Systematic Doping Control of CVD Graphene Transistors with Functionalized Aromatic Self‐Assembled Monolayers

Abstract

3464www.MaterialsViews.com wileyonlinelibrary.com result in a linear dispersion for low energy carriers, which can be described as zero rest-mass relativistic particles with exemplary transport properties. [1][2][3] Electron mobility as high as 200 000 cm 2 V −1 s −1 can be achieved once extrinsic factors such as scattering centers from underlying substrates, adsorbates, and defects within graphene itself are controlled. [4][5][6][7][8][9] In order to utilize graphene for next generation electronic devices it is necessary to have precise control of carrier concentration and polarity without disrupting its intrinsic properties. Carrier doping of graphene has so far been achieved via chemical doping, [10][11][12][13] substitutional doping, [14][15][16] electric fi eld modulation, [ 17,18 ] and metal contact doping. [ 19,20 ] Recent reports have also shown it is possible to modulate the properties of graphene by modifying the underlying dielectric surface with a self-assembled monolayer (SAM) resulting in doping control without compromising the intrinsic graphene performance. [21][22][23][24] However, these studies use exfoliated graphene rather than the more commercially viable CVD-based graphene. In addition, exfoliation severely limits the ability to do a systematic and statistical study based on multiple devices due to the taxing processing steps necessary to fabricate individual devices. In order to circumvent this issue, characterization of these devices is mainly attributed to multiple Raman scans on a few pieces of modifi ed graphene rather than multiple pieces of graphene. While such methodology is useful for obtaining an overall picture of the graphene doping environment it makes it diffi cult to understand the exact relationship between SAMs and graphene. SAMs are commonly used in organic fi eld-effect transistors to modify the work function of metal electrodes, [ 25,26 ] quench charge trap sites at the interface between semiconductor and metal or dielectric, [27][28][29] and modulate the position of the threshold voltage. [30][31][32] SAMs represent an ideal platform for control of graphene electronics as they can be designed and functionalized at the molecular scale to cater to specifi c device requirements. However, there is still a need for better understanding of how SAM-treated dielectrics modulate the doping of graphene devices. In particular, an understanding of how the SAM dipole, while taking into account metal electrode effects, infl uences graphene has yet to be studied. In this paper we Recent reports have shown that self-assembled monolayers (SAMs) can induce doping effects in graphene transistors. However, a lack of understanding persists surrounding the quantitative relationship between SAM molecular design and its effects on graphene. In order to facilitate the fabrication of next-generation graphene-based devices it is important to reliably and predictably control the properties of graphene without negatively impacting its intrinsic high performance. In this study, SAMs with varying dipo...

Electronic transport properties of transition metal dichalcogenide field-effect devices: surface and interface effects

“…134,178,179 The use of SAM dipoles remains largely unexplored for MX 2 devices. 134,178,179 The use of SAM dipoles remains largely unexplored for MX 2 devices.…”

Controllable Fabrication of Nanostructured Graphene Towards Electronics

“…By adjusting the functional radicals of para-position phosphoryl group in the phenylphosphonic acid, a series of mobilities could be achieved corresponding to required practical applications. [ 156 ] In conclusion, we can achieve devices with specifi c mobility values as we expected by using SAMs with different functional groups. Importantly, the substrate surface is relatively smooth and its size is quite large on the basis of selfassembling of molecules, thus we can overcome the limit of substrate size.…”

Interface engineering for high performance graphene electronic devices

“…Modification of the graphene/target substrate interface by SAM can be also used to tune the carrier type or density, namely doping control, without compromising the intrinsic electrical properties of graphene [81][82][83][84]: SAMs terminated with various functional groups induce n-or p-type doping of graphene by charge transfer from a specific functional group or the built-in potential generated from the dipole moment of the SAM. Here, we do not cover this in detail, but readers who are interested in this topic may refer to a recent in-depth review [85].…”