POSTMODERN ALCHEMY
Utilizing palladium for addressing contact issues of buried oxide thin film transistors
TOKYO INSTITUTE OF TECHNOLOGY
IMAGE:
A NOVEL METHOD THAT EMPLOYS PALLADIUM TO INJECT HYDROGEN INTO THE DEEPLY BURIED OXIDE-METAL ELECTRODE CONTACTS OF AMORPHOUS OXIDE SEMICONDUCTORS (AOSS) STORAGE DEVICES, WHICH REDUCES CONTACT RESISTANCE, HAS BEEN DEVELOPED BY SCIENTISTS AT TOKYO TECH. THIS INNOVATIVE METHOD PRESENTS A VALUABLE SOLUTION FOR ADDRESSING THE CONTACT ISSUES OF AOSS, PAVING THE WAY FOR THEIR APPLICATION IN NEXT-GENERATION STORAGE DEVICES AND DISPLAYS.
view moreCREDIT: ASSISTANT PROFESSOR MASATAKE TSUJI AND HONORARY PROFESSOR HIDEO HOSONO
A novel method that employs palladium to inject hydrogen into the deeply buried oxide-metal electrode contacts of amorphous oxide semiconductors (AOSs) storage devices, which reduces contact resistance, has been developed by scientists at Tokyo Tech. This innovative method presents a valuable solution for addressing the contact issues of AOSs, paving the way for their application in next-generation storage devices and displays.
Thin film transistors (TFTs) based on amorphous oxide semiconductors (AOSs) have garnered considerable attention for applications in next-generation storage devices such as capacitor-less dynamic-random access memory (DRAM) and high-density DRAM technologies. Such storage devices employ complex architectures with TFTs stacked vertically to achieve high storage densities. Despite their potential, AOS TFTs suffer from contact issues between AOSs and electrodes resulting in excessively high contact resistance, thereby degrading charge carrier mobility, and increasing power consumption. Moreover, vertically stacked architectures further exacerbate these issues.
Many methods have been proposed to address these issues, including the deposition of a highly conductive oxide interlayer between the contacts, forming oxygen vacancies on the AOS contact surface and surface treatment with plasma. Hydrogen plays a key role in these methods, as it, when dissociated into atomic hydrogen and injected into the AOS-electrode contact area, generates charge carriers, thereby reducing contact resistance. However, these methods are energy-intensive or require multiple steps and while they effectively address the high-contact resistance of the exposed upper surface of the semiconductors, they are impractical for buried contacts within the complex nanoscale architectures of storage devices.
To address this issue, a team of researchers (Assistant Professor Masatake Tsuji, doctoral student Yuhao Shi, and Honorary Professor Hideo Hosono) from the MDX Research Center for Element Strategy at the International Research Frontiers Initiative at Tokyo Institute of Technology has now developed a novel hydrogen injection method. Their findings were published online in the journal ACS Nano on 22 March 2024.
In this innovative method, an electrode made up of a suitable metal, which can catalyze the dissociation of hydrogen at low temperatures, is used to transport the atomic hydrogen to the AOS-electrode interface, resulting in a highly conductive oxide layer. Choosing suitable electrode material is therefore key for implementing this strategy. Dr. Tsuji explains, “This method requires a metal that has a high hydrogen diffusion rate and hydrogen solubility to shorten post-treatment times and reduce processing temperatures. In this study, we utilized palladium (Pd) as it fulfils the dual role of catalyzing hydrogen dissociation and transport, making it the most suitable material for hydrogen injection in AOS TFTs at low temperatures, even at deep internal contacts.”
To demonstrate the effectiveness of this method, the team fabricated amorphous indium gallium oxide (a-IGZO) TFTs with Pd thin film electrodes as hydrogen transport pathways. The TFTs were heat-treated in a 5% hydrogen atmosphere at a temperature of 150 0C for 10 minutes. This resulted in the transport of atomic hydrogen by Pd to the a-IGZO-Pd interface, triggering a reaction between oxygen and hydrogen, forming a highly conductive interfacial layer.
Testing revealed that due to the conductive layer, the contact resistance of the TFTs was reduced by two orders of magnitude. Moreover, the charge carrier mobility increased from 3.2 cm2V–1s–1 to nearly 20 cm2V–1s–1, representing a substantial improvement. “Our method enables hydrogen to rapidly reach the oxide-Pd interface even in the device interior, up to a depth of 100 μm. This makes it highly suitable for addressing the contact issues of AOS-based storage devices” remarks Dr. Tsuji. Additionally, this method preserved the stability of the TFTs, suggesting no side effects due to hydrogen diffusion in the electrodes.
Emphasizing the potential of the study, Dr. Tsuji concludes: “This approach is specifically tailored for complex device architectures, representing a valuable solution for the application of AOS in next-generation memory devices and displays.” IGZO-TFT is now a de facto standard to drive the pixels of flat panel displays. The present technology will put forward its application to memory.
JOURNAL
ACS Nano
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Approach to Low Contact Resistance Formation on Buried Interface in Oxide Thin-Film Transistors: Utilization of Palladium-Mediated Hydrogen Pathway
Good as gold - improving infectious disease testing with gold nanoparticles
ADVANCED INSTITUTE FOR MATERIALS RESEARCH (AIMR), TOHOKU UNIVERSITY
IMAGE:
GNDP PARTICLES
view moreCREDIT: HIROSHI YABU
By harnessing the power of composite polymer particles adorned with gold nanoparticles, a group of researchers have delivered a more accurate means of testing for infectious diseases.
Details of their research was published in the journal Langmuir.
The COVID-19 pandemic reinforced the need for fast and reliable infectious disease testing in large numbers. Most testing done today involves antigen-antibody reactions. Fluorescence, absorptions, or color particle probes are attached to antibodies. When the antibodies stick to the virus, these probes visualize the virus's presence. In particular, the use of color nanoparticles is renowned for its excellent visuality, along with its simplicity to implement, with little scientific equipment needed to perform lateral flow tests.
Gold color nanoparticles (AU-NP), with their high chemical stability and unique plasmon absorption, are widely employed as probes in immunoassay tests. They exhibit extreme versatility, with their colors fluctuating according to their size and shape. Additionally, their surface can be modified by using thiol compounds.
Conventional tests that use AU-NP often have to amplify AU-NP's optical density, so that scientists can easily measure the strength of the signal produced by the interaction between antibodies and the target substance.
Adding more gold nanoparticles is one means to do this. But because nanoparticles are tiny, it requires a large quantity of them to achieve a strong enough signal for accurate detection.
To overcome this, the researchers proposed a new method called self-organized precipitation (SORP). SORP works by dissolving polymers into organic solvents before adding a liquid that doesn't dissolve the polymers well, like water. After the original organic solvent is removed by evaporation, polymers assemble together, forming tiny particles.
"Using gold nanoparticle decorated polymers (GDNP) assembled by SORP, we set out to see how effective they would be in detecting the influenza virus, and whether they offered improved sensitivity in detecting antigen-antibody reactions," states Hiroshi Yabu, co-author of the paper and professor at Tohoku University's Advanced Institute for Materials Research (AIMR). "And it did. Our method resulted in a higher optical density than original AU-NPs and GNDPs decorated with smaller AU-NPs."
Yabu and his colleagues' findings reinforce that GNDP particles have broad utility, extending beyond laboratory settings to real-world diagnostic scenarios.
About the World Premier International Research Center Initiative (WPI)
The WPI program was launched in 2007 by Japan's Ministry of Education, Culture, Sports, Science and Technology (MEXT) to foster globally visible research centers boasting the highest standards and outstanding research environments. Numbering more than a dozen and operating at institutions throughout the country, these centers are given a high degree of autonomy, allowing them to engage in innovative modes of management and research. The program is administered by the Japan Society for the Promotion of Science (JSPS).
See the latest research news from the centers at the WPI News Portal: https://www.eurekalert.org/newsportal/WPI
Main WPI program site: www.jsps.go.jp/english/e-toplevel
Advanced Institute for Materials Research (AIMR), Tohoku University
Establish a World-Leading Research Center for Materials Science:
AIMR aims to contribute to society through its actions as a world-leading research center for materials science and push the boundaries of research frontiers. To this end, the institute gathers excellent researchers in the fields of physics, chemistry, materials science, engineering, and mathematics and provides a world-class research environment.
AIMR site: https://www.wpi-aimr.tohoku.ac.jp/en/
An immunoassay system that uses GNDP particles with antibodies
.
A scan electron micrograph of GNDP particles.
CREDIT
Hiroshi Yabu
JOURNAL
Langmuir
ARTICLE TITLE
Gold Nanoparticle-Decorated Polymer (GNDP) Particles for High-Optical-Density Immunoassay Probes
No comments:
Post a Comment