The role of charge trapping at grain boundaries on charge transport in polycrystalline chemical vapor deposited diamond based detectors

Abstract

We report a detailed investigation of the trapping and release of charge carriers from grain boundaries in polycrystalline diamond grown by chemical vapor deposition (poly-CVD). A model for charge trapping and release is presented for samples which display very different bulk characteristics as determined by photoluminescence, dark conductivity, and thermally stimulated current measurements. Experimental studies were performed as a function of temperature and applied electric field using ion beam induced charge to map the charge collection efficiency of charge induced by a scanned, focused, 2MeV He+ microprobe. Even though the carrier velocity and charge collection efficiency should begin to saturate at electric fields above 1×104V∕cm, the efficiency was found to increase by a factor of 3 when the electric field is increased to greater than 1×105V∕cm. A model based on the localized enhancement of the electric field caused by trapped charge at grain boundaries is found to account for this unexpected result. Further, we find that this localized variation in electric field strongly affects charge transport in poly-CVD diamond and is therefore an important consideration for optimizing detector performance.

A review of ion beam induced charge microscopy

“…The uniformity of charge response, temperature-dependent emptying of grain-boundary charge traps and the role of charge trapping at grain boundaries in CVD diamond [66][67][68] as well as polarisation and priming effects have been successfully investigated by IBIC, often in combination with other techniques, as PIXE [69], ion beam induced luminescence (IBIL) [70,71] or X-ray induced charge (XBIC) or light (XBIL) collection [72], providing valuable insights for the development of diamond detectors for tracking applications and for dosimetry [69]. Reviews of various IBIC applications in detectors and wide band gap semiconductors are given in [73,74].…”

Mapping of polarization and detrapping effects in synthetic single crystal chemical vapor deposited diamond by ion beam induced charge imaging

“…Recent IBIC studies of polycrystalline diamond detectors at elevated temperatures up to 600 K suggest that space charge and thus polarization effects concentrated at grain boundaries are reduced at higher temperatures leading to a more homogenous detector response. 47 Although the performance of the sample studied in this work is expected to be affected by the nitrogen impurities which had been introduced on purpose, intrinsic space charge ͑internal fields 19 ͒ and polarization effects 48 have also been found by other groups in single crystal diamonds grown by the same company; but more recent results suggest that these internal space charges and/or polarization may not occur in more recently produced highest quality material, also synthesized by Element Six Ltd. 49 The 10%-90% rise time image extracted from the digital IBIC data acquired simultaneously to the data shown in Fig. 8͑b͒ at +30 V is displayed in Fig.…”

Boron-doped diamond nano microelectrodes for biosensing and in vitro measurements

“…The atomic concentration ratio can be estimated from the peak area and the sensitivity factor of the atoms assigned from XPS (90, 91). Additionally, scanning tunneling microscopy (STM) (92), 11 B NMR (93, 94), secondary ion mass spectrometry (SIMS) (95), cathodoluminescence (95–98), and chemiluminescence (82, 99, 100) are also used for characterization of BDD thin films.…”