A single-crystal diamond X-ray pixel detector with embedded graphitic electrodes

Abstract

The first experimental results from a new transmissive diagnostic instrument for synchrotron X-ray beamlines are presented. The instrument utilizes a single-crystal chemical-vapour-deposition diamond plate as the detector material, with graphitic wires embedded within the bulk diamond acting as electrodes. The resulting instrument is an all-carbon transmissive X-ray imaging detector. Within the instrument's transmissive aperture there is no surface metallization that could absorb X-rays, and no surface structures that could be damaged by exposure to synchrotron X-ray beams. The graphitic electrodes are fabricated in situ within the bulk diamond using a laser-writing technique. Two separate arrays of parallel graphitic wires are fabricated, running parallel to the diamond surface and perpendicular to each other, at two different depths within the diamond. One array of wires has a modulated bias voltage applied; the perpendicular array is a series of readout electrodes. X-rays passing through the detector generate charge carriers within the bulk diamond through photoionization, and these charge carriers travel to the nearest readout electrode under the influence of the modulated electrical bias. Each of the crossing points between perpendicular wires acts as an individual pixel. The simultaneous read-out of all pixels is achieved using a lock-in technique. The parallel wires within each array are separated by 50 µm, determining the pixel pitch. Readout is obtained at 100 Hz, and the resolution of the X-ray beam position measurement is 600 nm for a 180 µm size beam.

Ultrafast Laser Processing of Diamond Materials: A Review

“…The obtained results were reproduced by multiple measurements [63]. Determining of the barrier potential could be a very important factor for the characterization of graphite wires fabricated by emerging methods, such as the use of Bessel beams [64] as well as for the design of wire junctions [65,66] or gaps in the conductive network [67].…”

Barrier potential for laser written graphitic wires in diamond

“…Evaluation of the barrier potential will be an important factor when characterising new schemes for laser processing wires, such as the use of Bessel beams [25,26]. The barrier potential is also a highly relevant consideration as more complicated device architectures utilising laser written wires in diamond start to emerge, with designs comprising wire junctions [27] and intentional gaps in the conductive network [28].…”

Laser-Induced Graphitization of Diamond Under 30 fs Laser Pulse Irradiation

“…The degree of laser-induced graphitization from a sp 3 -bonded to a sp 2 -bonded carbon fraction in a single crystal chemical vapor deposited (CVD) diamond under varying fluence of an ultrashort pulsed laser (30 fs, 800 nm, 1 kHz) irradiation has been studied. The tetrahedral CVD sp 3 phase is found to transition to primarily an sp 2 aromatic crystalline graphitic fraction below the critical fluence of 3.9 J/cm 2 , above which predominantly an amorphous carbon is formed. A fractional increase of fluence from 3.3 to 3.9 J/cm 2 (∼20%) results in a substantially (∼3-fold) increased depth of the sp 2 graphitized areas owing to the nonlinear interactions associated with a fs laser irradiation.…”

“…H ighly localized and geometrically confined structural transformations in diamond with intrinsic sp 3 diamond's tetrahedral phase converted into an sp 2 -rich graphitic fraction employing a laser light have been shown to significantly enhance light absorption in the irradiated areas and to open a new avenue for the emerging opto-photonic applications, including miniaturized thermionic solar cells, 1 broad-beam light detectors, 2,3 and most recently, robust broad-beam polarization filters for infrared (IR) applications. 4 These applications, however, may only become technologically accomplishable once the thermal stresses associated with laser processing and the formation of sp 2 fraction on the surface or in the bulk of the diamond crystal, are minimized while remaining spatially confined.…”