The new material is set to give us faster high resolution displays. Hokkaido University researchers explain what makes this material so special, opening the door to its applications and further development.
All displays are made up of a grid of tiny light points, called pixels, whose brightness can be adjusted individually. The total number of pixels — and thus the resolution and display Size – limited by how many of these pixels can be addressed in a given fraction of a second. So display manufacturers try to use materials in the pixel control units that exhibit very high “electron mobility,” which is a measure of how quickly current will flow through control unit in response to the applied voltage – and thus how fast pixel there is
A new material called ITZO (for the constituent elements indium, tin, zinc and oxygen) promises to be up to seven times faster than the current state-of-the-art material. However, it was not clear where this improvement came from, preventing its application for industrial applications.
Hokkaido University materials scientist Hiromichi Ohta and his team used their unique measurement technique to explain this point. In a recent paper published in the journal ACS Applied Electronic Materialsthey showed that the higher electron mobility results from the unusual fact that in ITZO films of sufficient thickness, free charges accumulate at the interface with the carrier material and thus allow passing electrons to move freely through the bulk of the material .
The unique ability comes down to a very simple formula: electron mobility is proportional to the free passage time of charge carriers — in this case, electrons — divided by their effective mass. And while measuring the electron mobility itself is a relatively standard technique, effective mass and free-path time cannot be measured so easily, and so it is difficult to say which factor is responsible for electron mobility.
But, measuring how electric field inside, the material changes in response to an applied magnetic field as well as to a temperature gradient, Ohta’s team could derive the effective mass of the electrons and then also calculate the free-path time. Turns out, both effective mass is much smaller than in current state-of-the-art materials, and the free travel time is much longer, and thus both factors contribute to higher electron mobility. Furthermore, by observing how their results depended on the thickness of the ITZO material, they could infer how the interface and bulk of the material contributed to these effects.
Ohta explains the importance of this analysis: “Using the knowledge we gained from this research, we can in the future develop other transparent oxide semiconductor thin-film transistors with different chemical compositions that exhibit even better electron mobility properties.” Therefore, this research is an important step towards the next generation of ultra-high resolution displays.
Hui Yang et al. Analysis of thermoelectric modulation of high-mobility transparent amorphous oxide semiconductor thin-film transistors, ACS Applied Electronic Materials (2022). DOI: 10.1021/acsaelm.2c01210
Citation: Analysis of new material that promises faster, higher-resolution displays (2022, October 14) Retrieved October 14, 2022, from https://phys.org/news/2022-10-material-faster-higher-resolution .html
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