Search results for "i.v."

Fabrication and characterization of low cost Cu 2 O/ZnO:Al solar cells for sustainable photovoltaics with earth abundant materials

2016

Abstract The low cost electrodeposition method was used to grow Cu2O thin films and experimentally determine the optimal absorber layer thickness. Raman scattering studies indicate the presence of solely crystalline Cu2O and SEM images show that the thin films consist of grains with a pyramidal shape. The influence of the thickness of the light absorbing Cu2O layer on the basic characteristic of the heterojunction and their properties have been investigated using reflectivity, current–voltage (J–V), capacitance–voltage (C–V) and the external quantum efficiency (EQE) measurements. The depletion layer, the charge collection length of the minority carrier, and reflectivity are the main factors…

Quartz resonators for penning traps toward mass spectrometry on the heaviest ions

2020

We report on cyclotron frequency measurements on trapped 206,207Pb+ ions by means of the non-destructive Fourier-transform ion-cyclotron-resonance technique at room temperature. In a proof-of-principle experiment using a quartz crystal instead of a coil as a resonator, we have alternately carried out cyclotron frequency measurements for 206Pb+ and 207Pb+ with the sideband coupling method to obtain 21 cyclotron-frequency ratios with a statistical uncertainty of 6 × 10−7. The mean frequency ratio R¯ deviates by about 2σ from the value deduced from the masses reported in the latest Atomic Mass Evaluation. We anticipate that this shift is due to the ion–ion interaction between the simultaneousl…

XUV diagnostic to monitor H-like emission from B, C, N, and O for the W7-X stellarator

2019

The “C/O Monitor” system for the Wendelstein 7-X (W7-X) stellarator is a dedicated spectrometer with high throughput and high time resolution (order of 1 ms) for fast monitoring of content of low-Z impurities in the plasma. The observed spectral lines are fixed to Lyman-α lines of H-like atoms of carbon (3.4 nm), oxygen (1.9 nm), nitrogen (2.5 nm), and boron (4.9 nm). The quality of the wall condition will be monitored by the measurements of oxygen being released from the walls during the experiments. The strong presence of carbon is an indication for enhanced plasma-wall interaction or overload of plasma facing components. The presence of nitrogen (together with oxygen) may indicate a poss…

3D magnetic and thermal fields for in the transformer with homogenised amorphous C-core under high frequency

2017

Current Spreading Length and Injection Efficiency in ZnO/GaN-Based Light-Emitting Diodes

2019

We report on carrier injection features in light-emitting diodes (LEDs) based on nonintentionally doped-ZnO/p-GaN heterostructures. These LEDs consist of a ZnO layer grown by chemical-bath deposition (CBD) onto a p-GaN template without using any seed layer. The ZnO layer (~1- $\mu \text{m}$ thickness) consists of a dense collection of partially coalesced ZnO nanorods, organized in wurtzite phase with marked vertical orientation, whose density depends on the concentration of the solution during the CBD process. Due to the limited conductivity of the p-GaN layer, the recombination in the n-region is strongly dependent on the spreading length of the holes, ${L}_{h}$ , coming from the p-contact…

A new Collinear Apparatus for Laser Spectroscopy and Applied Science (COALA).

2020

We present a new collinear laser spectroscopy setup that has been designed to overcome systematic uncertainty limits arising from high-voltage and frequency measurements, beam superposition, and collisions with residual gas that are present in other installations utilizing this technique. The applied methods and experimental realizations are described, including an active stabilization of the ion-source potential, new types of ion sources that have not been used for collinear laser spectroscopy so far, dedicated installations for pump-and-probe measurements, and a versatile laser system referenced to a frequency comb. The advanced setup enables us to routinely determine transition frequenci…

Guiding and splitting Lamb waves in coupled-resonator elastic waveguides

2018

Abstract We investigate experimentally Lamb wave propagation in coupled-resonator elastic waveguides (CREWs) formed by a chain of cavities in a two-dimensional phononic crystal slab with cross holes. Wide complete bandgaps, extending from 53 to 88 kHz, are first measured in a finite phononic crystal slab sample. A straight waveguide and a wave splitting circuit with 90° bends are then designed, fabricated and measured. Elastic Lamb waves are excited by a piezoelectric patch attached to one side of the phononic slab and detected using a scanning vibrometer. Strongly confined guiding and splitting at waveguide junctions are clearly observed for several guided waves. Numerical simulations are …

Determination of refractive index of submicron-thick films using resonance shift in a four-layer slab waveguide

2017

The measurement of refractive index of very thin films at the order of ten to hundred nanometers is cumbersome and usually requires employing sophisticated techniques such as the spectral ellipsometry. In this paper we describe a simple contact method for measuring the refractive index of thin films. Here we have used the prism-coupling technique for characterizing samples prepared as four-layer slab waveguides. The waveguide resonance condition can be calculated by solving simple analytic transcendental equations for the slab waveguide. Then the captured mode position as a function of cladding thickness is used for probing the refractive index of cladding layer. We used indium-tin-oxide la…

Multi-pulse characterization of trapping/detrapping mechanisms in AlGaN/GaN high electromobility transistors

2019

GaN high-electro mobility transistors (HEMTs) are among the most promising candidates for use in high-power, high-frequency, and high-temperature electronics owing to their high electrical breakdown threshold and their high saturation electron velocity. The applications of these AlGaN/GaN HEMTs in power converters are limited by the surface trapping effects of drain-current collapse. Charge-trapping mechanisms affect the dynamic performance of all GaN HEMTs used in power switching applications. This study analyzes the dynamic resistance of GaN HEMTs and finds that the effects of dynamic resistance can be suppressed by controlling switching conditions and on-off cycles.

Crystalline phase detection in glass ceramics by EPR spectroscopy

2018

The advances of EPR spectroscopy for the detection of activators as well as determining their local structure in the crystalline phase of glass ceramics is considered. The feasibility of d-element (Mn2+, Cu2+) and f-element (Gd3+, Eu2+) ion probes for the investigation of glass ceramics is discussed. In the case of Mn2+, the information is obtained from the EPR spectrum superhyperfine structure, for Gd3+ and Eu2+ probes – from the EPR spectrum fine structure, whereas for Cu2+ ions the changes in the EPR spectrum shape could be useful. The examples of EPR spectra of the above-mentioned probes in oxyfluoride glass ceramics are illustrated. ----/ / /---- This is the preprint version of the fol…