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A high magnetic field assisted pulsed laser deposition (HMF-PLD) system has been developed to in situ grow thin films in a high magnetic field up to 10 T. In this system, a specially designed PLD cylindrical vacuum chamber is horizontally located in the bore configuration of a superconducting magnet with a bore diameter of 200 mm. To adjust the focused pulsed laser into the target in such a narrow PLD vacuum chamber, an ingeniously built-in laser leading-in chamber is employed, including a laser mirror with a reflection angle of 65∠ and a damage threshold up to 3.4 J/cm². A laser alignment system consisting of a built-in video-unit leading-in chamber and a low-energy alignment laser is applied to monitor and align the pulsed laser propagation in the PLD vacuum chamber. We have grown La0.7Sr0.3MnO3 (LSMO) thin films on (LaAlO3)0.3(Sr2AlTaO6)0.7 (001) [LSAT (001)] substrates by HMF-PLD. The results show that the nanostructures of the LSMO films can be tuned from an epitaxially continuous film structure without field to a vertically aligned nanorod structure with an applied high magnetic field above 5 T, and the dimension size of the nanorods can be tuned by the strength of the magnetic field. The associated magnetic anisotropy is found to be highly dependent on the nanorod structures. We show how the HMF-PLD provides an effective route toward tuning the nanostructures and the physical properties of functional thin films, giving it an important role in development of nanodevices and their application. [ABSTRACT FROM AUTHOR]

Terahertz wave sensing and imaging have received a great deal of attention because of their significant scientific and technological potential in multidisciplinary fields. However, owing to the challenge of dealing with high ambient moisture absorption, the development of remote open-air broadband terahertz spectroscopy is lagging behind the urgent need for the technology that exists in homeland security and the fields of astronomy and environmental monitoring. The requirement for on-site bias or forward collection of the optical signal in conventional terahertz detection techniques has inevitably prohibited their use in remote sensing. We introduce an ‘all-optical’ technique of broadband terahertz wave detection by coherently manipulating the fluorescence emission from asymmetrically ionized gas plasma interacting with terahertz waves. Owing to the high atmospheric transparency and omnidirectional emission pattern of the fluorescence, this technique can be used to measure terahertz pulses at standoff distances with minimal water vapour absorption and unlimited directionality for optical signal collection. We demonstrate coherent terahertz wave detection at a distance of 10 m. [ABSTRACT FROM AUTHOR]

We report the first systematic study of broadband THz wave generation with ambient air as the nonlinear media. Generation of pulsed THz waves with mixing the fundamental and the second harmonic beams in air has been previously demonstrated by Cook et al. and Hartmut et al. while different groups obtained different results. To verify the proposed mechanism of strong THz wave generation, we measured dependence of generated THz field on the polarization, amplitude and phase of the individually controlled two beams. Our results confirm that four-wave-mixing rectification is the major mechanism this phenomenon, and the amplitude and polarity of generated THz wave can be controlled by the relative phase of the beams. This work is significant by providing the feasibility of THz wave generation and detection with a standoff distance greater than 50 meters. [ABSTRACT FROM AUTHOR]

Popcorn offers an environmentally friendly alternative to the commercial synthetic loose-fill packing materials. Popcorn could be used for cushioning purposes if the oil is extracted after the popping process. Conventional and microwave-assisted extraction methods were used for oil extraction from whole and ground, popped and unpopped kernels. The conventional extraction method achieved 68.5% oil recovery from whole popped kernels. However, whole unpopped kernels were not efficiently de-oiled with either of the methods. Extraction of oil from popped kernels is recommended; corn varieties with higher starch content and lower oil content should be used. [ABSTRACT FROM AUTHOR]

Degenerate two-photon absorption (TPA) spectral properties of five AFX chromophore solutions have been studied using a single and spectrally dispersed sub-picosecond white-light continuum beam. In a specially designed optical configuration, optical pathways inside the sample solution for different spectral components of the focused continuum beam were spatially separated from each other. Thus, the nondegenerate TPA processes coming from different spectral components can be eliminated, and the direct nonlinear absorption spectrum attributed to degenerate TPA processes can be readily obtained. Using this new technique, the complete TPA spectra for these five highly two-photon-active compounds (AF-380, AF-350, AF-295, AF-270, and AF-50) were obtained in the spectral range from 600 to 950 nm on an absolute scale of TPA cross section. The relationship between the molecular structures and their TPA spectral behaviors are discussed. In general the measured TPA spectra are not identical with the linear absorption spectra on the scale of absorbed photon(s) energy. Moreover, for some sample (such as AF-380), the TPA spectrum is totally different from the linear spectrum, which implies the difference of molecular transition pathways and selection rules for one- and two-photon excitation processes. At high excitation intensity levels (>=15 GW/cm2), the saturation behavior of TPA transition can be observed obviously in AF-350 and AF-380 solutions that exhibit much higher nonlinear absorptivity than the other chromophores investigated. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this paper we report the structural, electrical and optical properties of epitaxial Ba(SbxSn1[?]x)O3 (x = 0-0.30) (BSSO) films grown on SrTiO3(0 0 1) substrates by the pulsed laser deposition method. The investigation reveals that the transport and optical characteristics of BSSO films depend very sensitively on the Sb-doping content. Temperature-dependent resistivity measurements show that at low Sb contents (x = 0.03, 0.07) the metal-semiconductor transition occurs at 150 K and 80 K, respectively, and the semiconductor behaviour appears in high doped (x = 0.15, 0.30) films. The transmittance decreases significantly from about 80% to nearly zero in the visible region and the optical band gap shifts from 3.48 to 4.0 eV with increasing Sb content in the films. The lowest room-temperature resistivity of 2.43 mO cm with carrier density and mobility of 1.65 x 1021 cm[?]3 and 1.75 cm2 V[?]1 s[?]1 was obtained in the films with doping at x = 0.07. By employing them as bottom electrodes we have fabricated transparent Pb(Zr0.52Ti0.48)O3 ferroelectric capacitors showing square polarization-electric field hysteresis loops, indicating that these perovskite-type BSSO films at low doping can be potentially used in transparent devices especially based on all-perovskite heterostructures. [ABSTRACT FROM AUTHOR]

High coercivity CoFe2O4 (CFO) thin films with large-area are very desirable for applications. Here, we report La0.7Sr0.3MnO3 (LSMO) layer decoration effects on coercivity in CFO thin films by solution processing. With LSMO layer decoration, the coercivity increases initially and then decreases with increasing LSMO layer thickness. Strain induced by the mismatched thermal expansion coefficient and magnetostrictive coefficient as well as the interfacial magnetic exchange coupling between CFO and LSMO are investigated. The room temperature out-of-plane and in-plane coercivity reached 7.6 and 4.9 kOe, respectively, are obtained, which are the highest values in solution derived CFO thin films. The improved coercivity is beneficial for applications and provides a facile route to enhance coercivity of CFO thin films through surface modification by soft magnetic layers. [ABSTRACT FROM AUTHOR]

A black silicon structure with high-aspect-ratio surface spikes was designed and fabricated in vacuum, resulting in absorptance >90% over the range of 200-2500 nm. It is demonstrated that annealing, an essential step in the fabrication of semiconductor devices, has almost no effect on the infrared absorption of this material, while the infrared absorption of an identical structure fabricated in a SF6 drops dramatically after the annealing process. The characteristic of high infrared absorption and annealing-insensitivity is attributed to both the high-aspect-ratio structure and the phosphor-doped low impedance silicon. These results are important for the fabrication of highly efficient optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this article, the film of Sr0.775Y0.225CoO3-δ, which shows the highest ferromagnetic Curie temperature in perovskite ABO3-based cobaltates due to antiferrotype orbital order, was first prepared successfully on LaAlO3 (100) substrate using the simple chemical solution deposition (CSD) method. The results show that the derived film is (h00)-epitaxial, and the transport property is semiconductor like with room-temperature ferromagnetism (FM). The result will provide a feasible route to prepare Sr0.775Y0.225CoO3-d film with room-temperature FM using CSD with a low-cost and nonvaccum method. [ABSTRACT FROM AUTHOR]

The optical property of beta barium borate (β-BBO) in the terahertz region (0.2–12 THz) was studied using a broadband air photonic terahertz time-domain spectrometer. The crystal orientation and frequency dependence of β-BBO refractive index and absorption coefficient were experimentally investigated over the temperature range of 10–293 K. Four TO phonon modes were observed below 3.5 THz. The behavior of these phonon modes at different temperatures has been characterized. [ABSTRACT FROM AUTHOR]

Nanosized (Sr2FeMoO6)1-x/(CeO2)x composites were prepared by Sr2FeMoO6 (SFMO) obtained by sol-gel and nanosized CeO2 powders. The magnetoresistance (MR) of composites is explored as a function of the molybdate/insulator composition and magnetic field. The enhancement of the low-field magnetoresistance is observed with increasing CeO2. The MR ratio at 10 K with H=5 kOe is 7.9% and 10.2% for the x=0.05 and 0.3 samples, which are 1.1 times and 1.7 times as large as that for pure SFMO, respectively. The enhanced MR was attributed to the spin-dependent tunneling at the interface of grain boundaries. [ABSTRACT FROM AUTHOR]

Bulk liquid water is a strong absorber in the terahertz (THz) frequency range, due to which liquid water has historically been sworn off as a source for THz radiation. Here, we experimentally demonstrate the generation of broadband THz waves from liquid water excited by femtosecond laser pulses. Our measurements reveal the critical dependence of the THz field upon the relative position between the water film and the focal point of the laser beam. The THz radiation from liquid water shows distinct characteristics when compared with the THz radiation from air plasmas with single color optical excitation. First, the THz field is maximized with the laser beam of longer pulse durations. In addition, the p-polarized component of the emitted THz waves will be influenced by the polarization of the optical excitation beam. It is also shown that the energy of the THz radiation is linearly dependent on the excitation pulse energy. [ABSTRACT FROM AUTHOR]

High room temperature coercivity CoFe2O4 (CFO) thin films are desirable in view of many applications, which is seldom achieved over 3 kOe in solution deposited CFO thin films. Herein, grain growth kinetic is investigated in the solution derived CFO thin films with coercivity larger than 4 kOe, showing a relaxation mechanism. The coercivity and magnetization increase initially and then decrease with increasing dwell time. The high coercivity is originated mainly from the critical grain size and the growth strain induced by the small crystallites and poorly developed grains. The results will provide a route to fabricate larger-area CFO thin films with high coercivity on silicon wafers by low-cost solution processing. [ABSTRACT FROM AUTHOR]

A novel kind of microwave absorption composite in Ku-band with low cost, low density and strong absorption was prepared through Bio-template carbonization and solvothermal method. The phase structures and morphologies of the composite had been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The microwave absorption properties of carbonized kapok fibers and Fe3O4/kapok fibers were measured by vector network analysis (VNA). When the sample thickness is 1.5 mm, the Fe3O4/kapok fibers have an optimal absorption peak value of about -24.1 dB at 17.4 GHz and its effective absorption bandwidth lower than -10 dB reaches 2.4 GHz (from 15.6 to 18.0 GHz). The reflection loss results indicate that the Fe3O4/kapok fibers possess higher microwave absorption in the Ku-band. A possible mechanism of the improved microwave absorption performance of the composite was discussed. [ABSTRACT FROM AUTHOR]

M-type hexaferrites BaFe12-2x(NiTi)xO19 (x=0, 0.05, 0.1, 0.3, 0.5, 0.7, and 0.9) were synthesized by the solvothermal method. X-ray diffraction (XRD) analysis reveals that the samples are of pure-phase with the space group of p63/mmc. As the Ni-Ti substitution level increases from x=0 to 0.9, the results of field-emission scanning electronic microscopy indicate that the particles are agglomerated and the mean particle size decreases. With the increase in substitution concentration x, the saturation magnetization increases first, and then declines slowly, whereas the coercivity decreases gradually. The variation of magnetic properties can be explained by the effects of Ni-Ti substitution. The results above indicate that our samples have positive effects on high density perpendicular recording. [ABSTRACT FROM AUTHOR]

Ni0.5Zn0.5Fe2O4 particles with different particle sizes have been synthesized by sol-gel method. X-ray diffraction results show that all the samples are pure cubic spinel structure with their sizes ranging from 9 to 96 nm. The lattice constant significantly decreases with further increasing annealing temperature. The magnetic measurements show super paramagnetic nature below the particle size of 30 nm, while others show ferrimagnetic nature above the corresponding blocking temperature. The blocking temperature increases with the increase in particle size, which can be explained by Stoner-Wohlfarth theory. The saturation magnetization increases as the particle size increases, which can be explained by the cation redistribution on tetrahedral A and octahedral B sites and the domain wall motion. The variation of coercivity as a function of particle size is based on the domain structure. [ABSTRACT FROM AUTHOR]

ZnFe2O4 films have been prepared using a sol-gel route. The influences of annealing temperature as well as annealing atmosphere on the structural, morphological, magnetic, and optical properties were investigated. The TEM and SEM images show that ZnFe2O4 films are polycrystalline in nature and homogeneous with densely packed grains. ZnFe2O4 films exhibit ferromagnetic behavior at 300 K and high transparency (≥80%) above the absorption band edge. With decreasing annealing temperature and annealing oxygen partial pressure, the saturated magnetism at 300 K is improved and the optical band gap is decreased. The reasons are discussed, and the results show that semitransparent ZnFe2O4 films with room- temperature ferromagnetism can be successfully prepared using a sol-gel method. [ABSTRACT FROM AUTHOR]

Metallic and transparent La0.5Sr0.5TiO3+ x/2 films were prepared by the chemical solution deposition (CSD) method using topotactic reduction processing. The use of Si powder as the reducing agent was facile and allowed easy manipulation. It was observed that metallic (resistivity at 300 K ∼2.43 mΩ cm) and transparent (∼80% transmittance at visible light) La0.5Sr0.5TiO3+ x/2 films could be obtained with an annealing temperature of 900°C, which was significantly lower than the hydrogen reduction temperature (∼1400°C). The successful preparation of metallic and transparent La0.5Sr0.5TiO3+ x/2 films using CSD has provided a feasible route for depositing other perovskite-structured functional layers on La0.5Sr0.5TiO3+ x/2 films using this low-cost all CSD method. [ABSTRACT FROM AUTHOR]

Transparent conducting p-type Bi2Sr2Co2Oy thin films have been first grown on SrTiO3 substrates by a chemical solution deposition, showing c-axis self-orientation. The figure of merit can reach as high as 800 MΩ-1, which is the highest value for p-type transparent conducting thin films by solution methods. [ABSTRACT FROM AUTHOR]

Magnetic properties of charge ordered (CO) Bi0.4Ca00.6Mn1[?]xTixO3 (0 [?] x [?] 0.2) are investigated. It is observed that the charge order temperature Tco is depressed gradually with Ti content increasing, and then disappears completely when x is 0.16. The high temperature magnetization and Curie temperature decrease with Ti content, whereas the low temperature magnetization and Curie temperature are increased. Moreover, exchange bias (EB) is observed in the field cooling mode for all samples. The relative EB parameters depend strongly on the Ti doping content. In particular, the exchange field shows a nonmonotonic variation with a maximum at Bi0.4Ca0.6Mn0.92Ti0.08O3. The EB has been explained in terms of the density of ferromagnetic nanodomains superposed on the antiferromagnetic matrix. The results suggest that it is possible to tune the EB through the Mn-site doping in CO manganites by controlling the density of ferromagnetic nanodomains. [ABSTRACT FROM AUTHOR]

Nanocrystalline CaMoO4 (CMO) thin films were fabricated on Si and glass substrates via the chemical solution deposition (CSD) method. From x-ray diffraction, atomic force microscopy and Fourier transform infrared spectra results, relatively smooth Scheelite-type CMO thin films can be fabricated within the annealing temperature range from 400 to 700 °C. The band gap is 4.18 eV calculated from the optical transmission spectra and the photoluminescence (PL) emission spectra show that the CMO thin films on Si have a broad green emission band centred at 490 nm. Our experimental results show that the CSD method is an alternative method to prepare nanocrystalline CMO thin films with a great PL property at low annealing temperatures. [ABSTRACT FROM AUTHOR]