Reduction Of Surface Resistance Research Articles

High quality Mn-Co-Ni-O based infrared detectors enhanced by Pt nanoparticle decoration

The work developed a series of infrared detectors based on the Mn-Co-Ni-O (MCNO) films, which were grown using a radio frequency (RF) magnetron sputtering technique. It was observed that the characteristics of MCNO films were significantly impacted by the annealing temperature. Elevating the in-situ annealing temperature from 550 to 750 °C improved the performances of MCNO films. Additionally, it was found that in situ annealing was more advantageous than ex-situ annealing of 750 °C for the properties of MCNO films. The response value (light to dark) increased from 2.5 to 17.7 at 15 V bias, representing a 6.08-fold enhancement, and the response time decreased to 11.8 ms from 19.9 ms. Furthermore, sputtering Pt nanoparticles on the surface of the MCNO film further improved the I-V characteristics in the dark, resulting in a high on/off ratio of 38.15, which is five times higher than that without the Pt nanoparticles modification. This impressive improvement in photoproperties can be attributed to the Pt nanoparticles/MCNO film barrier, plasma resonance effect generated by the Pt nanoparticles, the extinction of the Pt nanoparticles, and the reduction of surface resistance caused by the Pt nanoparticles. This highlights the potential of metal nanoparticles in the development of infrared detectors.

High strength, anti-static, thermal conductive glass fiber/epoxy composites for medical devices: A strategy of modifying fibers with functionalized carbon nanotubes

Abstract A series of aliphatic amine-functionalized multiwalled carbon nanotubes (MWCNTs) wherein varied secondary amine numbers were grafted on the MWCNTs’ surface were synthesized and further dispersed onto the glass fibers for reinforcing epoxy-based composites. By tuning secondary amine numbers of aliphatic amines, the dispersion of MWCNTs and ultimately mechanical, thermal, and conductive properties of epoxy-based composites could be adjusted. Using an optimal secondary amine number of aliphatic amine (triethylenetetramine), the interlaminar shear strength, tensile strength, and flexural strength of epoxy-based composite increased by 43.9%, 34.8%, and 35.0%, respectively; the work of fracture after interlaminar shear tests increased by 233.9%, suggesting strengthening/toughening effects of functionalized MWCNTs; significant reduction in surface resistance and increased thermal conductivity were also obtained, implying the superior conductive properties for composites. This work offers a new strategy for designing fiber-reinforced composites with high strength, excellent antistatic properties, and good thermal conductivity for medical device applications.

Effect of Build Orientation and Laser Power on Microwave Loss in Metal Additive Manufactured Components

The adoption of metal additive manufacturing into the production of passive microwave components is still in its relative infancy. However, it is of increasing interest due to the offer of geometrical design freedom and significant weight reduction. The electrical properties of additive manufactured components are still inferior to traditional manufacturing techniques owing to the poor surface finish, especially on overhanging surfaces, which are unavoidable in three-dimensional microwave components. In this paper we present experimental findings on the disparity in microwave surface resistance values between three common build orientations, as well as findings that establish a connection between increasing downskin laser power and a reduction in surface resistance for overhanging surfaces. Finally, additive manufactured rectangular waveguide sections are measured to assess the influence of combined upward and downward facing surfaces on surface resistance.

Optoelectronic correlations for gold thin films in different annealing temperature

The manufacturing, characterization, and modification of noble nanomaterials such as gold have recently drawn important attention because of their unique characteristics that make them useful in technological applications. In some cases, we need special bulk properties in small objects or some properties should be eliminated in that scale and we must modify them. The mainstream of this project is to decrease surface resistance at an effective annealing temperature and to provide a comparable correlation between surface resistance and surface plasmon resonance (SPR) in gold thin films. Our experiments clearly explain the well-known dependence of optical and electrical properties of gold thin films on annealing temperature. A relation between absorption spectrum and electrical surface resistance in gold thin films have been found. It is understood that annealing temperature of 300° centigrade is a more reduction of surface resistance due to increasing of island size and participating more electrons in conduction band; In this time, the electrical resistance in nanoscale is tended to bulk resistance and plasmon peak is entirely eliminated. The surface resistance is decreased from 50 MΩ to about 5 KΩ. The plasmon absorption peak showed a significant blueshift with increasing annealing temperature at 500° centigrade in comparison with the early sample (unannealed thin-film).

Next-Generation Li[Ni0.8Co0.06Mn0.14]O2 Positive Electrode Material with a Dual Concentration Gradient for High-Energy Li-Ion Batteries

To increase the reversible capacity of layered lithium nickel-cobalt-manganese oxide, a Li [Ni0.8Co0.06Mn0.14]O2 positive electrode with a two-sloped full concentration gradient (TSFCG) was successfully synthesized via co-precipitation. The TSFCG maximizes the Ni concentration in the particle core and the Mn concentration on the particle surface. The TSFCG Li[Ni0.8Co0.06Mn0.14]O2 positive electrode showed improved overall electrochemical properties (i.e., reversible capacity, cycle life, and rate capability) and thermal stability compared to a conventional positive electrode (CC) Li [Ni0.8Co0.06Mn0.14]O2 without a concentration gradient. Electrochemical impedance spectroscopy showed that the high stability of the outer surface composition of Li[Ni0.64Co0.06Mn0.30]O2 is responsible for reduction in surface resistance and charge transfer resistance by decreasing the parasitic reaction with the electrolyte. These reduced resistances explain the superior rate capability of TSFCG positive electrodes.

Relative effect of solder flux chemistry on the humidity related failures in electronics

Purpose – This paper aims to investigate the effect of no-clean flux chemistry with various weak organic acids (WOAs) as activators on the corrosion reliability of electronics with emphasis on the hygroscopic nature of the residue. Design/methodology/approach – The hygroscopicity of flux residue was studied by quartz crystal microbalance, while corrosive effects were studied by leakage current and impedance measurements on standard test boards. The measurements were performed as a function of relative humidity (RH) in the range from 60 to ∼99 per cent at 25°C. The corrosiveness of solder flux systems was visualized by the ex situ analysis using a gel with tin ion indicator. Findings – The results showed that the solder flux residues are characterized by different threshold RH, above which a sudden increase in direct current leakage by 2–4 orders of magnitude and a significant reduction in surface resistance in the impedance measurements were observed. Practical implications – The findings are attributed to the deliquescence RH of the WOA(s) in the flux and chemistry of water-layer formation. The results show the importance of WOA type in relation to its solubility and deliquescence RH on the corrosion reliability of printed circuit boards under humid conditions. Originality/value – The classification of solder flux systems according to IPC J-STD-004 standard does not specify the WOAs in the flux; however, ranking of the flux systems based on the hygroscopic property of activators would be useful information when selecting no-clean flux systems for electronics with applications in humid conditions.

Direct-write pulsed laser processed silver nanowire networks for transparent conducting electrodes

Metal nanowire networks are promising alternatives for transparent conducting layers in flexible electronics. However, the inverse relationship between transparency and conductivity limits their viability in many critical applications. In this work, we demonstrate a direct-write refining technique in which a solution-processed nanowire network, deposited by spin coating, is exposed to monochromatic UV pulsed laser processing near a plasmonic resonance. Our results exhibit a 75 % reduction in surface resistance along with marginal improvements in optical transparency. The local nature of the laser technique enables direct-write or large area processing on a variety of substrates including flexible, and organic materials.

High-energy metal ion implantation for reduction of surface resistivity of alumina ceramic

In this work, the possibility to increase the surface conductivity of ceramic insulators through their treatment with accelerated metal ion beams produced by a MevvaV.Ru vacuum arc source is demonstrated. The increase in surface conductivity is made possible due to experimental conditions in which an insulated collector is charged by beam ions to a potential many times lower than the accelerating voltage, and hence, than the average beam ion energy. The observed effect of charge neutralization of the accelerated ion beam is presumably associated with electrons knocked out of the electrodes of the accelerating system of the source and of the walls of the vacuum chamber by the accelerated ions.

Influence of Surface Carburization of Machinable Ceramics on Its Pulsed Flashover Characteristics in Vacuum

For pulsed power devices, surface flashover phenomena across solid insulators greatly restrict their overall performance. In recent decades, much attention has been paid on enhancing the surface electric withstanding strength of insulators, and it is found that surface treatment of material is useful to improve the surface flashover voltage. The carburization treatment is employed to modify the surface components of newly-developed machinable ceramics (MC) materials. A series of MC samples with different glucose solution concentration (0%, 10%, 20%, 30% and 40%) are prepared by chemical reactions for surface carburization modification, and their surface flashover characteristics are investigated under pulsed voltage in vacuum. It is found that the surface carburization treatment greatly modifies the surface resistivity of MCs and hence the flashover behaviors. Based on the reduction of surface resistivity and the secondary electron emission avalanche (SEEA) theory, the adjustment of flashover withstanding ability can be reasonably explained.

Electron bombardment of films used for reducing spurious charge in electrostatic electron optics

In electrostatic electron optics charging on the surfaces of insulators separating the electrodes can cause undesired beam fluctuation. In prior work, the authors showed that coating the insulators with a film deposited by atomic layer deposition (ALD) could lead to acceptably low charging effects in the reflection electron beam lithography system. However, the stability of the resistivity can also be affected by contaminants present in the vacuum environment of the electron beam tool. The mechanism of formation for carbon layers typically involves the cracking of hydrocarbon contaminants adsorbed on the film surface by photon, electrons, or heat. This work describes changes in resistivity of ALD films of zinc–zirconium oxide and tantalum–niobium oxide 40 nm thick under different operating conditions. In a vacuum system utilizing an oil rough pump and a turbo pump, <0.01 C/cm2 bombardment with 309 V electrons results in about 1 order of magnitude reduction in surface resistance. This effect was not observed in an ion-pumped system suggesting that carbon contamination is the culprit. XPS measurements confirmed this suspicion. Improved results on a new material under development are presented.

Reduction of the microwave surface resistance in YBCO thin films by microscopic defects

The impact of microscopic defects upon the microwave properties of high- T c superconductor (HTS) films is examined. YBa 2Cu 3O 7 films with different size and densities of Y 2O 3 precipitates are grown on LaAlO 3 and sapphire by variation of the energy of the ions during sputter deposition. It is demonstrated, that the temperature dependence of the microwave surface resistance R s does not depend on the type of substrate material but on the density of the defects. Films grown at low ion energy (resulting in a low density of microscopic defects) show a characteristic shoulder in the R s( T) curve which shifts to higher temperature and decreases in size with increasing energy of the ions (i.e. increasing density of microscopic defects). Temperature dependence and reduction of the surface resistance with increasing density of defects are explained in terms of the two-fluid model with thermally excited quasiparticles characterised by a Drude-shaped conductivity spectrum. Values for the scattering rates can be derived from the measurements of the surface resistance, which agree with the classical Matthiesen rule. The impurity scattering rate increases with increasing defect density. Finally, the experimental data and the theoretical model demonstrate, that the surface resistance can be reduced by up to a factor of 2 over a wide temperature range. The reduction of the surface resistance is accompanied by an improvement of the mechanical properties of the HTS thin films which leads to an increased critical film thickness. Both properties, namely the increase of the critical thickness and the reduction of the microwave surface resistance, demonstrate the potential of microscopic defects for improvement of HTS films for applications.

Microwave surface resistance of YBa 2Cu 3O 7-δ thin films deposited by pulsed organometallic beam epitaxy

The microwave surface resistance of superconducting YBa 2Cu 3O 7-δ thin films deposited by pulsed organometallic beam epitaxy (POMBE) has been characterized using the parallel plate transmission line resonator method. POMBE is an advanced organometric chemical vapor deposition technique where precursor vapors are precisely metered onto the substrate under computer control. In this study, the POMBE reactor was used to deposit epitaxial films of varying thickness onto LaAlO 3 substrates. The deposition procedure and surface-resistance results for films of varying thicknesses are described. The reduction of surface resistance achieved supports the use of the POMBE technique as a possible method for preparing device-quality high- T c films and multi-layer structures.

Analysis of Erosion Thresholds, Channel Networks, and Landscape Morphology Using a Digital Terrain Model

To investigate the linkage between erosion process and channel network extent, we develop two simple erosion threshold theories driven by a steady state runoff model that are used in the digital terrain model TOPOG to predict the pattern of channelization. TOPOG divides the land surface into elements defined by topographic contours and flow lines, which can be classified as divergent, convergent and planar elements. The calibration parameter for the runoff model is determined using empirical evidence that the divergent elements which comprise the ridges in our study area do not experience saturation overland flow, where as the convergent elements in the valleys do during significant runoff events. A threshold theory for shallow landsliding predicts a pattern of instability consistent with the distribution of landslide scars in our study site and confirms the interpretation, based on field observations, that indicate the steeper channel heads to be at least partially controlled by slope instability. Most sites of predicted and observed slope instability do not, however, support a channel head, hence landslide instability alone is not sufficient for channelization. In contrast, most elements predicted to be eroded by saturation overland flow coincide with the observed location of the channel network. In addition, areas of predicted downslope decrease in relative sediment transport capacity were found to correspond to locations where channels became discontinuous. The topographic threshold given by the saturation overland flow erosion theory varies with the third power of critical boundary shear stress, suggesting that critical shear stress, although difficult to quantify with much precision in the field, is a dominant control on the extent of the channel network where saturation overland flow is significant. Current extent of the channel network in our field site, for example, may best be explained as resulting from grazing-induced reduction in surface resistance.

Kiloelectronvolt ion implantation sensitisation of HPR-204

Ion implantation of Hunt Positive resist (HPR-204) thin films (0.5 micro m) with ion beams of 10–40 keV causes a reduction of surface resistivity of 3–4 orders of magnitude. Copper implanted samples exhibited a resistivity of 1 MΩ cm. The improved surface conduction is thought to be due to the deposited ion energy causing the preferential disassociation of hydrogen and other volatile species and a precipitation of a carbon rich structure. Ion beam doping in the case of copper is not expected to play any role in this process. Subsequent exposure of the implanted samples to 2 MeV helium ion bombardment causes an extensive breakdown in the structure resulting in blistering and exfoliation of the entire thickness of the exposed region.

Reduction of surface resistance in superconducting thin films by microwave irradiation

We have experimentally observed dramatic reductions in the microwave surface resistance R s of superconducting aluminum thin films due to microwave pumping. For temperatures T > 0.97 T c , nearly complete suppression of the temperature-dependent component of R s occurred when the films were subjected to a microwave magnetic field s were observed before the transition to the normal state. The reduction of R s may provide stability against thermal breakdown in rf cavities currently limited by defect-nucleated quench.

The Prospects for Magneto-Aerodynamics

The equations describing the flow of an electrically conducting fluid in the presence of electric and magnetic fields are written down with the aid of certain simplifications appropriate to aeronautical applications. In order to estimate the probable significance of magneto-aerodynamic effects, some data on conductivity of pure and seeded air are first examined. Dimensionless quantities representing the ratios of forces and of currents are then formed and their values studied for conditions of flight in the atmosphere. Some examples of magneto-hydrodynamic and magnetogasdynamic effects in simple flows are given. These include two cases of Poiseuille flow of conducting liquids with applied magnetic fields and the case of quasi-one-dimensional gas flow with applied electrical and magnetic fields. In the last case, attractive possibilities are found for controlled acceleration or deceleration of gas at subsonic and supersonic speeds, even in constant-area channels. The behavior of the flow is characteristically different in different regimes of Mach Number and flow speed relative to certain significant speeds that are dependent on the ratio of electrical to magnetic field strengths. These are studied, and a chart is constructed to relate the length to the speed ratio of a maximum-acceleration constant-area channel. I t is concluded that the advantages that may accrue from magneto-aerodynamic methods are sufficiently attractive to justify the considerable research and engineering development that will be required. Among the unsolved engineering problems are the reduction of surface resistance of electrodes in contact with a conducting gas, development of techniques for seeding, and provision of the required magnetic fields in flight.