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We demonstrate, for the first time, 28-nm embedded STT-MRAM operating at full industrial temperature range (−40~125°C) with >1E+6 endurance and >10 year retention for high speed MCU/IoT application. Robust cell operation is also demonstrated after solder reflow (260°C, 90 second) and during external magnetic disturbance (550-Oe under writing). It is built on 28-nm FDSOI technology in modular format for IP reuse and has great potential to serve wide variety of applications such as IoT, and high performance MCU.

The time-series normalized difference vegetation index (NDVI) product has proven to be a powerful tool to investigate the phenological information because it can monitor the change of the forests with very high time-resolution, This study described the application of the DFT analysis over the 9 year MODIS data for the identification of the two types of vegetation cover, Pinus densiflora(Pd) and Querqus mongolica(Qm) which are dominant species of evergreen and broadleaved deciduous forest, respectively, The total number of samples was 5148 reference cycles which consist of 2160 Pd and 2988 Qm. They were extracted from the pixel-based MODIS scenes over the 9 years from 2000 to 2008 of South Korea. The DFT analysis was mainly focused on the 0th and harmonic components, each of which represents the mean value and the variation amplitude of the NDVI over the years, respectively. The harmonic values of the vegetation Pd and Qm averaged over the 9 years were 0.74 and 0.65, respectively. This implies that Pd has a higher NDVI than Qm. Similarly obtained harmonic values of Pd and Qm were 0.19 and 0.27, respectively. This can be intuitively understood considering that the seasonal variation of Qm is much larger than Pd. This distinctive difference of the harmonic value has been used to identify evergreen and deciduous forests. Overall agreement between the Fourier analysis-based map and the actal vegetation map has been estimated to be as high as 75%. This study found that the DFT analysis can be a concise and repeatable method to separate and trace the changes of evergreen and deciduous forest using the annual NDVI cycles.

Adsorption behavior of binary mixed alkanethiol molecules of octanethiol (OT) and dodecanethiol (DDT) on Au substrate has been investigated with a variation of molar fraction in solution at room temperature. Linear-scan voltammograms (LSV) taken from the binary mixed self-assembled monolayer (SAM) on Au/Si showed a single reductive desorption peak, continuously shifting with a variation of mixing ratio in solution. Molecule-resolved scanning tunneling microscope (STM) images obtained from the binary SAM on Au/mica showed the phase separation with a few nanometer sized domains. The difference in the chain length between OT and DDT was not large enough to induce the phase separation with much larger domains, which could be well detected by LSV. There was no preferential adsorption of DDT to OT.

The evolution of the surface structure in dodecanethiol self-assembled monolayer on Au(1 1 1) substrate has been studied with ultra high vacuum scanning tunneling microscopy at several temperatures. The structure of substrate Au(1 1 1) surface changed suddenly at a temperature of 110 °C. The enhanced mobility of the substrate gold atoms at this temperature is attributed to the desorption of the dodecanethiol molecules.

We propose a new process of fabricating nano-gap electrode pairs using an atomic-layer-deposited (ALD) thin film as a sacrificial layer. In this technique, we can control the width of a gap precisely by varying the number of deposition cycles of the ALD layer, and produce many identical gaps simultaneously. Using ALD Al2O3 as a sacrificial layer, we have fabricated poly-Si/Au nano-gaps of 10 nm width successfully. This new approach can provide a useful tool for the massive production of integrated molecular device circuits.

Scalability of interface driven perpendicular magnetic anisotropy (i-PMA) magnetic tunnel junctions (MTJs) has been improved down to 1X node which verifies STT-MRAM for future standalone memory. With developing a novel damage-less MTJ patterning process, robust magnetic and electrical performances of i-PMA MTJ cell down to 15 nm node could be achieved.

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.

We fabricated a free-standing structure of a GaN nanowire by selectively etching Si3N4, previously grown on a SiO2 substrate, for application to three-dimensional integrated circuits such as nanorelays and actuators. In the nanowire-deposition process we adopted electrophoresis and reactive ion etching techniques to achieve a well-aligned and free-standing nanowire. The electrical transport measurements were performed from room temperature down to liquid-nitrogen temperature. The current–voltage (I–V) characteristics showed a rectifying behavior in the whole temperature range. We analyze this property as a Schottky barrier formation between the nanowire and electrodes.

Magnetic damping of the spin, the decay rate from the initial spin state to the final state, can be controlled by the spin transfer torque. Such an active control of damping has given birth to novel phenomena like the current-driven magnetization reversal and the steady spin precession. The spintronic devices based on such phenomena generally consist of two separate spin layers, i.e., free and pinned layers. Here we report that the dipolar coupling between the two layers, which has been considered to give only marginal effects on the current driven spin dynamics, actually has a serious impact on it. The damping of the coupled spin system was greatly enhanced at a specific field, which could not be understood if the spin dynamics in each layer was considered separately. Our results give a way to control the magnetic damping of the dipolar coupled spin system through the external magnetic field.

Novel spin transfer torque MRAM cells with three dimensional freelayer structures were suggested for the high density memory below 20nm technology node. By folding the freelayer to a special geometry, the 3D MTJ Cell structure retains large freelayer volume without an increase of cell foot-print, scaling down the MRAM cells even with in-plane magnetic anisotropy materials. From the micromagnetic calculation with Nudged Elastic Band (NEB) method, we confirmed the thermal stability over 60 in 3D MTJ cell with 15× 30nm2 area.

We report first-principles calculations on the magnetocrystalline anisotropy energy (MAE) of an Fe monolayer sandwiched by MgO. We found that by increasing the interlayer distance between Fe and O by about 8% from its equilibrium value, the perpendicular interfacial magnetic anisotropy can be enhanced as high as 2.75 erg/cm2, which is three times larger than that at the equilibrium distance. The analysis of MAE based on the second-order interactions of the spin-orbit coupling shows that the energy position of the majority-spin dz2 orbital is of central importance in determining MAE. Our results suggest that increasing the Fe–O distance in the Fe/MgO system is an important material-design direction for high-performance magnetic memories.

We studied the steady state precession of the spins in the magnetic tunnel junctions. In the field range below the spin-flop transition of synthetic antiferromagnetic pinned layer, the precession mode depends upon the current bias polarity. Above the spin-flop transition, however, the spin precession shows symmetric behavior on the current bias. The dominant mechanism of the spin precession changes from the spin transfer torque to thermal excitation at around the spin-flop transition. The enhancement of thermal fluctuation above the spin-flop transition is analyzed in relation to the static magnetic susceptibility.

We devised a method to measure the virtual magnetic field induced by Rashba effect in ferromagnetic metal layer. Transverse Rashba magnetic field makes the magnetization direction tilted out of the easy axis, which could be detected by the change in anomalous hall resistances. Through a specified measurement of the second harmonics of the hall resistance, the Rashba field could be obtained with high sensitivity even at low current regime. The results are compared with the prior reports based on the measurement of the transverse field required for the nucleation of reversed domain.

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.

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.