Yunsoo Kim

High vacuum chemical vapor deposition of cubic SiC thin films on Si(001) substrates using single source precursor

Thin films of cubic SiC have been prepared on Si(001) substrates in situ by high vacuum metal-organic chemical vapor deposition (HVMO-CVD) method using a single source precursor at various growth temperatures in the range of 300–1000°C. 1,3-Disilabutane, H3Si-CH2-SiH2-CH3 (DSB) that contains the same amount of silicon and carbon atoms in the same molecule was used as precursor without carrier gas. During HVMO-CVD, moreover, a series of as-deposited SiC/Si(001) thin films were simultaneously characterized by in situ X-ray photoelectron spectrometry (XPS) under the UHV condition without air exposure. XPS and Rutherford backscattering spectroscopy (RBS) show that the SiC films grown at above 700°C have stoichiometric composition. However, the films grown at below 700°C show Si-rich stoichiometry. Transmission electron microscopy (TEM) confirms the crystalline nature of the SiC films. The optimum temperatures for the formation of the epitaxial 3C–SiC thin films were found to be between 900 and 1000°C on the basis of XRD and TED analysis. In this study, the best film with maximum growth rate of 0.1 μm/h was obtained from a SiC film grown at 900°C and 8.7×10−4 Pa of DSB. The SiC/Si interface is clearly shown in secondary ion mass spectroscopy (SIMS) depth profile as judged by the sharp decrease 13C signals. The thickness of the as-grown films was determined using cross-sectional scanning electron microscopy (SEM) and RBS, and two different activation energies for 3C–SiC formation were obtained from the Arrhenius plots.

Chemical vapor deposition of Al2O3 films using highly volatile single sources

Abstract Amorphous Al2O3 films were grown on Si(100) and Si(111) substrates by low-pressure chemical vapor deposition in the temperature range of 250–600°C using dimethylaluminum isopropoxide, dimethylaluminum tert-butoxide, and diethylaluminum isopropoxide as single sources. All these sources vaporize readily at room temperature under reduced pressure. The films were characterized by X-ray diffractometry, X-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning electron microscopy. Auger depth profiling analysis of the samples indicates no appreciable carbon incorporation in the films.

Epitaxial Growth of Cubic SiC Films on Si Substrates by High Vacuum Chemical Vapor Deposition Using 1,3‐Disilabutane

Heteroepitaxial cubic SiC films were grown on (001) Si substrates at 900 to 980°C using 1,3-disilabutane (H 3 SiCH 2 SiH 2 CH 3 ) as a single molecular precursor under high vacuum conditions (5.0 to 8.0 x 10 -6 Torr). A carbonized buffer layer, grown in situ by gas source molecular beam epitaxy (GSMBE) of propane (C 3 H 8 ) was employed to minimize the effect of lattice mismatch between the Si substrate and the SiC overlayer. The crystalline structure, chemical composition, and thickness of the deposited films were investigated by in situ reflection high-energy diffraction, X-ray diffraction, Rutherford backscattering, Auger electron spectroscopy and transmission electron microscopy. The results show that high quality epitaxial 3C-SiC films with correct stoichiometry can be deposited on Si in this temperature range. The single precursor 1,3-disilabutane has been found suitable for the epitaxial growth of cubic SiC on (001) Si substrates.

Growth of AlN and GaN Thin Films on Si(100) Using New Single Molecular Precursors by MOCVD Method

Thin films of hexagonal AlN and GaN have been deposited on Si(100) substrates by MOCVD in the temperature range of 650 to 850 °C using cyclic diethylaluminium amide (DEAA), bis [diethyl(t-butylamido)aluminium] (DETBAA), cyclic dimethylgallium amide (DMGA), and bis [diethyl(t-butylamido)gallium] (DETBAG), as new single molecular precursors. On Si(100) at temperatures as low as 750 °C, strong preferential growth of hexagonal GaN(0002) thin films were successfully grown from DMGA without carrier gas. In the case of AlN film growth, however, only polycrystalline h-AlN thin films were obtained at temperatures above 750 °C using the precursors of DEAA and DETBAA. The XP spectra of all deposited AlN and GaN films are indistinguishable from that of AlN and GaN powders, and the Auger depth profile confirms that the films are stoichiometric and do not contain an appreciable amount of carbon. This is the first report on the growth of the h-GaN films from the synthesized precursors of DMGA and DETBAG, and we investigated their physical properties by nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and gas chromatography (GC).

Characteristics of SiO x Thin Film Deposited by Atmospheric Pressure Plasma-Enhanced Chemical Vapor Deposition Using PDMS ∕ O2 ∕ He

Silicon oxide thin films were deposited using a modified, pin-to-plate, dielectric barrier discharge system with polydimethylsiloxane (PDMS), bubbled by He/O 2 gas mixtures at atmospheric pressure and a temperature of less than 50°C. Increasing PDMS flow rate in the gas mixture increased the deposition rate, but also increased the surface roughness due to the formation of particles in the gas phase as a result of increased PDMS and silanol groups, leading to incomplete decomposition or oxidation of PDMS. The increase in the ratio of oxygen flow rate to PDMS flow rate decreased the surface roughness with increasing deposition rate due to the efficient oxidation of PDMS. However, when the oxygen flow rate was raised above 1 slm, due to the increased oxidation of PDMS in the gas phase and the decreased PDMS dissociation by the decreased plasma density, the surface roughness was again increased with decreasing deposition rate. At the gas mixture of 9 slm PDMS/He and 1 slm oxygen, a smooth, SiO 2 -like thin film was obtained at a deposition rate of 12 nm/min.

Affordances in Interior Design: A Case Study of Affordances in Interior Design of Conference Room Using Enhanced Function and Task Interaction

Interior design of space is somewhat different from product design in view of followings: the space should afford the multiple users at the same time and afford appropriate interactions with human and objects which exist inside the space. This paper presents a case study of interior design of a conference room based on affordance concept. We analyzed all of users’ tasks in a conference room based on the human activities that are divided into human-object and human-human interactions. Function decomposition of an every object in conference room was conducted. The concept of a high-level function is used such as “configure the space” to satisfy the given condition of the number of humans, the types of conference, and so forth. The Function-Task Interaction (FTI) method was enhanced to analyze the interactions between functions and user tasks. Many low-level affordances were extracted, and high-level affordances such as enter/exitability, prepare-ability, present-ability, discuss-ability and conclude-ability were also extracted by grouping low-level affordances in the enhanced FTI matrix. In addition, the benchmarking simulation was conducted for several existing conference rooms and the results confirmed that the extracted affordances can be used for checklist and also for good guidance on interior design process.Copyright

Growth of AlN films using hydrazidoalane single-source precursors

Aluminum nitride (AlN) films were grown on Si(100) and Si(111) substrates by a low-pressure chemical vapor deposition method in the temperature range 400‐8008C using two hydrazidoalane dimers, [Me2Al-m-N(H)NMe2]2 (1) and [Et2Al-m-N(H)NMe2]2 (2) as single-source precursors. Polycrystalline AlN films were obtained on Si(111) at 8008C from precursor 1. Amorphous AlN films were observed under certain growing conditions, such as on Si(100) substrates from precursor 2, or at lower temperatures. The films were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. q 1999 Elsevier Science S.A. All rights reserved.

Personal Cognitive Characteristics in Affordance Perception: The User Activity Case Study in a Building Lobby

User activities in performing tasks are influenced by the way the user perceives the related surrounding context and environment and determined with user judgment preferences. Physical environment structures afford user activities when these are perceived. Thus, this paper addresses how user activities and perceived affordances are different reflecting personal creativity modes, which are determined by factual-intuitive perception inclination and subjective-objective decision preferences as well as introverted-extroverted nature. To design-in various affordance features for diverse users in varying contexts, understanding on relations between user personal characteristics and affordance perception would be helpful. We conducted a case study in a public space — building lobby — used by many general people. User activities and behaviors were analyzed in several specific tasks given to twenty students in the lobby of a building they have never been to before. The tasks were devised so that various affordance features could be relevant while eliminating other factors affecting the affordance perception than those due to user personal characteristics. User activities can be classified into several different groups for each task based on affordance features involved in their activities. These user activity differences are then compared with their personal creativity modes. For user of less common activities for some tasks, relevant personal cognitive characteristics have been identified.Copyright

Growth of Hexagonal Gallium Nitride Films On The (111) Surfaces of Silicon with Zinc Oxide Buffer Layers

The growth of gallium nitride films on sapphire substrates has not been straightforward because of the large lattice mismatch between gallium nitride and sapphire. Zinc oxide is structurally the closest material to gallium nitride and therefore is finding use as the substrate for gallium nitride. Single crystal wafers of zinc oxide are hard to obtain and very expensive. However, a thin layer of zinc oxide on a suitable substrate might solve this problem. In this work, highly c -axis oriented zinc oxide buffer layers were grown on Si(lll) substrates at temperatures 410–540 °C by chemical vapor deposition of bis(2,2,6,6-tetramethyl–3,5-heptanedionato)zinc, Zn(tmhd) 2 , and the hexagonal GaN films were subsequently deposited on them at 500 °C using the single precursor tris(diethyl -μ-amido-gallium), [(C 2 H 5 ) 2 GaNH 2 ] 3 . The compound Zn(tmhd) 2 was found to require oxygen for the deposition of zinc oxide. In the case of gallium nitride, low pressure chemical vapor deposition of tris(diethyl-μ-amido-gallium) worked reasonably well with or without a carrier gas. The buffer layers and the GaN films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), and reflection high energy elctron diffraction (RHEED).

Plasma oxidation and magnetoresistance in tunnel junction device

Abstract We have studied the tunneling junction magnetoresistance (TMR) and oxidation behavior of Al layer in glass\Co 100 A\Al–O x ( t A)\Co 30 A\Ni–Fe 120 A tunnel junction devices. The Al–O x thickness was controlled with a different oxidation time and Al thickness. The thin Al layer of 15 A showed a rapid variation of TMR ratio with a oxidation time and the maximum TMR ratio of x layer by a high resolution transmission electron microscopy. As an oxidation time increase, the initial Al film with some roughness became flat, which was consistent to a variation of a junction resistance. From results, the rough Al layer could be grown to a flat Al–O x in an optimum oxidation condition, which was based on the oxidation kinetics of Al.