Professor Seung-Hyun Kim's current research interest is in the area of ferroelectric and piezoelectric materials and devices, MEMS and NEMS devices, oxide thermoelectrics, high-K passive and/or power capacitors, piezoelectric energy harvesting devices, and flexible electronics etc. His research is currently aimed at the development of advanced materials science and engineering for energy, bio and environment applications using low cost chemical solution processing coupled with flexible electronics.
Prof. Kim's research covers a broad spectrum of advanced piezoelectric and thermoelectric micro- and nanostructured materials and devices including their design, fabrication, characterization, as well as the fundamental aspects for optimized physical and chemical properties and long-term reliability. The research goal is designing a novel electronic devices and material systems with desired electro-physical properties and behavior for portable electronics, and energy conversion and harvesting devices. The efforts are directed towards understanding of piezoelectric and thermoelectric micro- and nanostructured thin and thick film fabrication and prediction of their functional physical properties. This understanding will be used to enhance the efficiency of technological processing and device performance. Prof. Kim's research will provide a broad understanding of physics of small scale electronic devices and experimental skills needed by academic society and industry together in their current and future work.
1. Design and development of piezoelectric thin film-based vibration MEMS energy harvesting devices
The objective of this research is to design, fabricate, and demonstrate unique piezoelectric tunable MEMS energy harvesting device. New challenges to achieve a robust tunable energy harvesting device will overcome the limitations of current state-of-the-art devices that harvest energy within a narrow vibration frequency range. Process development of integrating piezoelectric materials into MEMS will significantly advance the functionality of the device.
2. Environmentally friendly non-lead based piezoelectric thin film ; materials and energy harvesting devices
As described previously, piezoelectric materials are of importance due to their high energy-conversion efficiency, in particular from mechanical energy into electrical energy, and vice versa. New piezoelectric materials are urgently required to replace the lead zirconate titanate (PZT) system, for which the toxicity of the lead component is a major concern. The objective of this research is to develop thin film-based piezoelectric materials from the promising sodium potassium niobate tantalate (K,Na)(Nb,Ta)O3 system and polymer-based piezoelectric films. These materials will be used to develop a new class of low cost flexural mode electromechanical transducers, suitable for use in a wide range of energy harvesting applications as an alternative material for conventional PZT system.
3. Oxide-based thermoelectric energy conversion materials and devices
This research is for the development of a new route to functional polymer based substrates and flexible electronics. It provides a processing platform to dramatically expand the functionality and capability of the ubiquitous flexible substrate, and also explores the addition of new functionality to flexible electronics. The objective of this research is to develop the capability to integrate additional electronic functionality onto low cost substrates such as printed circuit boards (PCBs) and flexible substrates. The priority functionality selected for this research is the demonstration of integrated oxide thermoelectrics. Our approach is to use a thermoelectric unit to recover the dissipated heat, and convert it back into useful power on the multifunctional substrates.
4. Small scale electromechanical devices based on functional oxide thin films
The application in this area includes actuators, sensors, and transducers. The development of microelectronic devices requires highly functionality and sensitivity of materials. One of candidates for MEMS device, in particularly in sensing and actuating component, is perovskite type materials due to their large piezoelectric coefficient. However, the properties of thin film ferroelectrics are not well known compared to those of bulk due to many sensitive processing parameters, different stress condition, scaling effect and so on. Therefore, we developed a robust chemical solution synthesis process affording the isolation and control of physical and chemical parameters that strongly influence the ferroelectric and piezoelectric response. Research into materials with ferroelectric and piezoelectric properties is at the vanguard of materials science research, due to their ability to make electronic devices smaller and perform more effectively.
5. High-k passive device and power capacitor applications
Many perovskite-structured films, including (Ba,Sr)TiO3, Pb(Zr,Ti)O3, and the relaxor ferroelectric do not match the properties of bulk single crystals or ceramics. Instead, significant deviations from the bulk properties are observed as consequences of non-stoichiometry, defects, internal fields and reduction of extrinsic contributions to the permittivity, substantial in-plane strains. The consequence is that films frequently show peak permittivities that are rarely within an order of magnitude of a well-processed ceramic. Due to this limitation, there is an interest in developing alternative materials and/or processing for applications including capacitors for integrated circuit applications, integrated resistor-capacitor networks, and tunable circuit components. The rapid development of industry will require more integrated components for facilitating miniaturization of devices. Although many interesting results were obtained, there are still lots of issues to be approached in developing process and understanding physics of materials and devices. Scientific issues we are trying to pursue in this subject include the source of the dielectric relaxation and the tunability, the structure-property relation in dielectric breakdown, understanding the role of dopants in thin film dielectrics on microstructure and phase transition. We would like to explore engineering issues such as performance and compatibility with industrial requirements as well.
1. A Technology Platform to Enable Microsystems with a Wide Variety of Functions ($250,000) Source of support : NSF PFI-TT (2021 - current)
2. Brown- Xerox Collaboration on Innovative Lead-Free Piezoelectric Materials and Actuators ($110,000/year) (2014 - current)
3. A Xerox-Brown Collaborative Investigation of Environmentally Friendly Piezoelectric Materials for High-Strain Actuator Applications ($350,000) Source of support : NSF ECCS (GOALI) 3 years project (2014-2017)
