Search results for: Atomic layer deposition

Authors: S. Zhuiykov, Zh. Hai, H. Xu, C. Xue

Abstract:

Unique and distinctive properties could be obtained on such two-dimensional (2D) semiconductor as tungsten trioxide (WO₃) when the reduction from multi-layer to one fundamental layer thickness takes place. This transition without damaging single-layer on a large spatial resolution remained elusive until the atomic layer deposition (ALD) technique was utilized. Here we report the ALD-enabled atomic-layer-precision development of a single layer WO₃ with thickness of 0.77±0.07 nm on a large spatial resolution by using (^tBuN)₂W(NMe₂)₂ as tungsten precursor and H₂O as oxygen precursor, without affecting the underlying SiO₂/Si substrate. Versatility of ALD is in tuning recipe in order to achieve the complete WO₃ with desired number of WO₃ layers including monolayer. Governed by self-limiting surface reactions, the ALD-enabled approach is versatile, scalable and applicable for a broader range of 2D semiconductors and various device applications.

Keywords: Atomic layer deposition, tungsten oxide, WO3, two-dimensional semiconductors, single fundamental layer.

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Authors: Kh. A. Abdullin, N. B. Bakranov, S. E. Kudaibergenov, S.E. Kumekov, V. N. Ermolaev, L. V. Podrezova

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A facile vapour deposition method of synthesis of vertically aligned ZnO nanowires on carbon seed layer was developed. The received samples were investigated on electronic microscope JSM-6490 LA JEOL and x-ray diffractometer X, pert MPD PRO. The photoluminescence spectra (PL) of obtained ZnO samples at a room temperature were studied using He-Cd laser (325 nm line) as excitation source.

Keywords: ZnO nanowires, vapor-phase deposition, Nicatalytic layer, facile method of synthesis, carbon catalytic layer, thephotoluminescence spectra, X-ray spectrum.

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Authors: D. Geringswald, B. Hintze

Abstract:

The miniaturization of circuits is advancing. During chip manufacturing, structures are filled for example by metal organic chemical vapor deposition (MOCVD). Since this process reaches its limits in case of very high aspect ratios, the use of alternatives such as the atomic layer deposition (ALD) is possible, requiring the extension of existing coating systems. However, it is an unsolved question to what extent MOCVD can achieve results similar as an ALD process. In this context, this work addresses the characterization of a metal organic vapor deposition of titanium nitride. Based on the current state of the art, the film properties coating thickness, sheet resistance, resistivity, stress and chemical composition are considered. The used setting parameters are temperature, plasma gas ratio, plasma power, plasma treatment time, deposition time, deposition pressure, number of cycles and TDMAT flow. The derived process instructions for unstructured wafers and inside a structure with high aspect ratio include lowering the process temperature and increasing the number of cycles, the deposition and the plasma treatment time as well as the plasma gas ratio of hydrogen to nitrogen (H₂:N₂). In contrast to the current process configuration, the deposited titanium nitride (TiN) layer is more uniform inside the entire test structure. Consequently, this paper provides approaches to employ the MOCVD for structures with increasing aspect ratios.

Keywords: ALD, high aspect ratio, PE-MOCVD, TiN.

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Authors: Won Song, Bo-Ra Koo, Seok Eui Choi, Yong-Taeg Oh, Dong-Chan Shin

Abstract:

Optical properties of sputter-deposited ZnS thin films were investigated as potential replacements for CBD(chemical bath deposition) CdS buffer layers in the application of CIGS solar cells. ZnS thin films were fabricated on glass substrates at RT, 150oC, 200oC, and 250oC with 50 sccm Ar gas using an RF magnetron sputtering system. The crystal structure of the thin film is found to be zinc blende (cubic) structure. Lattice parameter of ZnS is slightly larger than CdS on the plane and thus better matched with that of CIGS. Within a 400-800 nm wavelength region, the average transmittance was larger than 75%. When the deposition temperature of the thin film was increased, the blue shift phenomenon was enhanced. Band gap energy of the ZnS thin film tended to increase as the deposition temperature increased. ZnS thin film is a promising material system for the CIGS buffer layer, in terms of ease of processing, low cost, environmental friendliness, higher transparency, and electrical properties

Keywords: ZnS thin film, Buffer layer, CIGS, Solar cell.

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Authors: Abbas Nasir, Xiong Zhang, Sohail Ahmad, Yiping Cui

Abstract:

Non-polar a-plane AlGaN epilayers of high structural quality have been grown on r-sapphire substrate by using metalorganic chemical vapor deposition (MOCVD). A graded non-polar AlGaN buffer layer with variable aluminium concentration was used to improve the structural quality of the non-polar a-plane AlGaN epilayer. The characterisations were carried out by high-resolution X-ray diffraction (HR-XRD), atomic force microscopy (AFM) and Hall effect measurement. The XRD and AFM results demonstrate that the Al-composition-graded non-polar AlGaN buffer layer significantly improved the crystalline quality and the surface morphology of the top layer. A low root mean square roughness 1.52 nm is obtained from AFM, and relatively low background carrier concentration down to 3.9×  cm^-3 is obtained from Hall effect measurement.

Keywords: Non-polar AlGaN epilayer, Al composition-graded AlGaN layer, root mean square, background carrier concentration.

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Authors: Adnan A. Ugla, Hassan J. Khaudair, Ahmed R. J. Almusawi

Abstract:

Shaped Metal Deposition (SMD) in additive layered manufacturing technique is a promising alternative to traditional manufacturing used for manufacturing large, expensive metal components with complex geometry in addition to producing free structures by building materials in a layer by layer technique. The present paper is a comprehensive review of the literature and the latest rapid manufacturing technologies of the SMD technique. The aim of this paper is to comprehensively review the most prominent facts that researchers have dealt with in the SMD techniques especially those associated with the cold wire feed. The intent of this study is to review the literature presented on metal deposition processes and their classifications, including SMD process using Wire + Arc Additive Manufacturing (WAAM) which divides into wire + tungsten inert gas (TIG), metal inert gas (MIG), or plasma. This literary research presented covers extensive details on bead geometry, process parameters and heat input or arc energy resulting from the deposition process in both cases MIG and Tandem-MIG in SMD process. Furthermore, SMD may be done using Single Wire-MIG (SW-MIG) welding and SMD using Double Wire-MIG (DW-MIG) welding. The present review shows that the method of deposition of metals when using the DW-MIG process can be considered a distinctive and low-cost method to produce large metal components due to high deposition rates as well as reduce the input of high temperature generated during deposition and reduce the distortions. However, the accuracy and surface finish of the MIG-SMD are less as compared to electron and laser beam.

Keywords: Shaped metal deposition, additive manufacturing, double-wire feed, cold feed wire.

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Authors: Fitria Rahmawati, Nuryani, Liviana Wijayanti

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This research study the application of the immobilized TiO2 layer and Cu-TiO2 layer on graphite substrate as a negative electrode or anode for Li-ion battery. The titania layer was produced through chemical bath deposition method, meanwhile Cu particles were deposited electrochemically. A material can be used as an electrode as it has capability to intercalates Li ions into its crystal structure. The Li intercalation into TiO2/Graphite and Cu- TiO2/Graphite were analyzed from the changes of its XRD pattern after it was used as electrode during discharging process. The XRD patterns were refined by Le Bail method in order to determine the crystal structure of the prepared materials. A specific capacity and the cycle ability measurement were carried out to study the performance of the prepared materials as negative electrode of the Li-ion battery. The specific capacity was measured during discharging process from fully charged until the cut off voltage. A 300 was used as a load. The result shows that the specific capacity of Li-ion battery with TiO2/Graphite as negative electrode is 230.87 ± 1.70mAh.g-1 which is higher than the specific capacity of Li-ion battery with pure graphite as negative electrode, i.e 140.75 ±0.46mAh.g-1. Meanwhile deposition of Cu onto TiO2 layer does not increase the specific capacity, and the value even lower than the battery with TiO2/Graphite as electrode. The cycle ability of the prepared battery is only two cycles, due to the Li ribbon which was used as cathode became fragile and easily broken.

Keywords: Cu-TiO2, electrode, graphite substrate, Li-ion battery, TiO2 layer.

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Authors: Branko Skoric, Aleksandar Miletic, Pal Terek, Lazar Kovacevic, Milan Kukuruzovic

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In this paper, we present the results of a study of TiN thin films which are deposited by a Physical Vapour Deposition (PVD) and Ion Beam Assisted Deposition (IBAD). In the present investigation the subsequent ion implantation was provided with N⁵⁺ ions. The ion implantation was applied to enhance the mechanical properties of surface. The thin film deposition process exerts a number of effects such as crystallographic orientation, morphology, topography, densification of the films. A variety of analytic techniques were used for characterization, such as scratch test, calo test, Scanning electron microscopy (SEM), Atomic Force Microscope (AFM), X-ray diffraction (XRD) and Energy Dispersive X-ray analysis (EDAX).

Keywords: Steel, coating, super hard, ion implantation, nanohardness.

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Authors: Ibtissem Gammoudi, Ndeye Rokhaya Faye, Fabien Moroté, Daniel Moynet, Christine Grauby-Heywang, Touria Cohen-Bouhacina

Abstract:

The objective of the present investigation was to evaluate the morphology of Escherchia coli bacteria in interaction with SiO2 nanoparticles. This study was made by atomic force microscopy and quartz crystal microbalance using SiO2 nanoparticles with 10nm, 50nm and 100nm diameter and bacteria immobilized on polyelectrolyte multilayer films obtained by spin coating or by “layer by layer” (LbL) method.

Keywords: Atomic Force Microscopy, Escherichia coli, Quartz Crystal Microbalance, polyelectrolyte, silica nanoparticle.

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Authors: Dawid Stawski, Silviya Halacheva, Dorota Zielińska

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The surface properties of many materials can be readily and predictably modified by the controlled deposition of thin layers containing appropriate functional groups and this research area is now a subject of widespread interest. The layer-by-layer (lbl) method involves depositing oppositely charged layers of polyelectrolytes onto the substrate material which are stabilized due to strong electrostatic forces between adjacent layers. This type of modification affords products that combine the properties of the original material with the superficial parameters of the new external layers. Through an appropriate selection of the deposited layers, the surface properties can be precisely controlled and readily adjusted in order to meet the requirements of the intended application. In the presented paper a variety of anionic (poly(acrylic acid)) and cationic (linear poly(ethylene imine), polymers were successfully deposited onto the polypropylene nonwoven using the lbl technique. The chemical structure of the surface before and after modification was confirmed by reflectance FTIR spectroscopy, volumetric analysis and selective dyeing tests. As a direct result of this work, new materials with greatly improved properties have been produced. For example, following a modification process significant changes in the electrostatic activity of a range of novel nanocomposite materials were observed. The deposition of polyelectrolyte nanolayers was found to strongly accelerate the loss of electrostatically generated charges and to increase considerably the thermal resistance properties of the modified fabric (the difference in T50% is over 20oC). From our results, a clear relationship between the type of polyelectrolyte layer deposited onto the flat fabric surface and the properties of the modified fabric was identified.

Keywords: Layer-by-layer technique, polypropylene nonwoven, surface modification, surface properties.

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Authors: Xiaodong Gao, Pingchuan Dong, Qichao Gao

Abstract:

This work attempts to predict the deposition rate of asphaltene particles in blockage tube through CFD simulation. The Euler-Lagrange equation has been applied during the flow of crude oil and asphaltene particles. The net gravitational force, virtual mass, pressure gradient, Saffman lift, and drag forces are incorporated in the simulations process. Validation of CFD simulation results is compared to the benchmark experiments from the previous literature. Furthermore, the effects of blockage location, blockage length, and blockage thickness on deposition rate are also analyzed. The simulation results indicate that the maximum deposition rate of asphaltene occurs in the blocked tube section, and the greater the deposition thickness, the greater the deposition rate. Moreover, the deposition amount and maximum deposition rate along the length of the tube have the same trend. Results of this study are in the ability to better understand the deposition of asphaltene particles in production and help achieve to deal with the asphaltene challenges.

Keywords: Asphaltene deposition rate, blockage length, blockage thickness, blockage diameter, transient condition.

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Authors: R. Kumaravelan, V. C. Sathish Gandhi, S. Ramesh, M. Venkatesan

Abstract:

In the product design and development process, the prototyping or model making is one of the important step to finalize a product which helps in conceptualization of a design. Rapid Prototyping (RP) is layer-by-layer material deposition started during early 1980s with the enormous growth in Computer Aided Design and Manufacturing (CAD/CAM) technologies. The edges and surfaces of a complex solid model and their information are used for defining a product which is further manufactured as a finished product by CNC machining. This paper provides a better platform for researchers, new learners and product manufacturers for various applications of RP models. Subsequently it creates awareness among the peoples of recently developing RP method of manufacturing in product design, developments and its applications.

Keywords: Prototyping, layer-by-layer, CAD/CAM, product design.

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Authors: Zheng-Kuohai, Yang-Shengsheng, Li-Zhonghua, Zhao-Lin

Abstract:

Materials used on exterior spacecraft surfaces are subjected to many environmental threats which can cause degradation, atomic oxygen is one of the most threats. We prepared organic silicon atomic-oxygen-protection film using method of polymerization. This paper presented the effects on the film structure and its durability of the preparation processing, and analyzed the polymerization theory, the film structure and composition of the film. At last, we tested the film in our ground based atomic oxygen simulator, and indicated that the film worked well.

Keywords: Atomic oxygen, siloxane, protection, plasma, polymerization.

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Authors: Meftah O. Bashir, Fatma A. Karkory

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Rapid prototyping is a new group of manufacturing processes, which allows fabrication of physical of any complexity using a layer by layer deposition technique directly from a computer system. The rapid prototyping process greatly reduces the time and cost necessary to bring a new product to market. The prototypes made by these systems are used in a range of industrial application including design evaluation, verification, testing, and as patterns for casting processes. These processes employ a variety of materials and mechanisms to build up the layers to build the part. The present work was to build a FDM prototyping machine that could control the X-Y motion and material deposition, to generate two-dimensional and three-dimensional complex shapes. This study focused on the deposition of wax material. This work was to find out the properties of the wax materials used in this work in order to enable better control of the FDM process. This study will look at the integration of a computer controlled electro-mechanical system with the traditional FDM additive prototyping process. The characteristics of the wax were also analysed in order to optimise the model production process. These included wax phase change temperature, wax viscosity and wax droplet shape during processing.

Keywords: Rapid prototyping, wax, manufacturing processes, additive prototyping.

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Authors: Shilpesh R. Rajpurohit, Harshit K. Dave

Abstract:

Additive manufacturing gains the popularity in recent times, due to its capability to create prototype as well functional as end use product directly from CAD data without any specific requirement of tooling. Fused deposition modeling (FDM) is one of the widely used additive manufacturing techniques that are used to create functional end use part of polymer that is comparable with the injection-molded parts. FDM printed part has an application in various fields such as automobile, aerospace, medical, electronic, etc. However, application of FDM part is greatly affected by poor mechanical properties. Proper selection of the process parameter could enhance the mechanical performance of the printed part. In the present study, experimental investigation has been carried out to study the behavior of the mechanical performance of the printed part with respect to process variables. Three process variables viz. raster angle, raster width and layer height have been varied to understand its effect on tensile strength. Further, effect of process variables on fractured surface has been also investigated.

Keywords: 3D printing, fused deposition modeling, layer height, raster angle, raster width, tensile strength.

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Authors: M. M. Rahman

Abstract:

The present contribution deals with the thermophoretic deposition of nanoparticles over a rapidly rotating permeable disk in the presence of partial slip, magnetic field, thermal radiation, thermal-diffusion, and diffusion-thermo effects. The governing nonlinear partial differential equations such as continuity, momentum, energy and concentration are transformed into nonlinear ordinary differential equations using similarity analysis, and the solutions are obtained through the very efficient computer algebra software MATLAB. Graphical results for non-dimensional concentration and temperature profiles including thermophoretic deposition velocity and Stanton number (thermophoretic deposition flux) in tabular forms are presented for a range of values of the parameters characterizing the flow field. It is observed that slip mechanism, thermal-diffusion, diffusion-thermo, magnetic field and radiation significantly control the thermophoretic particles deposition rate. The obtained results may be useful to many industrial and engineering applications.

Keywords: Boundary layer flows, convection, diffusion-thermo, rotating disk, thermal-diffusion, thermophoresis.

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Authors: H. Hashim, B. F. Usher

Abstract:

InGaAsN and GaAsN epitaxial layers with similar nitrogen compositions in a sample were successfully grown on a GaAs (001) substrate by solid source molecular beam epitaxy. An electron cyclotron resonance nitrogen plasma source has been used to generate atomic nitrogen during the growth of the nitride layers. The indium composition changed from sample to sample to give compressive and tensile strained InGaAsN layers. Layer characteristics have been assessed by high-resolution x-ray diffraction to determine the relationship between the lattice constant of the GaAs1-yNy layer and the fraction x of In. The objective was to determine the In fraction x in an InxGa1-xAs1-yNy epitaxial layer which exactly cancels the strain present in a GaAs1-yNy epitaxial layer with the same nitrogen content when grown on a GaAs substrate.

Keywords: Indium, molecular beam epitaxy, nitrogen, straincancellation.

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Authors: K. Karami, S. Hassan, S. Taking, A. Ofiare, A. Dhongde, A. Al-Khalidi, E. Wasige

Abstract:

We have made a comparative study on the influence of Al2O3 and HfO2 grown using Atomic Layer Deposition (ALD) technique as dielectric in the AlGaN/GaN metal oxide semiconductor high electron mobility transistor (MOS-HEMT) structure. Five samples consisting of 20 nm and 10 nm each of A2lO3 and HfO2 respectively and a Schottky gate HEMT, were fabricated and measured. The threshold voltage shifts towards negative by 0.1 V and 1.8 V for 10 nm thick HfO2 and 10 nm thick Al2O3 gate dielectric layers, respectively. The negative shift for the 20 nm HfO2 and 20 nm Al2O3 were 1.2 V and 4.9 V, respectively. Higher gm/IDS (transconductance to drain current) ratio was also obtained in HfO2 than Al2O3. With both materials as dielectric, a significant reduction in the gate leakage current in the order of 104 was obtained compared to the sample without the dielectric material.

Keywords: AlGaN/GaN HEMTs, Al2O3, HfO2, MOSHEMTs.

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Authors: Watcharee Rattanasakulthong, Pichai Sirisangsawang, Supree Pinitsoontorn

Abstract:

Sputtered CoxCu100-x films with the different compositions of x = 57.7, 45.8, 25.5, 13.8, 8.8, 7.5 and 1.8 were deposited on Cr under-layer by RF-sputtering. SEM result reveals that the averaged thickness of Co-Cu film and Cr under-layer are 92 nm and 22nm, respectively. All Co-Cu films are composed of Co (FCC) and Cu (FCC) phases in (111) directions on BCC-Cr (110) under-layers. Magnetic properties, surface roughness and morphology of Co-Cu films are dependent on the film composition. The maximum and minimum surface roughness of 3.24 and 1.16nm are observed on the Co7.5Cu92.5 and Co45.8Cu54.2films, respectively. It can be described that the variance of surface roughness of the film because of the difference of the agglomeration rate of Co and Cu atoms on Cr under-layer. The Co57.5Cu42.3, Co45.8Cu54.2 and Co25.5Cu74.5 films shows the ferromagnetic phase whereas the rest of the film exhibits the paramagnetic phase at room temperature. The saturation magnetization, remnant magnetization and coercive field of Co-Cu films on Cr under-layer are slightly increased with increasing the Co composition. It can be concluded that the required magnetic properties and surface roughness of the Co-Cu film can be adapted by the adjustment of the film composition.

Keywords: Co-Cu films, Under-layers, Sputtering, Surface roughness, Magnetic properties, Atomic force microscopy (AFM).

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Authors: Yasser M. Moustafa, Rania E. Morsi, Mohammed Fathy

Abstract:

Multiwall carbon nanotubes, prepared by chemical vapor deposition, have an average diameter of 60-100 nm as shown by High Resolution Transmittance Electron Microscope, HR-TEM. The Multiwall carbon nanotubes (MWCNTs) were further characterized using X-ray Diffraction and Raman Spectroscopy. Mercury uptake capacity of MWCNTs was studied using batch adsorption method at different concentration ranges up to 150 ppm. Mercury concentration (before and after the treatment) was measured using cold vapor atomic absorption spectroscopy. The effect of time, concentration, pH and adsorbent dose were studied. MWCNT were found to perform complete absorption in the sub-ppm concentrations (parts per billion levels) while for high concentrations, the adsorption efficiency was 92% at the optimum conditions; 0.1 g of the adsorbent at 150 ppm mercury (II) solution. The adsorption of mercury on MWCNTs was found to follow the Freundlich adsorption isotherm and the pseudo-second order kinetic model.

Keywords: Cold Vapor Atomic Absorption Spectroscopy, Hydride System, Mercury Removing, Multi Wall Carbon Nanotubes.

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Authors: Fangfang Chen, Chunlu Wang, Zhihong Tian, Shuyuan Jin, Tianle Zhang

Abstract:

Attack graph is an integral part of modeling the overview of network security. System administrators use attack graphs to determine how vulnerable their systems are and to determine what security measures to deploy to defend their systems. Previous methods on AGG(attack graphs generation) are aiming at the whole network, which makes the process of AGG complex and non-scalable. In this paper, we propose a new approach which is simple and scalable to AGG by decomposing the whole network into atomic domains. Each atomic domain represents a host with a specific privilege. Then the process for AGG is achieved by communications among all the atomic domains. Our approach simplifies the process of design for the whole network, and can gives the attack graphs including each attack path for each host, and when the network changes we just carry on the operations of corresponding atomic domains which makes the process of AGG scalable.

Keywords: atomic domain, vulnerability, attack graphs, generation, computer security

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Authors: Ahmed A. D. Sarhan, Chong Feng Duan, Mum Wai Yip, M. Sayuti

Abstract:

Rapid Prototyping (RP) technologies enable physical parts to be produced from various materials without depending on the conventional tooling. Fused Deposition Modeling (FDM) is one of the famous RP processes used at present. Tensile strength and compressive strength resistance will be identified for different sample structures and different layer orientations of ABS rapid prototype solid models. The samples will be fabricated by a FDM rapid prototyping machine in different layer orientations with variations in internal geometrical structure. The 0° orientation where layers were deposited along the length of the samples displayed superior strength and impact resistance over all the other orientations. The anisotropic properties were probably caused by weak interlayer bonding and interlayer porosity.

Keywords: Building orientation, compression strength, rapid prototyping, tensile strength.

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Authors: Jyoti Narayan, S. Choudhary

Abstract:

Nanowire arrays of copper with uniform diameters have been synthesized by potentiostatic electrochemical metal deposition (EMD) of copper sulphate and potassium chloride solution within the nano-channels of porous Indium-Tin Oxide (ITO), also known as Tin doped Indium Oxide templates. The nanowires developed were fairly continuous with diameters ranging from 110-140 nm along the entire length. Single as well as poly-crystalline copper wires have been prepared by application of appropriate potential during the EMD process. Scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), small angle electron diffraction (SAED) and atomic force microscopy (AFM) were used to characterize the synthesized nano wires at room temperature. The electrochemical response of synthesized products was evaluated by cyclic voltammetry while surface energy analysis was carried out using a Goniometer.

Keywords: Electro-deposition, Metallic nano-wires, Nanomaterials, Template synthesis

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Authors: Shivalinge Gowda

Abstract:

The total mass attenuation coefficients m/r, of some halides such as, NaCl, KCl, CuCl, NaBr, KBr, RbCl, AgCl, NaI, KI, AgBr, CsI, HgCl₂, CdI₂ and HgI₂ were determined at photon energies 279.2, 320.07, 514.0, 661.6, 1115.5, 1173.2 and 1332.5 keV in a well-collimated narrow beam good geometry set-up using a high resolution, hyper pure germanium detector. The mass attenuation coefficients and the effective atomic cross sections are found to be in good agreement with the XCOM values. From these mass attenuation coefficients, the effective atomic cross sections s_a, of the compounds were determined. These effective atomic cross section s_a data so obtained are then used to compute the effective atomic numbers Z_eff. For this, the interpolation of total attenuation cross-sections of photons of energy E in elements of atomic number Z was performed by using the logarithmic regression analysis of the data measured by the authors and reported earlier for the above said energies along with XCOM data for standard energies. The best-fit coefficients in the photon energy range of 250 to 350 keV, 350 to 500 keV, 500 to 700 keV, 700 to 1000 keV and 1000 to 1500 keV by a piecewise interpolation method were then used to find the Z_eff of the compounds with respect to the effective atomic cross section s_a from the relation obtained by piece wise interpolation method. Using these Z_eff values, the electron densities N_el of halides were also determined. The present Z_eff and N_el values of halides are found to be in good agreement with the values calculated from XCOM data and other available published values.

Keywords: Mass attenuation coefficient, atomic cross-section, effective atomic number, electron density.

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Authors: Jeff Letcher, Dennis Tierney, Haider Raad

Abstract:

Antennas are devices for transmitting and/or receiving signals which make them a necessary component of any wireless system. In this paper, a thermal deposition technique is utilized as a method to fabricate antenna structures on substrates. Thin-film deposition is achieved by evaporating a source material (metals in our case) in a vacuum which allows vapor particles to travel directly to the target substrate which is encased with a mask that outlines the desired structure. The material then condenses back to solid state. This method is used in comparison to screen printing, chemical etching, and ink jet printing to indicate advantages and disadvantages to the method. The antenna created undergoes various testing of frequency ranges, conductivity, and a series of flexing to indicate the effectiveness of the thermal deposition technique. A single band antenna that is operated at 2.45 GHz intended for wearable and flexible applications was successfully fabricated through this method and tested. It is concluded that thermal deposition presents a feasible technique of producing such antennas.

Keywords: Thermal deposition, wearable antennas, Bluetooth technology, flexible electronics.

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Authors: S.Solaymani, T.Ghodselahi, N.B.Nezafat, H.Zahrabi, A.Gelali

Abstract:

The morphological parameter of a thin film surface can be characterized by power spectral density (PSD) functions which provides a better description to the topography than the RMS roughness and imparts several useful information of the surface including fractal and superstructure contributions. Through the present study Nanoparticle copper/carbon composite films were prepared by co-deposition of RF-Sputtering and RF-PECVD method from acetylene gas and copper target. Surface morphology of thin films is characterized by using atomic force microscopy (AFM). The Carbon content of our films was obtained by Rutherford Back Scattering (RBS) and it varied from .4% to 78%. The power values of power spectral density (PSD) for the AFM data were determined by the fast Fourier transform (FFT) algorithms. We investigate the effect of carbon on the roughness of thin films surface. Using such information, roughness contributions of the surface have been successfully extracted.

Keywords: Atomic force microscopy, Fast Fourier transform, Power spectral density, RBS.

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Authors: S. Sobhanian, H. Naghshara, N. Sadeghi, S. Khorram

Abstract:

The absolute Cu atoms density in Cu(2S1/2ÔåÉ2P1/2) ground state has been measured by Resonance Optical Absorption (ROA) technique in a DC magnetron sputtering deposition with argon. We measured these densities under variety of operation conditions: pressure from 0.6 μbar to 14 μbar, input power from 10W to 200W and N2 mixture from 0% to 100%. For measuring the gas temperature, we used the simulation of N2 rotational spectra with a special computer code. The absolute number density of Cu atoms decreases with increasing the N2 percentage of buffer gas at any conditions of this work. But the deposition rate, is not decreased with the same manner. The deposition rate variation is very small and in the limit of quartz balance measuring equipment accuracy. So we conclude that decrease in the absolute number density of Cu atoms in magnetron plasma has not a big effect on deposition rate, because the diffusion of Cu atoms to the chamber volume and deviation of Cu atoms from direct path (towards the substrate) decreases with increasing of N2 percentage of buffer gas. This is because of the lower mass of N2 atoms compared to the argon ones.

Keywords: Deposition rate, Resonance Optical Absorption, Sputtering.

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Authors: Ami Nomura, Ken Imanishi, Yukinori Taniguchi, Etsuko Ueda, Tadahiro Wada, Shinichi Enoki

Abstract:

Recently, there have been a lot of earthquakes in Japan. It is necessary to promote seismic isolation devices for buildings. The devices have been hardly diffused in attached houses, because the devices are very expensive. We should develop a low-cost seismic isolation device for detached houses. We suggested a new seismic isolation device which uses a two-layer circular tube as a unit. If hysteresis is produced in the two-layer circular tube under lateral compression load, we think that the two-layer circular tube can have energy absorbing capacity. It is necessary to contact the outer layer and the inner layer to produce hysteresis. We have previously reported how the inner layer comes in contact with the outer layer from a perspective of analysis used mechanics of materials. We have clarified that the inner layer comes in contact with the outer layer under a lateral compression load. In this paper, we explored contact area between the outer layer and the inner layer under a lateral compression load by using FEA. We think that changing the inner layer’s thickness is effective in increase the contact area. In order to change the inner layer’s thickness, we changed the shape of the inner layer. As a result, the contact area changes depending on the inner layer’s thickness. Additionally, we experimented to check whether hysteresis occurs in fact. As a consequence, we can reveal hysteresis in the two-layer circular tube under the condition.

Keywords: Contact area, energy absorbing capacity, hysteresis, seismic isolation device.

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Authors: Yu-Hsin Chen, Yuan-Tai Hsieh, Cheng-Shong Hong, Chia-Ching Wu, Cheng-Fu Yang, Yu-Jhen Liou

Abstract:

In this study, we investigated (In,Ga,Zn)O_x (IGZO) thin films and examined their characteristics of using Ga₂O₃-2 ZnO (GZO) co-sputtered In₂O₃ prepared by dual target radio frequency magnetron sputtering at room temperature in a pure Ar atmosphere. RF powers of 80 W and 70 W were used for GZO and pure In₂O₃, room temperature (RT) was used as deposition temperature, and the deposition time was changed from 15 min to 60 min. Structural, surface, electrical, and optical properties of IGZO thin films were investigated as a function of deposition time. Furthermore, the GZO co-sputtered In₂O₃ thin films showed a very smooth and featureless surface and an amorphous structure regardless of the deposition time due to the room temperature sputtering process. We would show that the co-sputtered IGZO thin films exhibited transparent electrode properties with high transmittance ratio and low resistivity.

Keywords: IGZO, co-sputter, Ga2O3-2 ZnO, In2O3.

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Authors: A. C. Sarmah

Abstract:

The Al-MoO3-P-CdTe-Al MOS sandwich structures were fabricated by vacuum deposition method on cleaned glass substrates. Capacitance versus voltage measurements were performed at different frequencies and sweep rates of applied voltages for oxide and semiconductor films of different thicknesses. In the negative voltage region of the C-V curve a high differential capacitance of the semiconductor was observed and at high frequencies (<10 kHz) the transition from accumulation to depletion and further to deep depletion was observed as the voltage was swept from negative to positive. A study have been undertaken to determine the value of acceptor density and some depletion layer parameters such as depletion layer capacitance, depletion width, impurity concentration, flat band voltage, Debye length, flat band capacitance, diffusion or built-in-potential, space charge per unit area etc. These were determined from C-V measurements for different oxide and semiconductor thicknesses.

Keywords: Debye length, Depletion width, flat band capacitance, impurity concentration.

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