• 한국융합학회논문지
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• 제11권7호
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• pp.157-162
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• 2020

최근 레이저를 이용하여 환원된 친환경 그래핀 패턴 기술(Laser Induced Graphene, LIG)은 간단하고 효율적으로 원하는 형태로 다양한 기판 위에 패터닝하는 것이 가능하여 신축 유연 전자 소자, 박막 형태의 에너지 저장 소자 등과 같이 새로운 친환경 전자 소자 제작에 많이 활용되고 있다. 이러한 그래핀 패턴 구조를 이용한 전자 소자의 성능과 효용성을 높이기 위해서는 그래핀 고유의 2차원 특성을 유지하면서 가능한 최소한의 선폭을 구현할 수 있는 최적화된 레이저 패터닝 조건에 대한 연구가 필수적이다. 본 논문에서는 최근 레이저 그래핀 패턴 연구에서 많이 사용되는 Ti:sapphire 펨토초 레이저를 이용해서 그래핀 광-열 산화반응을 분석하여 최적화된 그래핀의 최소선폭을 구현하였다. 레이저 에너지의 확산 효과를 최소화하기 위하여 레이저 광강도와 레이저 스캔 속도를 조절하여 최적의 그래핀 특성을 나타내는 패턴을 연구하였으며 18 ㎛의 집속된 빔을 이용하여 최소 30 ㎛의 이차원 그래핀 선폭을 구현하였다.

• Applied Science and Convergence Technology
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• 제26권4호
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• pp.55-61
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• 2017

Graphene, with a carrier mobility achieving up to $140,000cm^2/Vs$ at room temperature, makes it an ideal material for application in semiconductor devices. However, when the metal comes in contact with the graphene sheet, an energy barrier forms at the metal-graphene interface, resulting in a drastic reduction of the carrier mobility of graphene. In this review, the various methods of forming metal-graphene covalent contacts to lower the contact resistance are discussed. Furthermore, the graphene sheet in the area of metal contact can be cut in certain patterns, also discussed in this review, which provides a more efficient approach to forming covalent contacts, ultimately reducing the contact resistance for the realization of high-performance graphene devices.

• 반도체디스플레이기술학회지
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• 제17권4호
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• pp.16-20
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• 2018

Graphene is attracting attention due to its outstanding properties as line material for next-generation semiconductor. Graphene pattern technology is essential to apply graphene line. Selective graphene oxide reduction as one of graphene pattern method does not require a substrate thereby a high flexibility device can be applied. Particularly, the method using photon energy has advantages of short process time and environment friendly. In this review, we introduce the photocatalytic method and the photo-thermal energy conversion method using photon energy in the selective reduction process of graphene oxides.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.91-92
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• 2012

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.371.2-371.2
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• 2016

Graphene electronics is one of the promising technologies for the next generation electronic devices due to the outstanding properties such as conductivity, high carrier mobility, mechanical, and optical properties along with extended applications using 2 dimensional heterostructures. However, large contact resistance between metal and graphene is one of the major obstacles for commercial application of graphene electronics. In order to achieve low contact resistance, numerous researches have been conducted such as gentle plasma treatment, ultraviolet ozone (UVO) treatment, annealing treatment, and one-dimensional graphene edge contact. In this report, we suggest a fabrication method of one-dimensional graphene metal edge contact without using graphene exfoliation. Graphene is grown on Cu foil by low pressure chemical vapor deposition. Then, the graphene is transferred on $SiO_2/Si$ wafer. The patterning of graphene channel and metal electrode is done by photolithography. $O_2$ plasma is applied to etch out the exposed graphene and then Ti/Au is deposited. As a result, the one-dimensional edge contact geometry is built between metal and graphene. The contact resistance of the fabricated one-dimensional metal-graphene edge contact is compared with the contact resistance of vertically stacked conventional metal-graphene contact.

• 센서학회지
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• 제29권4호
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• pp.220-226
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• 2020

Graphene has been widely considered a promising candidate for high-quality chemical sensors, owing to its outstanding characteristics, such as sensitive gas adsorption at room temperature, high conductivity, high flexibility, and high transparency. However, the main drawback of a graphene-based gas sensor is the necessity for external heaters due to its slow response, incomplete recovery, and low selectivity at room temperature. Conventional heating devices have limitations such as large volume, thermal safety issues, and high power consumption. Moreover, metal-based heating systems cannot be applied to transparent and flexible devices. Thus, to solve this problem, a method of supplying the thermal energy necessary for gas sensing via the self-heating of graphene by utilizing its high carrier mobility has been studied. Herein, we provide a brief review of recent studies on self-activated graphene-based gas sensors. This review also describes various strategies for the self-activation of graphene sensors and the enhancement of their sensing properties.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.15-15
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• 2011

Atom-thick graphene membrane and nano-sized graphene objects (NGOs) hold substantial potential for applications in future molecular-scale integrated electronics, transparent conducting membranes, nanocomposites, etc. To realize this potential, chemical properties of graphene need to be understood and diagnostic methods for various NGOs are also required. To meet these needs, chemical properties of graphene and optical diagnostics of graphene nanoribbons (GNRs) have been explored by Raman spectroscopy, AFM and STM scanning probes. The first part of the talk will illustrate the role of underlying silicon dioxide substrates and ambient gases in the ubiquitous hole doping of graphene. An STM study reveals that thermal annealing generates out-of-plane deformation of nanometer-scale wavelength and distortion in $sp^2$ bonding on an atomic scale. Graphene deformed by annealing is found to be chemically active enough to bind molecular oxygen, which leads to a strong hole-doping. The talk will also introduce Raman spectroscopy studies of GNRs which are known to have nonzero electronic bandgap due to confinement effect. GNRs of width ranging from 15 nm to 100 nm have been prepared by e-beam lithographic patterning of mechanically exfoliated graphene followed by oxygen plasma etching. Raman spectra of narrow GNRs can be characterized by upshifted G band and strong disorder-related D band originating from scattering at ribbon edges. Detailed analysis of the G, D, and 2D bands of GNRs proves that Raman spectroscopy is still a reliable tool in characterizing GNRs despite their nanometer width.

• 한국재료학회지
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• 제26권11호
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• pp.635-643
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• 2016

Graphene has shown exceptional properties for high performance devices due to its high carrier mobility. Of particular interest is the potential use of graphene nanoribbons as field-effect transistors. Herein, we introduce a facile approach to the fabrication of graphene nanoribbon (GNR) arrays with ~200 nm width using nanoimprint lithography (NIL), which is a simple and robust method for patterning with high fidelity over a large area. To realize a 2D material-based device, we integrated the graphene nanoribbon arrays in field effect transistors (GNR-FETs) using conventional lithography and metallization on highly-doped $Si/SiO_2$ substrate. Consequently, we observed an enhancement of the performance of the GNR-transistors compared to that of the micro-ribbon graphene transistors. Besides this, using a transfer printing process on a flexible polymeric substrate, we demonstrated graphene-silicon junction structures that use CVD grown graphene as flexible electrodes for Si based transistors.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제42회 동계 정기 학술대회 초록집
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• pp.574-574
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• 2012

We report a simple way of fabricating high-quality carbon nanoscrolls (CNSs) by taking advantage of strain relief due to large difference in strain at the interface of graphene and underlying layer. This method allows strain-controlled self rolling-up of monolayer graphene during etching process at predefined positions on SiO2/Si substrates by photolithography. The size and the length of the CNSs can be easily controlled by adjusting the thickness of the underlying layer and by pre-patterning. Raman spectroscopy studies show that the CNSs is free of significant defects, and the electronic structure and phonon dispersion are slightly different from those of two-dimensional graphene. The preparation of high-quality CNSs may open up new opportunities for both fundamental and applied research of CNSs.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.142.1-142.1
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• 2013

The patterning and doping technique enables graphene to replace the metal electrode as a charge injection layer in the pentacene based thin film transistor. However, it is known that pentacene molecules form lying-down coordination on the graphene surface. Pentacene thin film showed that the highly occupied molecular orbital is 0.2~0.4 eV lower in the standing up coordination than in the lying down coordination. Here, we report the formation of standing-up coordination and lowered HOMO level of the pentacene layer grown on the graphene layer doped with CYTOP.