< The research team. From left: Dr. Hyeonwoo Lee (first author) and Professor Hee Cheul Choi of the Department of Chemistry at POSTECH, Professor Ji Hoon Park of Pukyong National University, and Professor Sarah S. Park of the Department of Chemistry at KAIST >
Smartphones and computers process information by switching the current that flows inside semiconductors on and off. The gate electrode delivers the signal that controls this switching. Until now, gate electrodes have typically been made from metals whose electronic properties are fixed. A KAIST-led joint research team has now built working semiconductor electrodes from a new material that combines metals and organic molecules. The study provides a basis for designing electrodes to meet the requirements of different semiconductors. It is also expected to support the development of low-power semiconductors that operate at lower voltages.
KAIST (President Choongsik Bae) announced on October 26 that a research team led by Professor Sarah S. Park from the Department of Chemistry, in collaboration with researchers from Pukyong National University, POSTECH, and Yonsei University, has processed electrically conductive metal–organic frameworks (MOFs) into thin, precisely patterned films and used them as gate electrodes in semiconductor devices.
The team applied the electrodes to field-effect transistors (FETs). A transistor is a basic semiconductor component that switches current on and off or regulates its flow in response to an electrical signal. Applying a voltage to the gate electrode controls the flow of current through the transistor.
Gate electrodes are currently made mainly from metals, which conduct electricity well. However, each metal has fixed electronic properties. This makes it difficult to adapt the electrode to the requirements of a given semiconductor.
Conductive MOFs are materials in which metal ions and organic molecules are linked in a regular structure. Changing the combination of metals and organic molecules alters the material's electronic properties. One of these properties is the work function, which is the energy an electron needs to escape from the surface of a material. The work function affects the voltage at which a semiconductor turns on. Varying the composition of a MOF could therefore help researchers design electrodes that set the voltage at which a semiconductor turns on. The Cu₃(C₆O₆)₂ film used in this study has a work function of 4.51 eV. This value lies between those of typical n-type and p-type semiconductors, so the same film can control both types of channels.
To be used as an electrode, a MOF must first be formed into a thin film of uniform thickness. It must then be patterned precisely so that only the required areas remain. The material must also be protected from damage during processing, because damage can reduce its ability to conduct electricity.
The researchers first produced a thin, uniform MOF film by reacting precursors in the gas phase, a method known as chemical vapor deposition (CVD). They then used light to define a fine pattern and removed the unwanted areas to form the electrodes. These two semiconductor processing steps are known as photolithography and etching, respectively.
To reduce damage during processing, the team used two etchants in sequence. Ammonium persulfate (APS), which reacts relatively slowly, was used to form the initial pattern. A fast-reacting chromium (Cr) etchant was then applied briefly to remove the remaining residue. After processing, the structure, chemical state, and electrical conductivity of the material were largely preserved.
The team applied the electrodes to three different semiconductors: n-type molybdenum disulfide (MoS₂), p-type molybdenum ditelluride (MoTe₂), and the oxide semiconductor indium gallium zinc oxide (IGZO). The electrodes switched the current on and off in all three.
In the MoS₂ device, the team fabricated a MOF gate and a conventional platinum (Pt) gate on the same channel, allowing a direct side-by-side comparison. The two gates showed similar threshold voltages, the voltage at which current begins to flow. They also showed similar field-effect mobility, a measure of how easily charges move through the channel. These results confirmed that an electrode made from the new material can control current as effectively as a conventional metal electrode.
The team also tested whether the electrodes could be fabricated at scale. They placed 23 IGZO transistors on a single substrate and formed the gate electrodes for all of them in a single patterning step. All 23 transistors functioned properly.
In stability tests, an IGZO transistor maintained stable performance after 400 consecutive gate-voltage cycles. A MoS₂ transistor also retained the operating characteristics of its MOF gate after about one year of storage in ambient air.
The study shows that a material combining metals and organic molecules can work as an electrode that switches current on and off in actual semiconductor devices. If the composition of the material is adjusted so that devices operate at lower voltages, this approach could help reduce power consumption. The researchers plan to test whether this approach can lower power consumption in practice. They also plan to examine whether the electrodes can be made smaller and more precise, and be produced uniformly over large areas, as well as assess process reproducibility and long-term reliability.
< Figure 1. Schematic illustration of micropatterned two-dimensional (2D) conductive MOF thin films integrated as gate electrodes in various field-effect transistors and a transistor array >
"We confirmed that the new material not only conducts electricity well, but also works as an electrode that switches actual semiconductor devices on and off," said Professor Sarah S. Park. She added that the team plans to develop the technology further, so that instead of choosing from existing metals, researchers can design electrodes with the properties each semiconductor requires.
Dr. Hyeonwoo Lee from POSTECH served as first author of the study. Professor Sarah S. Park from the KAIST Department of Chemistry, Professor Hee Cheul Choi from the POSTECH Department of Chemistry, and Professor Ji Hoon Park from Pukyong National University served as corresponding authors. The findings were published in Advanced Materials, an international journal in the field of materials science, on September 15.
Paper title: Lithography-Compatible Conductive Metal–Organic Frameworks for Scalable Electronics, DOI: 10.1002/adma.75003
Authors: Dr. Hyeonwoo Lee (POSTECH, first author), Dr. Han Joo Lee (Yonsei University, second author), Dr. Myeonggeun Choe (POSTECH, third author), Professor Hee Cheul Choi (POSTECH, corresponding author), Professor Ji Hoon Park (Pukyong National University, corresponding author), and Professor Sarah S. Park (KAIST, corresponding author)
This research was supported by grants from the National Research Foundation of Korea (NRF), funded by the Korean government (RS-2024-00451160, RS-2026-25582850, RS-2025-25431788, and RS-2024-00347241).
