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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>
Choi, Seung-Kyu,Jang, Jae-Min,Jhin, Jung-Keun,Jung, Woo-Gwang WILEY-VCH Verlag 2008 Physica status solidi. PSS. A, Applications and ma Vol.205 No.2
<P>A trial was carried out to fabricate self-assembled InGaN QD structures through periodic interruption growth, which is new method for supplying the source materials in a metal organic chemical vapor deposition (MOCVD) reactor. The growth of InGaN QDs was interrupted periodically by stopping the ammonia gas for selected time periods during periodic interruption growth. The change in surface morphology was investigated during the progress of InGaN QD growth. In addi- tion, the morphological and optical characteristics were compared with respect to the period time of 3 or 5 seconds for growth and interruption. InGaN QDs of 25–35 nm in lateral size were grown on GaN surfaces with a density of approximately 4–15 × 10<SUP>10</SUP> cm<SUP>–2</SUP>. The composition of QDs was estimated to be In<SUB>0.14</SUB>Ga<SUB>0.86</SUB>N. Periodic interruption growth enables the fabrication of self-assembled InGaN QDs with high density and uniform-size. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
A Mössbauer study of a Ge–Fe thin film
Ahn, G. Y.,Kim, C. S.,Lim, S. H. WILEY-VCH Verlag 2007 Physica status solidi. PSS. C, Current topics in s Vol.4 No.12
<P>Magnetic phases of a Ge<SUB>48.2</SUB>Fe<SUB>51.8</SUB> (in atomic%) thin film, fabricated by thermal co-evaporation onto an oxidized Si substrate, are analyzed by Mössbauer spectroscopy as well as magnetometry. Magnetic measurements indicate a superparamagnetic behavior due to the formation of Fe precipitates in an amorphous matrix with an average blocking temperature of 160 K and a spin glass behavior with a spin freezing temperature of 30 K. The superparamagnetic behavior is confirmed from the Mössbauer spectra taken at room temperature. The isomer-shift values indicate that the Fe atom in the amorphous phase is in the high-spin Fe<SUP>3+</SUP> charge state. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Control of magnetic anisotropy by ion-beam-mixing method under external magnetic field
Yune, J.-H.,Kim, H. B.,Kim, S. H.,Whang, C. N.,Chae, K. H. WILEY-VCH Verlag 2004 Physica status solidi. A, Applied research Vol.201 No.8
<P>Manipulation of magnetic anisotropy in ferromagnetic thin films was tried with ion-beam-mixing technique. Co/Pt multilayered films were deposited on Si(100) by electron beam evaporation and mixed with an energetic Ar<SUP>+</SUP> ion-beam under external magnetic field which was parallel to the sample surface. The magnetic easy axis was observed from the ion-beam-mixed samples along the direction of applied external magnetic field. When the ion dose was less than a critical dose, a small peak was measured along the magnetic hard axis. The small peak disappeared after ion-beam-mixing with a dose higher than the critical one. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Yoon, Tae-Sik,Kim, Hyun-Mi,Kim, Ki-Bum,Ryu, Du Yeol,Russell, Thomas P.,Zhao, Zuoming,Liu, Jian,Xie, Ya-Hong WILEY-VCH Verlag 2009 Physica Status Solidi. B Vol.246 No.4
<P>The growth behaviour and microstructure of epitaxially grown self-assembled Ge quantum dots on patterned SiO<SUB>2</SUB>/Si(001) substrates by molecular beam epitaxy were studied. The hexagonally ordered Si holes with 30 nm thick SiO<SUB>2</SUB> mask layer having ∼25 nm diameter, ∼40 nm center-to-center distance, and density of ∼7 × 10<SUP>10</SUP> cm<SUP>–2</SUP>, were formed using self-assembled diblock copolymer, composed of polystyrene and poly(methyl methacrylate) (PS-b -PMMA). The multiple Ge nuclei are selectively formed along the periphery of the individual Si holes and these nuclei subsequently coalesce forming single dot with an identical size of patterns. The strain of dots is relaxed up to 80%. The lattice planes of some Ge dots are found to be tilted from those of Si substrates. The Ge dots have dislocations at the interface with Si substrate even at the small size of ∼25 nm, resulting from the limited elastic relaxation in the confined patterned structure. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Characteristics of SnO<sub>2</sub> fishbone-like nanostructures prepared by the thermal evaporation
Kim, Hyoun Woo,Kim, Nam Ho,Myung, Ju Hyun,Shim, Seung Hyun WILEY-VCH Verlag 2005 Physica status solidi. PSS. A, Applications and ma Vol.202 No.9
<P>We have successfully grown the tin oxide (SnO<SUB>2</SUB>) fishbone-like nanostructures on titanium nitride (TiN)-coated substrates by the thermal evaporation of Sn powders. X-ray diffraction indicated that the product had the phase structure of the rutile form of SnO<SUB>2</SUB>. Transmission electron microscopy (TEM) revealed that the product consisted of fishbone-like structure, with branches and sub-branches attached to the main stem. High-resolution TEM and selected area diffraction pattern coincidentally indicated that both branches and sub-branches were single crystalline rutile SnO<SUB>2</SUB> structures. Room temperature photoluminescnece (PL) spectrum of the as-synthesized SnO<SUB>2</SUB> nanostructures exhibited peaks associated with the visible light emission. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Park, Sung-Min,Chung, Ha-Chang,Lee, Seong-Rae WILEY-VCH Verlag 2007 Physica status solidi. PSS. A, Applications and ma Vol.204 No.12
<P>We have investigated the composition dependence of magnetic tunnel junctions (MTJs) with Nb-alloyed Al-oxide (NbAlO<SUB>x</SUB>) and analyzed the microstructure changes and electrical property of Nb alloyed Al-oxide layer. After annealing, tunnel magnetoresistance (TMR) ratio of MTJ with Nb-alloyed Al-oxide barrier increased up to 38.5% at 9.26 at.% Nb. As the Nb concentration increases, the grain size decreases and the microstructure becomes a dense, fine equiaxed-type structure with fine, continuous selected area diffraction (SAD) patterns, until Nb concentration reaches 9 at.%. The microstructural changes of Nb-alloyed Al layer results in smooth interface roughness, so that we could achieve a high TMR ratio. Resistance decreased from 900 Ω to 220 Ω and barrier height decreased from 1.62 eV to 0.847 eV at 9.26 at.% Nb. We speculated that the reduction of junction resistance of the MTJ with Nb-doped Al-oxide barrier was due to Nb d states formation in the band gap. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Cho, Jaehee,Sone, Cheolsoo,Park, Yongjo,Yoon, Euijoon WILEY-VCH Verlag 2005 Physica status solidi. PSS. A, Applications and ma Vol.202 No.9
<P>The junction temperature rise of light emitting diodes due to self-heating effects during operation of the LED is measured using the electro-luminescence of the band-to-band recombination. This method is useful for the junction temperature monitoring of small geometry devices, indirectly. The junction temperature measured in InGaN/GaN multi-quantum well LEDs with 1 mm<SUP>2</SUP> device size rises to 180 °C when the input current is 380 mA. The relationship between the junction temperature and the LED efficiency is clarified with experimental results. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Magnetic properties of Mn-doped Bi<sub>2</sub>Te<sub>3</sub> and Sb<sub>2</sub>Te<sub>3</sub>
Choi, Jeongyong,Choi, Sungyoul,Choi, Jiyoun,Park, Yongsup,Park, Hyun-Min,Lee, Hee-Woong,Woo, Byung-Chul,Cho, Sunglae WILEY-VCH Verlag 2004 Physica status solidi. PSS. B, Basic solid state p Vol.241 No.7
<P>We have fabricated Mn-doped Bi<SUB>2</SUB>Te<SUB>3</SUB> and Sb<SUB>2</SUB>Te<SUB>3</SUB> single crystals by the vertical gradient solidification method. The compositions and crystal structures of Bi<SUB>2−x</SUB>Mn<SUB>x</SUB>Te<SUB>3</SUB> and Sb<SUB>2−x</SUB>Mn<SUB>x</SUB>Te<SUB>3</SUB> were determined using Electron Probe Micro-Analyzer (EPMA) and powder X-ray diffraction (XRD) patterns, respectively. Both crystal structures were rhombohedral with smaller lattice constants because of the smaller atomic radius of Mn than those of Bi and Sb. Based on the magnetization measurements, Mn-doped Bi<SUB>2</SUB>Te<SUB>3</SUB> and Sb<SUB>2</SUB>Te<SUB>3</SUB> compounds have ferromagnetic ordering at T<SUB>C</SUB> = 10 and 17 K, respectively. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Jin, Changhyun,Kim, Hyunsoo,Baek, Kyungjoon,Kim, Hyoun Woo,Lee, Chongmu WILEY-VCH Verlag 2010 Crystal research and technology Vol.45 No.2
<P>Ga<SUB>2</SUB>O<SUB>3</SUB>/SnO<SUB>2</SUB> coaxial nanowires were synthesized by thermal evaporation of GaN powders and then atomic layer deposition of SnO<SUB>2</SUB>. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis results indicate that the Ga<SUB>2</SUB>O<SUB>3</SUB> cores and the SnO<SUB>2</SUB> shells of the coaxial nanowires after thermal annealing are single crystals with monoclinic and simple orthorhombic structures, respectively, although the SnO<SUB>2</SUB> shells are amorphous before annealing. Our results also show that photoluminescence (PL) emission can be enhanced by thermal annealing in an H<SUB>2</SUB>/N<SUB>2</SUB> atmosphere. EDX concentration profile suggests that the enhancement in the bluish green emission is due to the increase in the concentration of the Ga vacancies in the cores during the H<SUB>2</SUB>/N<SUB>2</SUB> annealing. On the other hand, a red emission is newly formed while the bluish green emission is degraded by annealing in an oxygen or nitrogen atmosphere (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>