Search results for "Toe"

Electroplated Indium Bumps as Thermal and Electrical Connections of NTD-Ge Sensors for the Fabrication of Microcalorimeter Arrays

2012

We are developing a method to build arrays of Ge-based microcalorimeters for soft X-rays detection using micro-photolithographic techniques. A key element of the process is the electrical and thermal connection between the germanium sensors and the interconnection electrical tracks, that lay on a substrate acting as mechanical support and thermal sink. The geometry of the sensors, that have a square base truncated pyramid shape, makes feasible a connection through indium soldering. We describe a technique, based on microlithography and electroplating, adopted to grow indium bumps of a few tens of square microns of area and several microns high on top of the contact pads patterned on the sub…

Author response: The primary structural photoresponse of phytochrome proteins captured by a femtosecond X-ray laser

2020

Structure and composition of sputter-deposited nickel-tungsten oxide films

2011

Films of mixed nickel-tungsten oxide, denoted NixW1-x oxide, were prepared by reactive DC magnetron co-sputtering from metallic targets and were characterized by Rutherford backscattering spectrometry. X-ray photoelectron spectroscopy, X-ray diffractometry and Raman spectroscopy. A consistent picture of the structure and composition emerged, and at x<0.50 the films comprised a mixture of amorphous WO3 and nanosized NiWO4, at x = 0.50 the nanosized NiWO4 phase was dominating, and at x>0.50 the films contained nanosized NiO and NiWO4.

X‐Ray Photoelectron Spectroscopy

2021

X-ray photoelectron spectroscopy (XPS) is a spectroscopic technique in the family of electron spectroscopies, that is, those methods whose probe consists of electrons instead of photons. In the case of XPS, a soft, usually monochromatic X-ray causes the emission of electrons by means of the photoelectric effect. Differences in chemical potential and/or polarizability of the molecules can cause an alteration of the binding energy; in addition to photoelectrons, an ordinary XPS spectrum may also contain Auger electrons. In an XPS system, an electron gun is used to deliver a low-energy electron flux with a low current over the illuminated spot. In an XPS instrument, an ion gun may be used with…

The polarization dependence of x‐ray photoelectron yield of a Au photocathode

1994

We report a measurement of the total photoelectron yield of gold as a function of the incident x‐ray polarization. Polarized x rays with energies of 2.5, 2.7, and 4.0 keV were used to excite a gold photocathode at a glancing incidence angle between 5° and 50°. Contrary to a previous report, we found no measurable polarization dependence for all three x‐ray energies. We conclude that the modulation factor, i.e., the fractional change of the total yield when the polarization state is varied, is less than 4%.

Local Structure of Supported Keggin and Wells-Dawson Heteropolyacids and Its Influence on the Catalytic Activity

2019

[EN] Keggin [PW12O40]3– and Wells–Dawson [P2W18O62]6– heteropolyanions are nanosized transition-metal-oxygen clusters belonging to the heteropolyacids (HPAs) family. They are widely used as catalysts due to their high Brønsted acidity, and their dispersion on solid supports favors the accessibility to their acid sites generally increasing the catalytic activity. A series of binary materials composed of Keggin or Wells–Dawson HPAs and SiO2, TiO2, and ZrO2 have been prepared by impregnation or solvothermal methods. Remarkable differences have been found in the catalytic activities among the unsupported and supported HPAs. These differences have been correlated in the past to the structural ch…

Large 256-Pixel X-ray Transition-Edge Sensor Arrays With Mo/TiW/Cu Trilayers

2015

We describe the fabrication and electrical characterization of 256-pixel X-ray transition-edge sensor (TES) arrays intended for materials analysis applications. The processing is done on 6-in wafers, providing capabilities on a commercial scale. TES films were novel proximity coupled Mo/TiW/Cu trilayers, where the thin TiW layer in between aims to improve the stability of the devices by preventing unwanted effects such as Mo/Cu interdiffusion. The absorber elements were electrodeposited gold of thickness 2 μm. The single-pixel design discussed here is the so-called Corbino geometry. Most design goals were successfully met, such as the critical temperature, thermal time constant, and transit…

Microscopic defects and impurity analyses of multicrystalline silicon solar cells from different manufacturing routes

2013

It is important to fully understand the physical behavior of solar cells made by materials from alternative process routes. Solar cells from Elkem Solar Grade Silicon and standard polysilicon have been investigated with light beam induced current and electroluminescence imaging. The low efficiency regions have been further analyzed by Scanning Electron Microscopy under different imaging modes. It was found that cell regions of low performance had undergone plastic deformations resulting in the creation of crystalline defects appearing as subgrain patterns. Similar patterns were observed in both ESS™ and standard polysilicon. Energy-dispersive X-ray spectroscopy (EDS) and electron backscatte…

Time-dependent current-voltage characteristics of Al/p-CdTe/Pt x-ray detectors

2012

Current-voltage (I-V) characteristics of Schottky Al/p-CdTe/Pt detectors were investigated in dark and at different temperatures. CdTe detectors with Al rectifying contacts, very appealing for high resolution x-ray and gamma ray spectroscopy, suffer from bias-induced polarization phenomena which cause current increasing with the time and severe worsening of the spectroscopic performance. In this work, we studied the time-dependence of the I-V characteristics of the detectors, both in reverse and forward bias, taking into account the polarization effects. The I-V measurements, performed at different time intervals between the application of the bias voltage and the measurement of the current…

Using photoelectron emission microscopy with hard-X-rays

2001

We present several successful test cases of using photoelectron emission microscopy (PEEM) for photon energy up to 25 keV. First, the full extended X-ray absorption fine structure analysis was implemented in areas as small as 100 mum(2) for transition-metal K edge absorption spectra and, therefore, demonstrated the feasibility of combining structural and chemical analysis with hard-X-ray absorption spectroscopy with high lateral resolution. We also show that PEEM can be used in a transmission (radiography) mode as an imaging detector for hard-X-ray, This approach again leads to the unprecedented 0.3 mum lateral resolution, particularly critical for the use of coherence-based phase contrast …