In scintillation and dosimetry applications, the increasing interest on the use of colloidal quantum dots (QDs) in comparison with organic fluorophores is mainly due to their easier chemical ...processability, narrower photoluminescence (PL) emission, and higher cross-section for ionizing radiation. The development of scintillators and dosimeter based on QDs, however, relies on a deep understanding of the effects of ionizing radiation on QD structures. In this paper, we present the optical characterization of colloidal cadmium-free InGaP/ZnS core–shell QDs embedded in polydimethylsiloxane (PDMS) and irradiated with 2 MeV protons (H+) in the fluence range of 1014 to 1015 H+ cm–2. Steady-state PL measurements of the irradiated samples show a decrease of the average QD PL intensity, indicating the introduction of PL quenching centers. Time-resolved PL measurements, acquired with a time-correlated single photon counting system, provide a way to probe the radiation-induced change in the carrier recombination dynamics of the QDs. A detailed analysis of the time-resolved PL curves demonstrates the presence of PL quenching defects localized both at the inner (core) and at the outer (shell) structure of the nanocrystal. The radiation-induced change in the QD optical properties, coupled with a suitable radiation hardness of the PDMS in these irradiation conditions, open the way for possible future applications related to dosimetry systems based on QDs as nanostructured sensing elements.
Single-photon avalanche diode (SPAD) arrays fabricated in a 180-nm CMOS technology with a high-voltage option have been exposed to calibrated neutron and X-ray sources to evaluate their radiation ...tolerance. The technology is being investigated in view of the design of low material budget detectors for charged particle tracking based on the coincidence of the signals coming from two or more overlapping layers of SPAD sensors. Each element in the array is a monolithic detector including the processing electronics together with the diode in the same substrate. Different sensor dimensions and structures have been implemented in the test chip to thoroughly explore the technology features. This paper will present and discuss the results from the characterization, in terms of dark count rate, of SPAD arrays irradiated with X-ray doses reaching 1 Mrad(SiO 2 ) and with neutron fluences up to <inline-formula> <tex-math notation="LaTeX">10^{11}~1 </tex-math></inline-formula>-MeV neutron equivalent cm<inline-formula> <tex-math notation="LaTeX">^{-2} </tex-math></inline-formula>.
Dark count rate (DCR) increase in CMOS single-photon avalanche diodes (SPADs) exposed to a nonmonochromatic neutron source is modeled, taking into accountthe source spectrum and the geometry of the ...device under test. Experimental results from the characterization of SPADs fabricated in a 150-nm technology and irradiated with 1-MeV neutron equivalent fluences up to 1011 cm-2 are found to be in good agreement with the theoretically calculated distribution of the nonionizing energy deposited in the device substrate.
Metasurfaces and, in particular, metalenses have attracted large interest and enabled various applications in the near-infrared and THz regions of the spectrum. However, the metalens design in the ...visible range stays quite challenging due to the smaller nanostructuring scale and the limited choice of lossless CMOS-compatible materials. We develop a simple yet efficient design of a polarization-independent, broadband metalens suitable for many CMOS-compatible fabrication techniques and materials and implement it for the visible spectral range using niobium pentoxide (Nb2O5). The produced metalens demonstrates high transmittance and focusing ability as well as a large depth of focus, which makes it a promising solution for a new generation of silicon photomultiplier photodetectors with reduced fill factor impact on the performance and reduced electron–hole generation regions, which altogether potentially leads to improved photodetection efficiency and other characteristics.
Single-photon avalanche diodes (SPADs) fabricated using two different CMOS technologies were exposed to a neutron source up to a maximum fluence of <inline-formula> <tex-math notation="LaTeX">3\times ...10^{11}\,\,1 </tex-math></inline-formula>-MeV neutron equivalent cm −2 . Significant changes in the dark count rate (DCR), with a strong dependence on the fluence and the device active area, were detected after irradiation. A model for the probability of DCR degradation, accounting for the source spectrum and the geometry of the device under test (DUT), was proposed and proved to be in good agreement with experimental data. The model may be helpful in performing worst-case analysis of SPAD-based detection systems under neutron irradiation.
In this paper, different Silicon PhotoMultiplier (SiPM) sensors have been tested with charged particles to characterize the Cherenkov light produced in the sensor protection layer. A careful position ...scan of the SiPM response has been performed with different prototypes, confirming the large number of firing cells and proving almost full efficiency, with the SiPM filling factor essentially negligible. This study also allowed us to study the time resolution of such devices as a function of the number of firing cells, reaching values below 20 ps. These measurements provide significant insight into the capabilities of SiPM sensors in direct detection of charged particles and their potential for several applications.
In this paper, evidence that the increased response of SiPM sensors to the passage of charged particles is related mainly to Cherenkov light produced in the protection layer is reported. The response ...and timing properties of sensors with different protection layers have been studied.
3D integration technologies for custom SiPM: From BSI to TSV interconnections Parellada-Monreal, L.; Acerbi, F.; Ficorella, A. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
April 2023, 2023-04-00, Letnik:
1049
Journal Article
Recenzirano
Progress in 3D interconnecting technologies paved the way for a new generation of Silicon Photomultipliers (SiPM) and Single Photon Avalanche Diode (SPAD): hybrid devices which combine the integrated ...functionalities of the digital SiPM with the high performance of custom technologies, like low noise and high detection efficiency. Recently, Fondazione Bruno Kessler (FBK) has been working on the implementation of recently developed 3D integration technologies, on SiPMs devices, to improve both performances and functionalities by creating backside-illuminated (BSI) devices and Through Silicon Vias (TSV) interconnections.
Two different technology platforms have been investigated: a BSI design for near-infrared (NIR) sensitive SiPMs and TSV interconnections for near- and vacuum-ultraviolet (NUV/VUV) sensitive detectors.
For NIR applications, electrical characterization of ultra-thin (about 10μm) SiPM wafers with a metal reflector on the frontside has shown an improved photon detection efficiency (PDE) when operated in BSI configuration compared with non-thinned front-side illuminated (FSI) devices, allowing at the same time full high-segmentation access to the SiPM output from the front-side.
Instead, for NUV/VUV applications, a FSI stacked approach is considered more suitable since the junction depth needs to be shallower. In this case, TSV interconnections using two different approaches (named Via-Mid and Via-Last) have been implemented allowing the placement of the contacts on the backside of the wafer.
•A first demonstrator of BSI SiPM for NIR light detection was developed at FBK.•SiPMs with thick epitaxial layer and metal reflector on top show the highest PDE.•Two fabrication process flows with TSV for VUV detection are proposed.•Via-Mid approach shows proper electrical isolation between the TSV and bulk-silicon.•TSV filling with a dielectric polymer has been demonstrated for Via-Last approach.
The growing interest on the use of colloidal Quantum Dots (QDs) in scintillation and dosimetry applications in comparison with organic fluorophores relies in their narrower and tunable ...photoluminescence (PL) emission, easier chemical processability and higher cross-section for ionizing radiation. In this context, a deep understanding of the role of the embedding medium on the QD optical properties in unirradiated and irradiated samples represents an important issue. In this paper, we present the optical characterization of colloidal core-shell CdSe/ZnS QDs embedded in polyvinyl alcohol (PVOH) and irradiated with 2 MeV protons at different fluences. The characterization of the samples, performed by both steady-state and time-resolved PL measurements, indicates a damage of the QDs at the lowest fluence (1013 H+cm−2), demonstrated by a quenching of the QD PL intensity and by a shortening of the QD lifetime. At the middle fluence (5 × 1013 H+cm−2) a partial recovering of the QD optical properties are observed, due to energy transfer phenomena between radiation-induced PL defects in the PVOH, acting as donors, and the QDs, acting as acceptors. The higher concentration of PVOH PL defects in the most irradiated sample (1014 H+cm−2) led to an enhancement of the QD PL intensity in comparison with the unirradiated sample, highlighting the crucial role of the embedding medium in the post-irradiation QD optical response.
•The QD embedding medium has an important role on the irradiated QD optical response.•At the fluence of 1013 H+cm−2, QD PL intensity and lifetime decrease.•At the fluence of 5 × 1013 H+cm−2, QD PL intensity and lifetime are partly recovered.•At the fluence of 1014 H+cm−2, QD PL intensity and lifetime are enhanced.•Energy transfer phenomena arise between PVOH photoluminescent defects and QDs.
PDF
