Fill the key gaps in the material field

ARC Center of Excellence for Future Low Energy Electronic Technology

Picture: The optical transparency of new materials can realize futuristic, flexible and transparent electronic products. see more 

A new study released this week may pave the way for revolutionary transparent electronics.

This see-through device may be integrated into glass, flexible displays and smart contact lenses to bring futuristic devices that look like science fiction products to life.

For decades, researchers have been looking for a new type of electronic products based on semiconductor oxides whose optical transparency can make these completely transparent electronic products possible.

Oxide-based equipment can also be used in power electronics and communication technologies, thereby reducing the carbon footprint of utility networks.

The team led by RMIT has now introduced ultra-thin β-tellurite into the two-dimensional (2D) semiconductor material family, providing answers to decades of high-mobility p-type oxide searches.

"This new, high-mobility p-type oxide fills a key gap in the material spectrum to achieve fast and transparent circuits," said team leader Dr. Torben Daeneke, who led the collaboration of the three FLEET nodes .

Other major advantages of long-sought-after oxide-based semiconductors are their stability in air, low purity requirements, low cost, and ease of deposition.

"In our progress, the missing link is to find the right,'positive' approach," Torben said.

There are two types of semiconductor materials. "N-type" materials have a large number of negatively charged electrons, while "p-type" semiconductors have a large number of positively charged holes.

It is by stacking complementary n-type and p-type materials together that electronic devices such as diodes, rectifiers, and logic circuits can be manufactured.

Modern life relies heavily on these materials because they are the cornerstone of every computer and smartphone.

One obstacle to oxide devices is that although many high-performance n-type oxides are known, there is a severe lack of high-quality p-type oxides.

However, a calculation study in 2018 indicated that β-tellurite (β-TeO2) may be an attractive candidate for p-type oxide. The special position of tellurium in the periodic table means that it can both As a metal, it can also be used as a non-metal, providing oxides with unique and useful properties.

"This prediction encourages our team at RMIT University to explore its characteristics and applications," said FLEET associate researcher Dr. Torben Daeneke.

Liquid metal-a way to explore two-dimensional materials

Dr. Daeneke's team demonstrated the use of a specially developed synthetic technique that relies on liquid metal chemistry to separate β-tellurite.

“Prepare a molten mixture of tellurium (Te) and selenium (Se) and allow it to roll on the surface,” explains co-first author Patjaree Aukarasereenont.

"Thanks to the oxygen in the ambient air, the droplet will naturally form a thin layer of β-tellurite surface oxide. When the droplet rolls on the surface, this oxide layer will stick to it, thereby depositing an atomically thin layer. The oxide layer."

“The process is similar to painting: you use a glass rod as a pen, and liquid metal is your ink,” explains Ms. Aukarasereenont, a FLEET PhD student at RMIT.

Although the ideal β phase of tellurite grows below 300 °C, pure tellurium has a high melting point, above 500 °C. Therefore, adding selenium to design an alloy with a lower melting point makes synthesis possible.

"The ultra-thin flakes we obtained are only 1.5 nanometers thick-corresponding to only a few atoms. The material is highly transparent in the visible spectrum with a band gap of 3.7 eV, which means they are basically invisible to the human eye", co-author Explain that Dr. Arizawa Betty.

Assess β-tellurite: 100 times faster

In order to evaluate the electronic properties of the developed materials, field-effect transistors (FETs) were fabricated.

"These devices show typical p-type switching and high hole mobility (approximately 140 cm2V-1s-1), indicating that β-tellurite is ten to one hundred times faster than existing p-type oxide semiconductors. Excellent opening The /off ratio (over 106) also proves that the material is suitable for energy-saving and fast equipment," said Ms. Patjaree Aukarasereenont.

"These findings fill a key gap in the electronic material library," said Dr. Ali Zavabeti.

"Having a fast, transparent p-type semiconductor available for us to use is likely to revolutionize transparent electronic products, while also achieving better display effects and improved energy-saving equipment."

The team plans to further explore the potential of this new type of semiconductor. "Our further research on this exciting material will explore integration with existing and next-generation consumer electronics products," said Dr. Torben Daeneke.

The paper high-mobility p-type semiconductor two-dimensional β-TeO2 was published in Nature Electronics in April 2021. (DOI: 10.1038/s41928-021-00561-5)

FLEET researchers from RMIT, ANU and UNSW collaborated with colleagues from Deakin University and the University of Melbourne. Matthias Wurdack (ANU) of FLEET conducted 2D nanosheet transfer experiments, and Kourosh Kalantar-zadeh (UNSW) assisted in analyzing material and device characteristics.

The project was supported by the Australian Research Council (Centre of Excellence and DECRA Program). The authors also thank RMIT University’s Microscopy and Microanalysis Facility (RMMF), RMIT University’s MicroNano Research Facility (MNRF) for their support, and the funding received through McKenzie’s postdoc The University of Melbourne Scholarship Program.

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Torben Daeneke torben.daeneke@rmit.edu.au Office: 040-497-7831

ARC Center of Excellence for Future Low Energy Electronic Technology

Copyright © 2021 American Association for the Advancement of Science (AAAS)

Copyright © 2021 American Association for the Advancement of Science (AAAS)