• Bulletin of the Korean Chemical Society
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• v.16 no.2
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• pp.143-148
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• 1995

Ketene (CH2CO) adsorption on Ag(111) has been studied in ultrahigh vacuum using electron energy loss spectroscopy and temperature programmed desorption. Ketene adsorbs molecularly on Ag(111) at temperatures below 126 K. The coverage increases linearly with exposure until saturation. No multilayer formation and no shift in desorption temperature with coverage were observed, indicating a lack of attractive interaction between adsorbate molecules. The desorption activation energy is estimated to be 7.8 kcal/mol by assuming first order kinetics and a pre-exponential factor of 1013 sec-1. The adsorption geometry of ketene on the surface is determined from the relative intensities of the vibrational energy loss peaks. The CCO axis of CH2CO is found to be almost parallel to (∼4°away from) the surface and the molecular plane is almost perpendicular to the surface (∼3°tilt).

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.347-347
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• 2012

Nickel Oxide (NiO) is a transition metal oxide of the rock salt structure that has a wide band gap of 3.5 eV. It has a variety of specialized applications due to its excellent chemical stability, optical, electrical and magnetic properties. In this study, we concentrated on the application of NiO thin film for transparent conducting oxide. The energy band structure, electronic and optical properties of Nickel Oxide (NiO) thin films grown on Si by using electron beam evaporation were investigated by X-Ray Photoelectron Spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and UV-Spectrometer. The band gap of NiO thin films determined by REELS spectra was 3.53 eV for the primary energies of 1.5 keV. The valence-band offset (VBO) of NiO thin films investigated by XPS was 3.88 eV and the conduction-band offset (CBO) was 1.59 eV. The UV-spectra analysis showed that the optical transmittance of the NiO thin film was 84% in the visible light region within an error of ${\pm}1%$ and the optical band gap for indirect band gap was 3.53 eV which is well agreement with estimated by REELS. The dielectric function was determined using the REELS spectra in conjunction with the Quantitative Analysis of Electron Energy Loss Spectra (QUEELS)-${\varepsilon}({\kappa},{\omega})$-REELS software. The Energy Loss Function (ELF) appeared at 4.8, 8.2, 22.5, 38.6, and 67.0 eV. The results are in good agreement with the previous study [1]. The transmission coefficient of NiO thin films calculated by QUEELS-REELS was 85% in the visible region, we confirmed that the optical transmittance values obtained with UV-Spectrometer is the same as that of estimated from QUEELS-${\varepsilon}({\kappa},{\omega})$-REELS within uncertainty. The inelastic mean free path (IMFP) estimated from QUEELS-${\varepsilon}({\kappa},{\omega})$-REELS is consistent with the IMFP values determined by the Tanuma-Powell Penn (TPP2M) formula [2]. Our results showed that the IMFP of NiO thin films was increased with increasing primary energies. The quantitative analysis of REELS provides us with a straightforward way to determine the electronic and optical properties of transparent thin film materials.

• Korean Journal of Metals and Materials
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• v.50 no.7
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• pp.545-548
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• 2012

The optical and electronic properties of Indium Tin Oxide (ITO) thin films deposited on a RF-plasma treated glass substrate were investigated by X-Ray Photoelectron Spectroscopy (XPS), Ultra-violet Photoelectron Spectroscopy (UPS), Reflected Electron Energy Loss Spectroscopy (REELS). The modification of glass substrates was carried out by varying the time of the plasma surface treatment in an oxygen atmosphere. The focus of this research was to examine how the optical and electronic properties of ITO thin films change with the plasma treatment time. The surface energy increased since the carbon bonds were removed from the surface after the glass substrate received the surface treatment. The ITO thin films produced on the glass substrate with surface treatment showed that the high optical transmittance was approximately 85%. The measured band gap energy was as high as 3.23 eV when the plasma treatment time was 60 s and the work function after the treatment was increased by 0.5 eV in comparison to that before the treatment of 60 s. The ITO thin film exhibited an excellent sheet resistance of $2.79{\Omega}/{\Box}$. We found that the optical and electronic properties of ITO thin films can be improved by RF-plasma surface treatment.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.68.1-68.1
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• 2012

The best part of graphene is - charge-carriers in it are mass less particles which move in near relativistic speeds. Comparing to other materials, electrons in graphene travel much faster - at speeds of $10^8cm/s$. A graphene sheet is pure enough to ensure that electrons can travel a fair distance before colliding. Electronic devices few nanometers long that would be able to transmit charge at breath taking speeds for a fraction of power compared to present day CMOS transistors. Many researches try to check a possibility to make it a perfect replacement for silicon based devices. Graphene has shown high potential to be used as interconnects in the field of high frequency electrical devices. With all those advantages of graphene, we demonstrate characteristics of electrical and optical properties of graphene such as the effect of graphene geometry on the microwave properties using the measurements of S-parameter in range of 500 MHz - 40 GHz at room temperature condition. We confirm that impedance and resistance decrease with increasing the number of graphene layer and w/L ratio. This result shows proper geometry of graphene to be used as high frequency interconnects. This study also presents the optical properties of graphene oxide (GO), which were deposited in different substrate, or influenced by oxygen plasma, were confirmed using different characterization techniques. 4-6 layers of the polycrystalline GO layers, which were confirmed by High resolution transmission electron microscopy (HRTEM) and electron diffraction analysis, were shown short range order of crystallization by the substrate as well as interlayer effect with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups on its layers. X-ray photoelectron Spectroscopy (XPS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation, and Fourier Transform Infrared spectroscopy (FTIR) and XPS analysis shows the changes in oxygen functional groups with nature of substrate. Moreover, the photoluminescent (PL) peak emission wavelength varies with substrate and the broad energy level distribution produces excitation dependent PL emission in a broad wavelength ranging from 400 to 650 nm. The structural and optical properties of oxygen plasma treated GO films for possible optoelectronic applications were also investigated using various characterization techniques. HRTEM and electron diffraction analysis confirmed that the oxygen plasma treatment results short range order crystallization in GO films with an increase in interplanar spacing, which can be attributed to the presence of oxygen functional groups. In addition, Electron energy loss spectroscopy (EELS) and Raman spectroscopy confirms the presence of the $sp^2$ and $sp^3$ hybridization due to the disordered crystal structures of the carbon atoms results from oxidation and XPS analysis shows that epoxy pairs convert to more stable C=O and O-C=O groups with oxygen plasma treatment. The broad energy level distribution resulting from the broad size distribution of the $sp^2$ clusters produces excitation dependent PL emission in a broad wavelength range from 400 to 650 nm. Our results suggest that substrate influenced, or oxygen treatment GO has higher potential for future optoelectronic devices by its various optical properties and visible PL emission.

• Journal of electromagnetic engineering and science
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• v.16 no.3
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• pp.150-158
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• 2016

This paper reports on a study of LiNiZn-ferrite composite as a radiation absorbent material (RAM). The electromagnetic (EM) wave absorbers are composed of an EM wave absorbing material and a polymeric binder. The surface morphology, chemical composition, weight percent of the ferrite composite of the toroid sample, magnetic properties, and return loss are investigated using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and network analyzer. For preparing the absorbing sheet, chlorinated polyethylene (CPE) is used as a polymeric binder. The EM wave absorption properties of the prepared samples were studied at 4 - 8 GHz. We can confirm the effects of the thickness of the samples for absorption properties. An absorption bandwidth of more than a 10-dB return loss shifts toward a lower frequency range along with an increase in the thickness of the absorber.

• Korean Journal of Materials Research
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• v.1 no.4
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• pp.184-190
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• 1991

Oxygen chemisorption on single crystal ZrC(111) surface was studied by high-resolution electron energy loss and ultraviolet photoelectron spectroscopy. At a low amount of oxygen exposure, adsorbed oxygen atoms construct $(\sqrt{3}{\times}\sqrt{3})R30^{\circ}$ structure. On the other hand, oxygen adsorption changes into $1{\times}1$ structure as the amount of oxygen exposure increases. The adsorbed oxygen atoms show smaller vertical distance from the Zr topmost layer in the $1{\times}1$ structure than in the $(\sqrt{3}{\times}\sqrt{3})R30^{\circ}$ structure and approach to the bridge site rather than 3-fold hollow site. The two different oxygen adsorption behavior comes from the two different surface stales of the clean ZrC(111) surface.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.83-83
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• 1999

본 연구에서는 Auger Elecrtron Spectroscopy (AES) 장비를 이용하여 Silicone Wafer 표면에 BF 이온을 주입시킨 후 Dopping 농도 및 Implantation 에너지에 따른 Si KLL Peak의 변화를 관찰하였다. 또한 PVD Ti 계열 화학물의 시료에 대하여 Peak의 Shape 변화를 관찰하였다. 1)Dopping 농도 및 Implantation 에너지에 따른 Si KLL Peak의 변화 관찰 일반적으로 Silicone 기판에 Arsenic(3가)을 Dopping 하였을 경우, Si KLL Peak의 Kinetic Energy 값은 순수 Si Peak보다 더 작은 값으로 Shift 하며, Boron (5가)을 Dopping하였을 경우에는 더 큰 값으로 Shift 한다. 이론적으로 N-type Si의 에너지 차이는 약 1.0eV로 보고되어 있으며, AES를 이용하여 실험적으로 측정된 값은 약 0.6eV정도로 알려져 있다. 이러한 차이는 Dopping 농도에 따라 Valance Band의 에너지 값이 변화하기 때문이라고 알려져 있다. 본 연구에서는 BF2를 Si에 이온 주입하여 입사 에너지 및 dose 량에 따른 Si KLL Peak의 변화를 관찰하였다. 그림1과 같이 Si KLL Peak는 Implantation Energy가 작을수록 Kinetic Energy가 높은 곳으로 Shift 한다. 이는 LOw Energy로 이온 주입하면, Projected Range (Rp)가 High Energy로 이온 주입할 때보다 작기 때문이며, 이 결과를 Secondary Ion Mass Spectroscopy (SIMS) 및 TRIM simulation을 이용하여 확인하였다. 또한 표면에서의 전자 Density의 변화와 Implantation energy와의 관계를 시료의 표면에서 반사되어 나오는 전자의 에너지 손실(Reflected Electron Energy Loss Spectroscopy:REELS)을 통하여 고찰하였다. 2) PVD Ti 계열화합물의 시료에 대한 peak의 shape 가 변화하며, TiL3M23V (Ti2) 및 TiL3M23M23 (Til) Peak의 Intensity Ratio가 변화한다. 따라서 본 연구에서는 그림 2와 같이 Ti 결합 화합물에서의 Ti Auger Peak의 특성 에너지 값과 Peak Shape를 관찰하여, AES를 이용하여 Ti 계열의 화합물에 대한 Chemical state 분석의 가능성을 평가하였다.

• Journal of the Korean Vacuum Society
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• v.5 no.1
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• pp.1-5
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• 1996

Noncrystalline films of diamond-like carbon (DLC) have been prepared by laser ablation technique at room temperature. A Q-switched Nd-YAG laser beam with wavelength of 1064 nm and pulse duration of 10 ns was focused onto a graphite target with power densities of about $10^9 W/\textrm{cm}^2$. The physical properties of the resulting films were analyzed with density, hardness, and resistivity measurements. The surface and bonding structure were investigated by atomic force microscopy (AFM), Raman spectroscopy, electron energy loss spectroscopy (EELS).

• Applied Microscopy
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• v.47 no.3
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• pp.187-202
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• 2017

The classical electron band theory is a powerful tool to describe the electronic structures of solids. However, the band theory and corresponding density functional theory become inappropriate if a system comprises localized electrons in a scenario wherein strong electron correlations cannot be neglected. $SrRuO_3$ is one such system, and the partially localized d-band electrons exhibit some interesting behaviors such as enhanced effective mass, spectral incoherency, and oppression of ferromagnetism and itinerancy. In particular, a Metal-Insulator transition occurs when the thickness of $SrRuO_3$ approaches approximately four unit cells. In the computational studies, irrespective of the inclusion of on-site Hubbard repulsion and Hund's coupling parameters, correctly depicting the correlation effects is difficult. Because the oxygen atoms and the symmetry of octahedra are known to play important roles in the system, scrutinizing both the electronic band structure and the lattice system of $SrRuO_3$ is required to find the origin of the correlated behaviors. Transmission electron microscopy is a promising solution to this problem because of its integrated functionalities, which include atomic-resolution imaging and electron energy loss spectroscopy.

• Proceedings of the Korea Crystallographic Association Conference
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• 2003.05a
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• pp.6-6
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• 2003

Highly crystalline 5H-polytypic form of sp3-bonded boron nitride (BN) was grown by pulsed-laser-vaporization of BN, where synchronous reactive-plasma packets assisted the crystal growth in the vapor phase. The structure of the product crystallites (˙5 micrometers) was confirmed by using transmission electron diffraction and electron energy loss spectroscopy. This material proved to have a sharp and dominant band at 225 nm by cathode luminescence at room temperatures and corresponding monochromatic images revealed that they uniformly emitted the ultraviolet light. Considering that cubic BN has already been doped as p- and n- type semiconductors, this material may be applied to the light-emitting devices working at almost the deepest limit of the UV region that is functional without vacuum.