Reviewed by Lexie CornerFeb 6 2025
A research team at Osaka University is investigating an alternative method of enhancing device performance. This method involves applying a patterned metal layer, also known as a structural metamaterial, on top of a conventional substrate, like silicon, to speed up electron flow. Results were published in ACS Applied Electronic Materials.
Overview of this study: a diode containing a ‘living’ electrode with a dynamic structure, which can be controlled with sub-micrometer precision through temperature regulation, was fabricated on a silicon substrate. The diode demonstrated enhanced performance as a terahertz light detector. Image Credit: Ai I. Osaka
High-speed, low-power electronic devices are essential for wireless communication. While device miniaturization has historically improved performance, further scaling presents significant manufacturing challenges, limiting continued progress.
One challenge in metamaterial-based technologies is the need for tunable structures that can adapt their properties to changing conditions.
To address this, the research team investigated vanadium dioxide (VO2). When heated, localized regions of a VO2 layer transition from an insulating to a metallic state, forming dynamic microelectrodes capable of carrying charge. The researchers used this property to develop "living" microelectrodes, enhancing the sensitivity of silicon photodetectors to terahertz light.
We produced a terahertz photodetector containing VO2 as a metamaterial. A precise processing method was used to fabricate a high-quality VO2 layer on a silicon substrate. The size of the metallic domains in the VO2 layer, tens of times larger than what has been conventionally achieved, was controlled through temperature regulation, which in turn modulated the response of the silicon substrate to terahertz light.
Ai I. Osaka, Study Lead Author and Researcher, Osaka University
When the temperature was adjusted appropriately, the metallic domains in the VO2 created a conductive network that regulated the localized electric field in the silicon layer, improving its sensitivity to terahertz light.
Heating the photodetector to 56 °C led to strong signal enhancement. We attributed this enhancement to effective coupling between the silicon layer and a dynamic conductive VO2 microelectrode network at this temperature. That is, the temperature-controlled structure of the VO2 metamaterial regulated electric field enhancement and thus impact ionization in silicon.”
Azusa Hattori, Study Senior Author and Associate Professor, Osaka University
The temperature-controlled behavior of the ‘living’ VO2 metallic regions increased silicon’s responsiveness to terahertz light. These findings demonstrate the potential of metamaterials to drive the development of sophisticated electronics that exceed typical materials’ constraints in meeting speed and efficiency requirements.
Journal Reference:
Osaka, A. I. et. al. (2025) Si–VO2 Hybrid Materials with Tunable Networks of Submicrometer Metallic VO2 Domains Provide Enhanced Diode Functionality. ACS Applied Electronic Materials. doi.org/10.1021/acsaelm.4c01914