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Description
Diamond is a highly attractive material due to its excellent chemical and physical properties, making it suitable for various applications, including heavy particle detection, neutron detection, and radiotherapy dosimeters. Atomic and mass numbers 6 and 12 are considered to be almost tissue-equivalent, providing an important advantage over alternative materials such as silicon. Although single-crystal diamonds are extremely expensive, polycrystalline chemical vapor deposited (pCVD) diamond films offer a cost-effective alternative [1]. Data reported in the literature indicate that pCVD diamond exhibits similar behavior to single-crystal diamond.
In this study, we fabricated and tested charged particle detectors based on pCVD diamond films operated at zero bias. The pCVD diamond films were grown on a conductive silicon (100) substrate. Polycrystalline diamond films with varying thicknesses from 0.5 um to 10 um were prepared by microwave plasma-enhanced CVD. We investigated two types of polycrystalline diamond films, distinguished by the grain size: nanocrystalline and microcrystalline. The samples had a total area of about 1 cm2. On the back side (Si substrate), a full-area Ti/Au (5/50 nm) contact was evaporated using ultra-high vacuum deposition equipment. Circular contacts with a diameter of 1 mm to 3 mm were prepared on the diamond layer using the same metallization.
The current-voltage characteristics of the pCVD diamond detector were measured at RT using a custom-built picoampermeter/voltage source. The measurements were performed from -100 V to 100 V, with typical currents in the range of tens of picoamperes. The prepared pCVD diamond samples operate at zero bias and the current-voltage measurements conformed good ohmic contacts. The detector structures were subsequently placed in a vacuum chamber and connected to the spectrometric chain for alpha particle detection. A 241-Am radiosotope was used to generate monoenergetic alpha particles with an energy of 5489 keV. Samples with a contact diameter of 1 mm exhibited the best performance, achieving a relative energy resolution of 15%. Further investigation involved degradation of pCVD diamond with microcrystalline grains using 3.5 MeV protons at various fluences up to 1E15 p/cm2. Subsequent testing with alpha particles revealed a significant impact on the detected alpha particle spectrum. At a fluence of 1E13 p/cm2, the detected peak is shifted to the lower channels, corresponding to 20% of its original value. At the maximum proton fluences, the pCVD diamond detectors were unable to distinguish alpha particles from noise.
References:
[1] M. Bruzzi et al.: Diamond & Related Materials 20 (2011) 84.
Acknowledgement: This work was partially supported by grants of the Slovak Research and Development Agency No. APVV-22-0382, SK-CZ-RD-21-0116, the Ministry of Education, Youth and Sports of the Czech Republic No. LU-ASK22147 and the Scientific Grant Agency of the Ministry of Education of the Slovak Republic and the Slovak Academy of Sciences No. 2/0063/24.
| Workshop topics | Sensor materials, device processing & technologies |
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