• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.315-315
• /
• 2011

The ring formation and electronic properties of furan adsorbed on graphene layers grown on 6H-SiC(0001) has been investigated using atomic force microscopy (AFM), near edge X-ray absorption fine structure (NEXAFS) spectra for the C K-edge, and high resolution photoemission spectroscopy (HRPES). Moreover, we observed that furan molecules adsorbed on graphene could be used for chemical functionalization via the lone pair of electrons on the oxygen group, allowing chemical doping. We also found that furan spontaneously formed rings with one of three different bonding configurations and the electronic properties of the ring formed by furan on graphene can be described using by AFM, NEXAFS and HRPES, respectively.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.18 no.1
• /
• pp.1-4
• /
• 2008

The growth of composite-structured Nd:$GdVO_4$ single crystal rods by the double die EFG method is reported. Two crucibles are combined with an outer and inner die for ascending of different melt. The composite-structured Nd:$GdVO_4$ single crystal rods with a length of 50 mm and an outer diameter of 5 mm including of inner Nd-doped core region with diameter 3 mm were grown successfully. Nd distribution in the, radial direction has graded profile from result of EPMA. Absorption coefficient in the core region at 808 nm was $42cm^{-1}$. Finally, we demonstrated the laser oscillation using our composite crystal and 2-W output was obtained.

• Electrical & Electronic Materials
• /
• v.5 no.1
• /
• pp.52-70
• /
• 1992

Poly(3-alkythiophene)은 온도에 따라 전기적 광학적인 성질의 현저한 변화가 관측되었다. poly(3-alkylthiophene)의 전기전도도는 온도가 상승함에 따라 증가하지만 최대치를 유지한 후 용융점에서 단게적으로 감소한다. 가열과 냉각과정 동안 전기전도도의 온도의존성에서 hysteresis가 관측되었다. 이 변칙은 carrier확산에 따른 분자구조 변화의 강한 영향인 것으로 생각된다. 흡수 spectrum 또한 상전이에서 급격히 변화한다. poly(3-alkylthiophene)의 흡수 peak는 액체상태에서 가열하면 energy는 높게 이동한다. 그러나 흡수 edge의 이동은 비교적 작다. 그렇지만 고체-액체 상전이에서 흡수 edge는 energy가 높은 쪽으로 이동한다. 이러한 현상은 고체-액체 상전이에서 poly(3-alkylthiophene)의 구조가 현저하게 변화하고 있는 것으로 설명되며 공역 길이가 짧게되는 것은 큰 구조 변화에 의해 공역계의 평면성 감소에 의한 결과로 생각한다.

• Proceedings of the KIEE Conference
• /
• 1987.07a
• /
• pp.513-516
• /
• 1987

Hydrogenated amorphous silicon (a-Si:H) films have been deposited, for thye first time, by a remote plasma chemical vapor deposition. The hydrogen radical play a important role to control the deposition rate, The bonded hydrogen content to silicon is independent of hydrogen partial pressure in the plasma. Optical gap of deposited a-Si:H lies between 1.7eV and 1.8eV and all samples have sharp absorption edge. B-doped a-Si:H films by a RPECVD has a high doping efficiency compared with plasma CVD. The Fermi level of 100ppm B-doped film lies at 0.5eV above valence band edge.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.372-372
• /
• 2010

We have investigated adsorption of selenophene on Si(100) at room temperature using high resolution photoemission spectroscopy (HRPES) and near edge X-ray absorption fine structure (NEXAFS) in the partial electron yield (PEY) mode. The Si 2p, C 1s, Se 3d spectra of selenophene on Si(100) show that selenophene is nondissociatively chemisorbed on Si(100)-$2{\times}1$ through [2+2] cycloaddition. NEXAFS has been conducted to characterize the adsorption geometry of selenophene on Si(100). Since the $\pi^*$ orbital of C=C bond show good angular dependence in carbon K-edge NEXAFS spectra, the angle $53{\pm}5^{\circ}$ determined from NEXAFS spectra. This majority structure is consistent with the [2+2] cycloaddition of selenophene to the dimer of the Si(100)-$2{\times}1$ surface.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2003.10a
• /
• pp.58-58
• /
• 2003

Silver doped ZnO (SZO) films were prepared by rf magnetron sputtering on glass substrates with extraordinary designed ZnO target. With the doping source for target, use AgNO$_3$ powder on a various rate (0, 2, and 4 wt.%). We investigated dependence of coating parameter such as dopant content in target and substrate temperature in the SZO films. The SZO films have a preferred orientation in the (002) direction. As amounts of the Ag dopant in the target were increased, the crystallinity and the transmittance and optical band gap were decreased. And the substrate temperature were increased, the crystallinity and the transmittance were increased. But the crystallinity and the transmittance of SZO films were retrograde at 200$^{\circ}C$. Upside facts were related with composition. In addition, the Oxygen K-edge features of the SZO films were investigated by using near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Changes of optical band gap of the SZO films were explained compared with XRD, XPS and NEXAFS spectra.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.06a
• /
• pp.606-611
• /
• 2000

It has been noted that the low frequency absorption coefficient of a porous sample placed in a standing wave tube is affected by the nature of the sample's edge constraint. The edge constraint has the effect of stiffening the solid phase of the sample, which itself can be strongly coupled to the material's fluid phase, and hence the incident sound field, by viscous means at low frequencies. In recent work it has also been shown that such a circumferential constraint causes the low frequency transmission loss of a layer of fibrous material to approach a finite low frequency limit that is proportional to the flow resistance of the layer and which is substantially higher than that of an unconstrained sample of the same material. However, it was also found that the benefit of the circumferential edge constraint was reduced in a transitional frequency range by a shearing resonance of the sample. Here it will be shown that the effect of that resonance can be mitigated or eliminated by adding additional axial and radial constraints running through the sample. It will also be shown that the constraint effect can be modeled closely by using a finite element procedure based on the Biot poroelastic theory. Implications for low frequency barrier design are also discussed.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1999.07a
• /
• pp.171-171
• /
• 1999

We studied the charge redistribution in the Pt-M (M=Cu, Co) alloys by X-ray Absorption Near Edge Spectroscopy(XANES) and X-ray Photoelectron Spectroscopy(XPS). These analysis tools provide us information about the charge transfer in the valence band of intermetallic bonding. The samples were prepared by arc-melting method. After annealing this samples in vacuum for several hours, we cold get the ordered samples, which were confirmed with XRD analysis. the core and valence level energy shift in these system were investigated by Mg $K\alpha$(1253.6eV) x-ray source for Pt-Co alloys and monochromatized Al $K\alpha$ (1486.6eV) for Pt-Cu alloys. Pt L2, L3-edge, and Cu, Co K-edge XANES spectra were measured with the total electron-yield mode detector at the 3Cl beam line of the PLS (Pohang light source0. from the changes of White line (WL) area and the core level shifts of the each metal sites, we can obtain the information about the electrons participating in the intermetallic bonding of the Pt-Cu and Pt-Co alloys.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.398-398
• /
• 2010

To determine the molecular directionality of PI chains depending on rubbing condition, we measured the angle resolved near edge X-ray absorption fine structure (NEXAFS) spectra at C K-edge of the rubbed PI films. Twisted nematic mode PI (PI-TN) and in plane switching mode PI (PI-IPS) were introduced to examine the effect of rubbing conditions on the chain directionality. The average tilt angle a of the PI molecules was estimated through the measured intensity change of $C=C\;{\pi}^*$ in NEXAFS C K-edge spectrum by controlling the stage speed and the pile contact depth. After rubbing, the irregular molecular direction changed to a regular direction with a molecular tilt angle of $51.2^{\circ}$ for PI-TN and $49.6^{\circ}$ for PI-IPS at the rubbing condition of the roll speed of 1000 rpm, stage speed of 50 mm/sec, and file contact depth of 0.3 mm. The molecular tilt angle $\alpha$ was linearly decreased in the PI-TN and PI-IPS samples with increasing depth of the pile contact.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2006.08a
• /
• pp.925-928
• /
• 2006

With the high sustain frequency at 250 kHz, a three-dimensional diagnostics of excited xenon atoms was investigated by the emission and absorption microscopic spectroscopy for plasma display panels, spatiotemporally. As a typical feature of the emissions, a broad discharge peak was observed on the temporal cathode and a sharp one was monitored on the anode, at the high frequency. However, the discharge starts from the cathode edge, actually, that is a discharge space on the floated address (or data) electrode. Spatially, the dense emission and absorption peak were observed in the discharge space between the sustain electrodes gap. Overall, the microdischarge at high sustain frequency showed priming dominant characteristics.