• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.362-362
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• 2014

Atomic layer deposition (ALD) can be regarded as a special variation of the chemical vapor deposition method for reducing film thickness. ALD is based on sequential self-limiting reactions from the gas phase to produce thin films and over-layers in the nanometer scale with perfect conformality and process controllability. These characteristics make ALD an important film deposition technique for nanoelectronics. Tantalum pentoxide ($Ta_2O_5$) has a number of applications in optics and electronics due to its superior properties, such as thermal and chemical stability, high refractive index (>2.0), low absorption in near-UV to IR regions, and high-k. In particular, the dielectric constant of amorphous $Ta_2O_5$ is typically close to 25. Accordingly, $Ta_2O_5$ has been extensively studied in various electronics such as metal oxide semiconductor field-effect transistors (FET), organic FET, dynamic random access memories (RAM), resistance RAM, etc. In this experiment, the variations of chemical and interfacial state during the growth of $Ta_2O_5$ films on the Si substrate by ALD was investigated using in-situ synchrotron radiation photoemission spectroscopy. A newly synthesized liquid precursor $Ta(N^tBu)(dmamp)_2$ Me was used as the metal precursor, with Ar as a purging gas and $H_2O$ as the oxidant source. The core-level spectra of Si 2p, Ta 4f, and O 1s revealed that Ta suboxide and Si dioxide were formed at the initial stages of $Ta_2O_5$ growth. However, the Ta suboxide states almost disappeared as the ALD cycles progressed. Consequently, the $Ta^{5+}$ state, which corresponds with the stoichiometric $Ta_2O_5$, only appeared after 4.0 cycles. Additionally, tantalum silicide was not detected at the interfacial states between $Ta_2O_5$ and Si. The measured valence band offset value between $Ta_2O_5$ and the Si substrate was 3.08 eV after 2.5 cycles.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.1
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• pp.61-68
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• 2007

Interfacial fracture energy(${\Gamma}$) between $Al_2O_3$ thin film deposited by Atomic Layer Deposition(ALD) and sputter deposited Cu electrode for embedded PCB applications is measured from a $90^{\circ}$ peel test. While the interfacial fracture energy of $Cu/Al_2O_3$ is very poor, Cr adhesion layer increases the interfacial fracture energy to $39.8{\pm}3.2g/mm\;for\;Ar^+$ RF plasma power density of $0.123W/cm^2$, which seems to come from the enhancement of the mechanical interlocking and Cr-O chemical bonding effects.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.565-566
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• 2006

In this work, We study electrical characterization of $HfO_2$/Hf/Si films grown by Atomic Layer Deposition(ALD). Through AES(Auger Electron Spectroscopy), capacitance-voltage(C-V) and current-voltage(I-V) analysis, the role of Hf layer for the better $HfO_2$/Si interface property was investigated. We found that Hf metal layer in our structure effectively suppressed the generation of interfacial $SiO_2$ layer between $HfO_2$ film and silicon substrate.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.432-432
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• 2010

Organic light emitting diodes (OLED) thin films were fabricated by Electrostatic spray deposition (ESD). In this study, we reported the thickness, morphology, current efficiency, luminescence of OLED fabricated by ESD. These results were compared with the spin coating method, and showed that also ESD is a good fabrication method for OLED because of its characteristics similar with the results using spin coating. The active layer consists of organic blends with Poly(N-vinylcarbazole) (PVK), 2-(4-Biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), N,N'-Bis(3-methylphenyl) -N,N'-bis(phenyl)-benzidine (TPD), Tris(2-phenylpyridine)iridium(III) (Ir(ppy)3), and the structure of OLED consists of aluminum (Al), lithium fluoride (LiF), organic blends, PEDOT:PSS and Indium-tin-oxide (ITO), which was used as the top cathode, cathode interfacial layer, emitting layer and bottom anode, respectively. The results suggest that Electrostatic spray deposition is a promising method for the next generation of OLED fabrication since it has a probability fabricating large-area thin films.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.207.1-207.1
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• 2013

Tantalum oxide has been extensively investigated as one of the promising Resistive switching materials applicable to Resistive Dynamic Access Memories. Impedance spectroscopy offers simultaneous measurements of electrical and dielectric information, separation of electrical origins among bulk, grain boundaries, and interfaces, and the monitoring of electrical components. Such benefits have been combined with the resistive states of resistive switching devices which can be described in terms of equivalent circuits involving resistors, capacitors, and inductors, The current work employed pulsed laser deposition in order to prepare the oxygen-deficient tantalum oxide. The fabricated devices were controlled between highresistance and low-resistance states in controlled current compliance modes. The corresponding electrical phenomena were monitored both in the dc-based current-voltage characteristics and in the ac-based impedance spectroscopy. The origins of the electrical switching are discussed towards optimized ReRAM devices in terms of interfacial effects.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.140.2-140.2
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• 2013

Strong metal-support interaction effect is an important issue in determining the catalytic activity for heterogeneous catalysis. In this work, we report the catalytic activity of $Au/TiO_2$, $Au/Al_2O_3$, and $Au/Al_2O_3-CeO_2$ nanocatalysts under CO oxidation fabricated by arc plasma deposition (APD), which is a facile dry process with no organic materials involved. These catalytic materials were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and $N_2$-physisorption. Catalytic activity of the materials has measured by CO oxidation using oxygen, as a model reaction, in a micro-flow reactor at atmospheric pressure. Using APD, the catalyst nanoparticles were well dispersed on metal oxide powder with an average particle size (3~10 nm). As for catalytic reactivity, the result shows $Au/Al_2O_3-CeO_2$ nanocatalyst has the highest catalytic activity among three samples in CO oxidation, and $Au/TiO_2$, and $Au/Al_2O_3$ in sequence. We discuss the effects of structure and metal-oxide interactions of the catalysts on catalytic activity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.1
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• pp.47-52
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• 2008

As the packing density of IC devices gets ever higher, the thickness of the gate $SiO_2$ layer of the MOS devices is now required to be reduced down to 1 nm. For such a thin $SiO_2$ layer, the MOS device cannot operate properly because of tunneling current and threshold voltage shift. Hence there has been much effort to develop new dielectric materials which have higher dielectric constants than $SiO_2$ and is free from such undesirable effects. In this work, the physical and electrical characteristics of ALD $ZrO_2$ film have been studied. After deposition of a thin ALD $ZrO_2$ film, it went through thermal treatment in the presence of argon gas at $800^{\circ}C$ for 1 hr. The characteristics of morphology, crystallization kinetics, and interfacial layer of $Pt/ZrO_2/Si$ samples have been investigated by using the analyzing instruments like XRD, TEM and C-V plots. It has been found that the characteristics of the $Pt/ZrO_2/Si$ device was enhanced by the thermal treatment.

• Korean Journal of Materials Research
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• v.28 no.5
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• pp.268-272
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• 2018

An $Al_2O_3/AlN$ bilayer deposited on GaN by atomic layer deposition (ALD) is employed to prepare $Al_2O_3/AlN/GaN$ metal-insulator-semiconductor (MIS) diodes, and their interfacial properties are investigated using X-ray photoelectron spectroscopy (XPS) with sputter etch treatment and current-voltage (I-V) measurements. XPS analyses reveal that the native oxides on the GaN surface are reduced significantly during the early ALD stage, indicating that AlN deposition effectively clelans up the GaN surface. In addition, the suppression of Al-OH bonds is observed through the ALD process. This result may be related to the improved device performance because Al-OH bonds act as interface defects. Finally, temperature dependent I-V analyses show that the barrier height increases and the ideality factor decreases with an increase in temperature, which is associated with the barrier inhomogeneity. A Modified Richardson plot produces the Richardson constant of $A^{**}$ as $30.45Acm^{-2}K^{-2}$, which is similar to the theoretical value of $26.4Acm^{-2}K^{-2}$ for n-GaN. This indicates that the barrier inhomogeneity appropriately explains the forward current transport across the $Au/Al_2O_3/AlN/GaN$ interface.

• Composites Research
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• v.36 no.5
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• pp.377-382
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• 2023

To enhance the performance of graphene-based devices, it is of great importance to better understand the interfacial interaction of graphene with its underlying substrates. In this study, the adhesion energy of monolayer graphene placed on dielectric substrates was characterized using mode I fracture tests. Large-area monolayer graphene was synthesized on copper foil using chemical vapor deposition (CVD) with methane and hydrogen. The synthesized graphene was placed on target dielectric substrates using polymer-assisted wet transfer technique. The monolayer graphene placed on a substrate was mechanically delaminated from the dielectric substrate by mode I fracture tests using double cantilever beam configuration. The obtained force-displacement curves were analyzed to estimate the adhesion energies, showing 1.13 ± 0.12 J/m² for silicon dioxide and 2.90 ± 0.08 J/m² for silicon nitride. This work provides the quantitative measurement of the interfacial interactions of CVD-grown graphene with dielectric substrates.

• 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.