Biotechnology

The hot probe tip contributes to creating a “transformer” semiconductor.


How can we make wearables like the Spiderman suit that are thin and soft but also feature a wide range of electrical and optical functions? The answer lies in creating new materials that far exceed the performance of existing materials and developing technologies that allow precise control of the material’s physical properties.

How can we make wearables like the Spiderman suit that are thin and soft but also feature a wide range of electrical and optical functions? The answer lies in creating new materials that far exceed the performance of existing materials and developing technologies that allow precise control of the material’s physical properties.

Separating the transition metal dichalcogenide (TMD) into a single graphene-like layer makes it turn into a two-dimensional (2D) thin film material that exhibits high-performance semiconductor characteristics. By stacking two different layers of TMD, different combinations of TMD types and stacking methods can produce unique properties. For this reason, 2D semiconductors based on heterostructures are attracting attention as important next-generation materials for the electronics industry across academia and industry worldwide. However, it is still quite challenging to commercialize them due to the difficulty of precisely controlling the physical properties of their quasi-particles.

Professors Kyoung-Duck Park, Yeonjeong Koo, and Hyeongwoo Lee from the Department of Physics at POSTECH conducted joint research with a team from ITMO University in Russia led by Professor Vasily Kravtsov to develop multifunctional tip-enhanced spectroscopy that dynamically controls quasiparticles of 2D materials in small space. The team managed to control semiconductor particles such as the exciton interlayer and the trion interlayer that form on TMD heterobilalayers by using spectroscopy at a level of around 20nm.

Like excitons, interlayer excitons of TMD heterobilalayers exhibit photoluminescence (PL), which is one of the properties of semiconductor materials. Exciton interlayers, which are electrically neutral quasiparticles, can be used in next-generation semiconductor devices with less heat due to being part light and part material. They can also be used as light sources for quantum information technology due to their longer coherence times than stimuli. However, there are several hurdles to overcome in its implementation. They have very low light efficiency at room temperature, and it is difficult to modulate their light energy.

The POSTECH team led by Professor Park, who had proposed a technology for controlling excitability in nanoscale space in a previous study, successfully developed a multifunctional tip-enhanced spectroscope that can be tuned to gigapascal scale (GPa) pressure and near field intensity.

Spectroscopy can increase the efficiency of the interlayer excitation light by about 9,000 times and dynamically modulate its light energy (light color). Moreover, the tip is based on hot electrons the injection technology allowed the team to achieve the world’s first dynamic control of quasiparticle conversion between interlayer excitons and interlayer trions.

The most significant advantage of this research breakthrough is that it helps dynamically control the physical properties of quasi-particles under conditions of room temperature and atmospheric pressure and analyzes in real time the optical characteristics of semiconductor particles with a spatial resolution of about 20nm, which is much shorter than the wavelength of light.

Yeonjeong Koo, one of the two authors of the research paper, explained, “The spectroscopy the team developed can be used in identifying new physical properties of individual semiconductor particles such as the interlayer excitability of the TMD heterobilayer. I am looking forward to the next physical discovery.”

The research findings are expected to open up possibilities for various applications of 2D semiconductors based on heterostructures which are being studied extensively as next-generation materials. The fact that basic research into the development of measurement instruments contributes greatly to the results is gaining more and more attention in the field.

The technology is also expected to be used in developing ultrathin and ultrathin wearable optoelectronic devices. This achievement is all the more meaningful in the current situation where the US, Japan and China are competing to dominate the semiconductor equipment market and are placing technological barriers.

The research, recently published in Light: Science & Applicationsan international journal in the field of optics, supported by the Ministry of Science and ICT, the National Research Foundation of Korea, and the Samsung Science and Technology Foundation.




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