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Electronic structure of low-temperature solution-processed amorphous metal oxide semiconductors for thin-film transistor applications

DOI: 10.1002/adfm.201404375 DOI Help

Authors: Josephine Socratous (University of Cambridge) , Kulbinder K. Banger (University of Cambridge) , Yana Vaynzof (University of Cambridge) , Aditya Sadhanala (University of Cambridge) , Adam D. Brown (University of Cambridge) , Alessandro Sepe (University of Cambridge) , Ullrich Steiner (University of Fribourg) , Henning Sirringhaus (University of Cambridge)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Advanced Functional Materials , VOL 25 (12) , PAGES 1873 - 1885

State: Published (Approved)
Published: March 2015
Diamond Proposal Number(s): 8657

Open Access Open Access

Abstract: The electronic structure of low temperature, solution-processed indium–zinc oxide thin-film transistors is complex and remains insufficiently understood. As commonly observed, high device performance with mobility >1 cm2 V−1 s−1 is achievable after annealing in air above typically 250 °C but performance decreases rapidly when annealing temperatures ≤200 °C are used. Here, the electronic structure of low temperature, solution-processed oxide thin films as a function of annealing temperature and environment using a combination of X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and photothermal deflection spectroscopy is investigated. The drop-off in performance at temperatures ≤200 °C to incomplete conversion of metal hydroxide species into the fully coordinated oxide is attributed. The effect of an additional vacuum annealing step, which is beneficial if performed for short times at low temperatures, but leads to catastrophic device failure if performed at too high temperatures or for too long is also investigated. Evidence is found that during vacuum annealing, the workfunction increases and a large concentration of sub-bandgap defect states (re)appears. These results demonstrate that good devices can only be achieved in low temperature, solution-processed oxides if a significant concentration of acceptor states below the conduction band minimum is compensated or passivated by shallow hydrogen and oxygen vacancy-induced donor levels.

Journal Keywords: Indium–Zinc Oxide; Nitrates; Solution-Processing; Spectroscopy; Subgap Density Of States

Diamond Keywords: Semiconductors; Organic Light Emitting Diodes (OLEDs)

Subject Areas: Materials, Physics

Instruments: I07-Surface & interface diffraction

Added On: 30/04/2015 15:29

Adv Funct Materials - 2015 - Socratous - Electronic Structure of Low%E2%80%90Temperature Solution%E2%80%90Processed Amorphous Metal Oxide.pdf

Discipline Tags:

Surfaces Physics Hard condensed matter - structures Electronics Materials Science interfaces and thin films

Technical Tags:

Scattering Wide Angle X-ray Scattering (WAXS) Grazing Incidence Wide Angle Scattering (GIWAXS)