[Bio-inspired E-skin for artificial nerve system with monolithic 3D integrated neuromorphic device]
In recent, technology advances in neuromorphic is emerging. Neuromorphic is an electronic device that mimics the operation principle of a human brain. Since the conventional computing system has a separated component of the central processor unit and memory, it has a limitation on speed and the amount of storage. However, our brain can function as both computations and memorize in parallel. In addition to this, the system consisted of a sensor and neuromorphic device can be an artificial nerve. In this approach, we currently working on a ferroelectric Hf-Zr-O (HZO) based artificial nerve system. Ferroelectric is well-known material with an interesting behavior that can retain its electrical dipole characteristics even after removing the external field. Also, all ferroelectric material has pyroelectric and piezoelectric properties that respond to heat and pressure respectively. In comparison with lead-zirconium-titanium-oxide (PZT) which is widely used conventional ferroelectric material, HZO has no lead component and was able to use at nm scale. We hope that the approaches in our laboratory can be widely adopted in various industrial fields such as electronic skin for humanoid robots, health-care monitoring systems, and advanced prosthetic devices.
[Flexible/stretchable amorphous metal electrode for free-form factor next generation display]
Stretchable displays are the next-generation technology of flexible displays and are a goal that many researchers desire. The most likely candidate for stretchable display is separating device area for soft and rigid part. In this case, device doesn’t have to be stretched. All we need is stretchable electrode to connect between pixel which placed on rigid area. So that the metal interconnection is the key element. In our laboratory, we are working on stretchable electrode for these innovative device. In our approach, we adopted metallic glass as an electrode. The composition of an amorphous metal, which is well known for having no slip plane or slip direction, can be tailored for enhanced strength and a lower Young’s modulus under mechanical stress. Unlike crystalline metals, elastic amorphous metals can, in principle, be used as a flexible electrode in soft, wearable electronics. A metal with a lattice structure absorbs external energy, which causes structural deformations, while an amorphous metal does not absorb energy. Therefore, amorphous metals have excellent mechanical properties that can overcome the limitations of crystalline metals.
[Piezoresistive/electric strain gauge for reliable, low power consumption pressure sensor]
Piezoresistive or piezoelectric strain gauge are one of the very first products of MEMS technology, and are used in various fields like wearable devices, epidermal electronics and biomedical applications. Amongst various transduction principles, piezoresistive strain gauge mechanism is widely used for pressure sensor. Over a decade there has been tremendous improvement in the development of the design of piezoresistive pressure sensor starting with the invention of piezoresistance in the silicon to the recent piezoresistive pressure sensor materials. Because of its high sensitivity, high gauge factor, linear operation over a wide range of pressure, and many more advantages. Despite excellent property, resistance-based sensor has disadvantage such as hysteresis effect, temperature dependency and high-power consumption. Recently, Several groups has reported solution to overcome those limitation. Among them, we believe that our approaches could be one of solution.
[High-k dielectric gate insulator for Fe-TFT]
In recent years, high-performance TFT for high speed operation has been required to realize large-area, and high-resolution displays. In this regard, high-k gate insulator with relatively high thickness (~100 nm) is required for display backplane. But there are some bottleneck for realized formation of thick, high-k dielectrics with ALD process, which is long time process, and limitation of dielectric constants below εr~35. Therefore, a new approach is required for the formation of thick, high-k dielectrics.
In our lab, we are conducting research on improving leakage current and on current (ION) by using HfO2-based ferroelectric as the gate insulator of oxide TFTs. In addition, research on integrateing FeTFT devices is being conducted with various TFT characteristics measurements.