1 nm) will induce a change in types of majority charge carriers. Based on a similar idea, Yu et al recently achieved unipolar p‐ and n‐type WSe 2 using superatom Co 6 Se 8 as electron dopants . It was noted that this change between two unipolar conductions were only observed in thin (here bilayer) WSe 2 flakes, demonstrating that the surface‐decoration way only affects the top‐most layer/layers of 2DLSMs.…”

Van der Waals Bipolar Junction Transistor Using Vertically Stacked Two‐Dimensional Atomic Crystals

“…This can be improved by further increasing the WSe 2 base-region thickness to above three layers. [36,37] We are confident that using an electron-rich octahedral superatom as an electron dopant for MoS 2 [38] and choosing a Pd metal with a high work function for WSe 2 to reduce the Schottky barrier height [39] are two effective ways to further improve the V2D-BJT performance. With a threelayer WSe 2 base region (Figure 4f), I C first linearly increases with V CE and then nearly becomes unaffected by changing V CE (e.g., V CE > 2 V); instead, it is almost entirely controlled by V BE .…”

Synthesis and Properties of Two Dimensional Doped Transition Metal Dichalcogenides

“…However, it decreased for n-type doped MoS 2 with NADH. Yu et al (2016) reported the synthesis of superatom-doped MoS 2 and WSe 2 via a chemical doping method. The superatom, Co 6 Se 8 (PEt 3 ) 6 , is an electron-rich octahedral dopant as shown in Fig.…”