Abstract
AbstractZinc 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.
Highlights
Over the past decades, oxide semiconductors have found widespread applications in flexible and transparent large-area electronics such as active-matrix display forms, are still underexplored
It is demonstrated that the mobility and current density of Zinc oxide (ZnO) field-effect transistors (FETs) can be increased by two orders of magnitude as the precursor pattern width is decreased from 50 μm to 100 nm
We have presented novel DW-electron-beam lithography (EBL) patterning schemes of solution precursors Zn(NDN) and Zn(NPH) for top-down synthesis of ZnO nanowires
Summary
Oxide semiconductors have found widespread applications in flexible and transparent large-area electronics such as active-matrix display forms, are still underexplored. Due to the inherent resolution limit of photolithography-based direct-write techniques, majority of nanoscale ZnO devices are www.advelectronicmat.de fabricated from routes utilizing EBL, soft-EBL,[51,52] infiltration synthesis,[27,53] and direct-write EBL.[54,55,56] In addition to the conventional acrylate based precursors, other novel precursors such as zinc naphthenate (Zn(NPH)) and zinc neodecanoate (Zn(NDN)) are explored for fabricating nanopatterns using EBL[54,55] or direct-write extreme UV-interference lithography (EUV-IL).[57] reports of ZnO nanowire FETs from these precursors are rather rare (one report by Jones et al with Zn(NDN) precursor).[56] Towards this end, we have implemented an EBL-based direct-write approach to fabricate ZnO transistors with width varying from microns to nanometer scales. Upon scaling down ZnO channel width to nanoscale, a two orders of magnitude enhancement in the ZnO FET performance is reported and a comprehensive understanding of the charge transport in these nanostructured devices is developed based on structure–property correlation and parametric understanding of the trap dynamics
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