• Journal of the Microelectronics and Packaging Society
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• v.23 no.2
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• pp.49-55
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• 2016

The effects of post-annealing and temperature/humidity conditions on the interfacial adhesion energies of atomic layer deposited RuAlO diffusion barrier layer for Cu interconnects were systematically investigated. The initial interfacial adhesion energy measured by four-point bending test was $7.60J/m^2$. The interfacial adhesion energy decreased to $5.65J/m^2$ after 500 hrs at $85^{\circ}C$/85% T/H condition, while it increased to $24.05J/m^2$ after annealing at $200^{\circ}C$ for 500 hrs. The X-ray photoemission spectroscopy (XPS) analysis showed that delaminated interface was RuAlO/$SiO_2$ for as-bonded and T/H conditions, while it was Cu/RuAlO for post-annealing condition. XPS O1s peak separation results revealed that the effective generation of strong Al-O-Si bonds between $AlO_x$ and $SiO_2$ interface at optimum post-annealing conditions is responsible for enhanced interfacial adhesion energies between RuAlO/$SiO_2$ interface, which would lead to good electrical and mechanical reliabilities of atomic layer deposited RuAlO diffusion barrier for advanced Cu interconnects.

• Journal of the Korean Vacuum Society
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• v.16 no.3
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• pp.197-204
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• 2007

Ultra thin Er-silicide layers formed by Er deposition on the clean p-silicon and in situ post annealing technique were investigated with respect to change of the Schottky barrier height. The formation of Er silicides was confirmed by XPS results. UPS measurements revealed that the workfunction of the silicide decreased and was saturated as the deposited Er thickness increased up to $10{\AA}$. We found that the silicides were mainly composed of Er5Si3 phase through the XRD experiments. After Schottky diodes were fabricated with the Er silicide/p-Si junctions, the Schottky barrier heights were calculated $0.44{\sim}0.78eV$ from the I-V measurements of the Schottky diodes. There was large discrepancy in the Schottky barrier heights deduced from the UPS with the ideal junction condition and the real I-V measurements, so that we attributed the discrepancy to the $Er_5Si_3$ phase in the Er-silicides and the large interfacial density of trap state of it.

• Korean Journal of Materials Research
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• v.10 no.3
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• pp.204-211
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• 2000

The $(Y,Gd)BO_3:Eu$ red phosphors for PDP application were synthesized by ultrasonic spray method and then their photoluminance properties were investigated under 147nm VUV irradiation. The precursor solution of acetates of Y, GD and Eu and boric acid diluted in water was sprayed using 1.7 MHz ultra-sonic sprayer into the reaction tube held at high temperature. The as-sprayed particles were amorphous phase having C-C and C-H bonds due to the insufficient thermal reaction during the pass along the tube. But the sprayed samples followed by heat treatment at $1100^{\circ}C$ had the same crystal structure and chemical composition as those samples followed by solid state reaction. It was found that the $(Y_{0.7}Gd_{0.3})_{0.95} BO_3:Eu_{0.05}^{3+}$ phosphor particles synthesized by spray at $500^{\circ}C$ and then heat treated at $900^{\circ}C$ had a spherical-like shape and fine particle size at $0.7{\mu\textrm{m}}$ having a narrow size distribution, while the phosphor particles made by solid state reaction was $3{\mu\textrm{m}}$ coarse and non-uniform size distribution. The emitting intensity under 147nm VUV excitation for $(Y_{0.7}Gd_{0.3})_{0.95}BO_3:Eu_{0.05}^{3+}$ phosphor prepared by spray method was found to be higher than those phosphor made by solid state reaction and the commercial $(Y,Gd)BO_3:Eu$ product.

• Journal of the Korean Vacuum Society
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• v.13 no.2
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• pp.86-91
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• 2004

Transiton-metal gallides attract wide interest as a candidate for high-temperature structural materials. In a wide composition range, in which it was known that Co-Ga alloy have CsCl (B2) crystallographic structure, a systematic study on the correlation between physical properties and electronic structures of Co-gallides was performed. $Co_{l-x}Ga$ $_{x}$ alloys ($0.35\leq$x$\leq0.55$) were prepared by arc-melting method and were annealed at $1000 ^{\circ}C$ for 48hour to increase the homogeneity. In this composition range all the prepared alloys have the CsCl (B2) structure. The chemical states and the electronic structure were studied by using x-ray photoemission spectroscopy (XPS), and x-ray absorption near-edge structure (XANES), and exhibit different physical properties depending on the composition. During the annealing, a significant oxidation has happened and all the oxygen atoms are incorporated with the Ga atoms to form a $Ga_2O_3$ phase. In a view point of electronic structure, the $Co_{l-x}Ga$ $_{x}$ alloys were formed by the Ga(p) - Co(d) hybridization.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.92-92
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• 2014

Recently, many state-of-art spectroscopy techniques are used to unravel the mysteries of condensed matters. And numerous heterostructures have provided a new avenue to search for new emergent phenomena. Especially, near the interface, various forms of symmetry-breaking can appear, which induces many novel phenomena. Although these intriguing phenomena can be emerged at the interface, by using conventional measurement techniques, the experimental investigations have been limited due to the buried nature of interface. One of the ways to overcome this limitation is in situ investigation of the layer-by-layer evolution of the electronic structure with increasing of the thickness. Namely, with very thin layer, we can measure the electronic structure strongly affected by the interface effect, but with thick layer, the bulk property becomes strong. Angle-resolved photoemission spectroscopy (ARPES) is powerful tool to directly obtain electronic structure, and it is very surface sensitive. Thus, the layer-by-layer evolution of the electronic structure in oxide heterostructure can be investigated by using in situ ARPES. LaNiO3 (LNO) heterostructures have recently attracted much attention due to theoretical predictions for many intriguing quantum phenomena. The theories suggest that, by tuning external parameters such as misfit strain and dimensionality in LNO heterostructure, the latent orders, which is absent in bulk, including charge disproportionation, spin-density-wave order and Mott insulator, could be emerged in LNO heterostructure. Here, we performed in situ ARPES studies on LNO films with varying the misfit strain and thickness. (1) By using LaAlO3 (-1.3%), NdGaO3 (+0.3%), and SrTiO3 (+1.7%) substrates, we could obtain LNO films under compressive strain, nearly strain-free, and tensile strain, respectively. As strain state changes from compressive to tensile, the Ni eg bands are rearranged and cross the Fermi level, which induces a change of Fermi surface (FS) topology. Additionally, two different FS superstructures are observed depending on strain states, which are attributed to signatures of latent charge and spin orderings in LNO films. (2) We also deposited LNO ultrathin films under tensile strain with thickness between 1 and 10 unit-cells. We found that the Fermi surface nesting effect becomes strong in two-dimensions and significantly enhances spin-density-wave order. The further details are discussed more in presentation. This work was collaborated with Hyang Keun Yoo, Seung Ill Hyun, Eli Rotenberg, Ji Hoon Shim, Young Jun Chang and Hyeong-Do Kim.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.335-335
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• 2014

Over the past several years, transparent conducting oxides have been extensively studied in order to replace indium tin oxide (ITO). Here we report on fluorine doped zinc tin oxide (FZTO) films deposited on glass substrates by radio-frequency (RF) magnetron sputtering using a 30 wt% ZnO with 70 wt% SnO2 ceramic targets. The F-doping was carried out by introducing a mixed gas of pure Ar, CF4, and O2 forming gas into the sputtering chamber while sputtering ZTO target. Annealing temperature affects the structural, electrical and optical properties of FZTO thin films. All the as-deposited FZTO films grown at room temperature are found to be amorphous because of the immiscibility of SnO2 and ZnO. Even after the as-deposited FZTO films were annealed from $300{\sim}500^{\circ}C$, there were no significant changes. However, when the sample is annealed temperature up to $600^{\circ}C$, two distinct diffraction peaks appear in XRD spectra at $2{\Theta}=34.0^{\circ}$ and $52.02^{\circ}$, respectively, which correspond to the (101) and (211) planes of rutile phase SnO2. FZTO thin film annealed at $600^{\circ}C$ resulted in decrease of resistivity $5.47{\times}10^{-3}{\Omega}cm$, carrier concentration ~1019 cm-3, mobility~20 cm2 V-1s-1 and increase of optical band gap from 3.41 to 3.60 eV with increasing the annealing temperatures and well explained by Burstein-Moss effect. Change of work function with the annealing temperature was obtained by ultraviolet photoemission spectroscopy. The increase of annealing temperature leads to increase of work function from ${\phi}=3.80eV$ (as-deposited FZTO) to ${\phi}=4.10eV$ ($600^{\circ}C$ annealed FZTO) which are quite smaller than 4.62 eV for Al-ZnO and 4.74 eV for SnO2. Through X-ray photoelectron spectroscopy, incorporation of F atoms was found at around the binding energy of 684.28 eV in the as-deposited and annealed FZTO up to 400oC, but can't be observed in the annealed FZTO at 500oC. This result indicates that F atoms in FZTO films are loosely bound or probably located in the interstitial sites instead of substitutional sites and thus easily diffused into the vacuum from the films by thermal annealing. The optical transmittance of FZTO films was higher than 80% in all specimens and 2-3% higher than ZTO films. FZTO is a possible potential transparent conducting oxide (TCO) alternative for application in optoelectronics.

• Journal of the Korean Magnetics Society
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• v.18 no.1
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• pp.19-23
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• 2008

The mixed ferrite $V_xFe_{3-x}O_4$(x=0.0, 0.15, 0.5, 1.0) thin films were prepared by sol-gel method. Their crystallographic and magnetic hyperfine properties have been studied using X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS) and conversion electron $M\"{o}ssbauer$ spectroscopy(CEMS). The crystal structure is found to be cubic spinel throughout the series($x{\leq}1.0$), and the lattice parameter $a_0$ increases linearly with increasing V content. XRD, XSP and CEMS indicate that $V^{3+}$ substitution for $Fe^{3+}$ in B-site is superior to $V^{2+}$ substitution for $Fe^{2+}$ in B-site. It is noticeable that both quadrupole shift and hyperfine field decreases with increasing V composition, suggesting the change of local symmetry and accompanying line-broadening. The line-broadening on CEMS spectra can be explained by the distribution of magnetic hyperfine fields.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.169-174
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• 2015

In this research, pristine graphene was synthesized using methane ($CH_4$) gas, and N-doped graphene was synthesized using pyridine ($C_5H_5N$) liquid source by chemical vapor deposition (CVD) method. Basic optical properties of both pristine and N-doped graphene were investigated by Raman spectroscopy and XPS (X-ray photoemission spectroscopy), and electrical transport characteristics were estimated by current-voltage response of graphene channel as a function of gate voltages. Results for CVD grown pristine graphene from methane gas show that G-peak, 2D-peak and C1s-peak in Raman spectra and XPS. Charge neutral point (CNP; Dirac-point) appeared at about +4 V gate bias in electrical characterization. In the case of pyridine based CVD grown N-doped graphene, D-peak, G-peak, weak 2D-peak were observed in Raman spectra and C1s-peak and slight N1s-peak in XPS. CNP appeared at -96 V gate bias in electrical characterization. These result show successful control of the property of graphene artificially synthesized by CVD method.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.14-15
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• 2010

Recently there has been growing interest in topological insulators or the quantum spin Hall (QSH) phase, which are insulating materials with bulk band gaps but have metallic edge states that are formed topologically and robust against any non-magnetic impurity [1]. In a three-dimensional material, the two-dimensional surface states correspond to the edge states (topological metal) and their intriguing nature in terms of electronic and spin structures have been experimentally observed in bulk Bi1-xSbx single crystals [2,3,4]. However, if we want to know the transport properties of these topological metals, high purity samples as well as very low temperature will be needed because of the contribution from bulk states or impurity effects. In a recent report, it was also shown that an intriguing coupling between the surface and bulk states will occur [5]. A simple solution to this bothersome problem is to prepare a topological metal on an ultrathin film, in which the surface-to-bulk ratio is drastically increased. Therefore in the present study, we have investigated if there is a method to make an ultrathin Bi1-xSbx film on a semiconductor substrate. From reflection high-energy electron diffraction observation, it was found that single crystal Bi1-xSbx films (0${\sim}30\;{\AA}A$ can be prepared on Si(111)-$7{\times}7$. The transport properties of such films were characterized by in situ monolithic micro four-point probes [6]. The temperature dependence of the resistivity for the x=0.1 samples was insulating when the film thickness was $240\;{\AA}A$. However, it became metallic as the thickness was reduced down to $30\;{\AA}A$, indicating surface-state dominant electrical conduction. Figure 1 shows the Fermi surface of $40\;{\AA}A$ thick Bi0.92Sb0.08 (a) and Bi0.84Sb0.16 (b) films mapped by angle-resolved photoemission spectroscopy. The basic features of the electronic structure of these surface states were shown to be the same as those found on bulk surfaces, meaning that topological metals can be prepared at the surface of an ultrathin film. The details will be given in the presentation.

• Korean Journal of Dental Materials
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• v.45 no.4
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• pp.257-274
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• 2018

The purpose of this study was to evaluate the effect of acid-treatment conditions on the surface properties of the RBM (Resorbable Blast Media) treated titanium. Disk typed cp-titanium specimens were prepared and RBM treatments was performed with calcium phosphate ceramic powder. Acid solution was mixed using HCl, $H_2SO_4$ and deionized water with 4 different volume fraction. The RBM treated titanium was acid treated with different acid solutions at 3 different temperatures and for 3 different periods. After acid-treatments, samples were cleaned with 1 % Solujet solution for 30 min and deionized water for 30 min using ultrasonic cleanser, then dried in the electrical oven ($37^{\circ}C$). Weight of samples before and after acid-treatment were measured using electric balance. Surface roughness was estimated using a confocal laser scanning microscopy, crystal phase in the surface of sample was analyzed using X-ray diffractometer. Surface morphology and components were evaluated using Scanning Electron Microscope (SEM) with Energy Dispersive X-ray spectroscopy (EDX) and X-ray Photoemission Spectroscopy (XPS). Values of the weight changes and surface roughness were statistically analyzed using Tukey-multiple comparison test (p=0.05). Weight change after acid treatments were significantly increased with increasing the concentration of $H_2SO_4$ and temperature of acid-solution. Acid-treatment conditions (concentration of $H_2SO_4$, temperature and time) did not produce consistent effects on the surface roughness, it showed the scattered results. From XRD analysis, formation of titanium hydrides in the titanium surface were observed in all specimens treated with acid-solutions. From XPS analysis, thin titanium oxide layer in the acid-treated specimens could be evaluated. Acid solution with $90^{\circ}C$ showed the strong effect on the titanium surface, it should be treated with caution to avoid the over-etching process.