We do research on advanced semiconductor technology - Neuromorphic and Future Logic Device, Nano-electric Memory Device and Oxide Semiconductor Device - to bring about an innovation in the academic and industrial world. The lab focuses on Nano Electronics & Neuromorphic Device research.

연구실은 나노 전자 및 신경망 모사 소자 연구에 집중합니다.

Wrinkle-free graphene with spatially uniform electrical properties grown on hot-pressed copper

Resistive Random Access Memory Behaviors in Organic–Inorganic Hybrid Ultra‐Thin Films

Resonator Design for Multiway Thermo-Acoustic Loudspeaker

Improved electromigration-resistance of Cu interconnects by graphene-based capping layer

Effect of Reduced Graphene Oxide Cap Layer on Electromigration Reliability of Cu Interconnect

A wearable thermoelectric generator fabricated on a glass fabric

Graphene oxide thin films for flexible nonvolatile memory applications

Direct measurement of adhesion energy of monolayer graphene as-grown on copper and its application to renewable transfer process

Determination of work function of graphene under a metal electrode and its role in contact resistance

Energy gap and band alignment for on (100) Si

Self-powered wearable electrocardiography using a wearable thermoelectric power generator

Synthesis of ultrathin polymer insulating layers by initiated chemical vapour deposition for low-power soft electronics

High-performance flexible thermoelectric power generator using laser multiscanning lift-off process

Hybrid composite of screen-printed inorganic thermoelectric film and organic conducting polymer for flexible thermoelectric power generator

Electromagnetic interference shielding effectiveness of monolayer graphene

Large-Area Single-Layer MoSe 2 and Its van der Waals Heterostructures

Structural design of a flexible thermoelectric power generator for wearable applications

A high performance MIM capacitor using HfO 2 dielectrics

Flexible resistive switching memory device based on graphene oxide

Quasi-breakdown of ultrathin gate oxide under high field stress

Effect of surface anneal on the physical and electrical properties of films on Ge substrate

A high-density MIM capacitor (13 fF/μm 2 ) using ALD HfO 2 dielectrics

Over-erase phenomenon in SONOS-type flash memory and its minimization using a hafnium oxide charge storage layer

Electrical and Interfacial Characterization of Atomic Layer Deposited High- Gate Dielectrics on GaAs for Advanced CMOS Devices

Annealing and oxidation of silicon oxide films prepared by plasma-enhanced chemical vapor deposition

Woocheol Shin

Byung Jin Cho

The conversion of body heat into electrical energy using a thermoelectric (TE) power generator is useful for wearable self-powered mobile electronic systems such as medical sensors or smart watches. We herein demonstrate a glass fabric-based flexible TE generator using a screen printing technique and the self-sustaining structure of a TE device without top and bottom substrates. With this technique it is possible to make the device thin (∼500 μm), lightweight (∼0.13 g cm−2), and flexible. In addition, the developed TE generator achieved an unprecedentedly large output power density which is several tens of times higher than that of flexible TE generators reported to date. The developed TE generator shows an allowable bending radius of as low as 20 mm and no change in performance by repeated bending for 120 cycles. This work can expedite the development of wearable self-powered mobile devices.

There has been strong demand for novel nonvolatile memory technology for low-cost, large-area, and low-power flexible electronics applications. Resistive memories based on metal oxide thin films have been extensively studied for application as next-generation nonvolatile memory devices. However, although the metal oxide based resistive memories have several advantages, such as good scalability, low-power consumption, and fast switching speed, their application to large-area flexible substrates has been limited due to their material characteristics and necessity of a high-temperature fabrication process. As a promising nonvolatile memory technology for large-area flexible applications, we present a graphene oxide based memory that can be easily fabricated using a room temperature spin-casting method on flexible substrates and has reliable memory performance in terms of retention and endurance. The …

Direct measurement of the adhesion energy of monolayer graphene as-grown on metal substrates is important to better understand its bonding mechanism and control the mechanical release of the graphene from the substrates, but it has not been reported yet. We report the adhesion energy of large-area monolayer graphene synthesized on copper measured by double cantilever beam fracture mechanics testing. The adhesion energy of 0.72 ± 0.07 J m –2 was found. Knowing the directly measured value, we further demonstrate the etching-free renewable transfer process of monolayer graphene that utilizes the repetition of the mechanical delamination followed by the regrowth of monolayer graphene on a copper substrate.

Although the work function of graphene under a given metal electrode is critical information for the realization of high-performance graphene-based electronic devices, relatively little relevant research has been carried out to date. In this work, the work function values of graphene under various metals are accurately measured for the first time through a detailed analysis of the capacitance–voltage ( C–V ) characteristics of a metal–graphene–oxide–semiconductor (MGOS) capacitor structure. In contrast to the high work function of exposed graphene of 4.89–5.16 eV, the work function of graphene under a metal electrode varies depending on the metal species. With a Cr/Au or Ni contact, the work function of graphene is pinned to that of the contacted metal, whereas with a Pd or Au contact the work function assumes a value of ∼4.62 eV regardless of the work function of the contact metal. A study of the gate voltage …

High-resolution x-ray photoelectron spectroscopy (XPS) was applied to characterize the electronic structures for a series of high- k materials grown on (100) Si substrate with different mole fraction x . Al Hf O core levels spectra, valence band spectra, and O energy loss all show continuous changes with x in These data are used to estimate the energy gap for the valence band offset and the conduction band offset between and the (100) Si substrate. Our XPS results demonstrate that the values of and for change linearly with x .

A self-powered wearable electrocardiography (ECG) system is demonstrated. The ECG sensing circuit was fabricated on a flexible PCB and powered by a wearable thermoelectric generator (w-TEG) using body heat as the energy source. To allow the TEG to obtain a large temperature difference for high power generation and also be wearable, a polymer-based flexible heat sink (PHS) comprised of a superabsorbent polymer (SAP) and a fiber that promotes liquid evaporation was devised. Parametric studies on the PHS were conducted, and the structure of the w-TEG was also optimized for the PHS. The output power density from the w-TEG with the PHS was over 38 μW/cm 2 for the first 10 min and over 13 μW/cm 2 even after 22 consecutive hours of driving the circuits. This power level is high enough to continuously drive the wearable ECG system, including the sensors and the power management circuits.

Insulating layers based on oxides and nitrides provide high capacitance, low leakage, high breakdown field and resistance to electrical stresses when used in electronic devices based on rigid substrates. However, their typically high process temperatures and brittleness make it difficult to achieve similar performance in flexible or organic electronics. Here, we show that poly(1,3,5-trimethyl-1,3,5-trivinyl cyclotrisiloxane) (pV3D3) prepared via a one-step, solvent-free technique called initiated chemical vapour deposition (iCVD) is a versatile polymeric insulating layer that meets a wide range of requirements for next-generation electronic devices. Highly uniform and pure ultrathin films of pV3D3 with excellent insulating properties, a large energy gap (>8 eV), tunnelling-limited leakage characteristics and resistance to a tensile strain of up to 4% are demonstrated. The low process temperature, surface-growth character …

Flexible thermoelectric generators (f-TEGs) are emerging as a semipermanent power source for self-powered sensors, which is an important area of research for next-generation smart network monitoring systems in the Internet-of-things era. We report in this paper a f-TEG produced by a screen-printing technique (SPT) and a laser multiscanning (LMS) lift-off process. A screen-printed TEG was fabricated on a SiO 2 /a-Si/quartz substrate via the SPT process, and the LMS process completely separated the rigid quartz substrate from the original TEG by selective reaction of the XeCl excimer laser with the exfoliation layer (a-Si). Using these techniques, we fabricate a prototype f-TEG composed of an array of 72 TE couples that exhibits high flexibility at various bending radii, together with excellent output performance (4.78 mW/cm 2 and 20.8 mW/g at Δ T = 25 °C). There is no significant change in the device performance …

TEG (Thermoelectric power generator) modules are attractive energy harvesters, as they can deliver electrical output power from the temperature difference of all sorts of things. Recently, growing interests in self-powered wearable mobile electronics provoke the necessity of flexible TEG modules. However, the technology on flexible TEG modules is still at a very early stage. Here we demonstrate flexible high-performance TEG modules using a screen-printed inorganic thermoelectric thick film and organic conducting polymer hybrid composite. By infiltrating the organic conducting polymer, poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS), into the micropores of the screen-printed thermoelectric thick film, the flexibility of the module is greatly enhanced without degradation of the output characteristics of the module. This work provides a promising new approach which has the potential to achieve …

We report the first experimental results on the electromagnetic interference (EMI) shielding effectiveness (SE) of monolayer graphene. The monolayer CVD graphene has an average SE value of 2.27 dB, corresponding to∼ 40% shielding of incident waves. CVD graphene shows more than seven times (in terms of dB) greater SE than gold film. The dominant mechanism is absorption rather than reflection, and the portion of absorption decreases with an increase in the number of graphene layers. Our modeling work shows that plane-wave theory for metal shielding is also applicable to graphene. The model predicts that ideal monolayer graphene can shield as much as 97.8% of EMI. This suggests the feasibility of manufacturing an ultrathin, transparent, and flexible EMI shield by single or few-layer graphene.

Layered structures of transition metal dichalcogenides stacked by van der Waals interactions are now attracting the attention of many researchers because they have fascinating electronic, optical, thermoelectric, and catalytic properties emerging at the monolayer limit. However, the commonly used methods for preparing monolayers have limitations of low yield and poor extendibility into large-area applications. Herein, we demonstrate the synthesis of large-area MoSe 2 with high quality and uniformity by selenization of MoO 3 via chemical vapor deposition on arbitrary substrates such as SiO 2 and sapphire. The resultant monolayer was intrinsically doped, as evidenced by the formation of charged excitons under low-temperature photoluminescence analysis. A van der Waals heterostructure of MoSe 2 on graphene was also demonstrated. Interestingly, the MoSe 2 /graphene heterostructures show strong quenching of …

Self-powered wearable electronic devices are expected to be one of the mainstream technologies for future portable electronic systems. As an energy harvester to power wearable electronic devices, a flexible thermoelectric generator (f-TEG) can utilize human body heat as the energy source, creating an ideal solution. The f-TEG can make conformal contact to the human skin and fully utilize body heat with minimal energy loss, while also being comfortable to wear. However, to maximize the power generated by an f-TEG attached to the human body, a careful thermal and structural design analysis of the f-TEG must be carried out. Here, we fabricated flexible thermoelectric generators (f-TEGs) with different device parameters and evaluated their power generating performance using an artificial arm, which was carefully designed to mimic a real human arm. We demonstrated the impact of the f-TEG device parameters …

Metal-insulator-metal (MIM) capacitors with a 56 nm thick HfO/sub 2/ high-/spl kappa/ dielectric film have been fabricated and demonstrated for the first of time with a low thermal budget (/spl sim/200/spl deg/C). Voltage linearity, temperature coefficients of capacitance, and electrical properties are all characterized. The results show that the HfO/sub 2/ MIM capacitor can provide a higher capacitance density than Si/sub 3/N/sub 4/ MIM capacitor while still maintaining comparable voltage and temperature coefficients of capacitance. In addition, a low leakage current of 2/spl times/10/sup -9/ A/cm/sup 2/ at 3 V is achieved. All of these make the HfO/sub 2/ MIM capacitor to be very suitable for use in silicon RF and mixed signal IC applications.

A resistive switching memory device based on graphene oxide (GO) is presented. It is found that the resistive switching characteristic has a strong dependence on electrode material and GO thickness. In our experiment, an Al/GO/ITO structure with 30-nm-thick GO shows good switching performance with an on/off resistance ratio of , low set/reset voltage, and excellent data retention. The GO memory is also fabricated on a flexible substrate with no degradation in switching property, even when the substrate is bent down to 4-mm radius, indicating that the GO memory is an excellent candidate to be a memory device for future flexible electronics.

A new oxide failure mode of ultrathin gate oxide is reported. During high constant current stressing, V/sub G/ variation with time shows two distinct modes, i.e., a stable mode and a fluctuation mode named as quasi-breakdown. Once the quasi-breakdown starts, gate current in low field abruptly increases. From the experimental results, it could be concluded that the quasi-breakdown occurs when injected electrons travel in the oxide conduction band ballistically. Localized physical damage near the Si/SiO/sub 2/ interface is believed to be the cause of the quasi-breakdown, The great increase of gate current after the quasi-breakdown was modeled by a superposition of F-N tunneling current and direct tunneling current with a finite series resistance, and a good agreement has been found.<>

Metal-oxide-semiconductor capacitors were fabricated on germanium substrates by using metalorganic-chemical-vapor-deposited as the dielectric and TaN as the metal gate electrode. It is demonstrated that a surface annealing step in ambient before the deposition could result in significant improvement in both gate leakage current and the equivalent oxide thickness (EOT). It was possible to achieve a capacitor with an EOT of 10.5 Å and a leakage current of at 1 V gate bias. X-ray photoelectron spectroscopy analysis indicates the formation of GeON during surface anneal. The presence of Ge was also detected within the films. This may be due to Ge diffusion at the high temperature (∼400 °C) used in the chemical-vapor deposition process.

Metal-insulator-metal (MIM) capacitors with different HfO 2 thickness have been investigated. The results show that both the capacitance density and voltage coefficients of capacitance (VCCs) increase with decreasing HfO 2 thickness. In addition, it is found that the VCCs decrease logarithmically with increasing thickness. Furthermore, the MIM capacitor with 10-nm HfO 2 shows a record high capacitance density of 13 fF/μm 2 and a VCC of 607 ppm/V, which can meet the requirement of the International Technology Roadmap for Semiconductors. It can also provide a low leakage current of 5.95 × 10/sup -8/A/cm 2 at room temperature at 1 V, low tangent values below 0.05, and a small frequency dependence. These results indicate that the devices are suitable for use in silicon integrated circuit applications.

The over-erase phenomenon in the polysilicon-oxide-silicon nitride-oxide-silicon (SONOS) memory structure is minimized by using hafnium oxide or hafnium aluminum oxide to replace silicon nitride as the charge storage layer (the resulting structures are termed SOHOS devices, where the "H" denotes the high dielectric constant material instead of silicon nitride). Unlike SONOS devices, SOHOS structures show a reduced over-erase phenomenon and self-limiting charge storage behavior under both erase and program operations. These are attributed to the differences in band offset and the crystallinity of the charge storage layer.

In this paper, electrical and interfacial properties of MOS capacitors with atomic layer deposited (ALD) , , and HfAlO gate dielectrics on sulfur-passivated (S-passivated) GaAs substrates were investigated. HfAlO on p-type GaAs has shown superior electrical properties over or on GaAs, and it is attributed to the reduction of the Ga–O formation at the interfacial layer. HfAlO on p-type GaAs exhibits the best electrical properties after postdeposition annealing (PDA) at 500 . It is found that PDA, at above 500 , causes a significant amount of Ga and As out-diffusion into the high- dielectric, which degrades the interface, as well as bulk high- properties.

We have investigated phase separation, silicon nanocrystal (Si NC) formation and optical properties of Si oxide (⁠ Si O x⁠, 0< x< 2⁠) films by high-vacuum annealing and dry oxidation. The Si O x films were deposited by plasma-enhanced chemical vapor deposition at different nitrous–oxide/silane flow ratios. The physical and optical properties of the Si O x films were studied as a result of high-vacuum annealing and thermal oxidation. X-ray photoelectron spectroscopy (XPS) reveals that the as-deposited films have a random-bonding or continuous-random-network structure with different oxidation states. After annealing at temperatures above 1000 C, the intermediate Si continuum in XPS spectra (referring to the suboxide) split to Si peaks corresponding to Si O 2 and elemental Si. This change indicates the phase separation of the Si O x into more stable Si O 2 and Si clusters. Raman, high-resolution transmission …

Nanoelectronic And Neuromorphic Device Lab

교수님 소개

조병진

연구실 소개

연구실 키워드

알럼나이가 간 회사

연구실 지원 방법

대우 조건

연도별 논문 인용수

저널 & 학회 논문 출판 수

연구실 논문 목록

Resistive Random Access Memory Behaviors in Organic–Inorganic Hybrid Ultra‐Thin Films

Resonator Design for Multiway Thermo-Acoustic Loudspeaker

Wrinkle-free graphene with spatially uniform electrical properties grown on hot-pressed copper

연구실 보유 특허

대학별 입시끈

우리 연구실 모집

교수님 소개

조병진

연구실 키워드

알럼나이가 간 회사

연구실 지원 방법

대우 조건

연도별 논문 인용수

저널 & 학회 논문 출판 수

연구실 논문 목록

Resistive Random Access Memory Behaviors in Organic–Inorganic Hybrid Ultra‐Thin Films

Resonator Design for Multiway Thermo-Acoustic Loudspeaker

Wrinkle-free graphene with spatially uniform electrical properties grown on hot-pressed copper

연구실 보유 특허

최근 3년간 연구실적 높은 연구실

대학별 입시끈

우리 연구실 모집