Speaker
Description
One of the greatest milestones in scientific infrastructure in Brazil is concentrated in Sirius, installed at the Brazilian Center for Research in Energy and Materials (CNPEM), in Campinas. Just like the European Synchrotron Radiation Facility (ESRF), located in Grenoble, France, Sirius represents one of the most advanced fourth-generation synchrotron light sources in the world.
Both Sirius and ESRF operate with ultra-high brightness X-ray beams, being essential for experiments that investigate in detail the structures and properties of materials on various scales [1].
Currently, Sirius has multiple beamlines. It is an electron storage ring designed to operate at an energy of 3 GeV and beam current of up to 350 mA, with an ultra-low natural emittance of 0.28 nm·rad. The spectral brightness of Sirius for X-rays can reach values above 10²¹ photons/s/mm²/mrad²/0.1%BW, placing it among the brightest light sources in the world. The beamlines cover a wide spectral range, from infrared to hard X-rays, with maximum photon energies around 30 to 40 keV [1]. Each beamline is dedicated to different experimental techniques, enabling cutting-edge research in areas such as nanotechnology, biosciences, applied physics, among others. It is a strategic resource for scientific and technological development in Brazil.
To enable experiments on the Sirius beamlines, detectors that are robust to X-ray radiation are required, with low time resolution, high pixel density, and good efficiency across a wide energy range [1], [2].
Considering these requirements, studies are being conducted using the LGAD device, which meets the demands imposed on the beamlines, using the LGAD 3.2 HPK model developed in Japan and exposed to an X-ray source. The tests provided significant results related to the TID (Total Ionizing Dose) effect, which causes surface damage to the device.
Based on the analyses carried out, a TID-specific testing methodology for detectors was developed. An X-ray source with an effective energy of 10 keV was used to investigate the effects of aging and charge generation at the interfaces. This energy ensures high efficiency in the generation of electron-hole pairs through the photoelectric effect, providing data to estimate the robustness of detectors in harsh environments such as synchrotron accelerators [3].
In this context, irradiation tests were followed by detailed electrical characterization focused on essential parameters for LGAD performance. Among the tests performed, the forward and reverse current versus voltage (I × V) curves and capacitance versus voltage (C × V) measurements were highlighted, enabling a detailed assessment of the detector’s behavior when exposed to radiation.
To assess the effectiveness of LGAD detectors under ionizing radiation, electrical characterizations were carried out at different stages of the experiment, before, during, and after irradiation. These initial analyses indicated progressive degradation in the device's electrical parameters, prompting a more in-depth investigation of the effects caused by X-ray exposure [3].
The characterization and irradiation stages were carried out, respectively, at the Nanoelectronics and Integrated Circuits Laboratory and the Laboratory of the Effects of Ionizing Radiation (LERI), both located on the campus of Centro Universitário FEI, in Brazil. This integrated infrastructure enabled strict control of experimental conditions and the acquisition of relevant results.
Considering the specific irradiation conditions adopted, the results revealed significant changes in the device's electrical characteristics, especially in the I × V curves, which showed a reduction in conduction voltage and degradation in the avalanche region. It was also observed that, between irradiation steps, a slight recovery of electrical properties was achieved through Room Temperature Annealing (R.T.A.) processes. However, from the 91 krad(Si) dose onward, the degradation became irreversible, leading to the loss of the charge multiplication capability, an essential feature of LGADs, and causing the device to behave like a PIN diode, compromising its originais function in detecting high-energy particles.
As a continuation of this work, future steps intend to expand the analysis through the application of a more detailed comparative methodology using X-rays, involving different variants of LGAD detectors. The proposal follows the line of investigation evidenced in reference [4].
REFERENCES
[1] Centro Nacional de Pesquisa em Energia e Materiais (CNPEM), Projeto Sirius: A nova fonte de luz síncrotron brasileira, Campinas, SP, Brasil, 2014. [Online]. Available: https://lnls.cnpem.br/wp-content/uploads/2016/08/Livro-do-Projeto-Sirius-2014.pdf.
[2] M. Moll, “Displacement Damage in Silicon Detectors for High Energy Physics”, IEEE Trans. Nucl. Sci., vol. 65, no 8, p. 1561–1582, ago. 2018, doi: 10.1109/TNS.2018.2819506.
[3] T. A. Silva et al., “Analysis of Low Gain Avalanche Detector (LGAD) Response to 10 keV X-Rays”, in Proc. SEMINATEC 2025 (XIX Workshop on Semiconductors and Micro and Nano Technology), to be published.
[4] A. Doblas et al., “Inverse LGAD (iLGAD) Periphery Optimization for Surface Damage Irradiation”, Sensors, vol. 23, no 7, p. 3450, mar. 2023, doi: 10.3390/s23073450.
| Type of presentation (in-person/online) | online presentation (zoom) |
|---|---|
| Type of presentation (I. scientific results or II. project proposal) | I. Presentation on scientific results |
