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Coating Thickness Controls Crystallinity and Enables Homoepitaxial Growth of Ultra‐Thin‐Channel Blade‐Coated In 2 O 3 Transistors
Author(s) -
Kirmani Ahmad R.,
Chen Huilang,
Stafford Christopher M.,
Bittle Emily G.,
Richter Lee J.
Publication year - 2020
Publication title -
advanced electronic materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.25
H-Index - 56
ISSN - 2199-160X
DOI - 10.1002/aelm.202000354
Subject(s) - materials science , thin film transistor , thin film , crystallinity , optoelectronics , crystallite , texture (cosmology) , coating , composite material , saturation (graph theory) , layer (electronics) , nanotechnology , metallurgy , image (mathematics) , artificial intelligence , computer science , mathematics , combinatorics
Scalable, solution‐deposited metal oxide (MO) thin films could enable low‐cost, flexible, large‐area electronics; however, the poor morphology of the typically polycrystalline films limits performance. It is demonstrated that optimized coating thickness leads to high‐quality crystalline films in blade‐coated indium oxide (In 2 O 3 ) ultra‐thin‐film (8 nm) transistors (TFTs). TFTs are fabricated with total channel thickness ranging from 2 to 16 nm via varied multistep processes. Transport in channels fabricated from sequential, thin (≤4 nm) coatings significantly exceeds that from thicker coatings. A marked change is found in the In 2 O 3 crystal texture with coating thickness. Single, thin coatings ≤4 nm produce smooth films with strong (111) texture while thicker coatings are rougher and exhibit little texture. Sequential thin coatings exhibit homoepitaxy. In addition to the improved transport due to the smooth, aligned films, it is found that deposition of sequential thin layers leads to the highest mobility, with either In 2 O 3 or ZnO as the overcoat. This suggests defects at the air interface of the initial thin films limit performance. Optimizing coating thickness and sequence, it is demonstrated 8 nm thick channel In 2 O 3 TFTs exhibiting percolation conduction with an impressive average saturation electron mobility (μ sat ) of (36.1 ± 0.9) cm 2 V −1 s −1 (best‐performing device of 58.0 cm 2 V −1 s −1 ).