Deep levels and trapping mechanisms in chemical vapor deposited diamond

Abstract

Detector-grade undoped chemical vapor deposited ͑CVD͒ diamond samples have been studied with thermally stimulated currents ͑TSC͒ and photoinduced current transient spectroscopy ͑PICTS͒ analyses in the temperature range 300-650 K. Two previously unknown defects have been identified, characterized by activation energies E 1 ϭ1.14 eV and E 2 ϭ1.23 eV, cross sections of about Ϸ10 Ϫ13 cm 2 and concentrations of N t Ϸ10 16 cm Ϫ3. They have been clearly observed by PICTS and isolated in TSC measurements by use of a fractional annealing cycle in the temperature range 300-400 K. Due to their trap parameters, in particular the high cross section, the levels corresponding to E 1 and E 2 are characterized by capture times of the order of 10-100 ps. A dominant TSC peak observed at Ϸ500 K has been also investigated and has been resolved into four components with activation energies of the order of 1 eV and cross sections in the range 10 Ϫ19-10 Ϫ17 cm 2. Three of these levels exhibit a fast capture rate ͑0.1-10 ns͒ in spite of their small cross sections, due to their high concentration in the investigated sample. Correlating our results with room temperature charge collection studies, we propose that the observed traps with their fast capture rates can be effective in limiting the carrier lifetimes and, consequently, the charge collection efficiency of CVD diamond particle detectors

Improvement of the dosimetric properties of chemical-vapor-deposited diamond films by neutron irradiation

“…A detailed investigation revealed that this dominant feature is due to the emission from different deep levels. 11 At least four components are needed to fit the experimental results. The best fit is obtained using four deep levels ͑Nos.…”

Temperature-dependent hole detrapping for unprimed polycrystalline chemical vapor deposited diamond

“…A wide range of deeper levels has been reported, including Gonon et al 4 and Hearne et al, 5 who reported activation energies of 1.86 and 1.1 eV, respectively, measured using thermally stimulated current technique ͑TSC͒. Bruzzi et al 6 reported a variety of defect levels in electronic-grade polycrystalline CVD diamond, with activation energies in the range 0.3-1.5 eV, observed using both TSC and PICTS. Alpha particle response measurements are a powerful technique to separate the charge transport and carrier lifetimes of electrons and holes.…”

Zero-bias operation of polycrystalline chemically vapour deposited diamond films for Intensity Modulated Radiation Therapy

“…It was shown that an improved stability can be obtained by pre-irradiating the pCVD diamond films with a high fluence of fast neutrons [10], the method was demonstrated capable of improving the performance of low-to-medium crystalline quality pCVD diamond dosimeters to the level of the highest-purity pCVD diamond films [11]. Nonetheless, it is well known that in this high-quality material there is still a significant amount of native deep and shallow defects, which can be active at room temperature for trapping charges, thus affecting the stability of response of the devices [12]. A study recently performed on pCVD detectors based on state of-the-art polycrystalline diamond films demonstrated that this high quality pCVD diamond is still unsuitable for IMRT applications [9].…”