Thickness Of Top Layer Research Articles

Coherent control of nanoplasmonic surface-volume mode coupling in gold-silica-gold thin disk resonators

In this article we present a theoretical investigation of gold-silica-gold nanostructures and their properties depending on layer thickness and diameter. We found a remarkable sensitive behavior in the coupling of surface and bulk plasmons with respect to the outer geometry of the disk-like resonators leading to a superposition of distinct modes with a time-dependent amplitude structure. Furthermore, we show a rather complex temporal evolution of plasmonic surface modes depending on the top layer thickness and the asymmetry of the metal disk radii. The results suggest the coherent control of the time-dependent resonant coupling between surface and volume modes by adaptive pulse shaping and foster the field of time-dependent spectroscopy of thin film hybrid nanostructures with single layer thickness down to the two-dimensional limit.

Scratch behavior of multilayer polymeric coating systems

A three-dimensional finite element method modeling along with experimental study on multilayer acrylic coating systems on a hard and brittle substrate has been performed to understand their scratch-induced deformation and damage mechanisms. The experimental results show that, while all else kept the same, an increase in soft (i.e., low Young's modulus and low strength) base layer thickness or hard (i.e., high Young's modulus and high strength) top layer thickness improve the scratch resistance of brittle coating systems by delaying the onset of cracking. The onset of plowing is delayed with the increase in hard top layer thickness, whereas increase in soft base layer thickness results in an earlier onset of plowing. The numerical analysis of the stress and strain field explains the mechanics behind the observed scratch behavior in the multilayer coating systems. The study provides insights toward designing scratch-resistant multilayer coating systems.

Magnetization reversal and magnetoresistance behavior of exchange coupled SrRuO3 bilayer

Magnetic interlayer coupling of a bilayer structure composed of a tetragonal phase SrRuO3 (T-SRO) and a monoclinic phase SRO (M-SRO) was investigated by means of magnetization and magneto-transport measurements. The T-SRO showed large uniaxial perpendicular anisotropy and M-SRO exhibited longitudinal anisotropy. The thickness of the M-SRO top layer was varied and the bottom T-SRO layer remained unchanged. Magnetic hysteresis (M-H) loops showed that as thickness of the M-SRO layer is 4 nm, the M-SRO layer was fully perpendicularly coupled to the T-SRO layer. As the thickness of M-SRO further increased to 8 nm and above, the magnetization reversals of T- and M-SRO phase were clearly distinguished. The angular dependent magnetoresistance (MR) of the bilayers showed consistent results with the M-H loops, which suggests that angle dependent MR may offer a new way for the investigation of exchange coupling between two magnetic layers.

Fully tensile strained partial silicon-on-insulator n-type lateral-double-diffused metal-oxide-semiconductor field effect transistor using localized contact etching stop layers

The use of contact etching stop layer (CESL) stressors is a popular technique for introducing stress into a transistor channel. However, when tensile stress is applied to an n-type lateral double-diffused metal-oxide-semiconductor (LDMOS) by covering the whole device with a CESL, the drift region adjacent to the channel will be compressively strained, which is detrimental to device performance. The current work presents a strained partial silicon-on-insulator LDMOS in which tensile stress was introduced in both the channel and drift region via a CESL to reduce the device’s on-resistance and improve its frequency performance. An n-type LDMOS device with a top-layer Si thickness that was varied between 300 and 20 nm was simulated to investigate the effect of CESLs on device performance. Devices in which the channel and drift region were fully strained had larger carrier mobilities, and their cut-off frequencies were increased by 25% compared with a normal unstrained partial silicon-on-insulator LDMOS field effect transistor. Meanwhile stress was shown to have little impact on the breakdown voltage of the two types of LDMOS field effect transistor studied here.

An experimental study of solid source diffusion by spin on dopants and its application for minimal silicon-on-insulator CMOS fabrication

Solid source diffusions of phosphorus (P) and boron (B) into the half-inch (12.5 mm) minimal silicon (Si) wafers by spin on dopants (SOD) have been systematically investigated and the physical-vapor-deposited (PVD) titanium nitride (TiN) metal gate minimal silicon-on-insulator (SOI) complementary metal–oxide–semiconductor (CMOS) field-effect transistors (FETs) have successfully been fabricated using the developed SOD thermal diffusion technique. It was experimentally confirmed that a low temperature oxidation (LTO) process which depresses a boron silicide layer formation is effective way to remove boron-glass in a diluted hydrofluoric acid (DHF) solution. It was also found that top Si layer thickness of SOI wafers is reduced in the SOD thermal diffusion process because of its consumption by thermal oxidation owing to the oxygen atoms included in SOD films, which should be carefully considered in the ultrathin SOI device fabrication. Moreover, normal operations of the fabricated minimal PVD-TiN metal gate SOI-CMOS inverters, static random access memory (SRAM) cells and ring oscillators have been demonstrated. These circuit level results indicate that no remarkable particles and interface traps were introduced onto the minimal wafers during the device fabrication, and the developed solid source diffusion by SOD is useful for the fabrication of functional logic gate minimal SOI-CMOS integrated circuits.

Urchin-inspired ZnO-TiO2 core-shell as building blocks for dye sensitized solar cells

We applied the core-shell concept to an urchin-inspired ZnO nanowire photoanode building block as a means to increase the electron transport and reduce recombination between nanowire and electrolyte. Dye-sensitized solar cells (DSSCs) were prepared, for the first time, from arrays of urchin-like ZnO nanowire building blocks covered with a thin layer of anatase TiO2 by atomic layer deposition (ALD). An increase in the cell open-circuit voltage (VOC) and an improvement in the conversion efficiency were observed when the urchin-like ZnO building blocks were coated with 10nm thick TiO2 ALD shells in combination with 10μm thick top layer of TiO2 nanoparticles of 15.8nm size. Using urchin-like ZnO nanowires as building blocks can improve the light-scattering and provide a higher surface area with a great control of the nanowire dimensions to increase the dye loading and reduce the electron collection path. The addition of a thin TiO2 blocking layer decreases the recombination of charges in such a high surface area nanostructure.

Phase sensitive sensor on Tamm plasmon devices

This work proposes a refractive index sensing concept of a Tamm plasmon (TP) device by using spectroscopic ellipsometry and phase detection. A TP device is generally composed of a 1-D photonic crystal (PC) with a metallic film on top of it. We found that the sensing performance can be improved by adjusting the parameters of the incident angle of polarized light, the top layer thickness, and the central wavelength of the PC. By designing proper parameters, it was found that the change of the phase difference of p-polarized and s-polarized lights, δ∆, can reach 34° when the ambient environment is changed from air (n = 1.00028) to carbon dioxide (n = 1.00045). A sensitivity of δ∆/δn ~2 × 105 °/RIU can then be obtained for the proposed TP device.

Optimizing the Activity of Nanoneedle Structured WO3 Photoanodes for Solar Water Splitting: Direct Synthesis via Chemical Vapor Deposition

Solar water splitting is a promising solution for the renewable production of hydrogen as an energy vector. To date, complex or patterned photoelectrodes have shown the highest water splitting efficiencies, but lack scalable routes for commercial scale-up. In this article, we report a direct and scalable chemical vapor deposition (CVD) route at atmospheric pressure, for a single step fabrication of complex nanoneedle structured WO3 photoanodes. Using a systematic approach, the nanostructure was engineered to find the conditions that result in optimal water splitting. The nanostructured materials adopted a monoclinic γ-WO3 structure and were highly oriented in the (002) plane, with the nanoneedle structures stacking perpendicular to the FTO substrate. The WO3 photoanode that showed the highest water splitting activity was composed of a ∼300 nm seed layer of flat WO3 with a ∼5 μm thick top layer of WO3 nanoneedles. At 1.23 VRHE, this material showed incident photon-to-current efficiencies in the range ∼35–4...

Comparison of Ti/Pd/Ag, Pd/Ti/Pd/Ag and Pd/Ge/Ti/Pd/Ag contacts to n-type GaAs for electronic devices handling high current densities

In the quest for metal contacts for electronic devices handling high current densities, we report the results of Pd/Ti/Pd/Ag and Pd/Ge/Ti/Pd/Ag contacts to n-GaAs and compare them to Ti/Pd/Ag and AuGe/Ni/Au. These metal systems have been designed with the goal of producing an electrical contact with (a) low metal–semiconductor specific contact resistance, (b) very high sheet conductance, (c) good bondability, (d) long-term durability and (e) cost-effectiveness. The structure of the contacts consists of an interfacial layer (either Pd or Pd/Ge) intended to produce a low metal–semiconductor specific contact resistance; a diffusion barrier (Ti/Pd) and a thick top layer of Ag to provide the desired high sheet conductance, limited cost and good bondability. The results show that both systems can achieve very low metal resistivity (ρM ∼ 2 × 10−6 Ω cm), reaching values close to that of pure bulk silver. This fact is attributed to the Ti/Pd bilayer acting as an efficient diffusion barrier, and thus the metal sheet resistance can be controlled by the thickness of the deposited silver layer. Moreover, the use of Pd as interfacial layer produces contacts with moderate specific contact resistance (ρC ∼ 10−4 Ω cm2) whilst the use of Pd/Ge decreases the specific contact resistance to ρC ∼ 1.5 × 10−7 Ω cm2, as a result of the formation of a Pd4(GaAs, Ge2) compound at the GaAs interface.

Modeling and analysis of touch on flexible ultra-thin touch sensor panels for AMOLED displays employing finite element methods

The work employs the finite element method (FEM) to model the touch on the flexible ultra-thin touch sensor panel for analyzing touch characteristics and signals. Touch sensor panel readout circuits typically depend on touch signals to determine whether the touch sensor panel is touched or not. However, the ultra-thin touch sensor panel encountered a problem which cannot correctly recognize touch points on this type of touch sensor panel (TSP) on active-matrix organic light emitting diodes (AMOLED) displays since its electrical characteristics are different from the one of the conventional TSP. The modeling techniques for the flexible ultra-thin touch sensor panel on an AMOLED display is used to analyze touch signals from the influence of the thickness of top over layer of the flexible ultra-thin TSP and to observe the variations of mutual capacitance from touch on the flexible ultra-thin TSP. When the flexible ultra-thin touch sensor panel with the thickness of the top over layer less than the threshold thickness of the top over layer is on multi-touch, the phenomenon of the ghost points are generated. The simulation to find the threshold thickness of the top over layer based on the FEM model is conducted, and the simulation results show the top layer thickness should be larger than 107 µm to eliminate the ghost points. Furthermore, a new solution that is an optimization of the electrode pattern of transmitters and receivers in the ultra-thin touch sensor panel to further minimize the threshold thickness of the top over layer of TSP without changing the physical structure of TSP is proposed. The results conducted by using this proposed solution show that TSP top over layer threshold thickness can be reduced to 65 µm without appearance of the ghost points.

Performance Analysis of Perovskite on Si Tandem Solar Cell

In this paper, performance of 2-terminal Perovskite/Si tandem solar cell has been analyzed by varying different physical and device parameters. Some best possible designs for the enhanced efficiency of the device have also been proposed. Transfer matrix method has been used to calculate the intensity of incident light on the bottom cell after its absorption by the top perovskite layer. Generation of excitons, instead of free carriers, on incident of light in an organic material has been considered in this study. Results show that the efficiency of whole structure greatly depends on the thickness of top perovskite layer and a maximum value of power conversion efficiency (PCE) is obtained as 27% for an optimized thickness of perovskite layer, 170nm. Bottom cell thickness has also some role but unlike top cell thickness.

Investigation of block foundations resting on soil–rock and rock–rock media under coupled vibrations

In the present study, the dynamic response of block foundations of different equivalent radius to mass (Ro/m) ratios under coupled vibrations is investigated for various homogeneous and layered systems. The frequency-dependent stiffness and damping of foundation resting on homogeneous soils and rocks are determined using the half-space theory. The dynamic response characteristics of foundation resting on the layered system considering rock–rock combination are evaluated using finite element program with transmitting boundaries. Frequencies versus amplitude responses of block foundation are obtained for both translational and rotational motion. A new methodology is proposed for determination of dynamic response of block foundations resting on soil–rock and weathered rock–rock system in the form of equations and graphs. The variations of dimensionless natural frequency and dimensionless resonant amplitude with shear wave velocity ratio are investigated for different thicknesses of top soil/weathered rock layer. The dynamic behaviors of block foundations are also analyzed for different rock–rock systems by considering sandstone, shale and limestone underlain by basalt. The variations of stiffness, damping and amplitudes of block foundations with frequency are shown in this study for various rock–rock combinations. In the analysis, two resonant peaks are observed at two different frequencies for both translational and rotational motion. It is observed that the dimensionless resonant amplitudes decrease and natural frequencies increase with increase in shear wave velocity ratio. Finally, the parametric study is performed for block foundations with dimensions of 4 m × 3 m × 2 m and 8 m × 5 m × 2 m by using generalized graphs. The variations of natural frequency and peak displacement amplitude are also studied for different top layer thicknesses and eccentric moments.

Parametric Analysis of Floor Cooling

This study is aimed at parametric analysis of floor cooling. Impact of several design parameters such as air temperature, temperature of cooling water, distance of cooling pipes, thickness and thermal conductivity of top layer on total heat transfer of cooling floor is studied. The issue is solved by steady-state 2D numerical simulation of heat transfer to the floor construction. These parametric simulations are performed in software CalA. Impact of variable input parameters on total heat transfer is observed. Results of parametric analysis are displayed in a nomogram. This nomogram is useful for faster designing of floor cooling.

Assessment of Concrete Quality of Load-Bearing Structure of the Bridge across Otava River No. 121-006 near Zvikov after Fifty Years of Operation in Severe Environmental Conditions

This paper is introducing results of diagnostic survey of bridge no. 121-006 across Otava river near Zvikov [1], focusing on assessment of quality of concrete mix used for load-bearing structure of the bridge after more than 50 years of operation and assessment of reconstruction works (monolithic assembly of central joints of main fields) executed in 1994 [2]. Visual inspection of monolithic assembly joints, comparison of depth of concrete carbonation and thickness of top layer of reinforcement concrete and concrete compression strength are presented in this paper.

Control the cost, touch and step voltages of the grounding grids design

In this study, an evolutionary strategy is presented to get the optimal grounding grid design to minimise the design cost, the touch and step voltages of the grounding grid to ensure the economical constraint as well as the safety conditions. The proposed technique is used for one and two-layer soil. This technique is based on the comparison between the quality factors of the initial grid dimension according to the cost, touch and step voltages with the other quality factors obtained from new generations (offspring) of the grid dimensions. Effects of top layer thickness, number of grid meshes, vertical rods number and length, and the soil resistivity of the top and bottom layers on grounding resistance (R g) and earth surface potential are studied. Different case studies are introduced to evaluate the performance of the proposed technique and to provide the knowledge about the grid dimensions that is substantial for the economical design of the grounding grids.

Theoretical investigations on the N-polar GaN/AlxGa1-xN/GaN heterostructures: Considering the existence of both two-dimensional hole and electron gases

In this paper, a theoretical study of N-polar GaN/AlxGa1-xN/GaN heterostructures is conducted systematically. The dependence of two-dimensional hole gas (2DHG, at the bottom AlxGa1-xN/GaN interface) and electron gas (2DEG, at the upper GaN/AlxGa1-xN interface) sheet densities on variables, such as GaN top layer thickness, AlxGa1-xN back barrier thickness, and Al content, is investigated. The effect of n-type doping in AlxGa1-xN and δ-doping concentrations in the GaN buffer on 2DHG and 2DEG sheet densities is also presented. For the unintentionally doped structure, the 2DHG-induced electric field E2DHG provides the only driving force in the 2DEG formation. Thus, in order to get high dense of 2DEG in such heterostructure, 2DEG and 2DHG shall coexist through proper AlxGa1-xN back barrier design. While for intentionally doped structure (with the n-type doped AlxGa1-xN back barrier layer or δ-doped GaN buffer layer), ionized donor-induced electric field Edonor is another driving force for 2DEG. The obtained insight offers indications for the structure design of the N-polar GaN/AlxGa1-xN/GaN high electron mobility transistors.

In depth study of molybdenum silicon compound formation at buried interfaces

Angle resolved x-ray photoelectron spectroscopy (ARXPS) has been employed to determine non-destructively the in-depth interface formation during thin film growth. Buried interfaces underneath the nanometer thick layers are probed by identifying the chemical shift of compound materials in photoelectron spectroscopy and using the angular response to quantify the compound amounts from the measured intensities. The thin interfaces in molybdenum-silicon multilayers grown at ambient temperature are investigated. This system is an example of an almost perfect 1D-system, where the interface region is only a small part of the individual layer thicknesses of 3 to 5 nm. Despite the low growth temperature, both the interfaces of this multilayer show layer thickness dependent interface formation. While the silicon-on-molybdenum interface shows a limited interface thickness of 0.4 nm of Mo5Si3, the molybdenum-on-silicon interface shows a more complex evolution. For this interface, the composition of the first 2.0 nm of deposited layer thickness is best described as a molybdenum-silicon compound layer with a molybdenum rich top and a MoSi2 bottom layer. After 2.5 nm of the deposited layer thickness, the molybdenum rich compound at the top has transformed into polycrystalline molybdenum on top of 1.8 nm MoSi2 at the interface. The formation of the 1.8 nm MoSi2 precedes the formation of polycrystalline molybdenum on top. Angle resolved x-ray photoelectron spectroscopy (ARXPS) is shown to be a good tool to study the interface phenomena beneath the nanometer thick top layers. In the case of Mo/Si multilayer mirrors, this ARXPS study shows that the compound formation at the interface accounts for the majority of the extreme ultraviolet reflectance loss.

Influence of metal roughness on SPR sensor performance

Roughness of the nano-layer greatly affects the sensor performance. This study is done to quantify the effect of roughness on the sensor performance experimentally. It is seen that the increased thickness of the top metal layer degrades the sensor performance i.e. sensitivity and detection accuracy. The roughness effect on the surface is seen by varying the thickness of intermediate and top metal layers separately. It is seen that 2–5nm thick intermediate layer and 50nm thick top layer provides better performance of sensor. Also, mathematical equations are included for the sake of theoretical analysis which indicates the effect of surface roughness on the sensor performance.

Determination of Atomic-Layer-Deposited Multilayer Antireflection Coating Parameters Using a Novel X-Ray Reflectivity Approach

The thicknesses and densities of coatings prepared by atomic layer deposition (ALD) and by other deposition techniques are important to understand their optical, electrical and mechanical properties. Specular X-ray reflectivity (XRR) is a powerful tool that is capable of nondestructively extracting layer thicknesses with angstrom resolution, and what is distinct, determining the layer densities through modeling structures with simulation programs. Unfortunately, problem with modeling usually arises when other layers form at the surface or interfaces, and it is also common to other nondestructive techniques such as ellipsometry. A recent development1 has shown that with differentiating the specular XRR intensity with respect to vertical reciprocal space coordinate, a Fourier transform (FT) approach can provide straightforward information about the layer thicknesses in multilayer systems, which will make it easier to build the XRR simulation model. Therefore, a novel combination of FT and specular XRR simulation would be quite efficient in layer thickness extraction compared with other conventional techniques (e.g. transmission electron microscope (TEM) and ellipsometry). In this study, the novel XRR approach, together with other techniques including optical microscope (OR), spectroscopic ellipsometry (SE), TEM, energy dispersive X-ray spectroscopy and glancing incidence X-ray diffraction, was utilized to characterize the effect of annealing on optical properties of Al2O3/TiO2/Al2O3 multilayer antireflection stack. The films were deposited on (0 0 1) Si wafers using ALD which is a good candidate for multilayer antireflection coatings, due to the self-limiting nature of chemical reactions resulting in the precise control of film thickness and large-area uniformity. The thickness values of the as-deposited layers determined by XRR agree quite well with those obtained from OR, SE and TEM, with the difference below uncertainty levels. This, together with the good correlation between layer densities extracted from XRR and refractive indices measured by OR and SE, demonstrates the validity of the XRR approach. On the other hand, it is revealed that air annealing at 400 °Ϲ for 10 min induces the densification of the TiO2 layer as well as the initiation of crystallization. Meanwhile, both Al2O3 layers keep amorphous after annealing, with the thickness of top Al2O3 layer decreased that is likely due to interdiffusion of Al and Ti atoms between the top two layers, while the thickness of bottom Al2O3 layer increased accompanied with a decrease in density, which is probably attributed to the diffusion of Si atoms from the substrate into layers. Reference 1B. Poust, R. Sandhu, and M. Goorsky, Phys. Status Solidi A. 206, 1780 (2009).

Atomic layer deposition and high-resolution electron microscopy characterization of nickel nanoparticles for catalyst applications

Abstract Ni nanoparticles (diameter 2 ) and H 2 O as precursors. In the second step, the NiO films are reduced in H 2 atmosphere at 400–800 °C. The size of the resulting Ni nanoparticles is controlled by the temperature. The largest particles with a diameter of about 7 nm are obtained at 800 °C. NiO film and Ni nanoparticles deposited on Si substrates are characterized by high-resolution electron microscopy. It was found that the Ni(MeCp) 2 precursor reacts with the substrate, leading to the formation of NiSi 2 precipitates beneath the surface of the Si wafer and amorphization of the surrounding area, resulting in a 10 nm thick top layer of the Si wafer. After reductive annealing, NiSi 2 precipitates are preserved but Si recrystallizes and the amorphous NiO film transforms into crystalline Ni nanoparticles well distributed on the wafer surface. Process parameters were optimized for Si substrates and transfer of the process to ceramic LST/YSZ substrates is possible in principle. However, a much higher number of ALD cycles (1200 compared to 100 for Si) are necessary to obtain Ni nanoparticles of similar size and the number density of particles is lower than observed for Si substrates.