Jeonbuk National University (JBNU) Graduate School of Flexible Printed Electronics, Department of Flexible Printed Electronics Engineering doctoral candidate Yeongseok Song and master’s student Minyoung Seo (advisor Professor Taeuk Kim) received the KCS 2024 Excellent Poster Presentation Award at the recent 31st Korean Conference on Semiconductors.

Doctoral candidate Yeongseok Song induced photochemical crosslinking between the ferroelectric polymer P(VDF-TrFE) and a photocrosslinker (azide photocrosslinker, bis-FB-N3) by UV exposure. As a result, he successfully controlled the ferroelectricity of P(VDF-TrFE) thin films. After adding photocrosslinker at various concentrations, he used the films as a transistor insulating layer and evaluated their electrical characteristics.

In particular, he applied this approach to the increasingly prominent field of neuromorphic research and reported interesting results. Neuromorphic research is a field that mimics how external information received by humans is converted into electrical signals and transmitted to the brain through synapses.

Song demonstrated mimicry of signal loss during synaptic transmission and the reinforcement of synaptic transmission capability through repeated learning, earning high evaluation.

Meanwhile, master’s student Minyoung Seo conducted research to secure oxidation stability after fabricating high-efficiency electromagnetic shielding films using copper nanosheets. After producing two-dimensional single-crystalline copper nanosheet (Cu NSs) films, she fabricated high-shielding films exceeding 80 dB through a thermal annealing process. She then intentionally induced oxidation to form a Cu2O/Cu/Cu2O core–shell structure film to prevent degradation of shielding performance due to oxidation in the surrounding environment.

Electromagnetic shielding is considered commercially usable when it exceeds 30 dB. Analysis of electromagnetic shielding using two-dimensional single-crystalline copper nanosheet films shows an average shielding performance of approximately 80 dB, indicating high shielding efficiency. However, copper-based materials are vulnerable to oxidation from the surrounding environment, so securing stability is essential.

Therefore, by pre-oxidizing the copper nanosheet films to form a core–shell structure, Seo investigated the effects of oxidation annealing temperature and time to prevent unpredictable oxidation of the copper nanosheets over time and analyzed the electromagnetic shielding properties of the core–shell films.

As a result, the Cu@Cu2O core–shell films thermally treated at low temperature (100 °C) maintained a low sheet resistance of about 0.05 Ω/sq and a high shielding rate close to 80 dB. In contrast, films subjected to relatively high-temperature oxidation annealing at 175 °C for 5 hours showed an average sheet resistance of 2.12 Ω/sq and a high electromagnetic shielding efficiency of 50 dB, demonstrating conductivity while proving oxidation stability and presenting novel results using an oxide layer for oxidation prevention.

This research was supported by the National Research Foundation of Korea’s Collaborative Research Support Basic Research Laboratory Program and the NanoConnect Project.