Solution‐Processed High‐Performance ZnO Nano‐FETs Fabricated with Direct‐Write Electron‐Beam‐Lithography‐Based Top‐Down Route

Abstract

Zinc oxide (ZnO) has been extensively investigated for use in large‐area electronics; in particular, the solution‐processing routes have shown increasing promise towards low‐cost fabrication. However, top‐down fabrication approaches with nanoscale resolution, towards aggressively scaled device platforms, are still underexplored. This study reports a novel approach of direct‐write electron‐beam lithography (DW‐EBL) of solution precursors as negative tone resists, followed by optimal precursor processing to fabricate micron/nano‐field‐effect transistors (FETs). It is demonstrated that the mobility and current density of ZnO FETs can be increased by two orders of magnitude as the precursor pattern width is decreased from 50 µm to 100 nm. These nano‐FET devices exhibit field‐effect mobility exceeding ≈30 cm2 V−1 s−1 and on‐state current densities reaching 10 A m−1, the highest reported so far for direct‐write precursor‐patterned nanoscale ZnO FETs. Using atomic force microscopy and parametric modeling, the origin of such device performance improvement is investigated. The findings emphasize the influence of pre‐decomposition nanoscale precursor patterning on the grain morphology evolution in ZnO and, consequently, open up large‐scale integration, and miniaturization opportunities for solution‐processed, high‐performance nanoscale oxide FETs.

Review of metal-containing resists in electron beam lithography: perspectives for extreme ultraviolet patterning

“…124 Comparing zinc naphthenate and zinc neodecanoate as resists for fabricating ZnO nanowires and FETs, Tiwale et al demonstrated that both the precursors gave similar electronic properties. 125 Electron beam lithography of iron naphthenate and the post-heat treatment of its patterns gave Fe 2 O 3 , which was used as a catalyst to grow carbon nanotubes. 126 Likewise, nickel and copper naphthenates can also be patterned and heat-treated in air or a reducing atmosphere to give either their oxides or metals, respectively.…”

Conductive Materials with Elaborate Micro/Nanostructures for Bioelectronics

“…c,d) Reproduced under the terms of the CC‐BY Creative Commons Attribution 4.0 International license (http://creativecommons.org/licenses/by/4.0/). [ 89 ] Copyright 2020, The Authors, published by Wiley‐VCH. e) Schematic illustration for NIL, and nanoimprint mold and imprinted mask pattern featuring a 10 nm‐wide nanogap.…”

“…Besides, thanks to the precise manipulation of EBL, micro/nano field‐effect transistors (FETs) were constructed through novel method of direct‐write EBL (DW‐EBL), as shown in Figure 3c,d. [ 89 ] It was worth mentioning that ZnO FETs with a wide range of width variations from micro to nanometer dimensions have been successfully fabricated. Particularly, the mobility and current density of the FETs could be increased by decreasing the width of patterns.…”

“…Resist layers as molds and conductive layers as substrates Nanowires, [88] line patterns, [89,93,106] nanogaps, [83] film [99,104,105] Electric conductivity and surface wettability E-skins and biosensors…”

“…d) SEM images and atomic force microscopy (AFM) topography images of ZnO FETs with 500 nm linewidth 1 µm pitch. c,d) Reproduced under the terms of the CC-BY Creative Commons Attribution 4.0 International license (http://creativecommons.org/licenses/by/4.0/) [89]. Copyright 2020, The Authors, published by Wiley-VCH.…”