Ung Hwan Pi

V2O5 nanowire-based nanoelectronic devices for helium detection

The electrical responses of vanadium pentoxide nanowires to helium gas and environmental pressures are demonstrated. The devices feature well-aligned nanowires that are oriented by electrophoresis technique in the submicron scale. The electrical conductance is found to increase and decrease upon exposure to helium gas and air, respectively. This electrical response to helium is due to physical adsorption of the helium atoms into the interlayer of vanadium pentoxide nanowires. Furthermore, we observe flow-rate-dependent conductance variations such that the conductance is increased with stepwise behavior to the increase of flow rate of helium.

Domain Wall Dynamics under an In-Plane Rotating Magnetic Field in a Nanowire with Perpendicular Magnetic Anisotropy

As an alternative to current or static magnetic field driven domain wall (DW) motion, we studied the dynamics of DW motion under an in-plane rotating magnetic field (IRMF) in a metallic nanowire with a perpendicular magnetic anisotropy. An equation describing the DW motion was obtained with a one-dimensional analytical model based on a collective coordinate approach. The DW velocity can easily be controlled up to hundreds of meters per second by varying the IRMF amplitude and frequency. The validity of the equation for DW motion was confirmed with micromagnetic simulations.

Fabrication of Nano-Gap Electrode Pairs Using Atomic-Layer-Deposited Sacrificial Layer and Shadow Deposition

We propose a new fabrication process of nano-gap electrode pairs using an atomic-layer-deposited (ALD) sacrificial layer and the shadow deposition technique. In this process, gap width can be precisely controlled by the number of deposition cycles of the ALD process, whereas junction area is defined by the deposition angle of the second electrode material through an overhanging shadow mask on top of the first electrode. In comparison with our previous method, process reliability has been highly improved because the unintentional deposition of the second electrode material on the sidewall of the first electrode is completely prevented. We have fabricated 10 ×10 arrays of n-type polycrystalline silicon (n-poly-Si)/Au nano-gap electrode pairs with gap widths of 6 and 9 nm, which show good insulating properties at room temperature.