bluuebunny/crossref_metadata_2025_split huggingface dataset:
Self-organization of magnetic nanogroove arrays by LaserMBE and hydrogen reduction.
Authors: Matsuda Akifumi , Watanabe Takahiro , Akita Yasuyuki , Hosaka Makoto , Koyama Kouji , Takeuchi Atsuko , Yoshimoto Mamoru 
Published: April 2011

AbstractThe epitaxially grown magnetic nanostructures including nanodots, nanowires and nanorings have been attracting much scientific and engineering interests because of their expected unique physical characteristics due to quantum effects. These epitaxial nanomagnets and their array are undoubtedly thought to make major contribution to the development of future SPINTRONICS devices, ultra-high density magnetic random access memory (MRAM) and magnetic switching devices for examples, and other quantum devices. In this case, epitaxial growth of the nanomagnets and the resulting anisotropic properties are one of the largest interest as well as fine-nanostructuring. There have been some concerns such as throughput rate with conventional nanoprocessing techniques involving FIB lithography and e-beam lithography, and/or minimization-limit with photolithography due to the wavelength. On the other hand, self-assembly or self-organized methods could also be used for construction of nanopatterns, in which such nanostructures are directly built up from separate atoms. Here we report about formation and characterization of self-organized nanomagnet arrays made of metals and oxides. We have epitaxially grown ferrimagnetic Fe3O4 (111), (Mn0.55Zn0.35Fe0.10)Fe2O4 (111), ferromagnetic Ni (111) and antiferromagnetic NiO (111) nanodots, nanowires and nanogroove arrays on the atomically stepped ultra-smooth sapphire (0001) substrate by LaserMBE. The sapphire (a-Al2O3single crystal) substrates have atomic steps of 0.2 nm in height and atomically flat terraces of 50-100 nm in width so that self-assembly processes of nanomagnet arrays were strongly induced by the energetic instability at the straight and periodic step-edges. In this study, NiO worked as a antiferromagnetic exchange bias layer. On the other hand, NiO was also reduced into ferromagnetic Ni metal by annealing in hydrogen atmosphere in some situations for further applications. Crystallographic and morphology analyses of the nanomagnets were made by in-situ reflection high-energy electron diffraction (RHEED), ex-situ X-ray diffraction (XRD), transmission electron microscope (TEM). and atomic force microscopy (AFM). Magnetic properties were characterized by superconducting quantum interference device (SQUID) magnetometer and magnetic force microscopy (MFM). Further experimentals are conducted for magneto-optical characterizations for above mentioned metal and/or oxide nanomagnet arrays.
Magneto-transport Properties of Cobalt doped Indium Oxide Dilute Magnetic Semiconductors
Authors: Mamidi N. , Gupta R. K. , Ghosh K. , Mishra S. R. , Kahol P. K. 
Published: April 2011

AbstractRecently, oxide-based dilute magnetic semiconductors (DMS) have attracted an immense research interest to the scientists due to the possibility of inducing room temperature ferromagnetism and potential uses in novel spintronic devices. In2O3, a transparent opto-electronic material, is an interesting prospect for spintronics due to its unique combination of magnetic, electrical, and optical properties. High quality thin films of Co-doped In2O3 DMS were grown on quartz substrates using pulsed laser deposition technique. All the films have been characterized using different techniques such as x-ray diffraction, Raman spectroscopy, optical transmission spectroscopy, electrical resistivity, and Hall Effect measurement. The effect of growth temperature and oxygen pressure on the electrical, magnetic, and optical properties of these films have been studied in detail. The optical transparency in all the films is high. It has been observed that the optical transparency depends on growth temperature and oxygen pressure. The electrical parameters such as resistivity, carrier concentration, and mobility strongly depend on both oxygen pressure and growth temperature. The films grown at low temperature are semiconducting in nature while the films grown at high temperature are metallic. Detailed temperature and magnetic field dependent resistivity, magnetoresistance, and Hall effect data will be presented. This work is supported by Research Corporation (award number CC6166).
High Quality Deposition of Strontium Titanate (STO) Thin Films using Sol-Gel Method
Authors: Uchiyama Kiyoshi , Fukunaga Daiki , Shiosaki Tadashi 
Published: April 2011

AbstractHighly oriented strontium titanate (STO) thin films were successfully deposited on sapphire substrates using a sol-gel method. Sintering temperature of 1400°C and the use of c-cut sapphire for the substrates are the keys to obtain highly oriented thin films. The sample obtained on c-cut sapphire with a sintering temperature of 1400°C showed quite high (111)-orientation and a narrow full width half maximum (FWHM) value of 0.265°, which indicates a high quality deposition of the STO thin films.We believe this high quality STO deposition technique will bring a new scope of oxide material applications for future electronic devices.
Role of SrTiO3 Seed Layer on Low-temperature Crystallization of Pb(Zr, Ti)O3 Films Prepared by Metalorganic Chemical Vapor Deposition
Authors: Moon Ji-Won , Wakiya Naoki , Kiguchi Takanori , Yoshioka Tomohiko , Junzo Tanaka , Shinozaki Kazuo 
Published: April 2011

AbstractRole of SrTiO3 seed layer on low-temperature crystallization of Pb(Zr, Ti)O3 (PZT) film was investigated. The SrTiO3 seeds were prepared by pulsed laser deposition (PLD) with the temperature range of 400-600 °C and PZT films were prepared by thermal MOCVD. The pyrochlore free PZT films can be successfully crystallized at around 340 °C on SrTiO3 seed layers by thermal MOCVD. It was found that the role of SrTiO3 seed layer is not only pyrochlore suppression but also perovskite promotion. It is also considered that crystallinity, surface coverage and seed layer thickness are important parameters for low-temperature crystallization and electrical properties of PZT films.
Ozone Gas Generator Using Uniaxially Polarized LiTaO3 Single Crystal
Authors: Yoshikazu Nakanishi , Ide Junko , Kondo Jun , Fukao Shinji , Handa Katsumi , Tochio Tatsunori , Ito Yoshiaki , Tanaka Akikazu , Yoshikado Shinzo 
Published: April 2011

AbstractThe phenomenon that a ferroelectrics crystal carries out intrinsic polarization by the temperature change generally is known. The Ozone gas generation was investigated due to a strong electric field of this crystal under atmospheric pressure . When we added a rapid temperature change to the crystal, the charge non–equilibrium occurs around the crystal. Oxygen is influenced due to the non-equilibrium in charge and ozone is considered to be generated. Therefore, we used the high electric field induced due to the polarization of a ferroelectrics crystal in order to produce the ozone under atmospheric pressure.As a result, we were able to produce ozone of the density of 400ppb in a oxygen gas flow of 1.5 liters per minute using this simple system: The crystals (Yamaju Co. Ltd. and Sumitomo metal mining Co. Ltd.) are used in thickness of 3, 5, 7, 10, 20, and 30 mm with a diameter of 4 inches, respectively. They are poled crystals.Experiments on the maximum temperature (300 degree), the temperature gradient (100 degree/10 minite), and substrate materials(Cu and Al), the thickness of the crystal, and z face etc. were carried out during the temperature of LiTaO3 single crystal from 20C to about 300C. It is found that the amount of the ozone production increases rapidly, when the maximum temperature of LiTaO3 single crystal is raised and have a relation with the thickness of the crystal. However, the amount of the ozone production doesn't closely related with the X-ray generation that we use the crystal for.In the present study, when the thickness of the crystal became large, polarization voltage became high, but generated efficiency of ozone was not necessarily proportional to thickness.
FERROELECTRIC THIN FILM SYSTEM IN PACKAGE DEVICES WITH INTEGRATED CAPACITORS OF 100 nF/mm2 & BREAKDOWN VOLTAGES OF 90 V
Authors: Klee Mareike , Keur Wilco , Mauczok Ruediger , Roest Aarnoud , Reimann Klaus , Peters Linda , Neumann Kai , Kiewitt Rainer 
Published: April 2011

AbstractThin film ferroelectric capacitors have been integrated with resistors and active functions such as ESD protection into small miniaturized modules, which enable a board space saving of up to 80%. With the optimum materials and processes, integrated capacitors with capacitance densities of up to 100 nF/mm2 and breakdown voltages of up to 90 V have been achieved. The integration of these high density capacitors with extremely high breakdown voltage is a revolution in the world of integrated passive components and has not yet been achieved in any other passive integration technology.
New method of reducing threading dislocation in epitaxial ZnO films grown on c-sapphire
Authors: Sun Yuekui , Cherns David 
Published: April 2011

AbstractThe behavior of threading dislocations (TDs) in ZnO/(0001)sapphire heterostructures grown by a two-step method have been investigated. The initial template, grown by pulsed laser deposition, consisted of a continuous underlayer, which was O-polar and an overlayer comprising a high density of Zn-polar nanorods. High densities (∼7×1010cm−2) of TDs were found to be restricted to the underlayer, whereas the nanorods were almost defect-free. Subsequent treatments by either hydrothermal growth or chemical vapour deposition (CVD) achieved epitaxial lateral overgrowth of nanorods and led to continuous Zn-polar films. The low TD density of nanorods remained until misoriented grain boundaries and boundary dislocations were generated when neighbouring nanorods become coalesced. The lateral migration of TDs in the overgrowth led to dislocation interactions and reduction of TDs. The total TD density at the top of the overlayer was estimated to be ∼1×109cm−2for hydrothermal growth and ∼7×109cm−2for CVD growth.
Visible Luminescence of Rare Earth Ions Doped Amorphous Zinc Oxide Thin Films Grown by Sputtering Technique
Authors: Jadwisienczak Wojciech M. , Vemuru Ajay S. , Khan Saima , Khan Aurangzeb , Kordesch Marty E. 
Published: April 2011

AbstractWe report on the luminescence of rare earth (RE) (Sm, Er, Tm) ions doped ZnO films grown by the rf-magnetron sputtering technique. Samples were insitu doped with Sm ion or with Sm, Er, and Tm ions simultaneously without any intentional co-dopants and deposited on c-Si or quartz substrates at low temperatures. Selected ZnO:RE samples were thermally annealed in 200ºC-1000ºC temperature range in oxygen or argon gas at ambient pressure. As-grown and annealed samples were amorphous (a-ZnO) as was confirmed by the X-ray analysis. Furthermore, a-ZnO:RE samples were investigated by energy diffraction, photoluminescence and cathodoluminescence. In general, CL spectra of as-grown RE-doped a-ZnO films show characteristic emission lines due to 4f-shell transitions of RE3+ ions. Optical excitation of as-grown a-ZnO doped with RE ions using above the bandgap excitation resulted in strong host emission overlapped with weak RE3+ emission bands. It was observed that a thermal annealing process promotes changes of RE ions' environments resulting in significant 4f-shell transition luminescence intensity quenching.
Performance of ZnO TFTs with AlN as Insulator
Authors: De Souza Maria Merlyne , Cross Richard B , Jejurikar Suhas , Adhi K P 
Published: April 2011

AbstractThe performance of ZnO TFTs fabricated via RF sputtering, with Aluminium Nitride (AlN) as the underlying insulator are reported. The surface roughness of ZnO with AlN is lower than that with SiN by at least 5 times, and that with SiO2 by 30 times. The resulting mobility for the three insulators AlN, SiN, SiO2 using identical process is found to be 3, 0.2-0.7 and 0.1-0.25 cm2/Vs respectively. There does not appear to be any corresponding improvement in the stability of the AlN devices. The devices demonstrate significant positive threshold voltage shift with positive gate bias and negative threshold voltage shift with negative gate bias. The underlying cause is surmised to be ultra-fast interface states in combination with bulk traps in the ZnO.
Crystallization of yttrium-iron garnet (YIG) in thin films: Nucleation and growth aspects
Authors: Zaezjev Michael V. , Chandra Sekhar Manda , Ferrera Marcello , Razzari Luca , Holmes Barry M , Sorel Marc , Hutchings David C , Pignolet Alain , Morandotti Roberto 
Published: April 2011

AbstractWe have studied the crystallization of the yttrium - iron garnet (Y3Fe5O12, YIG) polycrystalline phase in thin films fabricated by means of pulsed laser deposition . Films were deposited on MgO substrates in vacuum, in argon, and in oxygen. A subsequent post-deposition heat treatment (annealing) was done at 800°C in air. We have shown that the crystallization of YIG was precluded by co-existent parasitic phases present in the as-deposited films. Specifically, the growth of the parasitic phase needs to be suppressed in order to get a single-phase polycrystalline YIG. Lowering the substrate temperature has been shown to be a simple and efficient way to suppress the growth of parasitic phase and to obtain good quality YIG films after thermal treatment. This procedure has been demonstrated to be successful even when the YIG films were grown in vacuum and their composition was significantly out of stoichiometry.
Enabling the Desktop NanoFab with DPN® Pen and Ink Delivery Systems
Authors: Fragala Joseph S. , Shile R. Roger , Haaheim Jason 
Published: April 2011

AbstractDepositing a wide range of materials as nanoscale features onto diverse surfaces with nanometer registration and resolution are challenging requirements for any nanoscale processing system. Dip Pen Nanolithography® (DPN®), a high resolution, scanning probe-based direct-write technology, has emerged as a promising solution for these requirements. Many different materials can be deposited directly using DPN, including alkane thiols, metal salts and nanoparticles, metal oxides, polymers, DNA, and proteins. Indirect deposition allows the creation of many interesting nanostructures. For instance, using MHA may be used to create arrays of antibodies, which then bond specifically to antigens on the surface of viruses or cells, to create cell or virus arrays. The DPN system is designed to allow registration to existing features on a writing substrate via optical alignment or nanoscale alignment using the core AFM platform. This allows, for instance, the nanoscale deposition of sensor materials directly onto monolithic electronic chips with both sensing and circuit features.To enable the DPN process, novel pen and ink delivery systems have been designed and fabricated using MEMS technology. These MEMS devices bridge the gap between the macro world (instrument) and the nano world (nanoscale patterns). The initial MEMS devices were simple and robust both in design and fabrication to get products into the marketplace quickly. The first MEMS-based DPN device was a passive pen array based on silicon nitride AFM probe technology from Cal Quate's group at Stanford. The next two devices (an inkwell chip and a thermal bimorph active pen) were more complicated and took considerable effort to commercialize. In this work, some of the difficulties in bringing brand new MEMS devices from the prototype stage into production will be shared. The subsequent MEMS products have become even more complicated both in design and fabrication, but the development process has improved as well. For example, the 2D nanoPrintArray has 55,000 pens in one square centimeter for high throughput writing over large areas. The 2D arrays enable templated self assembly of nanostructures giving researchers the ability to control the placement of self assembled features rather than allowing the self assembly to occur randomly.Applications of DPN technology vary from deposition of DNA or proteins in nanoarrays for disease detection or drug discovery, to deposition of Sol-gel metal oxides for gas sensors, and to additive repair of advanced phase-shifting photomasks.
Organic Semiconductors for Detection of Ionizing Radiation
Authors: Wilson Tiffany M.S. , Chinn Douglas A. , King Michael J. , Doty F. Patrick 
Published: April 2011

AbstractOrganic semiconductors are increasingly common in electronics and sensors, and are now under investigation for a novel type of radiation sensors at Sandia National Laboratories. This class of materials can offer wide band gaps, high resistivities, low dielectric constants, and high dielectric strengths, suggesting they may be suitable for solid-state particle counting detectors. A range of solution cast materials have been evaluated for this application, primarily in the family of poly(p-phenylene vinylene)s, or PPVs. The high ratio of hydrogen to carbon offers neutron sensitivity, while the low Z material provides some natural gamma discrimination. Compared to existing detectors, these materials could potentially offer large-scale radiation detection at a substantially reduced cost.While PPVs hold promise for radiation detection, the mechanical and electrical properties must be optimized and the processing effects understood. Polymers can offer significantly simplified processing compared to the more common crystals used in solid state detection, which can be size limited and fragile. However, organic semiconductors are very sensitive to processing conditions, and mobility can be affected by orders of magnitude by processing variables, without altering any chemistry. Additives can also have dramatic effects on both electrical and mechanical properties. We report on nanoparticle additives that cause an increase in photoresponse of approximately three orders of magnitude as compared to a polymer film without additives. We separately show an order of magnitude increase in photoresponse by exposing the polymer/fullerene composite to sub-bandgap light.Future work will analyze the feasibility of single particle detection and various geometries for optimization. Additional processing variables will also be investigated for further improvement of mobility and reduction of trap density.
Lutetium Oxide Coatings by PVD
Authors: Topping Stephen G , Park C H , Rangan S K , Sarin V K 
Published: April 2011

AbstractDue to its high density and cubic structure, Lutetium oxide (Lu2O3) has been extensively researched for scintillating applications. Present manufacturing methods, such as hot pressing and sintering, do not provide adequate resolution due to light scattering of polycrystalline materials. Vapor deposition has been investigated as an alternative manufacturing method. Lutetium oxide transparent optical coatings by magnetron sputtering offer a means of tailoring the coating for optimum scintillation and resolution. Low crystallization in the sputtering process adversely affects transparency and scintillation, and is critical in growing stress free, thick coatings. The effect of process parameters on the crystallization is being investigated via x-ray diffraction (XRD), scanning electron microscopy (SEM) and emission spectroscopy and will be presented and discussed.
Chemical Modification of Carbon Materials with Sulfur Functionalities
Authors: Nakamura Takako , Ohana Tsuguyori 
Published: April 2011

AbstractPhotolysis of cyclic disulfides in the presence of carbon materials such as diamond films and single-walled carbon nanotubes led to a surface modification to introduce thioalkylthiol functional groups, confirming by means of Raman, X-ray photoelectron spectroscopy and mass spectrometer measurements. The results on the value of S/C ratio of sulfur-modified diamond films depends on irradiation time by monitoring with XPS. Through thioalkylthiol moieties, an attachment of gold nanoparticles using self-assembly process was performed on carbon materials surfaces.
Multi-wavelength Raman Spectroscopy of Nanodiamond Particles
Authors: May Paul William , Overton Philip , Smith James A , Rosser Keith N 
Published: April 2011

AbstractWe have used Raman spectroscopy with 3 different laser excitation wavelengths (near infrared: 785 nm, green 514 nm, and ultraviolet 325 nm) to study diamond particles as a function of particle size, ranging from 5 nm to 100's of μm. We find that the position of the 1332 cm−1 diamond line varies with particle size as a direct result of heating by the laser. This effect is more significant for lower wavelengths, probably as a result of the increased absorbance by nanodiamond particles in the UV.
The Influence of Different Surface Terminations on Electrical Transport and Emission Properties for Freestanding Single Crystalline (100) CVD Diamond Samples
Authors: Deferme Wim , Bogdan Andrey , Haenen Ken , De Ceuninck Ward , Flipse Kees , Nesladek Milos 
Published: April 2011

AbstractThe surface density of states of hydrogen and oxygen terminated diamond is an important parameter from the point of view of electrical transport properties at the surface. In addition, the presence of surface states has a detrimental influence on the electrical contact properties. Therefore it is of great importance that the influence of different species on the surface-related properties of the diamond layer is well understood.In this work (100)-oriented CVD diamond films are terminated using hydrogen plasma with and without small additions of oxygen (1 to 4%). XPS and UPS measurements are performed to look at the influence of this addition on the surface band gap of the diamond samples. Using the TOF (Time-of-Flight) technique a comparison is made between oxidised and differently hydrogenated diamond surfaces. The results clearly show that the different terminations of the diamond surface have an influence on the electrical transport properties. For the oxidised surface, it is found that defect states are created in the surface band gap, increasing trapping. Contrary to this, fully hydrogenated layers behave differently suggesting that the surface DOS is significantly reduced. This fact can be confirmed when applying an electric field on the CVD diamond samples sandwiched between two metallic electrical contacts. In case of a metal deposited on a hydrogen terminated surface we can see a clear UV light emission, related to free exciton recombination in the contact-diamond-junction region. When the surface is oxidised the UV emission is damped, an effect which is attributed to the parallel recombination channels via the surface states.
Boron Doping of Microcrystalline and Nanocrystalline Diamond Films: Where is the Boron Going?
Authors: May Paul William , Ludlow William J , Hannaway Matthew , Smith James A , Rosser Keith N , Heard Peter J 
Published: April 2011

AbstractWe present data showing how the electrical conductivity and Raman spectra of boron doped ‘cauliflower’-type nanocrystalline (c-NCD) CVD diamond films vary as a function of B content. The conductivity is roughly linear as a function of B content between an onset threshold of ∼5×1020 cm−3 up to ∼6×1021 cm−3, with the higher concentrations giving near metallic conductivity values. The onset threshold may be due to compensating donors due to the large number of impurities and defects in these films. The position of the Lorentzian contribution to the 500 cm−1 Raman feature was used to estimate the B content and compared to the value measured using SIMS. We found that the Raman method overestimated the concentration of B by a factor of ∼5 for these c-NCD films. The shortfall may be explained if only a small fraction of the B found in the small-grained films is being incorporated into substitutional sites. We conclude that in diamond films with a high concentration of grain boundaries, the majority of the B (80% in some cases) must be present at or in the grain boundaries.