Advances in Condensed Matter Physics The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. E-k Relation of Valence Band in Arbitrary Orientation/Typical Plane Uniaxially Strained Wed, 16 Apr 2014 08:33:20 +0000 Uniaxial strain technology is an effective way to improve the performance of the small size CMOS devices, by which carrier mobility can be enhanced. The E-k relation of the valence band in uniaxially strained Si is the theoretical basis for understanding and enhancing hole mobility. The solving procedure of the relation and its analytic expression were still lacking, and the compressive results of the valence band parameters in uniaxially strained Si were not found in the references. So, the E-k relation has been derived by taking strained Hamiltonian perturbation into account. And then the valence band parameters were obtained, including the energy levels at Γ point, the splitting energy, and hole effective masses. Our analytic models and quantized results will provide significant theoretical references for the understanding of the strained materials physics and its design. Zhang Chao, Xu Da-Qing, Liu Shu-Lin, and Liu Ning-Zhuang Copyright © 2014 Zhang Chao et al. All rights reserved. Synthetic Strategies and Applications of GaN Nanowires Tue, 15 Apr 2014 16:27:03 +0000 GaN is an important III-V semiconductor material with a direct band gap of 3.4 eV at 300 K. The wide direct band gap makes GaN an attractive material for various applications. GaN nanowires have demonstrated significant potential as fundamental building blocks for nanoelectronic and nanophotonic devices and also offer substantial promise for integrated nanosystems. In this paper, we provide a comprehensive review on the general synthetic strategies, characterizations, and applications of GaN nanowires. We first summarize several growth techniques of GaN nanowires. Subsequently, we discuss mechanisms involved to generate GaN nanowires from different synthetic schemes and conditions. Then we review some characterization methods of GaN nanowires. Finally, several kinds of main applications of GaN nanowires are discussed. Guoquan Suo, Shuai Jiang, Juntao Zhang, Jianye Li, and Meng He Copyright © 2014 Guoquan Suo et al. All rights reserved. Photocatalytic Reduction of CO2 to Methane on Pt/TiO2 Nanosheet Porous Film Sun, 13 Apr 2014 16:32:53 +0000 Anatase TiO2 nanosheet porous films were prepared by calcination of the orthorhombic titanic acid films at 400°C. They showed an excellent photocatalytic activity for CO2 photoreduction to methane, which should be related to their special porous structure and large Brunauer-Emmett-Teller (BET) surface area. In order to further improve the photocatalytic activity, Pt nanoparticles were loaded uniformly with the average size of 3-4 nm on TiO2 porous films by the photoreduction method. It was found that the loading of Pt expanded the light absorption ability of the porous film and improved the transformation efficiency of CO2 to methane. The conversion yield of CO2 to methane on Pt/TiO2 film reached 20.51 ppm/h·cm2. The Pt/TiO2 nanosheet porous film was characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), and ultraviolet-visible light diffuse reflectance spectra (UV-vis DRS). Moreover, the transient photocurrent-time curves showed that the Pt/TiO2 nanosheet porous film exhibited higher photocurrent, indicating that the higher separation efficiency of the photogenerated charge carriers was achieved. Li Qiu-ye, Zong Lan-lan, Li Chen, Cao Yu-hui, Wang Xiao-dong, and Yang Jian-jun Copyright © 2014 Li Qiu-ye et al. All rights reserved. High Conductivity of Mg-Doped Al0.3Ga0.7N with Al0.4Ga0.6N/AlN Superlattice Structure Tue, 08 Apr 2014 07:04:15 +0000 The highly conductance of Mg-doped Al0.3Ga0.7N layer using low-pressure metal organic chemical vapour deposition (MOCVD) on Al0.4Ga0.6N/AlN superlattice structure was reported. The rapid thermal annealing (RTA) has been employed for the effective activation and generation of holes, and a minimum p-type resistivity of 3 Ω·cm for p-type Al0.3Ga0.7N was achieved. The RTA annealing impacted on electrical, doping profile and morphological properties of Mg-doped Al0.3Ga0.7N with Al0.4Ga0.6N/AlN superlattice structure have been also discussed. The quality of Mg-doped Al0.3Ga0.7N with Al0.4Ga0.6N/AlN superlattice structure degraded after annealing from HRXRD. At appropriate annealing temperature and time, surface morphology of Mg-doped Al0.3Ga0.7N can be improved. A step-like distribution of [Mg] and [H] in p-type Al0.3Ga0.7N was observed, and thermal diffusion direction of [Mg] and [H] was also discussed. Zhiming Li, Jinping Li, Haiying Jiang, Yanbin Han, Yingjie Xia, Yimei Huang, Jianqin Yin, and Shigang Hu Copyright © 2014 Zhiming Li et al. All rights reserved. Determination of the DC Electrical Conductivity of Multiwalled Carbon Nanotube Films and Graphene Layers from Noncontact Time-Domain Terahertz Measurements Mon, 07 Apr 2014 16:33:15 +0000 Measuring the DC conductivity of very thin films could be rather difficult because of the electrical contact issue. This DC conductivity can, however, be extracted from noncontact measurements at GHz and THz frequencies using elaborated conductivity models that nicely fit the experimental data. Here we employ this technique to study the DC conductivity of fragile nanometer-thick films of multiwalled carbon nanotubes and monolayer graphene. The THz response of the films is measured by THz time-domain spectroscopy. We show that the THz conductivity of the samples is well fitted by either Drude-Lorentz model or Drude-Smith model, giving information on the physics of electrical conductivity in these materials. This extraction procedure is validated by the good agreement between the so-obtained DC conductivity and the one measured with a classical 4-point probe in-line contact method. E. Dadrasnia, H. Lamela, M. B. Kuppam, F. Garet, and J.-L. Coutaz Copyright © 2014 E. Dadrasnia et al. All rights reserved. Investigation of Tribological Performances for Porous Structure of Diatom Frustule with FSI Method Mon, 17 Mar 2014 16:28:35 +0000 Tribological performances of the diatom frustule are investigated with the liquid-solid interaction (FSI) method. Take, for example, the representative Coscinodiscus sp. shell; the diatom frustule with the porous structure is achieved by the scanning electron microscope (SEM). Based on the frustule, the representative diatom frustule is modeled. Further, tribological performances of the diatom at its different geometry sizes and velocities are solved with FSI method and compared with corresponding values for the nonporous structure. The numerical result shows that the existence of the porous structure of the diatom helps to reduce friction between it and ambient water and to increase its load-carrying capacity. Fanming Meng, Guixiang Gao, and TingTing Li Copyright © 2014 Fanming Meng et al. All rights reserved. Modeling Surface Recombination at the p-Type Interface via Dangling Bond Amphoteric Centers Wed, 12 Mar 2014 11:06:10 +0000 An integral model is proposed for recombination at the silicon/silicon dioxide (Si/SiO2) interface of thermally oxidized p-type silicon via Pb amphoteric centers associated with surface dangling bonds. The proposed model is a surface adaptation of a model developed for bulk recombination in amorphous silicon based on Sah-Shockley statistics which is more appropriate for amphoteric center recombination than classical Shockley-Read-Hall statistics. It is found that the surface recombination via amphoteric centers having capture cross-sections larger for charged centers than for neutral centers is distinguished from Shockley-Read-Hall recombination by exhibiting two peaks rather than one peak when plotted versus surface potential. Expressions are derived for the surface potentials at which the peaks occur. Such a finding provides a firm and plausible interpretation for the double peak surface recombination current measured in gated diodes or gated transistors. Successful fitting is possible between the results of the model and reported experimental curves showing two peaks for surface recombination velocity versus surface potential. On the other hand, if charged and neutral center capture cross-sections are equal or close to equal, surface recombination via amphoteric centers follows the same trend as Shockley-Read-Hall recombination and both models lead to comparable surface recombination velocities. Moustafa Y. Ghannam and Husain A. Kamal Copyright © 2014 Moustafa Y. Ghannam and Husain A. Kamal. All rights reserved. Resistivity, ESR, and Radiation Shielding Properties of the Volcanic Rock Materials Thu, 06 Mar 2014 11:09:09 +0000 Pumices have been used in cement, concrete, brick, and ceramic industries as an additive and aggregate material. It will be important to study pumice types by using a different tool as EPR which is a new technique for related material to be used for industrial aims. Electron spin resonance (ESR) spectra of the pumice types were taken by EMX-type spectrometer. Also, the current-voltage (I-V) and surface resistivity probe stand of the thin films was studied using a four-point probe measurements. The relationship between radiation shielding properties of the pumice samples and their surface resistivity, chemical, and electrokinetic properties was evaluated using simple regression analysis. Simple regression analysis indicated a strong correlation between surface resistivity and density and SiO2, Fe2O3, CaO, MgO, and TiO2 content of pumice samples in this study. It is found that a correlation between determined -factor by EPR spectroscopy and radiation shielding is established for pumice samples. Çiğdem Nuhoğlu, Mucip Tapan, Mustafa Okutan, Süreyya Aydın, Zeynel Yalçın, Orhan İçelli, H. Birtan Kavanoz, and Salim Orak Copyright © 2014 Çiğdem Nuhoğlu et al. All rights reserved. Magnetism and Microstructure Characterization of Phase Transitions in a Steel Tue, 04 Mar 2014 11:36:54 +0000 We present phase transitions in a low carbon steel according to existing phases and their magnetism. Scanning electron microscope employed research to clarify and evaluate the microstructural details. Additionally, we utilized from Mössbauer spectroscopy for magnetic characteristics of different existed phases. Scanning electron microscope examinations showed that the pure state of the steel was fully in the ferrite phase with equiaxed grains. Moreover, subsequent heat treatments on the studied steel also ensured the first austenite and then pearlite phase formation. Mössbauer spectroscopy of these phases appeared as a paramagnetic single-line absorption peak for the austenite phase and ferromagnetic six-line spectra for both ferrite and pearlite phases. From Mössbauer data, we determined that the internal magnetic fields of ferrite and pearlite phases were as 32.2 Tesla and 31.3 Tesla, respectively. M. Güler Copyright © 2014 M. Güler. All rights reserved. Effect of Noise on the Decoherence of a Central Electron Spin Coupled to an Antiferromagnetic Spin Bath Tue, 04 Mar 2014 00:00:00 +0000 We analyze the influence of a two-state autocorrelated noise on the decoherence and on the tunneling Landau-Zener (LZ) transitions during a two-level crossing of a central electron spin (CES) coupled to a one dimensional anisotropic-antiferomagnetic spin, driven by a time-dependent global external magnetic field. The energy splitting of the coupled spin system is found through an approach that computes the noise-averaged frequency. At low magnetic field intensity, the decoherence (or entangled state) of a coupled spin system is dominated by the noise intensity. The effects of the magnetic field pulse and the spin gap antiferromagnetic material used suggest to us that they may be used as tools for the direct observation of the tunneling splitting through the LZ transitions in the sudden limit. We found that the dynamical frequencies display basin-like behavior decay with time, with the birth of entanglement, while the LZ transition probability shows Gaussian shape. G. C. Fouokeng, M. Tchoffo, S. Moussiliou, J. C. Ngana Kuetche, Lukong Cornelius Fai, and Massou Siaka Copyright © 2014 G. C. Fouokeng et al. All rights reserved. Modeling the Mechanical Properties of Functionalized Carbon Nanotubes and Their Composites: Design at the Atomic Level Wed, 26 Feb 2014 11:34:35 +0000 This investigation focuses on the design of functionalization configuration at the atomic level to determine the influence of atomic structure on the mechanical properties of functionalized carbon nanotubes (F-CNTs) and their composites. Tension and compressive buckling behaviors of different configurations of CNTs functionalized by H atoms are studied by a molecular dynamics (MD) method. It is shown that H-atom functionalization reduces Young’s modulus of CNTs, but Young’s modulus is not sensitive to the functionalization configuration. The configuration does, however, affect the tensile strength and critical buckling stress of CNTs. Further, the stress-strain relations of composites reinforced by nonfunctionalized and various functionalized CNTs are analyzed. Qing-Sheng Yang, Bing-Qi Li, Xiao-Qiao He, and Yiu-Wing Mai Copyright © 2014 Qing-Sheng Yang et al. All rights reserved. Fowler-Nordheim Tunneling Characterization on Poly1-Poly2 Capacitors for the Implementation of Analog Memories in CMOS 0.5 μm Technology Sun, 23 Feb 2014 07:36:38 +0000 The experimental results of the Fowler-Nordheim characterization using poly1-poly2 capacitors on CMOS ON Semi 0.5 μm technology are presented. This characterization allows the development, design, and characterization of a new current-mode analog nonvolatile memory. Experimental results of the memory cell architecture are presented and demonstrate the usefulness of the proposed architecture. Enrique J. Tinajero-Perez, Jesus Ezequiel Molinar-Solis, Rodolfo Z. Garcia-Lozano, Pedro Rosales-Quintero, Jose M. Rocha-Perez, Alejandro Diaz-Sanchez, and Arturo Morales-Acevedo Copyright © 2014 Enrique J. Tinajero-Perez et al. All rights reserved. Tuning of Transport and Magnetic Properties in Epitaxial LaMnO3+δ Thin Films Wed, 19 Feb 2014 16:07:41 +0000 The effect of compressive strain on the transport and magnetic properties of epitaxial LaMnO3+δ thin films has been investigated. It is found that the transport and magnetic properties of the LaMnO3+δ thin films grown on the LaAlO3 substrates can be tuned by the compressive strain through varying film thickness. And the insulator-metal transition, charge/orbital ordering transition, and paramagnetic-ferromagnetic transition are suppressed by the compressive strain. Consequently, the related electronic and magnetic transition temperatures decrease with an increase in the compressive strain. The present results can be explained by the strain-controlled lattice deformation and the consequent orbital occupation. It indicates that the lattice degree of freedom is crucial for understanding the transport and magnetic properties of the strongly correlated LaMnO3+δ. J. Chen, L. Hu, W. J. Lu, B. Yuan, K. J. Zhang, J. M. Dai, and Y. P. Sun Copyright © 2014 J. Chen et al. All rights reserved. Defects Induced Room Temperature Ferromagnetism in ZnO Thin Films Wed, 19 Feb 2014 14:24:02 +0000 Polycrystalline ZnO thin films are prepared by the co-sputtering method under different oxygen partial pressures. Films deposited in pure argon gas exhibit ferromagnetism, whereas other films deposited under different oxygen partial pressures are diamagnetism. XPS results show the presence of Zn interstitial and oxygen vacancy in all of samples. Further analysis indicates that Zn interstitial may play an important role in triggering magnetic order on the undoped ZnO thin films by inducing an alteration of electronic configuration. Xiao Zhang, Wei Zhang, Xinghua Zhang, Xuewen Xu, Fanbin Meng, and C. C. Tang Copyright © 2014 Xiao Zhang et al. All rights reserved. Transport Critical Current Density of (Bi1.6Pb0.4)Sr2Ca2Cu3O10 Ceramic Superconductor with Different Nanosized Co3O4 Addition Wed, 19 Feb 2014 11:57:24 +0000 The effect of different nanosized Co3O4 (10, 30, and 50 nm) addition on the Bi1.6Pb0.4Sr2Ca2Cu3O10(Co3O4)x superconductor with  wt.% has been investigated using X-ray diffraction method, scanning electron microscopy, transition temperature, and critical current density measurements. The samples were prepared by the conventional solid-state reaction method. Samples with  wt.% Co3O4 (10 nm) showed the highest at 102 K. The highest was observed in the  wt.% Co3O4 (10 nm) and  wt.% Co3O4 (30 nm) samples. At 77 K, of the 10 nm and 30 nm Co3O4 added samples was 6 and 13 times larger than the nonadded samples, respectively. Small addition of Co3O4 nanoparticles in the Bi1.6Pb0.4Sr2Ca2Cu3O10 (Bi-2223) samples enhanced the critical current density and the phase formation. The larger Co3O4 nanoparticle (50 nm) had a greater degradation affect on superconductivity of the Bi-2223 phase. Nur Jannah Azman, Huda Abdullah, and Roslan Abd-Shukor Copyright © 2014 Nur Jannah Azman et al. All rights reserved. Persistent Photoconductivity in ZnO Nanowires in Different Atmospheres Tue, 18 Feb 2014 07:49:01 +0000 We investigated the photoconductivity of single ZnO nanowire device as a function of the surrounding atmosphere, considering the comparison between reduced pressure, inert gas environments, and air. We show that after UV excitation the photocurrent persists for hours, in particular in vacuum, nitrogen, and argon. In the presence of oxygen, the photodecay rate is initially fast but then becomes considerably slower, resulting in a long persisting photo-conductivity tail. Our proposed model explains the persistence of the photoconductivity (PPC) in terms of band bending at the surface of the nanowires, which is related to the trapping of electrons from the conduction band. Davide Cammi and Carsten Ronning Copyright © 2014 Davide Cammi and Carsten Ronning. All rights reserved. Preparation and Photocatalytic Activity of Ag Modified Ti-Doped-Bi 2 O 3 Photocatalyst Mon, 17 Feb 2014 17:26:52 +0000 Ti doped Bi2O3 (TDB) and Ag ion modified Ti doped Bi2O3 (Ag@TDB) photocatalysts were prepared by framework replacement synthesis method with different Ag loadings (0.05, 0.3, 0.75, and 1.0 mol/L AgNO3). The structural properties of the prepared catalysts were studied by scanning electron microscope (SEM), X-ray diffraction (XRD), BET surface area, and UV/Vis diffuse reflectance (DRS). The XRD spectra of the Ti doped Bi2O3 calcined at 650°C showed the diffraction peaks of a mixture of Bi12TiO20 and Bi4Ti3O12, with bits of mixed crystallite consisting of TiO2 and B2O3. A high blue shift in the range 650–550 nm was detected in the DRS band. This blue shift increased with the decreasing Ag content. The photocatalytic activities of the catalysts were evaluated for the degradation of crystal violet (CV) under UV light irradiation. The results indicated that the degradation rate of CV by using 1.0 mol/L AgNO3 doped bismuth titanate composite photocatalyst (1.0 Ag@TDB) was 1.9 times higher than that by using the bare Ti doped Bi2O3 photocatalyst. The higher activity of Ag@TDB is due to the enhancement of electron-hole pair separation by the electron trapping of silver particles. Lilan Zhang, Junfeng Niu, Duo Li, Ding Gao, and Jianghong Shi Copyright © 2014 Lilan Zhang et al. All rights reserved. Synthesis and Dielectric Studies of Monoclinic Nanosized Zirconia Sun, 16 Feb 2014 14:11:20 +0000 Zirconium dioxide is a prospective high-κ material that can replace silicon dioxide. Zirconium dioxide nanoparticle has been synthesized using sol-gel process at room temperature. The structural and morphological characterization of the nanoscaled zirconium dioxide is done using FTIR, SEM, X-ray diffraction, and TEM. The particle size of the synthesized ZrO2 is observed in the range of 50–80 nm with an average crystallite size of 2–10 nm. The results are compared with commercial coarse zirconia which showed a particle size in the range of 900 nm–2.13 µm and crystallite size of 5.3 nm–20 nm. It is expected that both nanoscaling and the high dielectric constant of ZrO2 would be useful in replacing the low-κ SiO2 dielectric with high-κ ZrO2 for CMOS fabrication technology. The synthesized ZrO2 is subjected to impedance analysis and it exhibited a dielectric constant of 25 to find its application in short channel devices like multiple gate FinFETS and as a suitable alternative for the conventional gate oxide dielectric SiO2 with dielectric value of 3.9, which cannot survive the challenge of an end of oxide thickness ≤ 1 nm. I. Flavia Princess Nesamani, V. Lakshmi Prabha, Aswathy Paul, and D. Nirmal Copyright © 2014 I. Flavia Princess Nesamani et al. All rights reserved. Visible-Light-Driven Photocatalytic Degradation of Aniline over NaBiO 3 Thu, 13 Feb 2014 12:37:39 +0000 Aniline was almost completely degraded in 30 min in given conditions. It was found that pH and NaBiO3 dosage had played important role in the photocatalytic degradation. To scrutinize the mechanistic details of the aniline photodegradation, several critical analytical methods including spectroscopy and GC/MS were utilized to detect the temporal course of the reaction. Intermediates and several small molecular products were separated and identified, such as C2H5O3N, C10H13O2N, and C12H10N2. Then two possible photodegradation pathways of aniline over NaBiO3 were proposed: ring opening and mineralization. Guo Liu, Zhen Wang, Wenjie Zheng, Shaogui Yang, and Cheng Sun Copyright © 2014 Guo Liu et al. All rights reserved. Electron Band Alignment at Interfaces of Semiconductors with Insulating Oxides: An Internal Photoemission Study Thu, 13 Feb 2014 09:46:37 +0000 Evolution of the electron energy band alignment at interfaces between different semiconductors and wide-gap oxide insulators is examined using the internal photoemission spectroscopy, which is based on observations of optically-induced electron (or hole) transitions across the semiconductor/insulator barrier. Interfaces of various semiconductors ranging from the conventional silicon to the high-mobility Ge-based (Ge, , ) and group (GaAs, , InAs, GaP, InP, GaSb, InSb) materials were studied revealing several general trends in the evolution of band offsets. It is found that in the oxides of metals with cation radii larger than ≈0.7 Å, the oxide valence band top remains nearly at the same energy (±0.2 eV) irrespective of the cation sort. Using this result, it becomes possible to predict the interface band alignment between oxides and semiconductors as well as between dissimilar insulating oxides on the basis of the oxide bandgap width which are also affected by crystallization. By contrast, oxides of light elements, for example, Be, Mg, Al, Si, and Sc exhibit significant shifts of the valence band top. General trends in band lineup variations caused by a change in the composition of semiconductor photoemission material are also revealed. Valeri V. Afanas'ev Copyright © 2014 Valeri V. Afanas'ev. All rights reserved. Structural and Magnetic Properties of Ni Doped Tue, 11 Feb 2014 07:46:11 +0000 Nickel (Ni) doped SnO2 powder samples were prepared using solid-state reaction with dopant concentrations in the range of 3 at.% to 15 at.%. The influence of Ni doping on structural, optical, and magnetic properties of the powder samples has been investigated. All the Ni doped powder samples exhibited tetragonal structure of SnO2. A decrease in optical band gap was observed with increase of Ni doping levels. The vibrating sample magnetometer measurements revealed that the Ni doped SnO2 powder samples were ferromagnetic at room temperature. M. Kuppan, S. Kaleemulla, N. Madhusudhana Rao, N. Sai Krishna, M. Rigana Begam, and M. Shobana Copyright © 2014 M. Kuppan et al. All rights reserved. Effect of Nitrogen Impurity on Electronic Properties of Boron Nanotubes Thu, 06 Feb 2014 13:00:37 +0000 For the first time we present electronic band structure and density of states for nitrogen doped hexagonal ultrathin boron nanotubes in the framework of density functional theory. The considered models of nanotubes below 5 Å diameter are armchair (3,3), zigzag (5,0), and chiral (4,2). The impurity chosen for the study is nitrogen and concentration of impurity atoms is limited to two. The study reveals that (3,3) BNT retains its metallic nature after nitrogen doping. However, metallicity gets increased which is attributed by the excess electrons of nitrogen. Further, it also brings out that (5,0) BNT which is originally metal transforms into semiconductor after nitrogen interaction and the band gap at G point increases with the impurity. Moreover, the band gap of (4,2) BNT reduces significantly and turns into semimetal for nitrogen doping. Thus, the nitrogen impurity has the predominant effect on the electronic properties of BNTs and therefore can be regarded as suitable candidates for nanoelectronic and field emission devices. Sandeep Kumar Jain and Pankaj Srivastava Copyright © 2014 Sandeep Kumar Jain and Pankaj Srivastava. All rights reserved. Tunneling Control of Transmission Coefficient and Group Index in a Quantum Dot Nanostructure Wed, 29 Jan 2014 00:00:00 +0000 We theoretically study the transmission and group index properties of the probe field in a four-level quantum dot molecule. It is found that the tunnel coupling plays a very important role in realizing the transmission coefficient of the probe field. Moreover, the impact of an incoherent pump field on imaginary part of susceptibility is investigated. We show that probe transmission exhibits oppositional behavior against weak and strong incoherent pump rates. This approach allows substantial flexibility in the manipulation of group velocity of light. Hamid Reza Hamedi, A. Khaledi-Nasab, and H. Ghaforyan Copyright © 2014 Hamid Reza Hamedi et al. All rights reserved. Synthesis and Characterization of One-Dimensional Porous (Zn,Cd)S/SiO2 Composite Nanostructural Materials Wed, 29 Jan 2014 00:00:00 +0000 One-dimensional (1D) porous (Zn,Cd)S/SiO2 composite nanostructural materials were synthesized by thermal evaporation of ZnS and CdS mixture powder at 950°C. The nanomaterials were collected from silicon wafers which were coated with 10 nm thick gold and were set apart from the source about 10 cm away. The diameter of the as-prepared 1D porous composite nanostructures is in the range of 1–1.5 m and their lengths are up to tens to hundreds of micrometers. The photoluminescence spectra measured at different temperatures of the prepared nanostructures display a similar broadband signature, which can be fitted by Gaussian function into three emission peaks centered at 477, 536, and 588 nm and attributed to band edge emission, neutral oxygen vacancies, and antisymmetric stretching of Si–O–Si and nonstoichiometric SiOx (), respectively. Xiuli Fu, Guijun Ban, Dan Li, Hanyuan Chen, and Zhijian Peng Copyright © 2014 Xiuli Fu et al. All rights reserved. Larmor Precession and Debye Relaxation of Single-Domain Magnetic Nanoparticles Thu, 23 Jan 2014 16:17:50 +0000 The numerous phenomenological equations used in the study of the behaviour of single-domain magnetic nanoparticles are described and some issues clarified by means of qualitative comparison. To enable a quantitative application of the model based on the Debye (exponential) relaxation and the torque driving the Larmor precession, we present analytical solutions for the steady states in presence of circularly and linearly polarized AC magnetic fields. Using the exact analytical solutions, we can confirm the insight that underlies Rosensweig’s introduction of the “chord” susceptibility for an approximate calculation of the losses. As an important consequence, it can also explain experiments, where power dissipation for both fields was found to be identical in “root mean square” sense. We also find that this approximation provides satisfactory numerical accuracy only up to magnetic fields for which the argument of the Langevin function reaches the value 2.8. Zs. Jánosfalvi, J. Hakl, and P. F. de Châtel Copyright © 2014 Zs. Jánosfalvi et al. All rights reserved. Nanostructure and Optical Properties of Silver Helical Pentagon Nanosculptured Thin Films Mon, 20 Jan 2014 09:51:12 +0000 Silver helical pentagon shaped nanosculptured thin films (HPNSTFs) were produced using oblique angle deposition method in conjunction with the rotation of sample holder under controlled conditions. The -polarization extinction spectra obtained at different azimuthal angles () and low incidence angle (i.e., ) from the Ag (HPNSTF) did not show significant change in the plasmon peak position, while at higher incidence angle (i.e., ) a blue shift appeared for the broad peak which was observed for lower incidence angle (i.e., ) and occurred at lower wavelength. In case of -polarized light a very broad peak was obtained for the incidence angle and for different angles and when compared with the lower incidence angle results it can be concluded that it is gone under a red shift. Polar diagrams of the samples showed slight anisotropy that should be due to high symmetry of the pentagon helical structure. Hadi Savaloni, Fatemh Haydari-Nasab, and Mariam Malmir Copyright © 2014 Hadi Savaloni et al. All rights reserved. Phase- and Polarization-Controlled Two-Photon Rabi Oscillation of the Biexciton State in a Semiconductor Quantum Dot Sun, 19 Jan 2014 11:30:19 +0000 Under a degenerate two-photon resonant excitation, the Rabi oscillation of the four-level biexciton system in a semiconductor quantum dot is theoretically investigated. The influence of the laser phases on the state manipulation is modeled and numerically calculated. Due to the interference between different excitation paths, the laser phase plays an important role and can be utilized as an alternate control knob to coherently manipulate the biexciton state. The phase control can be facilely implemented by changing the light polarization via a quarter-wave plate. Erlin Sun, Donghai Feng, and Tianqing Jia Copyright © 2014 Erlin Sun et al. All rights reserved. Numerical Analysis of Oxygen Adsorption on SnO2 Surface Using Slab Geometry Thu, 16 Jan 2014 10:06:05 +0000 Oxidation of thin film SnO2 layer was simulated. In particular, the evolution of depletion layer was investigated by solving Poisson-Boltzmann equation for SnO2 slab geometry grains. On this basis, the surface energy barrier dependence on layer thickness (30–500 nm) was obtained. The effect of the donor mobility (oxygen vacancies in the bulk) and degree of donor ionization on electric potential inside layer with different thicknesses was discussed. Furthermore, the dependence of per-square conductance on temperature (from 400 K to 700 K) has been computed. It was assumed that the bulk oxygen vacancies (donors) are singly or doubly ionized and mobile. The temperature variations in the carrier mobility were also taken into account. Weronika Izydorczyk Copyright © 2014 Weronika Izydorczyk. All rights reserved. Structural, Optical, and Compactness Characteristics of Nanocrystalline Synthesized through an Autoigniting Combustion Method Thu, 09 Jan 2014 16:17:56 +0000 Nanoparticles of calcium metaniobate compound are prepared by an autoigniting combustion technique and its structural, optical, and dielectric properties are investigated. The X-ray diffraction, Fourier-transform Raman, and infrared studies reveal that calcium metaniobate possesses phase pure orthorhombic columbite structure with space group of Pbcn. The average particle size of the as-prepared nanoparticles obtained from both the Scherrer formula and transmission electron microscopy is ~37 nm. The optical band gap calculated from Tauc's Plot is 3.25 eV. Photoluminescence studies reveal that Calcium metaniobate can be used as an idealphotoluminarmaterial. The powders are pelletised and sintered at an optimized temperature of in a short duration of two hours, yielding a high density. The morphology of the sintered pellet is further examined using scanning electron microscopy. The dielectric constant and loss factor values measured at 5 MHz for a well-sintered Calcium metaniobate pellet are found to be 27.6 and respectively, at room temperature. K. C. Mathai, S. Vidya, Annamma John, Sam Solomon, and J. K. Thomas Copyright © 2014 K. C. Mathai et al. All rights reserved. Investigation on Growth, Structural, Spectral, Optical, and Mechanical Properties of an Organic Nonlinear Optical Material: Morpholinium Hydrogen Tartrate Sun, 05 Jan 2014 07:46:59 +0000 Organic nonlinear optical crystal morpholinium hydrogen tartrate (MHT), with molecular formula [C8H15NO7], has been grown by slow evaporation solution technique. Single crystal X-ray diffraction study confirms that MHT crystallizes in orthorhombic system with noncentrosymmetric space group P212121. FTIR spectrum was recorded to identify the various functional groups of MHT. The various kinds of protons and carbons of MHT have been identified using 1H and 13C NMR spectral analyses. The range of optical absorption was ascertained by recording UV-Vis-NIR spectral studies. The TG/DTA studies revealed that the grown crystal is thermally stable up to 159.26°C. The mechanical property of the grown crystal was studied using Vickers microhardness studies. The relative second harmonic generation efficiency of MHT was determined using Kurtz and Perry powder technique; it was observed to be greater than that of KDP crystal. R. Renugadevi and R. Kesavasamy Copyright © 2014 R. Renugadevi and R. Kesavasamy. All rights reserved.