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Electrical transport properties of a single wall carbon nanotube network
Hwang, J. S.,Kim, H. T.,Kim, H. K.,Son, M. H.,Hwang, S. W.,Ahn, D. WILEY-VCH Verlag 2009 Physica Status Solidi. B Vol.246 No.4
<P>A single wall carbon nanotube (SWCNT) network is fabricated and its electronic transport properties are investigated. It shows a typical p-type field-effect-transistor (FET) behavior and nonlinearities in the source current-source bias characteristics. The network also exhibits incomplete turn-off and a small mobility. These characteristics are explained by the fact that the network is a mixture of metallic and semiconducting SWCNTs connecting with one another. Various cross junctions such as SWCNT (semiconducting)-SWCNT (semiconducting), SWCNT (semiconducting)-SWCNT (metallic) are the source of nonlinearities and the small mobility. Incomplete turn-off can be explained by the parallel conduction paths consisting of metallic SWCNTs which are insensitive to the gate bias. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Inter-dot spin exchange interaction in coupled II–VI semiconductor quantum dots
Lee, S.,Dobrowolska, M.,Furdyna, J. K. WILEY-VCH Verlag 2006 Physica status solidi. PSS. B, Basic solid state p Vol.243 No.4
<P>We have performed polarization selective photoluminescence (PL) experiment on a series of self-assembled quantum dots (QDs) in the form of single- and double-QD layer systems. The double layers were formed from diluted magnetic semiconductor (DMS) (either CdMnSe or CdZnMnSe) and non-DMS (either CdSe or CdZnSe) layers, separated by non-DMS ZnSe barriers. The peaks from DMS and non-DMS QD layers are clearly resolved in the PL spectra taken at zero magnetic field. When a magnetic field is applied to the double layer QD (DLQD) system, the intensities of the circularly polarized PL peaks corresponding to the non-DMS (i.e., CdSe and CdZnSe) layers exhibit significant changes, reflecting correspondingly large changes in the degrees of spin polarization of the non-DMS QDs. This enhancement of spin polarization observed in the double-layer QD structures is interpreted in terms of anti-parallel spin interaction between carriers localized in the coupled QD pairs. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Sun, Chang Woo,Lee, Jeong Yong,Youm, Minsoo,Kim, Yong Tae WILEY-VCH Verlag 2007 Physica Status Solidi. Rapid Research Letters Vol.1 No.1
<P>The atomic crystal structure of the Sb<SUB>3</SUB>Te<SUB>2</SUB> binary alloy has been investigated with high-resolution transmission electron microscopy (HR-TEM) and fast Fourier transform patterns. As a result, there is inconsistency between the previous theoretical model and the experimental result. But, from the calculations of lattice parameters and the number of layers in the unit cell, it is found that the Sb<SUB>3</SUB>Te<SUB>2</SUB> alloy can be crystallized into the Sb<SUB>2</SUB>Te structure with P<TEX>$ \bar 3 $</TEX>m1 space group and the difference between stacking sequences of the Sb<SUB>3</SUB>Te<SUB>2</SUB> and the Sb<SUB>2</SUB>Te structures has been discussed with the proposed atomic arrangement model of unit cells. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Different nanostructure cathode catalysts application for direct methanol fuel cell
Dipti, Sharmin Sultana,Chung, Uoo-Chang,Kim, Jong-Pil,Chung, Won-Sub WILEY-VCH Verlag 2007 Physica status solidi. PSS. A, Applications and ma Vol.204 No.12
<P>Direct methanol fuel cell (DMFC) belongs to the same family of energy conversion device and the application of new hydrogen storage nanomaterials such as carbon nanotube (CNTs) supported catalysts is being addressed in an increasing industrial approach. In this present study, multiwall carbon nanotube supported Pt and Pt-Ni nanoparticles were prepared as cathode catalysts for direct methanol fuel cell application. Transmission electron microscopy and X-ray diffraction analyses indicated the formation of well-dispersed Pt and Pt-Ni nanoparticles having sizes of around 2 ∼ 4 nm on carbon nanotube. Furthermore, the electrochemical characterization by the cyclic voltammetry (CV) demonstrated that these catalysts have higher catalytic activity and the methanol oxidation reaction of the Pt-Ni/CNTs is respectively almost similar and slightly higher than Pt/CNTs electrocatalysts. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Thi, Ngoc Anh Nguyen,Thi, Hoang Yen Nguyen,Yi, Hyunjung,Joo, Sung-Jung,Shin, Kyung-Ho WILEY-VCH Verlag 2007 Physica status solidi. PSS. A, Applications and ma Vol.204 No.12
<P>Inverse giant magnetoresistance (IGMR) can be observed in multilayers with alternating two ferromagnetic layers F1 and F2 possessing opposite spin scattering asymmetries. We report here the observation of inverse current-in-plane giant magnetoresistance (CIP-IGMR) in Fe<SUB>1–x</SUB>Cr<SUB>x</SUB>/Cu/Co spin-valve systems with varying Cr concentration and FeCr-layer thickness. The highest magnitude of IGMR, –0.45%, has been achieved in the sample doped with 35 at.% Cr. It is shown that the proper substitution of Cr for Fe can alter spin-dependent scattering in the Fe layer, causing the inversion of the bulk spin scattering asymmetry coefficient therefore resulting in CIP-IGMR. The GMR has a dominant contribution to the observed inverse MR, rather than the anisotropic magnetoresistance (AMR) component. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Magnetic properties of Ni-Mn-Ga Heusler alloy films
Dubowik, J.,Goś,ciań,ska, I.,Kudryavtsev, Y. V.,Lee, Y. P.,Sová,k, P.,Konĉ,, M. WILEY-VCH Verlag 2006 Physica Status Solidi C Vol.3 No.1
<P>The films with composition Ni<SUB>x </SUB>Mn<SUB>y </SUB>Ga<SUB>z </SUB> (x = 50 ± 5, y = 25 ± 5, z = 25 ± 5) were deposited by flash-evaporation or sputtering on mica and glass substrates and annealed in a high vacuum at 673–973 K. X-ray diffraction at room temperature reveals the presence of B2 (or L2<SUB>1</SUB>) type of structure depending on annealing conditions. Magnetic properties were studied by ferromagnetic resonance at temperatures from 78 K to 400 K and compared with electric resistivity data. It is shown that the magnetic properties of the films critically depend on their structural ordering and microstructure. The films annealed at T < 800 K reveal a complex magnetic behavior due to their specific microstructure while those annealed at T > 800 K show magnetic properties comparable with those of bulk Ni-Mn-Ga alloys. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Effect of capping layer on the crystallization of amorphous CoFeB
Chung, Ha-Chang,Lee, Young-Ho,Lee, Seong-Rae WILEY-VCH Verlag 2007 Physica status solidi. PSS. A, Applications and ma Vol.204 No.12
<P>We investigated the effects of capping layer on the crystallization of amorphous top-CoFeB electrode in the glass/CoFeB/MgO(001)/CoFeB/cap stack. Evolution of texture and crystallization of the top-CoFeB electrode can be affected by the texture and the crystallinity of the capping layer. When the (002)-textured Ru capping layer was used, a (110) texture of CoFeB was developed during annealing at 350 °C for 90 min. On the other hand, when the amorphous TiAl capping layer was used, a (002) texture of the CoFeB was developed during crystallization due to MgO (001) texture seeding effect. Consequently, the texture evolution of the amorphous top-CoFeB electrode during annealing could be controlled by the texture and crystallinity of the adjacent capping layer. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Son, J. K.,Sakong, T.,Hwang, J. S.,Lee, S. N.,Paek, H. S.,Ryu, H. Y.,Ha, K. H.,Cho, Y. H.,Nam, O.,Park, Y. WILEY-VCH Verlag 2007 Physica Status Solidi C Vol.4 No.1
<P>Power dependent time-resolved photoluminescence measurements were performed on AlInGaN-based blue laser diode structures with different well widths. Emission peak shifts were monitored in evolving time at different power of excitation laser. We observed two types of shift. One is power dependent and the other is a constant shift with respect to excitation power density. In particular, the power dependent shift was explained by internal electric field effect but the constant one was not. The reduction of a peak shift was achieved by narrowing the quantum well thickness, mostly attributing to the reduction of the internal field effect. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Nano-floating gate capacitor with SnO<sub>2</sub> quantum dots distributed in polyimide dielectrics
Lee, Dong Uk,Seo, Ki Bong,Han, Seung Jong,Kim, Eun Kyu,Kim, Young-Ho WILEY-VCH Verlag 2009 Physica Status Solidi. B Vol.246 No.4
<P>Self-assembled SnO<SUB>2</SUB> quantum dots were fabricated by a chemical process between a BPDA-PDA polyamic acid and a Sn film. A nano-floating gate capacitor having metal–insulator–semiconductor structure has been formed on p-type Si substrate with SnO<SUB>2</SUB> quantum dots and dielectric polymer layer. The size and density of fabricated SnO<SUB>2</SUB> quantum dot were about 15 nm and 2.4 × 10<SUP>11</SUP> cm<SUP>–2</SUP>, respectively. The electrical properties of the nano-floating gate capacitor have been investigated by measuring capacitance–voltage characteristics. Then, the flat-band voltage shift due to charging of the electron in SnO<SUB>2</SUB> quantum dot was ranged from 1.2 V to 4 V. And the transmission electron microscopy and the optical absorption spectra have been measured to investigate the morphology and absorbance of the SnO<SUB>2</SUB> quantum dots embedded in polyimide. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Hong, Hyun-Gi,Kim, S.-S.,Kim, D.-Y.,Lee, Takhee,Kim, Kyoung-Kook,Song, June-O.,Cho, J. H.,Seong, Tae-Yeon WILEY-VCH Verlag 2007 Physica status solidi. PSS. A, Applications and ma Vol.204 No.3
<P>The effect of rapid-thermal-annealing on the performance of near-UV GaN-based light-emitting diodes (LEDs) fabricated with nano-patterned p-type electrodes has been investigated. One-dimensional (1-D) nano-patterns were formed on Cu-doped indium oxide (CIO)/indium tin oxide (ITO) p-electrode by sur- face relief grating and dry etching techniques. After the nano-patterning, some of the samples are rapid-thermal-annealed at 530 and 630 °C in either air or nitrogen ambient. LEDs made with samples annealed 530 °C show much better electrical characteristics as compared to unannealed samples. In particular, LEDs with samples annealed 530 °C in air show higher output power (at 20 mA) and much reduced leakage current as compared to LEDs with unannealed samples. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>