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Independent control of phases and defects in TiO 2 thin films for functional transistor channels
Author(s) -
Yajima Takeaki,
Oike Go,
Nishimura Tomonori,
Toriumi Akira
Publication year - 2016
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201600006
Subject(s) - anatase , materials science , amorphous solid , transistor , rutile , nanotechnology , fabrication , photocatalysis , thermal stability , optoelectronics , thin film , chemical engineering , electrical engineering , chemistry , crystallography , catalysis , medicine , biochemistry , alternative medicine , pathology , voltage , engineering
TiO 2 has various inherent advantages in practical devices: chemical stability, non‐toxicity, and abundance on earth, as highlighted in a range of applications of TiO 2 surfaces in photocatalysis/optoelectronics. However, the application of TiO 2 to three‐terminal devices has been limited; for example, TiO 2 ‐channel transistors, which may potentially modulate the TiO 2 surface properties by electrostatic back gating, has suffered from low field‐effect mobility ( μ FE < 1 cm 2 V −1 s −1 ) irrespective of fabrication methods. The major challenge is to control phases (rutile/anatase) and defects (oxygen vacancy) simultaneously in TiO 2 thin films. Here, we achieved μ FE ∼ 10 cm 2 V −1 s −1 in TiO 2 ‐channel transistors, one order higher than before and even comparable to InGaZnO channels. The major improvement is the independent control of phases and defects in TiO 2 thin films; we formed short‐range order of anatase phase in the amorphous deposition, and minimized the number of defects in the subsequent thermal treatment. Besides, we showed this independent control of phases and defects are underpinned by excellent thermal stability of TiO 2 /SiO 2 interfaces. These results demonstrate TiO 2 can be a transistor channel with a reasonable μ FE and ON/OFF ratio (>6 orders), not only changing the conventional image of this material, but also promising new functionalities based on unique properties of TiO 2 .