Hyunchang Kim

Development of a compact and long range XYθz nano-positioning stage

In this study, we describe the development of a novel, compact, and long range in-plane XYθ(z) nano-positioning stage with piezoelectric actuator and flexure mechanism. The stage is composed of an X-directional motion part and a Y, θ(z)-directional motion part, which are linked serially. The stage consists of a bridge-type amplifying mechanism for the amplification of deformation of the piezoelectric actuator, a double compound guide mechanism for performing only desired motion, and a circular hinge mechanism that permits rotational motion in the Y and θ(z)-stages. To set the design variables of the stage, optimal design is carried out. To verify the results of the optimal design process and the performance of the stage, the FEM simulation and experiment are carried out. The proposed XYθ(z) nano-positioning stage has a translational motion range of 700 μm and a rotational motion range of 0.3°; it has a closed-loop resolution of 5 nm, 5 nm, and 0.025 arcsec in the X-, Y-, and θ(z)-directional motions, respectively. The proposed stage is a novelty in that it has a compact size of 200 × 200 × 30 mm(3), and decoupled kinematic design.

Optimal design and experiment of a three-axis out-of-plane nano positioning stage using a new compact bridge-type displacement amplifier

This paper presents the development of a new compact three-axis compliant stage employing piezoelectric actuators and a new flexure structure. A proposed stage works out-of-plane (Z, θx, θy) direction. The stage consists of 4 amplification flexures mounted piezoelectric actuators. New structure of flexure reduces height and enhances dynamic performance of stage. To certify excellent performance of the stage, comparison accomplished between conventional amplification flexure and new compact bridge type flexure. Modeling and optimal design of new type nano positioning stage performed. The optimal design is executed on the geometric parameters of the proposed flexure structure using Sequential Quadratic Programming. Experiments are carried out to verify the static and dynamic performance of the stage. The proposed out-of-plane nano-positioning stage has a Z-directional motion range 190 μm and a θx, θy-directional motion range ±2 mrad. The resolution of the stage is 4 nm, 40 nrad, and 40 nrad in the Z-, θx-, and θy-directional motions, respectively. The size of stage is 150 × 150 × 30 mm(3).

Structural phase transitions of Ge2Sb2Te5 cells with TiN electrodes using a homemade W heater tip

The phase transitions of a Ge2Sb2Te5 cell with a volume of 20×20×0.1μm3 were carried out by applying a reset pulse (10V and 50ns) and a subsequent set pulse (5V and 300ns) using a homemade W heater tip fabricated by focused ion beam lithography. The phase transformation from a crystalline state to an amorphous state was confirmed by measuring the I-V curves and observation with a cross-sectional transmission electron microscope both before and after applying the reset pulse. The electron diffraction pattern obtained from the transformed area clearly showed the amorphous state. The resistance value of the transformed amorphous area was two orders higher than that of the original crystalline phase. This difference in the resistance value between the reset and set states was maintained for 20 reset/set pulse cycles. It is expected that this experimental setup can be used to evaluate the fatigue behavior of Ge2Sb2Te5 cells with reset/set pulse cycles.

Development of a Novel Spherical Actuator With Two Degrees of Freedom

This paper describes the design and implementation of a novel spherical actuator that can generate two tilt-motion degrees of freedom. Voice coil motors were adopted as actuators in a spherical actuator to utilize their simple driving principle and constant torque coefficient characteristic. The sensing and guiding mechanism was built inside the proposed spherical actuator and enabled compactness and ease of connection to other application systems. The actuator was designed using a design optimization framework to obtain high torque. A prototype actuator was manufactured with optimally designed parameters, and its performance was evaluated.

Note: Development of a compact aperture-type XYθz positioning stage

In this paper, we propose a new in-plane XYθz nano-positioning stage that utilizes piezoelectric actuators and flexure mechanisms. The proposed stage has an aperture and is compact, which facilitates its application in measurement equipment, especially those used for biological specimens. The stage has four piezoelectric actuators and four bridge-type flexure mechanisms, which are used to amplify the small motions produced by the piezoelectric actuators. This paper describes the modeling and design optimization of the stage, which has X- and Y-direction motion ranges of 300 μm and a θz-direction motion range of ±3.9 mrad. The stage measures 150 × 150 × 23 mm, and its aperture is 50 × 50 mm.

Design and optimization of voice coil actuator for six degree of freedom active vibration isolation system using Halbach magnet array

This paper describes the design, modeling, optimization, and validation of an active vibration isolation system using a voice coil motor. The active vibration isolating method was constructed with a passive isolator and an active isolator. A spring was used for passive isolating; an actuator was used for active isolating. The proposed active vibration isolation system (AVIS) can isolate disturbances for many kinds of instruments. Until now, developed AVIS were able to isolate a six degree-of-freedom disturbance effectively. This paper proposes the realization of such a six degree-of-freedom active vibration isolation system that can work as a bench top device for precision measuring machines such as atomic force microscope, scanning probe microscope, etc.

Fatigue measurement system designed for a chalcogenide-based device using a homemade heater tip.

A fatigue measurement system is designed using a homemade tungsten (W) heater tip. This system is composed of a pulse generator and an atomic force microscope with the W heater tip attached. Also included are a parameter analyzer and control devices. The entire measurement process is controlled by a designed program without communication errors. Additionally, a process to fabricate the sharp W heater tip that applies an electrical pulse and evaluates the electrical properties is introduced. The analysis of the tip, carried out by scanning electron microscopy and electron backscattering diffraction, shows that the tip has great thermomechanical stability. Using this fatigue measurement system, the resistance of the Ge(2)Sb(2)Te(5) (GST) cell was successfully measured as a function of the number of set/reset cycles. The specific area (both program area and failure area) was easily observed. It is expected that the expansion of GST is a source of information regarding the fatigue of a GST cell.

Development of a high-current microwave ion source for Korean Multipurposed Accelerator (abstract)

A high-current, proton linear accelerator, named as Korean multipurposed accelerator (KOMAC), is being proposed mainly for accelerator-driven transmutation technology (ADTT) by Korea Atomic Energy Research Institute (KAERI). High-current, low emittance continuous power (cw) linear accelerators favor electron cyclotron resonance (ECR) microwave ion sources as an injector (Ref. Reference 1). Recently, these microwave sources are developed and constructed by several institutes especially for high-current cw linear accelerators. A high-density microwave ion source has been designed and constructed as a prototype ion source for the proposed KOMAC linear accelerator. The design of microwave power injection system is similar to that of the 75 keV proton injector at Los Alamos National Laboratory (Ref. Reference 2). A 2.45 GHz, 1.5 kW magnetron source is introduced into the stainless steel plasma chamber with 10 cm diam and 20 cm length through a tapered, double-ridged waveguide and a quartz window. The microwave...