Self-Encapsulated Doping of n-Type Graphene Transistors with Extended Air Stability

Abstract

This paper presents an innovative approach to fabricating controllable n-type doping graphene transistors with extended air stability by using self-encapsulated doping layers of titanium suboxide (TiOx) thin films, which are an amorphous phase of crystalline TiO(2) and can be solution processed. The nonstoichiometry TiOx thin films consisting of a large number of oxygen vacancies exhibit several unique functions simultaneously in the n-type doping of graphene as an efficient electron-donating agent, an effective dielectric screening medium, and also an encapsulated layer. A novel device structure consisting of both top and bottom coverage of TiOx thin layers on a graphene transistor exhibited strong n-type transport characteristics with its Dirac point shifted up to -80 V and an enhanced electron mobility with doping. Most interestingly, an extended stability of the device without rapid degradation after doping was observed when it was exposed to ambient air for several days, which is not usually observed in other n-type doping methods in graphene. Density functional theory calculations were also employed to explain the observed unique n-type doping characteristics of graphene using TiOx thin films. The technique of using an "active" encapsulated layer with controllable and substantial electron doping on graphene provides a new route to modulate electronic transport behavior of graphene and has considerable potential for the future development of air-stable and large-area graphene-based nanoelectronics.

Reversible n-Type Doping of Graphene by H2O-Based Atomic-Layer Deposition and Its Doping Mechanism

“…19 As shown in Figure 2, after pre-H 2 O treatment and ALD-Al 2 O 3 growth, the 2D peak of graphene shifted down from 2690 to 2685 cm −1 , due to the effect of the Fermi level shift on the photon frequencies as a result of n-type doping of graphene. 19,22 In addition, the full width at half-maximum (fwhm) values of the 2D peak shifted up from 43 to 47 cm −1 . Both of these Raman spectroscopy results including the 2D peak left-shifting and blunting were consistent with those observed in typical n-type doping of graphene.…”

“…Both of these Raman spectroscopy results including the 2D peak left-shifting and blunting were consistent with those observed in typical n-type doping of graphene. 19,20,23 Notice that the 2D peak shifted up from 2685 to 2689 cm −1 , while the fwhm values of the 2D peak shifted down from 47 to 45 cm −1 after the n-type doped graphene was treated with RTA at 800°C…”

Surface Charge Transfer Doping of Low‐Dimensional Nanostructures toward High‐Performance Nanodevices

“…a) Mobility of pristine graphene, substitutional‐doped graphene (SDG), covalent‐doped graphene (CDG), graphene nanoribbon (GNR), and noncovalent‐doped graphene . b) E F shift of graphene (Δ E F , marked by circles) after SCTD by various surface dopants and their corresponding energy levels (marked by stars) .…”

Environment-insensitive and gate-controllable photocurrent enabled by bandgap engineering of MoS2 junctions

“…[1][2][3][4][5][6] Regarding the electrical property, the carrier transport in 2D materials is very sensitive to the presence of extrinsic adsorbents, which typically cause charged-impurity scattering, charge trapping, and recombination centers, [7][8][9][10][11] leading to degradation of the transport characteristics. [12][13][14] Although various encapsulation methods have been developed, [15][16][17][18][19] it is intriguing to explore methods to control the transport properties in the circumstance of no encapsulated layer. Here, we demonstrated that the short-circuit photocurrent enabled by the built-in electric field at the MoS2 junction is surprisingly insensitive to the gaseous environment, which is very uncommon in the photoresponse of thin transition-metal dichalcogenides (TMDCs).…”