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.
Highlights
As commonly observed, high device performance with mobility >1 cm2 V−1 s−1 making them attractive candidates, in paris achievable after annealing in air above typically 250 °C but performance decreases rapidly when annealing temperatures ≤200 °C are used
A grazing incidence wide angle X-ray scattering (GIWAXS) image of a film annealed in air for 4 h at 400 °C is shown in Figure 1c, which confirms the amorphous nature of this film even at www.afm-journal.de this high annealing temperature
We have demonstrated that the conversion from the water soluble metal hydroxide precursor to the fully coordinated oxide is incomplete at a low temperature of 200 °C as evident in the chemical shifts of the indium, zinc, and oxygen 1s X-ray photoelectron spectroscopy (XPS) core levels
Summary
High device performance with mobility >1 cm V−1 s−1 making them attractive candidates, in paris achievable after annealing in air above typically 250 °C but performance decreases rapidly when annealing temperatures ≤200 °C are used. 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 are positively charged by donating electrons to the oxygen. In comparison with the isolated atoms, the energy of the oxygen 2p- and the metal s-orbitals is shifted as a result of. There has been an increasing scientific oxygen 2p-orbitals and raising the energy of the empty metal interest in amorphous metal oxide semiconductors (MOS) for s-orbitals, which results in a high bandgap.[9,10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
