Carbon nanotubes and graphene towards soft electronics

Chae Sang Hoon,이영희 나노기술연구협의회 2014 Nano Convergence Vol.1 No.15

Although silicon technology has been the main driving force for miniaturizing device dimensions to improve cost and performance, the current application of Si to soft electronics (flexible and stretchable electronics) is limited due to material rigidity. As a result, various prospective materials have been proposed to overcome the rigidity of conventional Si technology. In particular, nano-carbon materials such as carbon nanotubes (CNTs) and graphene are promising due to outstanding elastic properties as well as an excellent combination of electronic, optoelectronic, and thermal properties compared to conventional rigid silicon. The uniqueness of these nano-carbon materials has opened new possibilities for soft electronics, which is another technological trend in the market. This review covers the recent progress of soft electronics research based on CNTs and graphene. We discuss the strategies for soft electronics with nano-carbon materials and their preparation methods (growth and transfer techniques) to devices as well as the electrical characteristics of transparent conducting films (transparency and sheet resistance) and device performances in field effect transistor (FET) (structure, carrier type, on/off ratio, and mobility). In addition to discussing state of the art performance metrics, we also attempt to clarify trade-off issues and methods to control the trade-off on/off versus mobility). We further demonstrate accomplishments of the CNT network in flexible integrated circuits on plastic substrates that have attractive characteristics. A future research direction is also proposed to overcome current technological obstacles necessary to realize commercially feasible soft electronics.

General Vacuum Electronics

Jinjun Feng,Xinghui Li,Jiannan Hu,Jun Cai 한국전자파학회JEES 2020 Journal of Electromagnetic Engineering and Science Vol.20 No.1

The electron devices in which electrons do not collide with other particles or in which the collision probability is very small in the transport process can be theoretically regarded as general vacuum electron devices. General vacuum electron devices include microfabricated vacuum nano-electronic devices, which can work in atmosphere, and some solid-state electron devices with nanoscale channel for electrons whose material characteristics are close to those of vacuum channels. Vacuum nano-electron devices (e.g., nanotriodes) are expected to be the fundamental elements for high-speed, radiation-resistant large-scale vacuum integrated circuits. The solid-state electron devices with spin semiconductor materials, multiferroics or topological crystal insulators are quite different from traditional semiconductor devices and are expected to operate under novel principles. Understanding vacuum electron devices from a microcosmic perspective and understanding solid-state electron devices from a vacuum perspective will promote a union of vacuum electronics and microelectronics, as well as the formation and development of general vacuum electronics.

세차전자회절을 이용한 $BaTiO_3$ 나노 결정의 구조분석

송경,김윤중,권기현,김진규,문선민,조남희,Song, Kyung,Kim, Youn-Joong,Kwon, Ki-Hyun,Kim, Jin-Gyu,Moon, Sun-Min,Cho, Nam-Hee 한국현미경학회 2009 Applied microscopy Vol.39 No.4

본 연구에서는 평균 입자크기가 100 nm인 $BaTiO_3$ 나노 결정체의 결정 구조를 전자회절을 이용하여 분석하였다. 전자회절을 이용하여 구조분석을 수행하기 위해 PED 장치의 실험인자를 보정한 후, PED와 일반적인 SAED를 이용하여 전자회절도형을 획득하여 비교 분석을 수행하였다. $BaTiO_3$ 나노 결정체에 대해 PED를 이용한 구조분석을 수행한 결과, $BaTiO_3$ 나노입자는 상온에서 입방정계와 정방정계의 구조가 혼합되어 존재함을 알 수 있었다. 또한 이론적 계산을 통해 두 상이 혼재된 $BaTiO_3$ 나노입자는 입방정계의 구조가 약 8.5nm의 표면을 형성하고 있는 coreshell 구조를 이루고 있음을 예측할 수 있었다. 이러한 $BaTiO_3$ 나노입자에 대한 입방정계와 정방정계 구조의 각각의 격자상수는 a=3.999${\AA}$과 a=3.999${\AA}$, c=4.022${\AA}$이었다. 이와 같이 일반적인 SAED에 비해 뛰어난 공간분해능과 다중산란 효과를 억제할 수 있는 PED 기법은 복합 나노 구조체의 결정구조분석에 보다 유용한 분석 기술로 활용할 수 있을 것으로 기대된다. The crystal structure of nano-crystalline, $BaTiO_3$, with the average particle size of 100 nm was investigated using electron diffraction techniques. We characterized the precession electron diffraction system and then carried out the structure determination using precession electron diffraction and conventional selected area electron diffraction. As a result, it was revealed that $BaTiO_3$ nano-crystalline exist as a mixture of tetragonal structure and cubic structure by precession electron diffraction technique. In addition, it could be turned out that $BaTiO_3$ nano-crystalline is a core-shell structure consisted of a tetragonal phased core and a cubic phased surface layer by theoretical calculation. The thickness of the cubic surface layer was approximately 8.5 nm and the lattice parameters of cubic and tetragonal phases were a=3.999${\AA}$ and a=3.999${\AA}$, c=4.022${\AA}$, respectively. Finally, it is expected that precession electron diffraction is more useful technique for structure determination of complicated nano-crystalline materials because of its higher spatial resolution and minimization of dynamical scattering effect.

Defected graphene nano-platelets for enhanced hydrophilic nature and visible light-induced photoelectrochemical performances

Khan, Mohammad Ehtisham,Khan, Mohammad Mansoob,Cho, Moo Hwan Elsevier 2017 The Journal of physics and chemistry of solids Vol.104 No.-

<P><B>Abstract</B></P> <P>This paper reports an optimized electron beam irradiation (60kGy and 90kGy) approach for defects-related engineering of graphene nano-platelets for optical and structural properties dependent photoelectrochemical performances. The defects in the electron beam irradiated pristine graphene nano-platelets were studied, analyzed and confirmed using standard characterization techniques such as, diffuse reflectance spectroscopy (DRS), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), high resolution-transmission electron microscopy (HR-TEM) and contact angle measurements. DRS clearly revealed the increment in the absorption band using electron beam irradiation doses of 60kGy and 90kGy. Contact angle measurements confirm the additional hydrophilic nature of the defects engineered graphene nano-platelets in comparison with pristine graphene. The photoelectrochemical performances such as linear sweep voltammetry and electrochemical impedance spectroscopy further confirms the enhancement in the optical, spectroscopic, and photoelectrochemical properties of the 90kGy defected graphene in comparison to pristine graphene nano-platelets. Therefore, the proposed method is a reliable way of fine-tuning the properties (optical, spectroscopic and photoelectrochemical) of pristine graphene nano-platelets using electron beam irradiation for enhanced photoelectrochemical performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electron beam irradiated (60 kGy and 90 kGy) pristine graphene. </LI> <LI> Defects engineered graphene for visible light induced photoelectrochemical performances. </LI> <LI> Detailed analysis of defects engineered graphene with standard characterization techniques. </LI> <LI> Defects engineered pristine graphene used as a photoelectrode. </LI> <LI> Defects engineered graphene as an enhanced hydrophilic in nature. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Proposed electron transfer mechanism of defect engineered graphene nano-platelets under visible light irradiation.</P> <P>[DISPLAY OMISSION]</P>

Charge transport in graphene oxide

Chang, Dong Wook,Baek, Jong-Beom Elsevier 2017 Nano today Vol.17 No.-

<P><B>Abstract</B></P> <P>The transport of ionic species in nano-fluidic channels has recently attracted tremendous interest in various research areas. This is because extraordinary nanoscale transport phenomena have been achieved in these materials, including ultrafast and highly selective ion movement. A variety of organic and inorganic materials have been employed to construct nano-channels or nano-pores with controlled sizes and dimensions. In particular, because of its unique two-dimensional planar architecture, as well as the possession of numerous oxygenated functionalities, GO has emerged as a promising building block for high-performance nano-fluidic ion channels. The simple exfoliation-reconstruction approach can readily assemble individual GO sheets into a free-standing, layered, film-like structure. In addition to its utilization as a versatile solid support for nano-fluidic ion transport, GO can play different but positive roles as a filler in composite electrolytes, as a mixed proton/electron conductor, and as a selective ion permeation membrane. Herein, we summarize the recent advances in the transport of ionic species within GO-based electrolytes. Moreover, the perspectives and current challenges of this promising field are discussed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nanoscale transport phenomena have been summarized. </LI> <LI> Graphene oxide (GO) has emerged as high-performance nano-fluidic ion channels. </LI> <LI> An exfoliation-reconstruction process is utilized as a versatile method for GO electrolytes. </LI> <LI> GO can play positive roles as a mixed proton/electron conductor. </LI> <LI> In this review, the recent advances and perspectives in GO-based electrolytes are discussed. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

나노물질의 선택적 레이저 소결을 이용한 유연전기소자의 구현

고승환(Seung Hwan Ko),여준엽(Jun Yeob Yeo),홍석준(Sukjun Hong),한승용(SeungYong Han),이진환(JinHwan Lee),노윤수(YoonSoo Rho),서영덕(Young Duk Seo),전진아(JinA Jeon),남구현(Koo Hyun Nam) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

The development of electric circuit fabrication on heat and chemically sensitive polymer substrates has attracted significant interest as a pathway to low-cost or large-area electronics. Flexible electronics are the electronics on flexible substrates such as a plastic, fabric or paper, so that they can be folded or attached on any curved surfaces. They are currently recognized as one of the most innovating future technologies especially in the area of portable electronics. The conventional vacuum deposition and photolithographic patterning methods are well developed for inorganic microelectronics. However, flexible polymer substrates are generally chemically incompatible with resists, etchants and developers and high temperature processes used in conventional integrated circuit processing. Additionally, conventional processes are time consuming, very expensive and not environmentally friendly. Therefore, there are strong needs for new materials and a novel processing scheme to realize flexible electronics. This paper introduces current research trends for flexible electronics based on (a) nanoparticles, and (b) novel processing schemes: nanomaterial based direct laser patterning methods to remove any conventional vacuum deposition and photolithography processes. Among the several unique nanomaterial characteristics, dramatic melting temperature depression (Tm, 3㎚ particle~150℃) and strong light absorption can be exploited to reduce the processing temperature and to enhance the resolution. This opens a possibility of developing a cost effective, low temperature, high resolution and environmentally friendly approach in the high performance flexible electronics fabrication area.

Significant enhancement of direct electric communication across enzyme-electrode interface <i>via</i> nano-patterning of synthetic glucose dehydrogenase on spatially tunable gold nanoparticle (AuNP)-modified electrode

Lee, Hyeryeong,Lee, Yoo Seok,Lee, Soo Kyung,Baek, Seungwoo,Choi, In-Geol,Jang, Jae-Hyung,Chang, In Seop Elsevier 2019 Biosensors & bioelectronics Vol.126 No.-

<P><B>Abstract</B></P> <P>In this study, the effect of inter-enzyme steric hindrance that occurs during enzyme immobilization on the electrode, on direct electrical communications of enzyme with electrode was investigated <I>via</I> nano-patterning of enzymes on the electrode. Here, the nano-patterning of enzymes was achieved through the combination of DET-capable enzyme that was produced <I>via</I> fusion of site-specific gold binding peptide (GBP) to catalytic subunit of enzyme and gold nanoparticle (AuNP) array with highly tunable dimensions of AuNPs, resulting in spatially controllable enzyme-electrode. The nano-scale spatial control between immobilized enzymes on the highly tuned AuNPs shows different DET efficiency across the enzyme-electrode interface, showing 18.47% of maximum electron recovery which is 3.2-fold enhanced electron recovery efficiency compared to spatially non-controlled enzymes on the electrode where showed 5.7% of electron recovery. The result affirms that inter-enzyme interaction is a significant parameter that decides the enzyme-electrode performance.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The fusion of GBP to the catalytic subunit of GDH enabled interfacial DET in the enzyme-electrode. </LI> <LI> The effect of inter-enzyme agglomeration on efficiency of interfacial DET was investigated, related to its effect on <I>R</I> <SUB>ct</SUB>. </LI> <LI> The enzyme nano-patterning was developed via combination of synthetic enzyme and AuNP-modified electrode. </LI> <LI> The nano-scale spatial control of synthetic GDHs on the electrode enhanced electroactive coverage of enzyme-electrode. </LI> <LI> The inter-enzyme agglomeration is the important parameter to consider for the development of DET-based bioelectronics. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Analysis of nano-crystals: Evaluation of heavy metal-embedded biological specimen by high voltage electron microscopy

Jeong, Hyeongseop,Yoo, Seung Jo,Won, Jonghan,Lee, Hyun-Ju,Chung, Jeong Min,Kim, Han-ul,Kim, Gwang Joong,Kim, Jin-Gyu,Jung, Hyun Suk,Hyun, Jaekyung Elsevier 2018 Ultramicroscopy Vol.194 No.-

<P><B>Abstract</B></P> <P>Heavy metal compounds are adsorbed onto biological specimen in order to enhance the contrast as well as to preserve the structural features of the specimen against electron beam-induced radiation damage. In particular, in combination with computational image processing, negative staining is widely used for structural analysis of protein complexes to moderate resolutions. Image analysis of negatively stained biological specimen is known to suffer from limited achievable resolution due to dehydration and large grain size of staining molecules although the extent of such effect remains somewhat dubious.</P> <P>Stain molecules exist as grains under electron beam. However, clear observation of the crystalline nature of the grains and their association with biological specimen has not been thoroughly demonstrated. In this study, we attempted high-resolution TEM (HRTEM) using high voltage electron microscopy and electron crystallography analysis for the detailed characterization of negatively stained biological specimen, focusing on physical state and chemical composition of the stain molecules. The electron crystallography analysis allowed for the identification of the crystal constituents of widely used stains, hence revealing the chemical nature and the morphology of the stain molecules at specimen level. This study re-evaluated generally accepted notions on negative staining, and may help correctly interpreting the structural analysis of stained biological specimen.</P> <P><B>Highlights</B></P> <P> <UL> <LI> High voltage electron microscopy (HVEM) visualized nano-crystals surrounding of heavy metal-embedded biological specimen. </LI> <LI> Electron crystallography determined chemical composition of the stain molecules. </LI> <LI> The grain size of nano-crystals of stained molecules from uranyl acetate and uranyl formate were nearly identical, and consistent with that of uranium dioxide (UO<SUB>2</SUB>). </LI> <LI> It identified that UO<SUB>2</SUB> is the main contributor of image contrast of heavy metal-embedded biological specimen. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Synthesis, Luminescence and Optical Properties of a CaMoO4 Nano-Powder Prepared by Using the Precipitation Method

Sujita Karki,Pabitra Aryal,하대훈,김홍주,박향규,Indra Raj Pandey 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.7

Nano powders of CaMoO$_4$ were synthesized by using the precipitation method, and the obtained powders were dried inside a vacuum oven at 120 $^\circ$C. The phases of powders were analyzed by using X-ray diffraction (XRD), which revealed that CaMoO$_4$ was free from any extra phases. The surface morphologies of the powders were studied by using transmission electron microscopy (TEM), and the average particle sizes were quite small, being in the range of 7 nm. The optical properties were characterized by using ultraviolet-visible (UV-vis) absorption spectroscopy and the optical energy band gap was found to be 5.51 eV. The fluorescence decay time and the luminescence spectrum of the sample were measured under the excitation by Laser (266 nm), X-ray and proton sources. The obtained results were compared with the CaMoO$_4$ bulk crystal and sintered powder obtained from the solid state reaction.

Rietveld Analysis of Nano-crystalline MnFe₂O₄ with Electron Powder Diffraction

Kim, Jin-Gyu,Seo, Jung-Wook,Cheon, Jin-Woo,Kim, Youn-Joong Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.1

The structure of nano-crystalline $MnFe_2O_4$ was determined and refined with electron powder diffraction data employing the Rietveld refinement technique. A nano-crystalline sample (with average crystal size of about 10.9 nm) was characterized by selected area electron diffraction in an energy-filtering transmission electron microscope operated at 120 kV. All reflection intensities were extracted from a digitized image plate using the program ELD and then used in the course of structure refinements employing the program FULLPROF for the Rietveld analysis. The final structure was refined in space group Fd-3m (# 227) with lattice parameters a=8.3413(7) $\AA$. The reliability factors of the refinement are $R_F$=7.98% and $R_B$=3.55%. Comparison of crystallographic data between electron powder diffraction data and reference data resulted in better agreement with ICSD-56121 rather than with ICSD-28517 which assumes an initial structure model.