Acoustic characterization of AlN films using a High Overtone Bulk acoustic wave resonator

Abstract

Using the composite resonator with additional thick AlN film with the FWHM of rocking curve of 2.53° under investigation, the bulk acoustic wave attenuation constant and sound velocity along c-axis were directly measured. The method of High Overtone Bulk acoustic wave Resonator (HBAR) spectroscopy based on frequency, measurements of the positions of the resonator peculiarities of phase and amplitude of electromagnetic wave reflection coefficient from composite resonator structure was applied. The method provides attenuation and velocity measurement in a wide frequency band, using the same sample. For the measurements, standard and modified HBAR spectroscopy based on the analysis of only parallel resonance properties of composite resonator structures were used.     

High frequency response of Bragg reflector type film bulk acoustic wave resonator

Abstract

We fabricated a Bragg reflector type FBAR using AlN piezoelectric with quarter wavelength thickness, where the Bragg reflector was composed of W-SiO₂ pairs. By numerical simulation considering actual acoustic losses of each layer, we analyzed the frequency response of the resonator and could explain it using an equivalent circuit with parasitic elements. The Effective electromechanical coupling constant (K ² _eff ) and the Quality factor (Q_s ), figures of merit of the resonator, were about 1.1% and 307, respectively.</ab>     

Interferometric measurement using bimorph actuated staggered mirror (BASM) microsensor

For physical and chemical sensing applications, a bimorph actuated staggered mirror (BASM) microsensor was designed and fabricated by surface micromachining using a transparent quartz substrate. While the conventional cantilever sensors have angular deflection, BASM’s moving mirror performs piston-type pure vertical motion in response to environmental stimuli like temperature change and surface stress change due to molecular adsorption. Since the sensor itself has a fixed or reference mirror as well as a moving mirror, 1) an interferometric measurement is possible without an additional reference mirror in off-axis measurement setup, and 2) vibration measurement noise can be reduced. For preliminary test purposes, interferometric measurement using an optical setup was performed for temperature change. At He-Ne line (632.8 nm), a temperature change of ∼0.8 K caused a minimum-to-maximum interferometric light intensity change which corresponds to ∼144 nm shift of the moving mirror part. An optical diffraction analysis was performed and optimal device parameters were found to maximize the sensor sensitivity.     

In-situ observation of a dendrite growth in an aqueous condition and a uranium deposition into a liquid cadmium cathode in an electrowinning system

A zinc-gallium system was setup to observe the growth process of dendrites and to compare the performance of the stirrers which would prevent a dendrite formation. In a no-stirring condition, zinc was easily deposited on a liquid gallium cathode in the form of dendrites. It was difficult for a paddle stirrer to directly fracture the zinc dendrites to fine particles. However, a harrow stirrer was observed to fracture the dendrite to some extent at high speeds. Not only their rotation speed but also the length of their blades needed to be properly adjusted to enhance their performance. In the uranium-cadmium experiment, the diffusion coefficient of the uranium species was obtained by the cyclic voltammetry method, which is around 1 × 10⁻⁵ cm²/s. In a no-stirring condition, most of the uranium deposited at the current densities of 35, 100 and 200 mA/cm² did not sink into the liquid cadmium cathode.     

Multi-layer alignment control of a large area nano-imprinting stage

An XYθ stage for large area UV Nano-Imprinting Lithography (UV-NIL), which consists of linear actuators, translational/revolute joints, etc., has been modeled as flexible bodies. Multi-layer alignment control for the translation and angle offset cancellation has been performed in a virtual simulation environment using both ADAMS/Control and Matlab/SIMULINK. Furthermore, the vertical motions of three and four axis stages during the control action have been analyzed and compared to each other. The performed analysis can provide useful information for a high precision NIL stage development in the future. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Hong Jae Yim received B.S. and M.S degrees in mechanical engineering from Seoul National University, Korea, in 1979, 1983. He received Ph.D degree from Univ. of Iowa, USA. He is currently a professor in School of Mechanical & Automotive Engineering, Kookmin University. His research interests are in the area of computer aided kinematics and dynamics of mechanical systems.     

Electrochemical properties of Co-less layered transition metal oxide as high energy cathode material for Li-ion batteries

High energy nickel manganese cobalt oxide materials (HENMC) are one of the most viable cathode materials for a high energy density lithium ion battery (LIB), but they contain expensive and toxic cobalt (Co). We synthesized Co-free high energy nickel manganese oxide cathode materials (HENM) via a solid state reaction method and a coprecipitation method. Their structural and electrochemical properties were comparatively investigated using X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), inductively coupled plasma (ICP), electron probe micro-analysis (EPMA), particle size analysis (PSA) and electrochemical impedance spectroscopy (EIS). The co-precipitated HENM and the solid state fabricated HENM showed high capacities of 250 mAhg^?1 and 240 mAhg^?1, respectively. It suggests that the solid state fabricated method of HENM would be a good candidate for practical application as well as the co-precipitated one.     

Nanomechanical assay to investigate the selectivity of binding interactions between volatile benzene derivatives

Understanding the interactions between aromatic gas molecules and various simple aromatic receptor molecules is important in developing selective receptors for volatile organic compounds (VOCs). Here, five benzene thiols with different functional end groups were used to investigate the weak binding of aromatic vapors such as dinitrotolouene (DNT) and toluene. A multiplexed microcantilever array in conjunction with a very low concentration vapor generation system was developed to study multiple receptor-target interactions simultaneously. Differential nanomechanical responses of such devices provided insight into the influence of various chemical and structural features of such molecules.     

Theoretical and experimental analysis of material deformation by microcontact

This paper reports on an investigation of contact damage induced in molds and substrate materials used in micro- and nanoimprint lithography. Silicon, polydimethylsiloxane (PDMS), glass, and silicon carbide were studied. A finite element analysis using ABAQUS software was conducted to investigate the stress induced in mold and substrate materials when they come in contact with each other at a uniaxial pressure of 1 MPa. A spherical indentation experiment was conducted for a model study for various indentation loads and numbers of contact cycles. We examined the contact damage during the spherical indentation. Indentation stress-strain curves, surface views of contact damage, and mechanical properties were characterized for the mold and substrate materials.     

Heat transfer analysis during a curing process for UV nanoimprint lithography

A heat transfer analysis during the curing process in UV-Nanoimprint lithography was carried out. To imprint nano/micro patterns into a large-area target glass such as LCD panels, a mold with a poly-urethane-acrylate layer is often used, on which layer the micro/nano patterns are inscribed for the UV-NIL process. After UV resin is coated between the target glass and the flexible mold, the UV resin is cured by exposing UV light on the resin. In the curing process, heat from the phase change of the resin and the radiation by UV lamp would induce a temperature change and thermal distortion of the mold. In this study, we measured the temperature change of the flexible mold, and established an analytic model of the heat transfer. From the result, we derived the thermal properties of the PUA layer, and a thermal resistance layer between the PUA and the cured resin layer. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Jay Jeong received Ph.D. degree from Seoul National University in 2002. He held a Post-doctorate at Johns Hopkins University, USA from 2003 to 2006. Dr. Jeong is currently an assistant professor at the School of Mechanical and Automotive Engineering in Kookmin University in Seoul, Korea. His research interests are in the area of nano-robotics and intelligent mechanism.     

Numerical study on leakage detection and location in a simple gas pipeline branch using an array of pressure sensors

Pressure signals measured in gas pipelines provide useful information for monitoring the status of pipeline network operations. This study numerically investigates leakage detection and location in a simple gas pipeline branch using transient signals from an array of pressure sensors. A pipeline network simulation model was developed and used to predict one-dimensional compressible flow in gas pipelines. Two monitoring methods were tested for leakage detection and location; these include cross-correlation monitoring and pressure differential monitoring. The performance and reliability of the two monitoring methods were numerically assessed based on simulation results for a simple pipeline branch operation with a prescribed leakage rate (5% of total flow rate in the gas pipeline).