Nucleation control of the In
2
O
3
deposition by ultrasonic spray pyrolysis
for high performance thin film transistors
Ivan Isakov, Hendrik Faber, Max Grell, Satyajit Das and Thomas D. Anthopoulos
Department of physics and Centre for Plastic Electronics, Imperial College London,
London, SW7 2AZ, United Kingdom
E-mail
Solution processed metal oxide thin film transistors (TFTs) are promising candidates for the use
in ubiquitous flexible electronics due to their low cost, high charge carrier mobility and optical
transparency. However, in order to be able to compete with the incumbent amorphous and
polycrystalline silicon, the metal oxides TFTs should simultaneously overcome the charge carrier
mobility limit of 30-50 cm
2
/Vs and be processed in air at temperatures below 300 °C (compatible with
flexible polyimide films). Recently, our group has achieved unprecedented electronic performance in
ultrathin indium oxide thin film transistors deposited from solution via ultra-sonic spray pyrolysis [1]
and in multilayer metal oxide thin films prepared from solution via spin-coating [2], with electron
mobility reaching up to 20 and 40 cm
2
/Vs, respectively.
Building on the previous results, here we report routes to further improve electrical performance
of spray-coated In
2
O
3
devices by optimising growth conditions and by fabricating In
2
O
3
/ZnO bilayers.
First, we investigate the nucleation and formation of the In
2
O
3
film by thoroughly correlating
deposition parameters, film morphology, computer simulation results and electronic properties of the
thin film. We show that the Leidenfrost effect plays a crucial role in the smooth film formation. As a
result we fabricate high performance In
2
O
3
TFTs by spray pyrolysis reaching electron mobility up to
35 cm
2
/Vs at temperatures below 300
°
C. Second, we study bilayer TFTs prepared from the optimised
spray-coated In
2
O
3
bottom layer with various ZnO-containing top layers. We show that the In
2
O
3
/ZnO
interface substantially enhances electronic performance of the oxide TFTs, with electron mobility
reaching up to 50-55 cm
2
/Vs.
[1] H Faber
et al
- ACS Appl. Mater. Interfaces,
2015
,
7
(1), pp 782–790
[2] Y-H Lin
et al
- Adv. Sci.,
2015
,
2
, 1500058
O 34
-92-
