Surface Of Dielectric Substrate Research Articles

Mobility of electrons on helium film capillary condensed on two dimensionally corrugated surface of dielectric substrate

Electrical conductivity of electrons on helium film covering a two dimensionally corrugated dielectric substrate was measured in a temperature interval between 0.4 and 1.64 K. As the temperature decreased from 1.5 K, the electrical conductivity decreases and approaches gradually to zero around 0.4 K. This temperature dependence is different from that measured in 2D electron system on bulk liquid helium. In order to understand the effect of the dielectric substrate, the dependences of electrical conductivity on magnetic field were measured by using a Corbino electrode and the mobility was evaluated in different temperatures. The results revealed that the mobility of electrons increases as the temperature decreases. Combining the data of electrical conductivity and the mobility, it is deduced that the decrease in conductivity as the temperature decreases is due to the decrease in number of mobile electrons.

General principles in formation of monolayer colloidal crystals using the moving meniscus method

Factors affecting the formation of two-dimensional periodic structure from the particles of hydrosol disperse phase on the surface of dielectric substrate using the moving meniscus method are analyzed. The analytical model and its numerical realization for calculating the deposition of nanoparticle from bulk hydrosol onto a planar substrate by the Brownian dynamics are represented. Van der Waals, elastic, gravitational, dissipative, and stochastic forces, as well as the action of capillary forces and convective transfer, are taken into account in the model. The influence of various parameters of the disperse system on the degree of imperfection of forming crystalline structure is studied. The dominant factors of structurization during the use of this technique are revealed, and a key role of convective transfer is demonstrated.

Evolution of extinction spectra of monolayer plasmon-resonant colloidal crystals in the process of their synthesis by the moving meniscus method

Regularities of the evolution of the extinction spectra of periodic colloidal structure composed of silver nanoparticles formed from bulk hydrosol on the surface of dielectric substrate are studied using the moving meniscus method. Spectra were calculated by the coupled dipole method. The effect of individual parameters of disperse system on the pattern of extinction contour in the band of plasmon absorption of a synthesized two-dimensional crystalline structure is analyzed.

Transmittance investigation on capacitive mesh on thick dielectric substrates as output windows for optically pumped terahertz lasers

This paper reports that an output window for optically pumped terahertz (THz) laser has been fabricated by depositing a capacitive nickel-mesh on a thick high-resistivity silicon substrate (approximating to 5 mm thick). Unlike the conventional process of depositing a gold film approximating to 100 nm on negative photoresist using electron-beam evaporation, a nickel film approximating to 1.5 μm thick is directly deposited on the clean surface of dielectric substrate using magnetron sputtering and then a positive photoresist is spun onto the nickel metal surface at 6000 r for 60 s. A transmittance spectrum of the output window in a certain frequency range (say, from zero to 1 THz) has been obtained by using THz time domain spectroscopy. Moreover a transmittance spectrum simulated numerically has also been estimated with respect to the output window using the transmission-line model (TLM) containing attenuation component from dielectric substrate. The simulation results show that the TLM can explain well the experimental curve in a certain frequency range from zero to 1 THz. Thus it is demonstrated that the improved optical component can be efficiently used as both output coupler and output window for optically pumped THz lasers.

Reduced frequency noise in superconducting resonators

We report a reduction in the frequency noise in coplanar waveguide superconducting resonators. The reduction of 7 dB is achieved by removing the exposed dielectric substrate surface from the region with high electric fields and by using NbTiN. In a model-analysis the surface of NbTiN is found to be a negligible source of noise, experimentally supported by a comparison with NbTiN on SiOx resonators. The reduction is additive to decreasing the noise by widening the resonators.

Fractal structure of gold clusters formed under vacuum deposition on dielectric substrates

The growth of gold island films under vacuum deposition on the surface of dielectric substrates are investigated. Fractal dimensions of the clusters formed under film deposition at different substrate temperatures and evaporation rates are estimated. The correlation between surface morphology and optical properties of the films deposited are discussed.

Two-Dimensional Fluid Model of Pulse Sheath in Plasma Immersion Ion Implantation With Dielectric Substrates

A 2D fluid model is developed to describe the charging effects during plasma immersion ion implantation with dielectric substrates. The spatiotemporal evolution of the surface potential, the accumulated charge dose, and the ion impact angle at the surface of dielectric substrates are calculated with the model. The numerical results demonstrate that the charging effects lead to reduction of the surface potential with time, and the surface potential is nonuniform along the dielectric surface. The lowest value of surface potential is near but not at the edge of the dielectric target. Therefore, the charge accumulation on the dielectric surface is also a function of surface position. The dose nonuniformity is more severe near the edge of the dielectric target. To lengthen the width of the metal electrode that is located below the dielectric target, one can improve the nonuniformity of the accumulated charge dose on the dielectric surface.

Effects of corotron size and parameters on the dielectric substrate surface charge

Effects of variation of parameters of a corona device (corotron) used in electro-photographic machines on the amount of surface charge build-up on the surface of dielectric substrate were studied. Particular attention was given to the effect of corotron dimension including wire–shields and wire–plate distances, substrate thickness, shields insulation and the substrate speed on the amount of substrate surface charge. The computational analyses were performed for a two-dimensional cross-section of the corotron under steady-state condition. The Maxwell equations were solved and the electrical quantities in a rectangular positive single wire corotron were evaluated. The simulation results showed that for a fixed wire voltage, the corotron size, the substrate thickness, insulation of shields and the substrate speed will affect the distributions of electrical quantities in the corotron. The wire–substrate distance and the substrate speed, however, were found to be the main parameters that control the amount of surface charge build-up on the substrate.

A model of multichannel mode formation in a sliding electric gas discharge

An approximate model of multiple spark channel formation in a sliding gas discharge on a dielectric substrate surface is discussed. Each of the parallel sparks is treated as a constant-radius channel being quasi-static in space with a time-dependent resistance approximated by a falling function. The number of active channels as a function of discharge current is obtained empirically from the experiments being analysed. The spark model is then used for computer simulation of multiple spark formation in a conventional pulsed power supply source. The results of simulations for particular setups of earlier published works are shown to be in good agreement with the experimental data of these works.

Investigation of secondary electron emission effects in plasma immersion ion implantation with dielectric substrates

A one-dimensional fluid sheath model is developed for describing the charging effects with secondary electron emission during plasma immersion ion implantation with dielectric substrates. The temporal evolution of the sheath thickness, surface potential of dielectric substrates and the charge dose accumulated on the surface of dielectric substrates are calculated with the model. The numerical results demonstrate that secondary electron emission effects increase the charging effects greatly, so the sheath thickness becomes thinner and the surface potential of dielectric decreases fast.

Programmable motion and patterning of molecules on solid surfaces.

Adsorbed on a solid surface, a molecule can migrate and carry an electric dipole moment. A nonuniform electric field can direct the motion of the molecule. A collection of the same molecules may aggregate into a monolayer island on the solid surface. Place such molecules on a dielectric substrate surface, beneath which an array of electrodes is buried. By varying the voltages of the electrodes individually, it is possible to program molecular patterning, direct an island to move in a desired trajectory, or merge several islands into a larger one. The dexterity may lead to new technologies, such as reconfigurable molecular patterning and programmable molecular cars. This paper develops a phase field model to simulate the molecular motion and patterning under the combined actions of dipole moments, intermolecular forces, entropy, and electrodes.

Growth of germanium quantum dots on different dielectric substrates by chemical-vapor deposition

The growth of Ge quantum dots on various nitrided oxides has been achieved by ultra-high-vacuum chemical-vapor deposition with GeH4 gas at temperatures between 550 and 650 °C. The characteristics of the Ge dots were investigated using atomic-force microscopy, Auger electron spectroscopy, and x-ray photoelectron spectroscopy in order to find the mechanism of the Ge dot formation. On N2O-annealed nitrided oxide films, we obtained Ge dots with height and diameters of 3.2 and 11 nm, respectively. No Ge dots were formed on surfaces of other dielectric substrates at 550 °C. From our experimental results, we suggest that the surface of N2O-annealed nitrided oxide contains a large amount of defects such as dangling bonds, which act as Ge nucleation sites. This is further confirmed by studying the growth kinetics and the influence of in situ annealing of the samples.

Radiation of a line source mounted between two dielectric substrates

The radiation characteristics of a line source lying on the bottom surface of a dielectric substrate that is mounted on the top of another one are presented. The pattern is calculated for two different cases. One is for infinite thickness of the second substrate and the other is for finite thickness. Some interesting considerations useful for applications in remote sensing, microstrip antennas, and antenna arrays are made.