Low-temperature grown phase transition vanadium dioxide for applications to energy savings

Significance 

Recently, studies involving the growth of vanadium dioxide films on glass substrates have attracted significant interest amongst various researchers. This is due to its excellent structural phase transition (SPT) and insulator-metal transition (IMT) that can be triggered by an electrical voltage. The optical transmittance of vanadium oxide depends on the changes in the IMT. For instance, insulator-metal transition characteristics enable fast transmission of infrared-light with wavelength larger than 1μm. This has increased the use of vanadium oxide in several optical and thermochromics applications like in the case of intelligent optical windows.

Presently, different methods have been devised to achieve better growth of vanadium dioxide films on glass substrates. Zinc oxide has been used for effective growth of vanadium dioxide films owing to its hexagonal plane orientation. Consequently, transparent conductive Al-doped zinc oxide has effectively controlled infrared-light transmittance. This has led to the fabrication of vanadium dioxide film on Al-doped zinc oxide layer to control optical properties through voltage addition. However, deposition of vanadium dioxide films on Al-doped zinc oxide layer has not been fully explored. The resultant layer enables optical transmittance of infrared light at low voltage.

Recently, a group of researchers at Tokai University: Kenta Sato, Hiroaki Hoshino, Dr. Suruz Mian and Professor Kunio Okimura investigated the growth of vanadium dioxide films on both transparent conductive Al-doped zinc oxide layer /glass and transparent zinc oxide glass substrates. They used both inductively coupled plasma assisted radio frequency magnetron sputtering and conventional radio frequency magnetron sputtering. Also, they determined the advantages of vanadium dioxide deposition at low temperatures. Their work is published in the journal, Thin Solids Films.

The research team observed that at low temperatures of 250 °C, vanadium dioxide films grown successfully on ZnO/glass substrates due to the introduction of inductively coupled plasma assisted sputtering. Also, the formation of zinc vanadate occurred at the interface region of radio-frequency magnetron sputtering at a temperature of 350°C. Furthermore, a resistivity drop above two magnitude orders was observed in the vanadium dioxide films with the infrared-light transmittance changing from 45-10% in comparison to substrate temperature.

From the scanning electron microscope images and XPS depth results, the authors concluded that the formation of zinc vanadate greatly led to the deterioration of the transmittance of the infrared light. Consequently, the steep interface between the interface of vanadium dioxide and zinc oxide was formed without contaminants compounds. The use of inductively coupled plasma assisted method enabled the growth of vanadium dioxide films on conductive Al-doped zinc oxide at low temperatures.

According to Professor Kunio Okimura and his research team, the simultaneous steep changes in transmittance and resistivity will open new doors for the applications of vanadium dioxide films in different fields including thermochromics devices like smart windows. For instance, the transmittance change observed in vanadium oxide on AZO glass forms the basis of controlling intelligent optical windows electrically.

Low-temperature grown phase transition vanadium dioxide energy savings - Advances Engineering

About the author

Kenta Sato is currently a circuit designer of LAPIS semiconductor Co., Ltd., a subsidiary company of ROHM Co., Ltd. He received B. E. degree of Electrical and Electronic Engineering in 2016, and M. E. degree in 2018 from Tokai University. He made researches of functional electronic materials synthesis and characterizations throughout his B. E and M. E. courses in Tokai University.

About the author

Hiroaki Hoshino is currently a graduate student in the Course of Electrical and Electronic Engineering, Tokai University. He received his B. E. degree from Tokai University in 2017. His research field is the characterization of optical properties of phase transition oxide thin films and their applications to energy savings.

About the author

Md. Suruz Mian is currently a post-doctoral researcher in the department of Prime Mover Engineering at Tokai University. He received Ph. D degree from Tokai University in 2016. During his Ph. D course, he studied on synthesis, characterization, and applications of functional oxide materials.

His current research focuses on development of high efficiency thermoacoustics devices with the aim of waste heat recovery. He is also a part-time lecturer in the department of International Education Center of Tokai University.

About the author

Kunio Okimura is currently a professor of Department of Electrical and Electronic Engineering, Tokai University. He received B. E degree from Tokyo University of Agriculture and Technology in 1985, and M. E. degree from Kyoto University in 1987. He received Ph. D degree from Kyushu University in 1995. He worked as assistant professor in Fukui National College of Technology from 1987 to 1998. Since joining Tokai University in 1998, he engaged in the research on functional electronic materials synthesis and characterizations. He was in Harvard University as visiting researcher in 2009. He published more than 70 peer reviewed journal papers.

Reference

Sato, K., Hoshino, H., Mian, M., & Okimura, K. (2018). Low-temperature growth of VO2 films on transparent ZnO/glass and Al-doped ZnO/glass and their optical transition propertiesThin Solid Films651, 91-96.

Go To Thin Solid Films

Check Also

The combination of optical trapping and photonic crystal fiber enables distributed whispering-gallery-mode based measurements, Advances in Engineering

The combination of optical trapping and photonic crystal fiber enables distributed whispering-gallery-mode based measurements