Electron-Beam Patterning of Polymer Electrolyte Films To Make Multiple Nanoscale Gates for Nanowire Transistors

Abstract

We report an electron-beam based method for the nanoscale patterning of the poly(ethylene oxide)/LiClO 4 polymer electrolyte. We use the patterned polymer electrolyte as a high capacitance gate dielectric in single nanowire transistors and obtain subthreshold swings comparable to conventional metal/oxide wrap-gated nanowire transistors. Patterning eliminates gate/contact overlap which reduces parasitic effects and enables multiple, independently controllable gates. The method's simplicity broadens the scope for using polymer electrolyte gating in studies of nanowires and other nanoscale devices.

Near-thermal limit gating in heavily doped III-V semiconductor nanowires using polymer electrolytes

“…For PE-gated devices, the Ti/Au gate electrode terminated 2 µm from the nanowire and was defined by EBL and thermal evaporation [13]. Patterning of the PE was the final step.…”

“…The solution was left to stand overnight with the supernatant spin-coated onto the device at 3000 rpm for 60 s. The device was baked at 90 • C for 30 mins to remove residual methanol. Polyethylene oxide acts as a positive EBL resist [13] and was directly patterned by EBL with beam energy 7 keV and dose 300 µC/cm 2 . Development in H 2 O removed unexposed regions giving nanoscale PE strips between the gate electrode and nanowire [13].…”

“…Polyethylene oxide acts as a positive EBL resist [13] and was directly patterned by EBL with beam energy 7 keV and dose 300 µC/cm 2 . Development in H 2 O removed unexposed regions giving nanoscale PE strips between the gate electrode and nanowire [13]. Electrical measurements were performed at room temperature in ambient.…”

“…The resulting strong gating has seen electrolyte gating become a well-known approach to improved performance in materials ranging from organic semiconductors to chalcogenides [16]. Electrolyte gating also provides a simpler route to achieving concentric gating action for nanowire devices [13,17]. The key result of this work is a demonstration that electrolyte-gated nanowire transistors remain functional even in the limit where the doping density becomes sufficiently high that traditional gating approaches fail.…”

“…Our polymer electrolyte (PE) gate consists of an electron-beam patterned polymer gel, e.g., polyethylene oxide, spanning the gap between a metal electrode and the nanowire [13]. The gel absorbs water providing an environment for mobile ions, either H + /OH − from dissociated H 2 O, or added salt, e.g., LiClO 4 [14].…”