• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.145.1-145.1
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• 2013

A prerequisite for the development of graphene-based field effect transistors (FETs) is reliable control of the type and concentration of carriers in graphene. These parameters can be manipulated via the deposition of atoms, molecules, and polymers onto graphene as a result of charge transfer that takes place between the graphene and adsorbates. In this work, we demonstrate a unique and facile methodology for the homogenous and stable p-type doping of graphene by hybridization with ZnO thin films fabricated by MeV electron beam irradiation (MEBI) under ambient conditions. The formation of the ZnO/graphene hybrid nanostructure was attributed to MEBI-stimulated dissociation of zinc acetate dihydrate and a subsequent oxidation process. A ZnO thin film with an ultra-flat surface and uniform thickness was formed on graphene. We found that homogeneous and stable p-type doping was achieved by charge transfer from the graphene to the ZnO film.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.186.1-186.1
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• 2014

Graphene, which is a 2-dimensional carbon material, has been attracting much interest due to its unique properties and potential applications. So far, many interesting experimental and theoretical works have been done concerning the electronic properties of graphene on various substrates. Especially, there are many experimental reports about doping in graphene which is caused by interaction between graphene and its supporting substrates. Here, we report the study of charge transfer between graphene and oxide substrates using density functional theory (DFT) calculations. In this study, we have investigated the charge transfer related with graphene considering various oxide substrates such as SiO2(0001) and MgO(111). Details in charge transfer between graphene and oxides are analyzed in terms of charge density difference, band structure and work function.

• Applied Science and Convergence Technology
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• 제24권6호
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• pp.268-272
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• 2015

We report the systematic study to reduce extrinsic doping in graphene grown by chemical vapor deposition (CVD). To investigate the effect of crystallinity of graphene on the extent of the extrinsic doping, graphene samples with different levels of crystal quality: poly-crystalline and single-crystalline graphene (PCG and SCG), are employed. The graphene suspended in air is almost undoped regardless of its crystallinity, whereas graphene placed on an $SiO_2/Si$ substrate is spontaneously p-doped. The extent of p-doping from the $SiO_2$ substrate in SCG is slightly lower than that in PCG, implying that the defects in graphene play roles in charge transfer. However, after annealing treatment, both PCG and SCG are heavily p-doped due to increased interaction with the underlying substrate. Extrinsic doping dramatically decreases after annealing treatment when PCG and SCG are placed on the top of hexagonal boron nitride (h-BN) substrate, confirming that h-BN is the ideal substrate for reducing extrinsic doping in CVD graphene.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제40회 동계학술대회 초록집
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• pp.430-430
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• 2011

Graphene, one single atomic layer of graphite, has attracted extensive attention in various research fields since its first isolation from graphite. Application in the future electronics requires better understanding and manipulation of electronic properties of graphene supported on various solid substrates. Here, we present a study on charge doping and morphology of graphene prepared on atomically flat and highly polar mica substrates. Ultra-flat single-layer graphene was prepared by micro-exfoliation of graphite followed by deposition on cleaved mica substrates. Atomic force microscopy (AFM) revealed presence of ultra-thin water films formed in a layer-by-layer manner between graphene and mica substrates. Raman spectroscopy showed that a few angstrom-thick water films efficiently block electron transfer from graphene to mica. Hole doping in graphene caused by underlying mica substrates was also visualized by scanning Kelvin probe microscopy (SKPM).

• 전기화학회지
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• 제7권3호
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• pp.138-142
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• 2004

본 연구에서 CSA로 도핑된 EB와 LEB 형태의 폴리아닐린 필름을 ITO전극위에 m-cresol, chloroform 혼합용액을 도포시켜 제조하였다. UV 실험결과로부터 m-cresol에 의한 이차 도핑 효과를 확인 할 수 있었으며, m-cresol의 양이 증가할수록 폴리아닐린 필름의 전도도는 증가하였다. 폴리아닐린의 전기화학적 실험결과 LEB로 제작된 폴리아닐린 전극의 산화$\cdot$환원 피크 전류는 EB로 제작된 폴리아닐린 전극보다 더 크고 가역적인 것을 CV를 통해 구할 수 있었다. 또한 전하전달 저항은 m-cresol의 양이 증가할수록 감소하였으며, LEB/CSA전극의 전하 전달 저항 갈이 EB/CSA 전극보다 작았다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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• pp.382.1-382.1
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• 2014

Graphene field-effect transistors (GFET) is one of candidates for future high speed electronic devices since graphene has unique electronic properties such as high Fermi velocity (vf=10^6 m/s) and carrier mobility ($15,000cm^2/V{\cdot}s$) [1]. Although the contact property between graphene and metals is a crucial element to design high performance electronic devices, it has not been clearly identified. Therefore, we need to understand characteristics of graphene/metal contact in the GFET. Recently, it is theoretically known that graphene on metal can be doped by presence of interface dipole layer induced by charge transfer [2]. It notes that doping type of graphene under metal is determined by difference of work function between graphene and metal. In this study, we present the GFET fabricated by contact metals having high work function (Pt, Ni) for p-doping and low work function (Ta, Cr) for n-doping. The results show that asymmetric conductance depends on work function of metal because the interfacial dipole is locally formed between metal electrodes and graphene. It induces p-n-p or n-p-n junction in the channel of the GFET when gate bias is applied. In addition, we confirm that charge transfer regions are differently affected by gate electric field along gate length.

• Journal of Information Display
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• 제2권3호
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• pp.1-5
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• 2001

The effect of doping on the energy transfer and charge carrier trapping processes has been studied in organic light-emitting diodes (OLEDs) doped with a fluorescent laser dye. The devices consisted of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1-biphenyl-4,4'-diamine (TPD) as a hole transporting layer, tris(8-hydroxyquinoline) aluminum ($Alq_3$) as the host, and a fluorescent dye, 4-dicyanomethylene-2-methyl-6-[2-(2,3,6,7-tetrahydro-1 H,5H-benzo[i,j]quinolizin-8-yl) vinyl]-4H-pyran) (DCM2) as the dopant. Temperature dependence of the current-voltage-luminescence (I-V-L) characteristics, the electroluminescence (EL) and photoluminescence (PL) spectra are studied in the temperature ranging between 15 K and 300 K. The emission from DCM2 was seen to be much stronger compared with the emission from $Alq_3$, indicative of efficient energy transfer from $Alq_3$ to DCM2. In addition, the EL emission from DCM2 increasd with increasing temperature while the emission from the host $Alq_3$ decreased. The result indicates that direct charge carrier trapping becomes efficient with increasing temperature. The EL emission from DCM2 shows a slightly sublinear dependence on the current density, implying the enhanced quenching of excitons at high current densities due to the exciton-exciton annihilation.

• Bulletin of the Korean Chemical Society
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• 제35권10호
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• pp.3077-3080
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• 2014

• Bulletin of the Korean Chemical Society
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• 제31권10호
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• pp.2809-2812
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• 2010

The Chemical Doping of epitaxial graphene (EG) due to p-tert-butylcalix[4]arene was investigated using high resolution photoemission spectroscopy (HRPES). The measured work function changes verified that increased adsorption of the p-tert-butylcalix[4]arene on EG showed p-type doping characteristics due to charge transfer from the graphene to the p-tert-butylcalix[4]arene through the hydroxyl group. A single oxygen bonding feature associated with the O 1s peak was clearly observed in the core-level spectra, indicating the presence of one equivalent adsorption state.

• Bulletin of the Korean Chemical Society
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• 제32권7호
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• pp.2199-2202
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• 2011

The electronic properties of altretamine(2,4,6-tris [dimethylamino]-1,3,5-triazine) adsorbed on epitaxial graphene (EG) were investigated by core-level photoemission spectroscopy (CLPES) in conjunction with low energy electron diffraction (LEED). We found that altretamine molecule adsorbed onto interface layer (S1) of graphene as we confirm decrement of S1 peak using CLPES and haziness of LEED pattern. Moreover, the measured work function changes verified that increased adsorption of the altretamine on graphene layer showed n-type doping characteristics due to charge transfer from altretamine to graphene through the nitrogens. Two distinct nitrogen bonding feature associated with the N 1s peak was clearly observed in the core-level spectra indicating two different chemical environments.