손종엽 교수

The Hg∕NiO∕Pt capacitor with a Hg top electrode diameter of about 35μm showed the typical bistable resistive switching characteristic. After the removal of the Hg top electrode, we directly observed the formation and removal of filaments for a high resistive state (Roff) and a low resistive state (Ron) by conducting atomic force microscope (CAFM). CAFM images for Roff and Ron states directly exhibit evidence of the formation and removal of filaments on the surface, which supports well the filame

In this study, a NiO RRAM nanocapacitor array was fabricated on a graphene sheet, which was on a Nb-doped SrTiO(3) substrate containing terraces with a regular interval of about 100 nm and an atomically smooth surface. For the formation of the NiO RRAM nanocapacitor (Pt/NiO/graphene capacitor) array, an anodic aluminum oxide (AAO) nanotemplate with a pore diameter of about 30 nm and an interpore distance of about 100 nm was used. NiO and Pt were subsequently deposited on the graphene sheet. The

We investigated the ferroelectric characteristics of an epitaxial perovskite ZnSnO(3) thin film on a (111) SrRuO(3)/(111) SrTiO(3) substrate fabricated by pulsed laser deposition. We confirmed that the ZnSnO(3) thin film was epitaxially grown on the substrate, forming large terraces on the surface of the ZnSnO(3) thin film. The ZnSnO(3) thin film exhibited a high ferroelectric polarization of approximately 47 microC/cm(2), which was further supported by first-principles calculations.

We report the multiferroic properties of epitaxially (100) oriented BiMnO3 thin film on (100) LaAlO3 substrate and preferentially (111) oriented BiMnO3 thin film on (111) Pt/TiO2/SiO2/Si substrate. Nano-size bits of ferroelectric polarization on the BiMnO3 thin film on (111) Pt/TiO2/SiO2/Si substrate can be easily written and read by Kelvin force microscope (KFM). We found that, for the preferentially (111) oriented BiMnO3 thin film, only ferroelectric polarization has been induced at the low wr

Multiferroics that show simultaneous ferroic responses have received a great deal of attention by virtue of their potential for enabling new device paradigms. Here, we demonstrate a high-density four-states multiferroic memory using vertically aligned Mn-doped BaTiO3 nanorods prepared by applying the dip-pen nanolithography technique. In the present nanorods array, the polarization (P) switching by an external electric field does not influence the magnetization (M) of the nanorod owing to a negl

We demonstrate a field-effect nonvolatile memory device made of a ferroelectric copolymer gate nanodot and a single-walled carbon nanotube (SW-CNT). A position-controlled dip-pen nanolithography was performed to deposit a poly(vinylidene fluoride-ran-trifluoroethylene) (PVDF-TrFE) nanodot onto the SW-CNT channel with both a source and drain for field-effect transistor (FET) function. PVDF-TrFE was chosen as a gate dielectric nanodot in order to efficiently exploit its bipolar chemical nature. A

We developed step edge decoration method for the fabrication of semiconductor ZnO nanodots and nanowires using pulsed laser deposition. We synthesized high quality ZnO nanowires with the small diameter of about 20nm and the uniform interval of about 80nm between each nanowire, which has a simple structure for the formation of contact electrodes. The ZnO nanowire-based sensor was prepared only with the simple process of a gold electrode formation. The ZnO nanowire-based sensor exhibited the high

We report on the ferromagnetism of conducting filaments formed in a NiO thin film, which exhibited a typical bistable resistive switching characteristic. The NiO thin film showed an antiferromagnetic hysteresis loop for a high resistive state (R(OFF)). However, for a low resistive state (R(ON)), the conducting filaments exhibited a ferromagnetic hysteresis loop for the field cooling. The ferromagnetic hysteresis behavior of the R(ON) state reveals switchable exchange coupling between the ferroma

Dip-pen nanolithography of ferroelectric PTO nanodots is described. This position-controlled dip-pen nanolithography using a silicon nitride cantilever produced an array of ferroelectric nanodots with a minimum lateral dimension of approximately 37 nm on a Nb-doped SrTiO(3) substrate. This minimum-sized PTO dot is characterized by single-domain epitaxial growth with an enhanced tetragonality (c/a ratio) of 1.08.

We fabricated high quality epitaxial BiAlO3 thin films that exhibited a relatively high c∕a ratio of about 1.05 with a pseudotetragonal structure. On the atomic force microscope morphology of the BiAlO3 thin film, we observed large terraces with a width of about 1000Å and terrace heights of nearly the same to one lattice constant. This indicates that the BiAlO3 thin film has an ideal layer-by-layer growth mode. The BiAlO3 thin film also showed a good ferroelectric property with a high remanent p

Polycrystalline ferroelectric thin films of SrBi2Ta2O9 (SBT) and PbZr0.53Ti0.47O3 (PZT) were deposited on Pt/Ti/SiO2/Si substrate by pulsed laser deposition using an eclipse method and the surface potentials were observed by Kelvin probe force microscopy. The data suggest that the surface charge trap is a dominant effect over the ferroelectric polarization when a high electric field is applied on a cantilever during writing. This results from the increase of surface trapped charge and the satura

High quality BiMnO3 thin films with double SrTiO3 buffer layers were fabricated on Pt∕Ti∕SiO2∕Si and SrTiO3 substrates, in which SrTiO3 buffer layers were used to reduce leakage current in BiMnO3 thin films. The SrTiO3 buffer layers had a thickness of about 5nm obtained from the fitting of ellipsometer data, which gave the remarkable enhancement in leakage current. BiMnO3 thin films exhibited the ferromagnetic transition with the Curie temperature of about 105K. The Pt∕SrTiO3∕BiMnO3∕SrTiO3∕Pt an

We report the effects of bottom electrode shapes on resistive random-access memory (RRAM) devices composed of Nb (bottom electrode)/NiO (dielectric)/Nb (top electrode) structures. By adopting a nano-fabrication process using an anodic aluminum oxide (AAO) nanotemplate, a well-aligned Nb nanopin array bottom electrode was formed on the surface of a Si substrate. For comparison, a Nb thin film was employed as a different type of bottom electrode. Then, a NiO thin film dielectric was prepared on bo