Yang-kyu Choi - Academia.edu (original) (raw)

Papers by Yang-kyu Choi

Research paper thumbnail of Analyses of unpredictable properties of a wind-driven triboelectric random number generator

Scientific Reports

Wind-driven triboelectric nanogenerators (W-TENGs) are a promising candidate for an energy harves... more Wind-driven triboelectric nanogenerators (W-TENGs) are a promising candidate for an energy harvester because wind itself possesses unexhausted, ubiquitous, and clean properties. W-TENG has also been used as a random number generator (RNG) due to the inherent chaotic properties of wind that is also an entropy source. Thus, a W-TENG which simultaneously generates both power and true random numbers with a two-in-one structure, is a wind-driven RNG (W-RNG) like the Janus. However, a root cause of W-RNG unpredictability has not been elucidated. In this work, the unpredictability, which is essential and critical for an RNG, is statistically and mathematically analyzed by auto-correlation, cross-correlation, joint entropy, and mutual information. Even though the overall shape of the total output analog signals from the W-RNG looks like a sinusoidal wave that is not obviously unpredictable, discretized digital signals from the continuous analog output become unpredictable. Furthermore, part...

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Research paper thumbnail of Geometric effects of nanocrystals in nonvolatile memory using block copolymer nanotemplate

Solid-state Electronics, Jun 1, 2009

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Research paper thumbnail of Designed Workfunction Engineering of Double-Stacked Metal Nanocrystals for Nonvolatile Memory Application

IEEE Transactions on Electron Devices, Mar 1, 2009

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Research paper thumbnail of Bio-Inspired Complementary Photoconductor by Porphyrin-Coated Silicon Nanowires

Advanced Materials, Jul 22, 2011

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Research paper thumbnail of Methods for fabrication of positional and compositionally controlled nanostructures on substrate

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Jul 16, 2013

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Research paper thumbnail of Low-voltage pentacene OTFTs with high-K gate dielectric and its application to AMOLED

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Research paper thumbnail of The gate injection-based field-effect synapse transistor with linear conductance update for online training

Nature Communications

Neuromorphic computing, an alternative for von Neumann architecture, requires synapse devices whe... more Neuromorphic computing, an alternative for von Neumann architecture, requires synapse devices where the data can be stored and computed in the same place. The three-terminal synapse device is attractive for neuromorphic computing due to its high stability and controllability. However, high nonlinearity on weight update, low dynamic range, and incompatibility with conventional CMOS systems have been reported as obstacles for large-scale crossbar arrays. Here, we propose the CMOS compatible gate injection-based field-effect transistor employing thermionic emission to enhance the linear conductance update. The dependence of the linearity on the conduction mechanism is examined by inserting an interfacial layer in the gate stack. To demonstrate the conduction mechanism, the gate current measurement is conducted under varying temperatures. The device based on thermionic emission achieves superior synaptic characteristics, leading to high performance on the artificial neural network simul...

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Research paper thumbnail of Triboelectrification driven fin-fact (flip-flop actuated channel transistor) for security application

2017 IEEE 30th International Conference on Micro Electro Mechanical Systems (MEMS), 2017

A silicon-nanowire (Si-NW) switch with triboelectricity is proposed for the first time for future... more A silicon-nanowire (Si-NW) switch with triboelectricity is proposed for the first time for future electronics with enhanced security application. The dimensions of the mechanical NW switch are width 50 nm and thickness 100 nm with a 50-nm-thick airgap, fabricated with aid of CMOS fabrication technology. By hand-touch on gate pad, the fabricated switch can turn-on as well as turn-off by destruction of fin-channel which comes from electrostatic force by triboelectricity. This technology is expected as a security-enhanced future electronics.

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Research paper thumbnail of Low-Power True Random Number Generator Based on Randomly Distributed Carbon Nanotube Networks

IEEE Access, 2021

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Research paper thumbnail of Si–MoS2 Vertical Heterojunction for a Photodetector with High Responsivity and Low Noise Equivalent Power

ACS Applied Materials & Interfaces, 2019

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Research paper thumbnail of Performance-enhanced triboelectric nanogenerator using the glass transition of polystyrene

Nano Energy, 2016

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Research paper thumbnail of Size Reduction Lithography and Nanoimprint Lithography for the Fabrication of Platinum Nanocatalysts: A Reaction Study

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Research paper thumbnail of Itinerant Helimagnetic Single-Crystalline MnSi Nanowires

ACS Nano, 2010

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Research paper thumbnail of Reconfigurable Yagi-Uda antenna based on a silicon reflector with a solid-state plasma

Scientific reports, Jan 8, 2017

This paper describes the fabrication and characterization of a reconfigurable Yagi-Uda antenna ba... more This paper describes the fabrication and characterization of a reconfigurable Yagi-Uda antenna based on a silicon reflector with a solid-state plasma. The silicon reflector, composed of serially connected p-i-n diodes, forms a highly dense solid-state plasma by injecting electrons and holes into the intrinsic region. When this plasma silicon reflector is turned on, the front-realized gain of the antenna increases by more than 2 dBi beyond 5.3 GHz. To achieve the large gain increment, the structure of the antenna is carefully designed with the aid of semiconductor device simulation and antenna simulation. By using an aluminum nitride (AlN) substrate with high thermal conductivity, self-heating effects from the high forward current in the p-i-n diode are efficiently suppressed. By comparing the antenna simulation data and the measurement data, we estimated the conductivity of the plasma silicon reflector in the on-state to be between 104 and 105 S/m. With these figures, silicon materi...

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Research paper thumbnail of On-Chip Curing by Microwave for Long Term Usage of Electronic Devices in Harsh Environments

Scientific Reports, 2018

Microwave-induced thermal curing is demonstrated to improve the reliability and to prolong the li... more Microwave-induced thermal curing is demonstrated to improve the reliability and to prolong the lifetime of chips containing nanoscale electron devices. A film containing graphite powder with high microwave absorbing efficiency was fabricated at low cost. The film is flexible, bendable, foldable, and attachable to a chip. A commercial off-the-shelf chip and a representative 3-dimensional (3D) metal-oxide-semiconductor field-effect transistor (MOSFET), known as FinFET, were utilized to verify the curing behaviors of the microwave-induced heat treatment. The heat effectively cured not only total ionizing dose (TID) damage from the external environment, but also internal electrical stress such as hot-carrier injection (HCI), which are representative sources of damages in MOSFET insulators. Then, the characteristics of the pre- and post-curing electron devices are investigated using electrical measurements and numerical simulations.

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Research paper thumbnail of Resistive-Memory Embedded Unified RAM (R-URAM)

IEEE Transactions on Electron Devices, 2009

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Research paper thumbnail of A Compact Model of Quantum Electron Density at the Subthreshold Region for Double-Gate Junctionless Transistors

IEEE Transactions on Electron Devices, 2012

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Research paper thumbnail of Designed Workfunction Engineering of Double-Stacked Metal Nanocrystals for Nonvolatile Memory Application

IEEE Transactions on Electron Devices, 2009

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Research paper thumbnail of A Universal Core Model for Multiple-Gate Field-Effect Transistors. Part I: Charge Model

IEEE Transactions on Electron Devices, 2013

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Research paper thumbnail of Analysis of Trapped Charges in Dopant-Segregated Schottky Barrier-Embedded FinFET SONOS Devices

IEEE Electron Device Letters, 2009

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Research paper thumbnail of Analyses of unpredictable properties of a wind-driven triboelectric random number generator

Scientific Reports

Wind-driven triboelectric nanogenerators (W-TENGs) are a promising candidate for an energy harves... more Wind-driven triboelectric nanogenerators (W-TENGs) are a promising candidate for an energy harvester because wind itself possesses unexhausted, ubiquitous, and clean properties. W-TENG has also been used as a random number generator (RNG) due to the inherent chaotic properties of wind that is also an entropy source. Thus, a W-TENG which simultaneously generates both power and true random numbers with a two-in-one structure, is a wind-driven RNG (W-RNG) like the Janus. However, a root cause of W-RNG unpredictability has not been elucidated. In this work, the unpredictability, which is essential and critical for an RNG, is statistically and mathematically analyzed by auto-correlation, cross-correlation, joint entropy, and mutual information. Even though the overall shape of the total output analog signals from the W-RNG looks like a sinusoidal wave that is not obviously unpredictable, discretized digital signals from the continuous analog output become unpredictable. Furthermore, part...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Geometric effects of nanocrystals in nonvolatile memory using block copolymer nanotemplate

Solid-state Electronics, Jun 1, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Designed Workfunction Engineering of Double-Stacked Metal Nanocrystals for Nonvolatile Memory Application

IEEE Transactions on Electron Devices, Mar 1, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Bio-Inspired Complementary Photoconductor by Porphyrin-Coated Silicon Nanowires

Advanced Materials, Jul 22, 2011

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Methods for fabrication of positional and compositionally controlled nanostructures on substrate

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Jul 16, 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Low-voltage pentacene OTFTs with high-K gate dielectric and its application to AMOLED

Bookmarks Related papers MentionsView impact

Research paper thumbnail of The gate injection-based field-effect synapse transistor with linear conductance update for online training

Nature Communications

Neuromorphic computing, an alternative for von Neumann architecture, requires synapse devices whe... more Neuromorphic computing, an alternative for von Neumann architecture, requires synapse devices where the data can be stored and computed in the same place. The three-terminal synapse device is attractive for neuromorphic computing due to its high stability and controllability. However, high nonlinearity on weight update, low dynamic range, and incompatibility with conventional CMOS systems have been reported as obstacles for large-scale crossbar arrays. Here, we propose the CMOS compatible gate injection-based field-effect transistor employing thermionic emission to enhance the linear conductance update. The dependence of the linearity on the conduction mechanism is examined by inserting an interfacial layer in the gate stack. To demonstrate the conduction mechanism, the gate current measurement is conducted under varying temperatures. The device based on thermionic emission achieves superior synaptic characteristics, leading to high performance on the artificial neural network simul...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Triboelectrification driven fin-fact (flip-flop actuated channel transistor) for security application

2017 IEEE 30th International Conference on Micro Electro Mechanical Systems (MEMS), 2017

A silicon-nanowire (Si-NW) switch with triboelectricity is proposed for the first time for future... more A silicon-nanowire (Si-NW) switch with triboelectricity is proposed for the first time for future electronics with enhanced security application. The dimensions of the mechanical NW switch are width 50 nm and thickness 100 nm with a 50-nm-thick airgap, fabricated with aid of CMOS fabrication technology. By hand-touch on gate pad, the fabricated switch can turn-on as well as turn-off by destruction of fin-channel which comes from electrostatic force by triboelectricity. This technology is expected as a security-enhanced future electronics.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Low-Power True Random Number Generator Based on Randomly Distributed Carbon Nanotube Networks

IEEE Access, 2021

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Si–MoS2 Vertical Heterojunction for a Photodetector with High Responsivity and Low Noise Equivalent Power

ACS Applied Materials & Interfaces, 2019

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Performance-enhanced triboelectric nanogenerator using the glass transition of polystyrene

Nano Energy, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Size Reduction Lithography and Nanoimprint Lithography for the Fabrication of Platinum Nanocatalysts: A Reaction Study

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Itinerant Helimagnetic Single-Crystalline MnSi Nanowires

ACS Nano, 2010

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Reconfigurable Yagi-Uda antenna based on a silicon reflector with a solid-state plasma

Scientific reports, Jan 8, 2017

This paper describes the fabrication and characterization of a reconfigurable Yagi-Uda antenna ba... more This paper describes the fabrication and characterization of a reconfigurable Yagi-Uda antenna based on a silicon reflector with a solid-state plasma. The silicon reflector, composed of serially connected p-i-n diodes, forms a highly dense solid-state plasma by injecting electrons and holes into the intrinsic region. When this plasma silicon reflector is turned on, the front-realized gain of the antenna increases by more than 2 dBi beyond 5.3 GHz. To achieve the large gain increment, the structure of the antenna is carefully designed with the aid of semiconductor device simulation and antenna simulation. By using an aluminum nitride (AlN) substrate with high thermal conductivity, self-heating effects from the high forward current in the p-i-n diode are efficiently suppressed. By comparing the antenna simulation data and the measurement data, we estimated the conductivity of the plasma silicon reflector in the on-state to be between 104 and 105 S/m. With these figures, silicon materi...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of On-Chip Curing by Microwave for Long Term Usage of Electronic Devices in Harsh Environments

Scientific Reports, 2018

Microwave-induced thermal curing is demonstrated to improve the reliability and to prolong the li... more Microwave-induced thermal curing is demonstrated to improve the reliability and to prolong the lifetime of chips containing nanoscale electron devices. A film containing graphite powder with high microwave absorbing efficiency was fabricated at low cost. The film is flexible, bendable, foldable, and attachable to a chip. A commercial off-the-shelf chip and a representative 3-dimensional (3D) metal-oxide-semiconductor field-effect transistor (MOSFET), known as FinFET, were utilized to verify the curing behaviors of the microwave-induced heat treatment. The heat effectively cured not only total ionizing dose (TID) damage from the external environment, but also internal electrical stress such as hot-carrier injection (HCI), which are representative sources of damages in MOSFET insulators. Then, the characteristics of the pre- and post-curing electron devices are investigated using electrical measurements and numerical simulations.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Resistive-Memory Embedded Unified RAM (R-URAM)

IEEE Transactions on Electron Devices, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Compact Model of Quantum Electron Density at the Subthreshold Region for Double-Gate Junctionless Transistors

IEEE Transactions on Electron Devices, 2012

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Designed Workfunction Engineering of Double-Stacked Metal Nanocrystals for Nonvolatile Memory Application

IEEE Transactions on Electron Devices, 2009

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A Universal Core Model for Multiple-Gate Field-Effect Transistors. Part I: Charge Model

IEEE Transactions on Electron Devices, 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Analysis of Trapped Charges in Dopant-Segregated Schottky Barrier-Embedded FinFET SONOS Devices

IEEE Electron Device Letters, 2009

Bookmarks Related papers MentionsView impact