• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.65-65
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• 2010

Extreme ultraviolet lithography (EUVL) is expected to be applied for making patterns below 32 nm in device industry. An ultrathin EUV photoresist (PR) of a few nm in thickness is required to reduce minimum feature size further. Here, we show that pentacene molecular layers can be employed as a new EUV resist for the first time. Dots and lines in nm scale are successfully realized using the new molecular resist. We clearly provide the mechanism for forming the nanopatterns with scanning photoemission microscope (SPEM), EUV interference lithography (EUV-IL), atomic force microscope (AFM), photoemission spectroscopy (PES), etc. The molecular PR has several advantages over traditional polymer EUV PRs; for example, high thermal/chemical stability, negligible outgassing, ability to control the height and width on the nanometer scale, leaving fewer residuals, no need for a chemical development process and thus reduction of chemical waste to make the nanopatterns. Besides, it could be applied to any substrate to which pentacene bonds chemically, such as $SiO_2$, SiN, and SiON, which is of importance in the device industry.

• Journal of the Korean Magnetics Society
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• v.5 no.5
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• pp.442-446
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• 1995

Electronic structures of Fe overlayers on Cr(Fe/Cr) films, with an Fe coverage of $1-20{\AA}$, have been investigated by using photoemission spectroscopy. Experimental results are compared with supercell band structure calculations for a system with monolayer (ML) Fe on each side of five layer Cr, Fe(1ML)/Cr(5ML)/Fe(1ML). The extracted Fe 3d partial spectral weight in Fe/Cr exhibits very interesting features for very thin Fe overlayers. First, a sharp emissionnear the Fermi energy is observed, which is expected to originate primarily from hybridization between Fe and Cr 3d electrons at the Fe/Cr interface, and partially from the Fe 3d surface states in the Fe overlayer. Second, other structures are observed at higher binding energies which resemble the Cr 3d valence bands, also suggesting large hybridization between Fe and Cr 3d states at the Fe/Cr interface. These conjectures are confirmed by band structure calculations for Fe(1ML)/Cr(5ML)/Fe(1ML).

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.302-302
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• 2011

The binary chalcogenide semiconductor Bi2Se3 is at the center of intensive research on a new state of matter known as topological insulators. It has Dirac point in their band structures with robust surface states that are protected against external perturbations by strong spin-orbit coupling with broken inversion symmetry. Such unique band configurations were confirmed by recent angle-resolved photoelectron emission spectroscopy experiments with an unwanted n-type doping effect, showing a Fermi level shift of about 0.3 eV caused by atomic defects such as Se vacancies. Since the number of defects can be reduced using the molecular beam epitaxy (MBE) method. We have prepared the Bi2Se3 film on noble metal Au(111) and semiconductor Si(111) substrates by MBE method. To characterize the film, we have introduced several surface sensitive techniques including x-ray photoemission electron spectroscopy (XPS) and micro Raman spectroscopy. Also, crystallinity of the film has been confirmed by x-ray diffraction (XRD). Using home-built scanning tunneling microscope, we observed the atomic structure of quintuple layered Bi2Se3 film on Au(111).

• Journal of the Korean Magnetics Society
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• v.25 no.5
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• pp.156-161
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• 2015

The electronic structures of the potential candidate semiconductor nanoparticles for dye-sensitized solar cell (DSSC), such as $ZnSnO_3$ and $Zn_2SnO_4$, have been investigated by employing X-ray photoemission spectroscopy (XPS). The measured X-ray diffraction patterns show that $ZnSnO_3$ and $Zn_2SnO_4$ samples have the single-phase ilmenite-type structure and the inverse spinel structure, respectively. The measured Zn 2p and Sn 3d core-level XPS spectra reveal that the valence states of Zn and Sn ions are divalent (Zn 2+) and tetravalent (Sn 4+), respectively, in both $ZnSnO_3$ and $Zn_2SnO_4$. On the other hand, the shallow core-level measurements show that the binding energies of Sn 4d and Zn 3d core levels in $ZnSnO_3$ are lower than those in $Zn_2SnO_4$. This work provides the information on the valence states of Zn and Sn ions and their chemical bonding in $ZnSnO_3$ and $Zn_2SnO_4$.

• JSTS:Journal of Semiconductor Technology and Science
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• v.5 no.2
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• pp.77-82
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• 2005

We compare electrical and optical properties of organic light emitting diodes (OLEDs) using rhodium-oxide-coated indium-tin-oxide ($O_2$-Rh/ITO) to that using $O_2$-plasma-treated ITO (ITO) anodes. The turn-on voltage decreased from 7 V to 5 V and luminance value increased when the $O_2$ plasma treated Rh layer was deposited on ITO. Synchrotron radiation photoelectron spectroscopy results showed the dipole energies of both ITO and $O_2$-Rh/ITO were same with each other, - 0.3 eV, meaning the formation of same amount of interface dipole. The secondary electron emission spectra revealed that the work function of $O_2$-Rh/ITO is higher hy 0.2 eV than that of ITO, resulting in the decrease of the tum-on voltage via reduction ofhole injection barrier.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.204.2-204.2
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• 2014

Among various metal oxides, ZrO2 is of particular interests and has received widespread attention thanks to its ideal mechanical and chemical stability. As a cheap metal, Ag nanoparticles are also widely used as catalysts in ethylene epoxidation and methanol oxidation. However, the nature of Ag-ZrO2 interfaces is still unknown. In this work, the growth, interfacial interaction and thermal stability of Ag nanoparticles on ZrO2(111) film surfaces were studied by low-energy electron diffraction (LEED), synchrotron radiation photoemission spectroscopy (SRPES), and X-ray photoelectron spectroscopy (XPS). The ZrO2(111) films were epitaxially grown on Pt(111). Three-dimensional (3D) growth model of Ag on the ZrO2(111) surface at 300 K was observed with a density of ${\sim}2.0{\times}1012particles/cm2$. The binding energy of Ag 3d shifts to low BE from very low to high Ag coverages by 0.5 eV. The Auger parameters shows the primary contribution to the Ag core level BE shift is final state effect, indicating a very weak interaction between Ag clusters and ZrO2(111) film. Thermal stability experiments demonstrate that Ag particles underwent serious sintering before they desorb from the zirconia film surface. In addition, large Ag particles have stronger ability of inhibiting sintering.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.8
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• pp.325-329
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• 2003

Effects of thermal treatment on the structural properties of diamond-like carbon (DU) films were examined. The DLC films were deposited by using a modified filtered cathodic vacuum arc (FCVA) deposition system and by varying the negative substrate bias voltage, deposition time, and nitrogen flow rate. Thermal treatment on DLC films was performed using a rapid thermal annealing (RTA) process at $600^{\circ}C$ for 2min. Raman spectroscopy, x-ray photoemission spectroscopy (XPS), atomic force microscope (AFM), and surface profiler were used to characterize the I$_{D}$I$_{G}$ intensity ratio, sp$^3$ hybrid carbon fraction, internal stress, and surface roughness. It was found for all the deposited DLC films that the RTA-treatment results in the release of internal compressive stress, while at the same time it leds to the decrease of sp$^3$ fraction and the increase of I$_{D}$I$_{G}$ intensity ratio. It was also suggested that the thermal treatment effect on the structural property of DLC films strongly depends on the diamond-like nature (i.e., sp$^3$ fraction) of as-deposited film.ed film.

• Current Applied Physics
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• v.18 no.11
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• pp.1190-1195
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• 2018

By employing soft X-ray magnetic circular dichroism (XMCD), soft X-ray absorption spectroscopy (XAS), and photoemission spectroscopy (PES), we have investigated the electronic structure of the candidate zero-moment half-metallic $Mn_3Ga$. We have studied the ball-milled and annealed $Mn_3Ga$ powder samples that exhibit nearly zero magnetization. Mn 2p XAS revealed that Mn ions in $Mn_3Ga$ are nearly divalent for both of the Mn ions having the locally octahedral symmetry and those having the locally tetrahedral symmetry. The measured Mn 2p XMCD spectrum of $Mn_3Ga$ is very similar to that of ferrimagnetic $MnFe_2O_4$ having divalent Mn ions. The sum-rule analysis of the Mn 2p XMCD spectrum shows that both the spin and orbital magnetic moments of Mn ions in $Mn_3Ga$ are negligibly small, in agreement with the nearly compensated-ferrimagnetic ground state of $Mn_3Ga$. The valence-band PES spectrum of $Mn_3Ga$ agrees well with the calculated density of states, supporting the half-metallic electronic structure of $Mn_3Ga$.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.235-235
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• 2012

We investigated the energy levels of valence region at the planar junction of poly (3-hexylthiophene) (P3HT) and C61-butyric acid methylester (PCBM) using ultraviolet photoemission spectroscopy (UPS) with ultra high vacuum. These are the most widely used materials for bulk heterojunction (BHJ) organic solar cells due to their high efficiency. In order to make the planar junction, we carried out the electrospray vacuum deposition (EVD) of PCBM onto spin-coated P3HT in high vacuum conditions (${\sim}10^{-5}-10^{-6}$). The planar junction interface exhibited 0.71 eV for the offset between P3HT HOMO and PCBM LUMO, which is different from the gap (0.85 eV) of individual values and is closer to the open circuit voltage of solar cells fabricated with the same material combination.

• Bulletin of the Korean Chemical Society
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• v.31 no.7
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• pp.1973-1975
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• 2010

The electronic and adsorption structure of o-phthalaldehyde (OPA) on the H-Si(100) surface was investigated by using Near Edge X-ray Fine Structure (NEXAFS) and high resolution photoemission spectroscopy (HRPES). We confirmed that the OPA grown on the H-Si(100) surface showed good dependency with about 60 degree tilting angle using NEXAFS and a single O 1s peak by using HRPES. Hydrogen atom passivated on the Si(100) surface was found to be a seed for making one dimensional organic line that uses a chain reaction as the H-Si(100) surface was compared with the hydrogen free Si(100) surface.