Supervisors: Prof. JIHOON KIM Address: Sujaykumar V
PhD Student
Division of Advanced Materials Engineering
Kongju National University
Chungnam, 331-717, Korea.
Abstract In this paper, the effects of hydrogen (H 2 ) plasma treatment on the molybdenum (Mo)-do... more Abstract In this paper, the effects of hydrogen (H 2 ) plasma treatment on the molybdenum (Mo)-doped indium oxide (InO) thin film that was formed on glass using the polymer-assisted deposition (PAD) process were investigated. The sheet resistance for the sample treated at the ICP power of 15 W was quenched to 167 Ω/sq. from the 680 Ω/sq. for the as-deposited sample. Compared with the as-deposited sample, both the mobility and the concentration of the sample treated at the 15 W ICP power were also increased simultaneously, resulting in an increased conductivity. From these results, it was concluded that the H 2 plasma treatment is an efficient method for the enhancement of the electrical property, as well as to remove nano-sized cracks on the surface of the PAD-Mo-doped InO without a deterioration the optical transmittance.
In this letter, we propose a method to enhance resistive switching properties in SiCN-based condu... more In this letter, we propose a method to enhance resistive switching properties in SiCN-based conductive-bridge resistive switching memory (CBRAM) devices by inserting a thin Al2O3 layer between the SiCN resistive switching layer and the TiN bottom electrode. Compared with the Cu/Ta/SiCN/TiN single-layer device, the Cu/Ta/SiCN/Al2O3/TiN double layer device exhibits uniform resistive switching, long stable endurance cycles (>1.6 × 104), and stable retention (104 s) at 125 °C. These substantial improvements in the resistive switching properties are attributed to the location of the formation and rupture of conductive filaments that can be precisely controlled in the device after introducing the Al2O3 layer. Moreover, a multilevel resistive switching characteristic is observed in the Cu/Ta/SiCN/Al2O3/TiN double layer CBRAM device. The distinct six-level resistance states are obtained in double layer devices by varying the compliance current. The highly stable retention characteristics...
2019 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS), 2019
Flexible sensors have been developed over the decades due to their potential in various applicati... more Flexible sensors have been developed over the decades due to their potential in various applications. However, recent developments in interactive user interface, healthcare device, tactile sensor, and artificial electronic skin require device with multifunctional properties such as various detection ability and good mobility. Research on such devices are still under developing. In this report, we demonstrate a flexible multimodal (pressure, temperature) sensor using embedded indium tin oxide (ITO). For the pressure sensor, the embedded ITO was adopted as a conductive layer with triple layer pyramid structure. We utilized water-soluble sacrificial layers for eco-friendly method. The triple layer pyramid-structured pressure sensor shows excellent sensitivity in dynamic range of 100 Pa to 10 kPa with high reliability of 105 cycles. For the temperature sensor, we used comb like structure with ITO. It shows negative temperature coefficient on resistance with good linearity. Due to the vertically stacked structure, we were able to ignore interface effect. This work present that the opportunity of transparent electrode towards flexible multimodal sensors that can beemployed for various flexible applications.
Sensory information processing in robot skins currently rely on a centralized approach where sign... more Sensory information processing in robot skins currently rely on a centralized approach where signal transduction (on the body) is separated from centralized computation and decision-making, requiring the transfer of large amounts of data from periphery to central processors, at the cost of wiring, latency, fault tolerance and robustness. We envision a decentralized approach where intelligence is embedded in the sensing nodes, using a unique neuromorphic methodology to extract relevant information in robotic skins. Here we specifically address pain perception and the association of nociception with tactile perception to trigger the escape reflex in a sensorized robotic arm. The proposed system comprises self-healable materials and memtransistors as enabling technologies for the implementation of neuromorphic nociceptors, spiking local associative learning and communication. Configuring memtransistors as gated-threshold and -memristive switches, the demonstrated system features in-mem...
Flexible electronic circuits when integrated with different sensors to mimic the human skin can b... more Flexible electronic circuits when integrated with different sensors to mimic the human skin can be referred to as E-skin. E-skin can be used for the monitoring of human health, human-machine interface and humanoids. To mimic skin, a variety of sensors have been studied, including those sensitive to different pressures, temperatures, flows, and strain and humidity levels. Herein, we demonstrate a multifunctional sensor encompassed in a single pixel which is inspired by human skin. The proposed device contains a pressure sensor, a temperature sensor and a piezoresistive hair-type flow sensor, the latter of which is fabricated using mixture of carbon nanotubes and polydimethylsiloxane piezoresistive materials. Additionally, the temperature sensor is printed by means of inkjet printing with MWCNT and Ag nanoparticle ink. Finally, all three sensors are vertically stacked to mimic the human skin, demonstrating interference-free characteristics. This study provides a new and cost-effective approach for multimodal sensor applications.
Rhynchostylis retusa-like α-NiMoO4 was synthesized using a simple, single-step, and cost-effectiv... more Rhynchostylis retusa-like α-NiMoO4 was synthesized using a simple, single-step, and cost-effective wet-chemistry approach, and it exhibited the superior electrochemical properties.
Resistive switching devices, which are dominated by metal cation based conductive filament format... more Resistive switching devices, which are dominated by metal cation based conductive filament formation/rupture, are called programmable memory, or conductive bridge random access memory (CBRAM), and are widely expected to replace existing memory devices. In this letter, CuBi alloy was used as an active electrode to control the over-diffusion of Cu ions into the solid electrolyte of a CBRAM. In addition, resistive switching performance was improved by inserting lutetium and dysprosium metals, which acted as a buffer layer at the interface of the active electrode (CuBi) and the dielectric layer (Al2O3). When optimized, the Cu0.55Bi0.45/Lu(Dy)/Al2O3/Pt showed excellent resistive switching performance. This improvement can be explained by the high controllability of Cu in Cu-Bi electrode with the Lu (Dy) buffer layer. The formation of intermediate oxide buffer layers at the CuBi/Lu(Dy) interface was analysed using XPS. Moreover, conductive-atomic force microscope measurements helped to de...
Transparent and conducting flexible electrodes have been successfully developed over the last few... more Transparent and conducting flexible electrodes have been successfully developed over the last few decades due to their potential applications in optoelectronics. However, recent developments in smart electronics, such as a direct human-machine interface, health-monitoring devices, motion-tracking sensors, and artificially electronic skin also require materials with multifunctional properties such as transparency, flexibility and good portability. In such devices, there remains room to develop transparent and flexible devices such as pressure sensors or temperature sensors. Herein, we demonstrate a fully transparent and flexible bimodal sensor using indium tin oxide (ITO), which is embedded in a plastic substrate. For the proposed pressure sensor, the embedded ITO is detached from its Mayan-pyramid-structured silicon mold by an environmentally friendly method which utilizes water-soluble sacrificial layers. The Mayan-pyramid-based pressure sensor is capable of six different pressure ...
The conductive-bridge random access memory (CBRAM) has become one of the most suitable candidates... more The conductive-bridge random access memory (CBRAM) has become one of the most suitable candidates for non-volatile memory in next-generation information and communication technology. The resistive switching (RS) mechanism of CBRAM depends on the formation/annihilation of the conductive filament (CF) between the active metal electrode and the inert electrode. However, excessive ion injection from the active electrode into the solid electrolyte reduces the uniformity and reliability of the RS devices. To solve this problem, we investigated the RS characteristics of a CuSn alloy active electrode with different compositions of Cux-Sn1-x (0.13 < X < 0.55). The RS characteristics were further improved by inserting a dysprosium (Dy) or lutetium (Lu) buffer layer at the interface of Cux-Sn1-x/Al2O3. Electrical analysis of the optimal Cu0.4-Sn0.73/Lu-based CBRAM exhibited stable RS behavior with low operation voltage (SET: 0.7 V and RESET: -0.3 V), a high on state/off state resistive ratio (106), AC cyclic endurance (>104), and stable retention (85 °C/10 years). To achieve these performance parameters, CFs were locally formed inside the electrolyte using a modified CuSn active electrode, and the amount of Cu-ion injection was reduced by inserting the Dy or Lu buffer layer between the CuSn active electrode and the electrolyte. In particular, conductive-atomic force microscopy results at the Dy or Lu/Al2O3 interface directly showed and defined the diameter of the CF.
The next-generation electronic society is dependent on the performance of nonvolatile memory devi... more The next-generation electronic society is dependent on the performance of nonvolatile memory devices, which has been continuously improving. In the last few years, many memory devices have been introduced. However, atomic switches are considered to be a simple and reliable basis for next-generation nonvolatile devices. In general, atomic switch-based resistive switching is controlled by electrochemical metallization. However, excess ion injection from the entire area of the active electrode into the switching layer causes device nonuniformity and degradation of reliability. Here, we propose the fabrication of a high-performance atomic switch based on Cu x-Se1- x by inserting lanthanide (Ln) metal buffer layers such as neodymium (Nd), samarium (Sm), dysprosium (Dy), or lutetium (Lu) between the active metal layer and the electrolyte. Current-atomic force microscopy results confirm that Cu ions penetrate through the Ln-buffer layer and form thin conductive filaments inside the switching layer. Compared with the Pt/Cu x-Se1- x/Al2O3/Pt device, the optimized Pt/Cu x-Se1- x/Ln/Al2O3/Pt devices show improvement in the on/off resistance ratio (102-107), retention (10 years/85 °C), endurance (∼10 000 cycles), and uniform resistance state distribution.
Tungsten-doped indium oxide transparent conducting thin films, to be applied to inverted organic ... more Tungsten-doped indium oxide transparent conducting thin films, to be applied to inverted organic solar cells, were prepared by a polymer-assisted solution process.
Abstract In this paper, the effects of hydrogen (H 2 ) plasma treatment on the molybdenum (Mo)-do... more Abstract In this paper, the effects of hydrogen (H 2 ) plasma treatment on the molybdenum (Mo)-doped indium oxide (InO) thin film that was formed on glass using the polymer-assisted deposition (PAD) process were investigated. The sheet resistance for the sample treated at the ICP power of 15 W was quenched to 167 Ω/sq. from the 680 Ω/sq. for the as-deposited sample. Compared with the as-deposited sample, both the mobility and the concentration of the sample treated at the 15 W ICP power were also increased simultaneously, resulting in an increased conductivity. From these results, it was concluded that the H 2 plasma treatment is an efficient method for the enhancement of the electrical property, as well as to remove nano-sized cracks on the surface of the PAD-Mo-doped InO without a deterioration the optical transmittance.
In this letter, we propose a method to enhance resistive switching properties in SiCN-based condu... more In this letter, we propose a method to enhance resistive switching properties in SiCN-based conductive-bridge resistive switching memory (CBRAM) devices by inserting a thin Al2O3 layer between the SiCN resistive switching layer and the TiN bottom electrode. Compared with the Cu/Ta/SiCN/TiN single-layer device, the Cu/Ta/SiCN/Al2O3/TiN double layer device exhibits uniform resistive switching, long stable endurance cycles (>1.6 × 104), and stable retention (104 s) at 125 °C. These substantial improvements in the resistive switching properties are attributed to the location of the formation and rupture of conductive filaments that can be precisely controlled in the device after introducing the Al2O3 layer. Moreover, a multilevel resistive switching characteristic is observed in the Cu/Ta/SiCN/Al2O3/TiN double layer CBRAM device. The distinct six-level resistance states are obtained in double layer devices by varying the compliance current. The highly stable retention characteristics...
2019 IEEE International Conference on Flexible and Printable Sensors and Systems (FLEPS), 2019
Flexible sensors have been developed over the decades due to their potential in various applicati... more Flexible sensors have been developed over the decades due to their potential in various applications. However, recent developments in interactive user interface, healthcare device, tactile sensor, and artificial electronic skin require device with multifunctional properties such as various detection ability and good mobility. Research on such devices are still under developing. In this report, we demonstrate a flexible multimodal (pressure, temperature) sensor using embedded indium tin oxide (ITO). For the pressure sensor, the embedded ITO was adopted as a conductive layer with triple layer pyramid structure. We utilized water-soluble sacrificial layers for eco-friendly method. The triple layer pyramid-structured pressure sensor shows excellent sensitivity in dynamic range of 100 Pa to 10 kPa with high reliability of 105 cycles. For the temperature sensor, we used comb like structure with ITO. It shows negative temperature coefficient on resistance with good linearity. Due to the vertically stacked structure, we were able to ignore interface effect. This work present that the opportunity of transparent electrode towards flexible multimodal sensors that can beemployed for various flexible applications.
Sensory information processing in robot skins currently rely on a centralized approach where sign... more Sensory information processing in robot skins currently rely on a centralized approach where signal transduction (on the body) is separated from centralized computation and decision-making, requiring the transfer of large amounts of data from periphery to central processors, at the cost of wiring, latency, fault tolerance and robustness. We envision a decentralized approach where intelligence is embedded in the sensing nodes, using a unique neuromorphic methodology to extract relevant information in robotic skins. Here we specifically address pain perception and the association of nociception with tactile perception to trigger the escape reflex in a sensorized robotic arm. The proposed system comprises self-healable materials and memtransistors as enabling technologies for the implementation of neuromorphic nociceptors, spiking local associative learning and communication. Configuring memtransistors as gated-threshold and -memristive switches, the demonstrated system features in-mem...
Flexible electronic circuits when integrated with different sensors to mimic the human skin can b... more Flexible electronic circuits when integrated with different sensors to mimic the human skin can be referred to as E-skin. E-skin can be used for the monitoring of human health, human-machine interface and humanoids. To mimic skin, a variety of sensors have been studied, including those sensitive to different pressures, temperatures, flows, and strain and humidity levels. Herein, we demonstrate a multifunctional sensor encompassed in a single pixel which is inspired by human skin. The proposed device contains a pressure sensor, a temperature sensor and a piezoresistive hair-type flow sensor, the latter of which is fabricated using mixture of carbon nanotubes and polydimethylsiloxane piezoresistive materials. Additionally, the temperature sensor is printed by means of inkjet printing with MWCNT and Ag nanoparticle ink. Finally, all three sensors are vertically stacked to mimic the human skin, demonstrating interference-free characteristics. This study provides a new and cost-effective approach for multimodal sensor applications.
Rhynchostylis retusa-like α-NiMoO4 was synthesized using a simple, single-step, and cost-effectiv... more Rhynchostylis retusa-like α-NiMoO4 was synthesized using a simple, single-step, and cost-effective wet-chemistry approach, and it exhibited the superior electrochemical properties.
Resistive switching devices, which are dominated by metal cation based conductive filament format... more Resistive switching devices, which are dominated by metal cation based conductive filament formation/rupture, are called programmable memory, or conductive bridge random access memory (CBRAM), and are widely expected to replace existing memory devices. In this letter, CuBi alloy was used as an active electrode to control the over-diffusion of Cu ions into the solid electrolyte of a CBRAM. In addition, resistive switching performance was improved by inserting lutetium and dysprosium metals, which acted as a buffer layer at the interface of the active electrode (CuBi) and the dielectric layer (Al2O3). When optimized, the Cu0.55Bi0.45/Lu(Dy)/Al2O3/Pt showed excellent resistive switching performance. This improvement can be explained by the high controllability of Cu in Cu-Bi electrode with the Lu (Dy) buffer layer. The formation of intermediate oxide buffer layers at the CuBi/Lu(Dy) interface was analysed using XPS. Moreover, conductive-atomic force microscope measurements helped to de...
Transparent and conducting flexible electrodes have been successfully developed over the last few... more Transparent and conducting flexible electrodes have been successfully developed over the last few decades due to their potential applications in optoelectronics. However, recent developments in smart electronics, such as a direct human-machine interface, health-monitoring devices, motion-tracking sensors, and artificially electronic skin also require materials with multifunctional properties such as transparency, flexibility and good portability. In such devices, there remains room to develop transparent and flexible devices such as pressure sensors or temperature sensors. Herein, we demonstrate a fully transparent and flexible bimodal sensor using indium tin oxide (ITO), which is embedded in a plastic substrate. For the proposed pressure sensor, the embedded ITO is detached from its Mayan-pyramid-structured silicon mold by an environmentally friendly method which utilizes water-soluble sacrificial layers. The Mayan-pyramid-based pressure sensor is capable of six different pressure ...
The conductive-bridge random access memory (CBRAM) has become one of the most suitable candidates... more The conductive-bridge random access memory (CBRAM) has become one of the most suitable candidates for non-volatile memory in next-generation information and communication technology. The resistive switching (RS) mechanism of CBRAM depends on the formation/annihilation of the conductive filament (CF) between the active metal electrode and the inert electrode. However, excessive ion injection from the active electrode into the solid electrolyte reduces the uniformity and reliability of the RS devices. To solve this problem, we investigated the RS characteristics of a CuSn alloy active electrode with different compositions of Cux-Sn1-x (0.13 < X < 0.55). The RS characteristics were further improved by inserting a dysprosium (Dy) or lutetium (Lu) buffer layer at the interface of Cux-Sn1-x/Al2O3. Electrical analysis of the optimal Cu0.4-Sn0.73/Lu-based CBRAM exhibited stable RS behavior with low operation voltage (SET: 0.7 V and RESET: -0.3 V), a high on state/off state resistive ratio (106), AC cyclic endurance (>104), and stable retention (85 °C/10 years). To achieve these performance parameters, CFs were locally formed inside the electrolyte using a modified CuSn active electrode, and the amount of Cu-ion injection was reduced by inserting the Dy or Lu buffer layer between the CuSn active electrode and the electrolyte. In particular, conductive-atomic force microscopy results at the Dy or Lu/Al2O3 interface directly showed and defined the diameter of the CF.
The next-generation electronic society is dependent on the performance of nonvolatile memory devi... more The next-generation electronic society is dependent on the performance of nonvolatile memory devices, which has been continuously improving. In the last few years, many memory devices have been introduced. However, atomic switches are considered to be a simple and reliable basis for next-generation nonvolatile devices. In general, atomic switch-based resistive switching is controlled by electrochemical metallization. However, excess ion injection from the entire area of the active electrode into the switching layer causes device nonuniformity and degradation of reliability. Here, we propose the fabrication of a high-performance atomic switch based on Cu x-Se1- x by inserting lanthanide (Ln) metal buffer layers such as neodymium (Nd), samarium (Sm), dysprosium (Dy), or lutetium (Lu) between the active metal layer and the electrolyte. Current-atomic force microscopy results confirm that Cu ions penetrate through the Ln-buffer layer and form thin conductive filaments inside the switching layer. Compared with the Pt/Cu x-Se1- x/Al2O3/Pt device, the optimized Pt/Cu x-Se1- x/Ln/Al2O3/Pt devices show improvement in the on/off resistance ratio (102-107), retention (10 years/85 °C), endurance (∼10 000 cycles), and uniform resistance state distribution.
Tungsten-doped indium oxide transparent conducting thin films, to be applied to inverted organic ... more Tungsten-doped indium oxide transparent conducting thin films, to be applied to inverted organic solar cells, were prepared by a polymer-assisted solution process.
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Papers by Sujaya kumar Vishwanath