Search results for "detector"

Planar Array Technology for the Fabrication of Germanium X-Ray Microcalorimeters

2008

Several technologies are presently competing for measuring the temperature increase in cryogenic micro-calorimeters used as high resolution energy-dispersive X-ray detectors. Doped germanium, whose resistivity depends on temperature, is a promising material for this purpose, because of its comparatively low specific heat and the possibility of making wafers with high doping uniformity by neutron transmutation. Presently, Ge-based microcalorimeters are still micro-machined and manually assembled. Here we present a planar approach to the fabrication of 2-D arrays of microcalorimeters and show the preliminary technological results.

Planar Technology for NDT-Ge X-Ray Microcalorimeters: Absorber Fabrication

2009

We have investigated the electroplating process to deposit thick uniform films of tin on a Ge wafer coated with Spin‐On Glass, in order to fabricate the absorbers for Ge microcalorimeter arrays. Here we discuss some technological details and propose two alternative metal bilayer to be used as seed for the electroplating.

Effects of the Buffer Layers on the Performances of (Al,Ga)N Ultraviolet Photodetectors

2004

The fabrication of (Al,Ga)N-based metal–semiconductor–metal (MSM) photovoltaic detectors requires the growth of high-quality (Al,Ga)N films. Inserting a low-temperature deposited buffer layer enables the growth of an epitaxial layer with a reduced density of defects. Two structures using GaN and AlN buffer layers have been deposited by low-pressure metalorganic chemical vapor deposition and used to fabricate MSM interdigitated detectors. The devices have been characterized to investigate the effects of the buffer layers on the detector performances.

Electroplated bismuth absorbers for planar NTD-Ge sensor arrays applied to hard x-ray detection in astrophysics

2018

Single sensors or small arrays of manually assembled neutron transmutation doped germanium (NTD-Ge) based microcalorimeters have been widely used as high energy-resolution detectors from infrared to hard X-rays. Several planar technological processes were developed in the last years aimed at the fabrication of NTD-Ge arrays, specifically designed to produce soft X-ray detectors. One of these processes consists in the fabrication of the absorbers. In order to absorb efficiently hard X-ray photons, the absorber has to be properly designed and a suitable material has to be employed. Bismuth offers interesting properties in terms of absorbing capability, of low heat capacity (needed to obtain h…

Ultra-broad spectral photo-response in FePS3 air-stable devices

2021

Van der Waals materials with narrow energy gaps and efficient response over a broadband optical spectral range are key to widen the energy window of nanoscale optoelectronic devices. Here, we characterize FePS as an appealing narrow-gap p-type semiconductor with an efficient broadband photo-response, a high refractive index, and a remarkable resilience against air and light exposure. To enable fast prototyping, we provide a straightforward guideline to determine the thickness of few-layered FePS nanosheets extracted from the optical transmission characteristics of several flakes. The analysis of the electrical photo-response of FePS devices as a function of the excitation energy confirms a …

Simultaneous photonic and excitonic coupling in spherical quantum dot supercrystals

2020

Semiconductor nanocrystals, or quantum dots (QDs), simultaneously benefit from inexpensive low-temperature solution processing and exciting photophysics, making them the ideal candidates for next-generation solar cells and photodetectors. While the working principles of these devices rely on light absorption, QDs intrinsically belong to the Rayleigh regime and display optical behavior limited to electric dipole resonances, resulting in low absorption efficiencies. Increasing the absorption efficiency of QDs, together with their electronic and excitonic coupling to enhance charge carrier mobility, is therefore of critical importance to enable practical applications. Here, we demonstrate a ge…

Technical Program

2015

A Penning Trap for Studying Cluster Ions

1986

We propose to use a Penning trap for spectroscopy of stored cluster ions. A similar device has been built for the purpose of mass measurements of short-lived nuclei produced at the on-line isotope separator ISOLDE/CERN. A resolving power of 500,000 in a mass measurement of39K and an accuracy of 2 × 10−7 for the85Rb/39K mass ratio were obtained. An efficiency for in-flight capture as high as 70% was achieved. The method provides very high sensitivity since typically only 10 to 100 ions are stored in the trap. We intend to perform laser spectroscopy on trapped Na clusters as a first application of the trap technique.

Polarized neutron reflectivity from monolayers of self-assembled magnetic nanoparticles

2015

We prepared monolayers of iron oxide nanoparticles via self-assembly on a bare silicon wafer and on a vanadium film sputter deposited onto a plane sapphire substrate. The magnetic configuration of nanoparticles in such a dense assembly was investigated by polarized neutron reflectivity. A theoretical model fit shows that the magnetic moments of nanoparticles form quasi domain-like configurations at remanence. This is attributed to the dipolar coupling amongst the nanoparticles.

Ultrasonic detection by photo-EMF sensor and by wideband air-coupled transducer

2004

Two non-contact remote ultrasonic detection systems are compared. The first consists of a continuous wave (CW) Nd:YVO4 laser operating at 532 nm used in conjunction with a photo-induced electromotive-force (EMF) sensor. The second system employs an air-coupled capacitance transducer that has a bandwidth from 100 kHz up to 2 MHz. Both systems exhibit higher sensitivity to out-of-plane than in-plane measurements of stress wave signals. Ultrasound generation is carried out by an Nd:YAG pulsed laser at 532 nm in the thermoelastic regime in a 1.6 mm aluminum plate. A0 Lamb mode is generated at frequency-thickness product with strong out-of-plane displacements. Ultrasonic waveforms acquired are r…