Multistrip synthetic single-crystal-diamond photodiode based on a p-type/intrinsic/Schottky metal transverse configuration

A synthetic multistrip single-crystal-diamond detector based on a p -type/intrinsic diamond/Schottky metal transverse configuration, operating at zero-bias voltage, was developed. The device was characterized at the Diamond Light Source synchrotron in Harwell (UK) under monochromatic high-flux X-ray beams from 6 to 20 keV and a micro-focused 10 keV beam with a spot size of ~3 μm . No significant pixel-to-pixel variation of both spectral responsivity and time response, high spatial resolution and good signal uniformity along each strip were found, suggesting the tested device structure as a promising sensor for X-ray and UV radiation imaging

Polycrystalline diamond detectors - compared with silicon X-ray dosimeters for clinical use

Physical and metering characteristics of three room temperature X-ray dosimeters used in clinical applications, PTW diamond, Thompson MOSFET and Scanditronix silicon diode are compared with polycrystalline diamond X-ray detectors. Development of dosimeters based on natural diamond carried out by PTW have provided superior characteristics with respect to other solid state silicon devices such diodes or MOSFETs. Radiation hardness, soft tissue equivalence, lack of toxicity, negligible energy dependence and optimal sensitivity and reproducibility, have made PTW the ideal metering device for clinical dosimetry. However general use of natural dosimeters have been hindered by their rarity, very high cost and unpredictable electronic behavior due to lack of control on impurity content and crystal defects. Therefore, there have been a growing use of silicon dosimeters especially for on line configuration and in vivo dosimetry. However, both MOSFET and silicon diode do not appear to be ideal for such application for their short lifetime. Detectors based on polycrystalline diamonds seem to be the best candidate for future dosimetry since they have most of the characteristics of natural diamonds at potentially much lower cost. In this context, the performances of a laboratory made polycrystalline diamond device are compared to those of the three, PTW, Scanditronix and Thomson commercial dosimeter

X ray diamond 2D array

X-ray 2D array detectors based on polycrystalline diamond have been fabricated and tested in the dark and under low energy X-ray beams, as well as under UV laser pulses. Depending on the metallic contacts distance or crossover-area, each pixel exhibit low dark current values down to 2 pA and light to dark current ratio as large as 20 when biased at 50 V. The intensity dependence of X-ray photocurrent, as measured for different thickness of Al absorbers, changes according the square root of the beam intensity, thereby suggesting a good crystalline quality of the used diamond slab. A similar behaviour is found when UV laser pulses of high energy are used for device irradiation. At lower energies, a larger photocurrent change with the beam intensity is found, eventually becoming a linear dependence. Such a result confirms the expected good diamond sample quality and suggests a device use for X-ray beam profiler with a large dynamics. The diamond sample and detector uniformity has been also tested under UV laser pulses. The observed pixel response uniformity further support the possible device application as image senso

Optoelectronic Cellular Neural Network Based on Amorphous Silicon Thin Film Technology

In this paper, hardware realization of Cellular Neural Networks in amorphous silicon thin film technology is proposed. In this way, it is possible to realize inexpensive large-scale, easily programmable circuits, with integrated light-sensing and-emitting devices. 1. Introduction Hardware implementation of Cellular Neural Networks (CNN) [1] is necessary to take full advantage of this parallel analog computing paradigm. Much research has been carried out to this purpose, and prototypes of special-purpose CNNs, and of the CNN Universal Machine [2], have been or are currently being tested. Most projects are based on VLSI realization, while some employ optical processing. In order to envision large scale application of CNNs as fast and inexpensive image processing devices, it is desirable to build large arrays of cells, so as to have one cell per pixel (no multiplexing). This requirement is already conflicting with maximum chip dimension in VLSI. Moreover, in most projects presented to d..

Diamond microstrip detector for deep UV imaging

CVD diamond detectors with metal diamond metal (MDM) microstrip structures have been constructed and characterized for image sensor and large area applications. These sensors are suitable for UV and soft X-ray detection. The device photoelectrical characterization under deep UV (k=193 nm) laser pulses has been performed both on the nucleation and growth sides of a diamond slab, by varying bias voltage, contacts interspacing and light intensity. Such a characterization was also performed on a laser-smoothed part of the growth side. Reflecting the true electronic quality, largely different photocurrent peak shapes were detected on the untreated and laser-treated parts of the growth side, as well as on the nucleation side. Pulse amplitude and duration appear to decrease according to the different defect density value, which turns out to be larger on the laser-treated growth side of the diamond slab. Independent of pulsed illumination intensity, a linear photoresponse increase with the applied electric field is found in the range 10 1 –10 4 V/cm. Depending on the defect density value, the photocurrent versus pulse energy changes according to a different power law, the linear dependence extending into a wider pulse energy range when larger defect densities are involved. Such a characteristics is also a figure of the wide signal dynamics. The sensor uniformity has been also tested both on as grown and laser-treated surface, as well as on the nucleation side surface where a linear signal increase has been found by adding adjacent strips connected in parallel. These results suggest the suitability of the sensor for image acquisition