Radiation hardness of three-dimensional polycrystalline diamond detectors

The three-dimensional concept in particle detection is based on the fabrication of columnar electrodes perpendicular to the surface of a solid state radiation sensor. It permits to improve the radiation resistance characteristics of a material by lowering the necessary bias voltage and shortening the charge carrier path inside the material. If applied to a long-recognized exceptionally radiation-hard material like diamond, this concept promises to pave the way to the realization of detectors of unprecedented performances. We fabricated conventional and three-dimensional polycrystalline diamond detectors, and tested them before and after neutron damage up to 1.2 × 1016cm-2, 1 MeV-equivalent neutron fluence. We found that the signal collected by the three-dimensional detectors is up to three times higher than that of the conventional planar ones, at the highest neutron damage ever experimented

Copper distribution among physical and chemical fractions in a former vineyard soil

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Copper distribution among physical and chemical fractions in a former vineyard soil

L'articolo è disponibile sul sito dell'editore: www.edizioniplus.i

Strain state in single quantum well GaAs/1ML-InAs/GaAs(100) analysed by high-resolution X-ray diffraction

dépôt d'une copie effectué avec l'aimable autorisation de EDP SciencesThe epitaxy-induced tetragonal strain in one monolayer of InAs buried in a GaAs(100) crystal is determined by measuring weak oscillations in X-ray reflectivity profiles. It is shown that the reflectivity of such heterostructure consists of a sinusoidal modulation of the usual rocking curve of a thick crystal. The oscillation period provides the distance of the buried layer from the crystal surface and the maximum positions in oscillations give the displacement induced by the buried layer. The vertical spacing between the In and As atom planes is found to be 1.64 ± 0.02 Å, which is consistent with an elastic behaviour

A study of charge collection processes on polycrystalline diamond detectors

Abstract We performed a study of charge collection distance (CCD) on medium to high-quality prototypes of diamond sensors prepared by Chemical Vapor Deposition (CVD). We studied the Charge Collection Efficiency in these materials supposing that it is limited by the presence of a recombination level and a distribution of trap levels centered at 1.7 eV from the band-edge. We also supposed that the exposition to ionizing radiation can make the trap levels ineffective (pumping effect). We have shown that these assumptions are valid by correlating the CCD to the pumping efficiency. Moreover, we have shown that the pumping efficiency is bias-dependent. We have explained our experimental results assuming that trapped carriers generate an electric field inside the diamond bulk

Numerical Modelling of Polycrystalline Diamond device for Advanced Sensor Design

Abstract Technology Computer Aided Design (TCAD) simulation tools are routinely adopted within the design flow of semiconductor devices to simulate their electrical characteristics. However, the device level simulation of diamond is not straightforward within the state-of-the-art TCAD tools. Physical models have to be specifically formulated and tuned for single-crystal CVD (scCVD) and polycrystalline (pcCVD) diamond in order to account for, among others, incomplete ionization, intrinsic carrier free material, dependences of carrier transport on doping and temperature, impact ionization, traps and recombination centers effects. In this work, we propose the development and the application of a numerical model to simulate the electrical characteristics of polycrystalline diamond conceived for sensors fabrication. The model is based on the introduction of an articulated, yet physically based, picture of deep-level defects acting as recombination centers and/or trap states. This approach fosters the exploration and optimization of innovative semiconductor devices conjugating the capabilities of CMOS electronics devices and the properties of diamond substrates, e.g. for biological sensor applications or single particle detectors for High Energy Physics experiments