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Non-Kolmogorov−Avrami−Ishibashi Switching Dynamics in Nanoscale Ferroelectric Capacitors
Kim, Yunseok,Han, Hee,Lee, Woo,Baik, Sunggi,Hesse, Dietrich,Alexe, Marin American Chemical Society 2010 Nano letters Vol.10 No.4
<P>Switching dynamics of nanoscale ferroelectric capacitors with a radius of 35 nm were investigated using piezoresponse force microscopy. Polarization switching starts with only one nucleation event occurring only at the predetermined places. The switching dynamics of nanoscale capacitors did not follow the classical Kolmogorov−Avrami−Ishibashi model. On the basis of the consideration of two separate (nucleation and growth) steps within a nonstatistical finite system, we have proposed a model which is in good agreement with the experimental results.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2010/nalefd.2010.10.issue-4/nl9038339/production/images/medium/nl-2009-038339_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl9038339'>ACS Electronic Supporting Info</A></P>
Ultrahigh Density Array of Epitaxial Ferroelectric Nanoislands on Conducting Substrates
Kim, Youngsuk,Han, Hee,Kim, Yunseok,Lee, Woo,Alexe, Marin,Baik, Sunggi,Kim, Jin Kon American Chemical Society 2010 NANO LETTERS Vol.10 No.6
<P>An ultrahigh density array of epitaxial PbTiO<SUB>3</SUB> (PTO) nanoislands with uniform size was fabricated on a single-crystalline Nb-doped SrTiO<SUB>3</SUB> (100) substrate over a large area (cm<SUP>2</SUP> scale) by simple but robust method utilizing polystyrene-<I>block</I>-poly(4-vinylpridine) copolymer micelles. Each nanoisland has an average volume of 2.6 × 10<SUP>3</SUP> nm<SUP>3</SUP> (a height of 7 nm and a diameter of 22 nm). Because of uniform nanoislands over a large area, a synchrotron X-ray diffraction experiment was successfully employed to analyze the domain structures of PTO nanoislands. They showed well-defined epitaxy on the substrate, which was also confirmed by high-resolution transmission electron microscopy. All of the nanoislands existing in the entire area showed distinct piezoresponse that confirms the existence of ferroelectricity at this size. The results indicate that the critical size of ferroelectrics could be scaled-down further, thereby much increasing the density of ferroelectric devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2010/nalefd.2010.10.issue-6/nl100819d/production/images/medium/nl-2010-00819d_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl100819d'>ACS Electronic Supporting Info</A></P>
Piezo-controlled Dielectric Phase Shifter
Victor Kazmirenko,Yuriy Poplavko,Moongi Jeong,Beomjin Kim,Yuriy Prokopenko,Sunggi Baik 한국전자파학회JEES 2006 Journal of Electromagnetic Engineering and Science Vol.6 No.1
A sandwich structure of dielectric material and air gap inside a rectangular waveguide is proposed as a fast electrically tunable low-loss phase shifter. As the dielectric material is shifted up and down by piezoelectric actuator and, thereby, the thickness of air gap is changed, the effective dielectric constant of the sandwich structure is varied. Phase shifters based on the sandwich structure with different dielectric materials showed phase shift of 20~200˚/㎝ at X-band as the thickness of air gap varied up to 30 ㎛. The idea can be extended toward low-loss millimeter wave phase shifters since modern microwave ceramics have been developed to show very low dielectric loss(tanδ~10<SUP>-4</SUP>).
이찬우,노용래,정종식,백성기 ( Chanwoo lee,Yongrae Roh,Jongshik Chung,Sunggi Baik ) 한국센서학회 1996 센서학회지 Vol.5 No.3
We developed SAW gas sensor for monitoring SOx gas with high sensitivity. It was fabricated as a microsensor for detecting SOx gas by depositing sensing material on SAW device. As a detecting layer material, CdS was selected. Deposition of CdS in the form of thin films was carried out by the ultrasonic spray pyrolysis method using ultrasonic spray nozzle. Thin films with the uniform and large surface area for sensors were deposited. The stable pyrolysis environment provided by uniform and fine droplets formed by spray nozzle made it possble to obtain thin films with excellent quality. The minimum grain size of the CdS thin films was about 50 nm when deposited at 300℃. SAW gas sensors showed reasonable sensitivity and reproducibility. Further studies are required to investigate the interference of other gases to SOx gas detection.
Kim, Dae Hong,Kim, Yong Kwan,Hong, Seungbum,Kim, Yunseok,Baik, Sunggi IOP Pub 2011 Nanotechnology Vol.22 No.24
<P>PbTiO<SUB>3</SUB> (PTO) ferroelectric films on Pt(111) bottom electrode layers covering Ta/glass were prepared using pulsed laser deposition. X-ray diffraction patterns revealed that the PTO films were preferentially (111)-oriented. The films were highly crystalline and had a smooth surface with root mean square (RMS) roughness of 1.5 nm. Ferroelectric properties of the PTO films were characterized using piezoresponse force microscopy (PFM). PFM techniques achieved ferroelectric polarization bits with a minimum width of 22 nm, which corresponds to a potential recording density of 1.3 Tbit/in<SUP>2</SUP> in ferroelectric storage devices. </P>