Jinseo Lee

Characteristics and field emission of conducting poly (3,4-ethylenedioxythiophene) nanowires

Conducting poly (3,4-ethylenedioxythiophene) nanowires were synthesized by using an electrochemical polymerization method with a nanoporous template. Scanning and transmission electron microscopy confirmed the formation of conducting polymer nanowires (CPNWs) with an open end. The formation and the electrical properties of the CPNWs formed were dependent on synthetic conditions, such as the doping level, the polymerization time, and the applied current. The measured electrical conductivity of a single strand of CPNW was ∼3.4×10−3 S/cm at room temperature. From the ultraviolet and visible absorbance spectra, we observed a π–π* transition at ∼2.1 eV for the de-doped systems. A field emission cell of CPNW nanotips was fabricated. The turn-on field of the CPNWs was 3.5∼4 V/μm at 10 μA/cm2, and the current density increased up to 100 μA/cm2 at ∼4.5 V/μm. The field enhancement factor of CPNW nanotips was ∼1200, which is comparable to those of carbon nanotubes.

Conducting Polymer Nanotube and Nanowire Synthesized by Using Nanoporous Template: Synthesis, Characteristics, and Applications

We synthesized nanotubes and nanowires of conducting polypyrrole, poly(3,4-ethylenedioxythiophene), and polyaniline by using nanoporous template through electrochemical polymerization method. The DBSA, CSA, TBAPF 6 , or HClO 4 was used for dopant, and distilled water, acetonotrile, or NMP was used for solvent. From the SEM and TEM pictures, the formation of conducting polymer nanotube (CPNT) and nanowire (CPNW) was confirmed. The diameter and length of CPNT and CPNW were 200 nm and 10 40 μm. The length, nanotube, nanowire, and thickness of wall were determined from synthetic conditions such as polymerization time, current, and dopant. For structure, we investigated UV/Vis absorbance spectra and X-ray diffraction patterns. DC conductivity and I-V characteristic curve were measured for the systems prepared with various conditions of synthesis. For applications for CPNT and CPNW, we measured field emission characteristic curve for FED and capacitance.

Trap distribution and field effect transistor (FET) of perylene by organic molecular beam deposition (OMBD)

Organic semiconducting perylene molecule was deposited as active layer on the FET pattern by using organic molecular beam deposition (OMBD) method. For the morphology and structure, we performed the atomic force microscopy, scanning electron microscopy, and X-ray diffraction experiments. From the I-V characteristics, bulk trap density, trap distribution, and electric field dependent mobility were estimated. Thin film field effect transistor based on perylene molecule was fabricated. From the results of the current modulation with different gate voltages of the FET, gate induced carrier concentration and field effect mobility were obtained. We observed Gaussian-like deep trap distribution, and that mobility was 3×10 -7 cm 2 /Vs.

Lymphadenectomy increases the prognostic value of the revised 2009 FIGO staging system for endometrial cancer: a multi-center study.

BACKGROUND We investigated whether pelvic or para-aortic lymphadenectomy increases the prognostic value of the revised 2009 FIGO staging system in patients with endometrial cancer (EC). METHODS We reviewed 786 patients with EC from six tertiary medical centers between July 1996 and June 2008. All patients were classified according to the 1988 FIGO staging system: IA (n = 234); IB (n = 270); IC (n = 109); IIA (n = 35); IIB (n = 29); IIIA (n = 37); IIIB (n = 3); IIIC (n = 69), and the revised 2009 FIGO staging system was also applied to divide them: IA (=542); IB (=125); II (n = 29); IIIA (n = 18); IIIB (n = 3); IIIC1 (n = 43); IIIC2 (n = 26). Prognostic values between the 1988 and the revised 2009 FIGO staging systems were compared by multivariate Coxs proportional hazard analysis. RESULTS The 1988 FIGO stage IC, IIB, IIIA + IIIB and IIIC, and the revised 2009 FIGO stage IB, II, IIIA + IIIB and IIIC2 diseases were prognostic factors for poor PFS, whereas the 1988 FIGO stage IIB and IIIC, and the revised 2009 FIGO stage II, IIIA + IIIB and IIIC2 diseases were unfavorable prognostic factors for OS. Although these results were similar to those in 595 patients who underwent pelvic or para-aortic lymphadenectomy, the revised 2009 FIGO stage IIIC1 disease was an additional prognostic factor for poor PFS and OS (adjusted HRs, 4.19 and 11.25; 95% CIs, 1.39-12.60 and 2.23-36.74). CONCLUSIONS The revised 2009 FIGO staging system had a higher prognostic value than the 1988 FIGO staging system, and pelvic or para-aortic lymphadenectomy increased the prognostic value of the revised 2009 FIGO staging system for EC.

An electrical switching device controlled by a magnetic field-dependent impact ionization process

An abrupt change of conductance at a threshold magnetic field was observed in a device consisting of a nonmagnetic narrow-gap semiconductor. The conductance varies more than 25 times as the magnetic field increases. The threshold magnetic field can be tuned using a bias voltage from zero to several hundred Gauss. This large magnetoconductance effect is caused by the magnetic field-dependent impact ionization process. A theoretical model is proposed, and calculations based on this model simulate the experimental results closely. This device may be a good candidate for an electrical switching device controlled by a magnetic field.

All-polymer based flexible field effect transistor using poly(3,4-ethylenedioxythiophene) (PEDOT) and polypyrrole (PPy)

We fabricated all-polymer based flexible field effect transistors (FETs) using poly (3,4-ethylenedioxythiophene) (PEDOT) or polypyrrole (PPy) as the active layer and gate electrode. Polyvinyle cinnamate (PVCN) and epoxy were used for a dielectric layer. The PEDOT and PPy as the active layer and electrode were patterned through simple photo-lithography, and PVCN and epoxy as insulating layers were coated by using a spin-coater. We estimated the threshold voltage and trans-conductance through measuring the drain-source current (Ids) as a function of gate bias (Vg). We suggest that ionic motion in the active layer plays an important role for electrical properties.

Purification of CdZnTe by electromigration

Electro-migration of ionized/electrically active impurities in CdZnTe (CZT) was successfully demonstrated at elevated temperature with an electric field of 20 V/mm. Copper, which exists in positively charged states, electro-migrated at a speed of 15 μm/h in an electric field of 20 V/mm. A notable variation in impurity concentration along the growth direction with the segregation tendency of the impurities was observed in an electro-migrated CZT boule. Notably, both Ga and Fe, which exist in positively charged states, exhibited the opposite distribution to that of their segregation tendency in Cd(Zn)Te. A CZT detector fabricated from the middle portion of the electro-migrated CZT boule showed an improved mobility-lifetime product of 0.91 × 10−2 cm2/V, compared with that of 1.4 × 10−3 cm2/V, observed in an as-grown (non-electro-migrated) CZT detector. The optimum radiation detector material would have minimum concentration of deep traps required for compensation.

Large spin susceptibility of HgCdTe two dimensional electron gas in the extreme quantum limit regime

The spin susceptibility of HgCdTe 2DEG system was measured in this study with two independent methods which yielded the same value. It is remarkably large compared to any other 2DEG system. The large value of spin susceptibility as well as the large g-factor are the unique properties of HgCdTe which can be utilized as spintronic material.

A set of experiments and test rig to fully characterize linear PM oscillatory machines

The paper presents a set of static and dynamic experiments and the test rig to fully characterize a linear permanent magnet oscillatory machine. The proposed set of tests was performed on a PM brushless linear oscillatory machine with surface PM and, respectively, PM flux concentration movers.