ABSTRACT Diamond exhibits high interests for the fabrication of radiation detection devices. Conventional detectors relay on planar electrode geometries. However, the usefulness of 3D geometries for radiation detectors has been well... more
ABSTRACT Diamond exhibits high interests for the fabrication of radiation detection devices. Conventional detectors relay on planar electrode geometries. However, the usefulness of 3D geometries for radiation detectors has been well investigated e.g. on silicon. In such a configuration the distance between buried electrodes does not depend on the sample thickness, enabling higher electric fields (for a given applied bias voltage), thus faster drift velocities, shorter drift path of charge carriers, and improved detection performances. Here, for the first time we demonstrate the interests of the fabrication of a 3D diamond detector prototype made of single crystal CVD diamond. The conductive graphitic micro-channels have been fabricated within the diamond bulk using a UV laser (337 nm) with a dedicated focusing system. The graphite-diamond phase transformation has been characterized with micro-Raman 2D mapping. The strain formation in the vicinity of the channels has been studied using birefringence microscopy. After metal plating and inter-connecting of the channel matrices, the electronic properties of the 3D prototypes have been evaluated, including: current-voltage, transient-current, and charge collection efficiency characteristics under particle and photon beams e.g. synchrotron micro beam. The results show that the fabrication of such an efficient 3D diamond detector is of high interests and opens up new possibilities for radiation detectors for extreme applications.
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Pour stimuler electriquement une structure nerveuse, notamment la retine, l'implant comprend un substrat electriquement isolant (1), un reseau de cavites (2) formees dans une surface superieure du substrat, des electrodes de... more
Pour stimuler electriquement une structure nerveuse, notamment la retine, l'implant comprend un substrat electriquement isolant (1), un reseau de cavites (2) formees dans une surface superieure du substrat, des electrodes de stimulation (3) disposees au fond des cavites, et une couche electriquement conductrice formant un plan de masse (4) en partie superieure des cavites. Les dimensions des cavites et des electrodes de l'implant peuvent etre dimensionnees pour maximiser la selectivite spatiale du courant de stimulation applique a la structure nerveuse.
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We report on the development of sensor arrays comprising synthetic boron doped diamond (BDD) electrodes modified with metal catalyst nanoparticles. The latter are deposited onto the BDD electrodes surface by a physical vapor deposition... more
We report on the development of sensor arrays comprising synthetic boron doped diamond (BDD) electrodes modified with metal catalyst nanoparticles. The latter are deposited onto the BDD electrodes surface by a physical vapor deposition process followed by de-wetting under oxygen-free atmosphere in high temperature conditions. The mean size of the particles is in the order of 10 nm, as characterized by scanning electron microscopy (SEM) image processing and small-angle X-ray scattering (SAXS). The particles are made of e.g. platinum, iridium, gold, ruthenium or alloys thereof and showed good adhesion, and good electrochemical reactivity towards a wide range of redox analytes. Sensor arrays composed of 4 BDD electrodes each modified with a different nano-catalyst were mounted and tested for various analytical applications. For instance such a sensor array was able to detect online and discriminate the presence in tap water of the following contaminants: Imidacloprid, Dimethyl methylph...
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In this work, we investigate a novel approach to prepare high-performance alpha-particle solid sources fabricated on diamond thin support layers, offering the properties of diamond such as a low-Z material with corrosion and mechanical... more
In this work, we investigate a novel approach to prepare high-performance alpha-particle solid sources fabricated on diamond thin support layers, offering the properties of diamond such as a low-Z material with corrosion and mechanical hardness. As-prepared solid sources onto boron-doped-diamond (BDD) substrate exhibited high performance of the autoradiography and spectroscopic resolution at the level of other more conventional materials such as stainless steel. A straightforward precipitation process in the Na2SO4 or NaNO3 simple electrolytes under mild experimental conditions with a low current of several mA.cm−2 were successfully developed onto BDD substrates for deposition of single 241Am as well as 239Pu, 241Am, and 244Cm mixed radionuclides. The results demonstrate that solid sources deposited onto such BDD substrates can match the performance of those prepared onto stainless steel substrates with excellent uniformity and high-resolution spectroscopy, together combining the ro...
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Vulnerability of drinking water distribution systems which would have major public health, economic and psychosocial consequences, has become a big concern to governmental agencies and water supply authorities. In case of an extremely... more
Vulnerability of drinking water distribution systems which would have major public health, economic and psychosocial consequences, has become a big concern to governmental agencies and water supply authorities. In case of an extremely alerting situation, such as Fukushima, the alpha emitters in water are probed on samples after very long chemical operations and time for the delivery of results extends over several days. The main objective of the ActiFind project is the realization of a high sensitivity alpha particles sensor working into water for the rapid detection and identification of traces of actinides at the 1 Bq/L level, after a short electro precipitation step. A 200 μm thick BDD layer is deposited on a CANBERRA PIPS detector. Under low cathodic current density, nitrate reduction occurs and produces a layer of (OH-) at the BDD surface and solid actinides hydroxides are accumulated at the entrance window of the PIPS sensor. After deposition, the ActiFind sensor is directly connected to a spectrometry chain. The coupling of the system to an integrated microfluidic F.F.E. platform has been developed in order to render the system compatible with more complex aqueous solutions in real environments containing interfering ions or substances. Further extension of the system will explore the possibility to use it as a decontaminating system on a scale up basis. The ability to perform alpha spectrometry directly in liquid media at trace levels constitutes a real breakthrough. Bq/L range is reachable within 10 minutes, opening the field to the development of a portable system with low energy requirement, and enabling real time monitoring of media at risk. This new technology can be used in the analysis of water used for cleaning surfaces in fuel reprocessing plants, sampling of environmental water around waste storage facilities, analysis of water samples after a nuclear accident or in the Mining sector where water quality should be assessed in the surrounding area.
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:Boron Doped Diamond (BDD) electrodes exhibit excellent properties including a wide potential window in aqueous media, high corrosion resistance, chemical inertness, bio-compatibility and low background current. In order to increase their... more
:Boron Doped Diamond (BDD) electrodes exhibit excellent properties including a wide potential window in aqueous media, high corrosion resistance, chemical inertness, bio-compatibility and low background current. In order to increase their selectivity for analytical applications, several studies were carried out recently on the possibility to deposit metal nanoparticles such as Pt or Ir on such BDD electrodes1,2,3,4. Indeed these nanoparticles bring interesting electro-catalytic properties to the electrodes, thus offering the possibility to address new analytes. Here an electrode array was developed, based on multiple BDD electrodes casted with various metal nanoparticles. The simultaneous detection of analytes by each electrode composing the array gives potentially a unique fingerprint to the analytes, thus increasing the specificity and the selectivity of the sensor.
Research Interests: Materials Science and MRS
Boron delta-doping of diamond has appeared as a promising viable approach for the fabrication of high performance RF power transistors taking advantage of diamond properties. Here structures based on p-/p+/p- multilayers were synthesised... more
Boron delta-doping of diamond has appeared as a promising viable approach for the fabrication of high performance RF power transistors taking advantage of diamond properties. Here structures based on p-/p+/p- multilayers were synthesised on (100) HPHT Ib substrates using MPCVD. An original gas injector system was developed enabling to significantly improve the sharpness of both interfaces between p+ and p- layers with a good reproducibility. SIMS profiles recorded on the doping transients still demonstrate an asymmetry of the interface sharpness from 7nm/decade to 2nm/dec on the p-/p+ and the p+/p- interfaces, respectively. The observed differences are here explained and confirmed experimentally, and result from the combination of ion mixing with the effect of the surface roughness, thus limiting the SIMS resolution in depth. The MRI (Mixing Roughness Information) model then allows to evaluate the real value of the delta thickness achievable using this technique to 7 nm and the negative and positive gradients to identical values, namely of 1.4 nm/dec.
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Diamond is a resilient material with rather extreme electronic properties. As such it is an interesting candidate for the fabrication of high performance solid state particle detectors. However, the commercially accessible form of... more
Diamond is a resilient material with rather extreme electronic properties. As such it is an interesting candidate for the fabrication of high performance solid state particle detectors. However, the commercially accessible form of diamond, grown by chemical vapour deposition (CVD) methods, is polycrystalline in nature and often displays rather poor electrical characteristics. This paper considers ways in which this material may be used to form alpha particle detectors with useful performance levels. One approach adopted has been to reduce the impurity levels within the feed-stock gases that are used to grow the diamond films. This has enabled significant improvements to be achieved in the mean carrier drift distance within the films leading to alpha detectors with up to 40% collection efficiencies. An alternative approach explored is the use of planar device geometries whereby charge collection is limited to the top surface of the diamond which comprises higher quality material than...
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Surface electronic states of the partially hydrogenated diamond C(100)-(2×1):H surface were studied by near-edge x-ray absorption fine structure and C 1s core level photoemission. Partially hydrogenated surfaces were prepared by... more
Surface electronic states of the partially hydrogenated diamond C(100)-(2×1):H surface were studied by near-edge x-ray absorption fine structure and C 1s core level photoemission. Partially hydrogenated surfaces were prepared by synchrotron irradiation of the monohydride-terminated surface or by hydrogen adsorption on the clean surface. A new surface core-exciton state produced at a photon energy of 282.5 eV has been assigned
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This paper presents an autonomous instrument based on an array of 8 MEMS micro cantilevers for gas sensor application. The main contribution of this system to the MEMS domain lies on the way the micro cantilevers are optimally exposed to... more
This paper presents an autonomous instrument based on an array of 8 MEMS micro cantilevers for gas sensor application. The main contribution of this system to the MEMS domain lies on the way the micro cantilevers are optimally exposed to a constant gas flow in a gas cell where the electrical connections to the sensors are done without any wire-bonding. Sensors can therefore be easily changed for another application or for maintenance. Moreover, this complete and autonomous system is able to extract in real time (1 reading/sec) the frequency response of all the MEMS cantilevers by using an innovative mixed-signal processing circuit featuring self-diagnostic and automatic-calibration. Other novelties are the simultaneous piezo-electric excitation of the sensor-array, a low-noise polarization circuit and the detection circuit optimized for piezo-resistive micro cantilevers. From a system point of view this instrument provides the ability to monitor the frequency profiles of an array of resonant gas sensors.
Research Interests: Engineering and IEEE
The publisher regrets p 98,“The electrode yield, i.e. the fraction of electrodes produced with a continuous conducting path over the thickness of the diamondsample, was estimated by optical and electrical inspection and found to... more
The publisher regrets p 98,“The electrode yield, i.e. the fraction of electrodes produced with a continuous conducting path over the thickness of the diamondsample, was estimated by optical and electrical inspection and found to be9273%.”(Was“9270.3%”) p101, Figure 8 of the paper misses the legend, corrected figure: p103, Figure 13b) of the paper misses 3 blue bin entries (corner bins) of the four, only one entry is visible.
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We describe here a new approach for the detection and identification of actinides (Am, Pu, Cm etc) at very low activity levels in aqueous solution. The measurement consists at first in the electroprecipitation of the actinides ions as... more
We describe here a new approach for the detection and identification of actinides (Am, Pu, Cm etc) at very low activity levels in aqueous solution. The measurement consists at first in the electroprecipitation of the actinides ions as insoluble hydroxides directly onto a boron doped nanocrystalline diamond (BNCD) electrode deposited on an α-particle detector (Si or Si-PIN diode), followed by α-particles detection using frontend nuclear electronics. After α-particles counting, spectrometry, the detector can be easily decontaminated using anodization in aqueous solution to be able to be reused at once. The detection limit of the described prototype system can be estimated as low as a few mBq/L (for one day counting) to several mBq/L for 5h counting and currently achieved energy resolution amounts to ΔEFWHM/Eα = 2.3% for pulse height spectra of 5.486 MeV α-particles emitted by 241Am, measured directly in water.
We describe here a new approach for the detection and identification of actinides (Am, Pu, Cm etc) at very low activity levels in aqueous solution. The measurement consists at first in the electroprecipitation of the actinides ions as... more
We describe here a new approach for the detection and identification of actinides (Am, Pu, Cm etc) at very low activity levels in aqueous solution. The measurement consists at first in the electroprecipitation of the actinides ions as insoluble hydroxides directly onto a boron doped nanocrystalline diamond (BNCD) electrode deposited on an α-particle detector (Si or Si-PIN diode), followed by α-particles detection using front-end nuclear electronics. After α-particles counting, spectrometry, the detector can be easily decontaminated using anodization in aqueous solution to be able to be reused at once. The detection limit of the described prototype system can be estimated as low as a few mBq/L (for one day counting) to several mBq/L for 5h counting and currently achieved energy resolution amounts to ΔEFWHM/Eα = 2.3% for pulse height spectra of 5.486 MeV α-particles emitted by 241Am, measured directly in water.
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We report on the development of detection devices enabling the direct activity monitoring of liquid sources containing alpha emitters, with interests for nuclear waste process monitoring. The devices rely upon the use of a synthetic... more
We report on the development of detection devices enabling the direct activity monitoring of liquid sources containing alpha emitters, with interests for nuclear waste process monitoring. The devices rely upon the use of a synthetic diamond active layer, used for detection, a material being totally inert and not affected by its direct contact with the corrosive media used here (concentrated HNO3, typ. 1M). Those devices convincingly passed all preliminary tests as reported here and were produced at a very small scale for measurements in a reprocessing nuclear plant.
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CVD diamond is a remarkable material for the fabrication of radiation detectors. The radiation hardness, chemical resistance and high-temperature operational capabilities of diamond motivate its use in the fabrication of devices operating... more
CVD diamond is a remarkable material for the fabrication of radiation detectors. The radiation hardness, chemical resistance and high-temperature operational capabilities of diamond motivate its use in the fabrication of devices operating in hostile environments such as those encountered in the nuclear industry and high-energy physics. Synthetic diamond can be grown using the microwave plasma-enhanced chemical vapour deposition technique. However,
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ABSTRACT
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There is a growing interest in the deposition and processing of thin films at low temperatures to eliminate the inherent problems associated with high temperature processing. Photo enhanced processing is one of the techniques which has... more
There is a growing interest in the deposition and processing of thin films at low temperatures to eliminate the inherent problems associated with high temperature processing. Photo enhanced processing is one of the techniques which has received considerable interest. One of the major limitations of photo processing is the lack of sufficiently intense ultra-violet (UV) sources. To date the low pressure Hg lamp has been the only available source for large area UV processing and this has limited the types and quality of films deposited.In this paper we will outline the design of a novel, variable wavelength excimer discharge lamp which can be used for depositing thin films over large substrate areas. We shall also discuss the direct (i.e. without intermediate photosensitisation reactions) photo induced deposition of thin silicon dioxide films using SiH4 and N2O which are photo dissociated by 126nm photons generated by the excimer lamp described.
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ABSTRACTThe methane effects on nucleation and growth of diamond during bias enhanced nucleation treatment have been studied on 3C-SiC (100) surfaces. At low methane concentration of 1%, no diamond nucleation was observed, whether at 3 %,... more
ABSTRACTThe methane effects on nucleation and growth of diamond during bias enhanced nucleation treatment have been studied on 3C-SiC (100) surfaces. At low methane concentration of 1%, no diamond nucleation was observed, whether at 3 %, nucleation density values as high as 4×1010/cm2 were reached. A further increase of the methane concentration up to 5% induces a significant enhancement of the diamond nucleation density that was observed only slightly higher at 7×1010/cm2. Moreover, the Field Emission Gun Scanning Electron Microscopy (FEG-SEM) pictures well emphasized that the methane content affects both the nucleation and growth mechanisms.
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ABSTRACT Focused and linear-antenna microwave plasma reactors are used to grow undoped nanocrystalline diamond (NCD) thin films with grain sizes of 30–300 nm on glass. The surface chemical affinity of each NCD film type is investigated by... more
ABSTRACT Focused and linear-antenna microwave plasma reactors are used to grow undoped nanocrystalline diamond (NCD) thin films with grain sizes of 30–300 nm on glass. The surface chemical affinity of each NCD film type is investigated by X-ray photoelectron spectroscopy and water contact angle measurements after the surface treatments. The samples were treated by plasma process using hydrogen, oxygen, NH3, and CF4 gases or by wet chemical oxidation in boiling acids. X-ray photoelectron spectroscopy and water contact angle measurements reveal that the surface of NCD films grown by linear-antenna plasma with grain sizes 30 nm as well as 300 nm is functionalized in comparable (and sometimes even better) quality as the diamond films grown by the standard deposition process, i.e., by focused plasma. A monotonous trend of water contact angles as a function of treatment procedure is observed for all sample types allowing a controllable surface wettability in the range of 14°–99°. The degree of surface saturation by different moieties is discussed.
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ABSTRACT Excimer lamp deposited ultra-thin (< 250 angstrom) silicon dioxide and silicon oxynitride films were characterized using spectroscopic ellipsometry (SE) and Fourier transform infrared (FTIR) spectroscopy. SE analysis of... more
ABSTRACT Excimer lamp deposited ultra-thin (< 250 angstrom) silicon dioxide and silicon oxynitride films were characterized using spectroscopic ellipsometry (SE) and Fourier transform infrared (FTIR) spectroscopy. SE analysis of the photo-deposited SiO2 films revealed no variation in the refractive index (n) of the films for deposition temperatures of 200 degree(s)C and 300 degree(s)C. Using a Bruggeman effective medium approximation (EMA), SE analysis was employed to determine both the silicon oxynitride layer thicknesses and compositions as a function of deposition temperatures and gas ratio, defined as (N2O/(N2O + NH3)). From this analysis the optical properties of the silicon oxynitride thin films were extracted. It was observed that the refractive index for the 200 degree(s)C and 300 degree(s)C series of samples decreased from n equals 1.81 to 1.46 and n equals 1.72 to 1.46 respectively as a function of increasing gas flow ratio. FTIR analysis revealed spectral features characteristic of Si-O, Si-N, Si-H and N-H bonding. The most significant feature in all recorded spectra was a mixed spectral absorption band ranging from 800 cm-1 to 1300 cm-1. Both the integrated band area and peak wavenumber of this absorption band was found to be sensitive to the degree of nitridation and layer thickness of the thin films. The N-H stretching bond density was calculated from the N-H peak at 3360 cm-1 using appropriate calibration factors. A slight decrease in the N-H bond density with increasing gas flow rate was observed. This variation in bond density was significantly less than that observed for PECVD silicon oxynitride films.
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Single crystal (SC) CVD diamond is known to exhibit superior electronic properties than polycrystalline ones for detection applications. In our study, tested samples were grown using CVD in an ASTEX type reactor, at various microwave... more
Single crystal (SC) CVD diamond is known to exhibit superior electronic properties than polycrystalline ones for detection applications. In our study, tested samples were grown using CVD in an ASTEX type reactor, at various microwave powers and keeping all other parameters constant. The crystalline quality and purity of the samples were investigated using Raman spectroscopy and birefringence microscopy measurements.The diamonds layers were chemically cleaned and oxidized, towards ionization chamber fabrication using Ni and Au contacts for rectifying properties. The devices electronics and detection properties were then evaluated: leakage currents were probed from I(V) measurements and the contacts behavior were tested under 60Co source at various dose rates. Time Of Flight (TOF) and Charge Collection Efficiency (CCE) measurements were evaluated under an 241Am alpha source and enabled the measurement of the mobility, carrier diffusion lengths and lifetime as a function of the growth ...
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Diamond polycrystalline films synthesized by chemical vapor deposition techniques present interesting feature for laser spectroscopy due to several advantages arising from their optical, electronic, thermal and mechanical properties.... more
Diamond polycrystalline films synthesized by chemical vapor deposition techniques present interesting feature for laser spectroscopy due to several advantages arising from their optical, electronic, thermal and mechanical properties. Their wide transmission band from the far IR to the UV make them attractive as optical devices for high-power laser beam. Moreover, with a wide band gap, a short carrier lifetime and
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CVD diamond combines attractive properties for the fabrication of detection devices operating in specific environments. One problem that remains critical for device stability is the presence of defect levels that alter the detection... more
CVD diamond combines attractive properties for the fabrication of detection devices operating in specific environments. One problem that remains critical for device stability is the presence of defect levels that alter the detection performances, and the detection characteristics often appear as they are very depending on time, temperature, and history of the preceding irradiations.One issue we have proposed is to adapt one technique that is commonly used for time of flight spectroscopy in order to maintain a uniform electric field in the probed device, and based on the synchronisation of the device bias with the period of the excitation source. This can be applied to several types of detection applications, as long as we can rely on periodical triggering in order to synchronise the device polarisation. We apply it here to a LINAC electron accelerator used for photon pulse generation at the frequency of 25Hz. The result is a remarkable improvement of the performance of a polycrystal...
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ABSTRACTDiamond polycrystalline films have been synthesised using the Chemical Vapour Deposition (CVD) technique in order to fabricate new types of photo-detectors for the characterisation of x-ray light sources as encountered in... more
ABSTRACTDiamond polycrystalline films have been synthesised using the Chemical Vapour Deposition (CVD) technique in order to fabricate new types of photo-detectors for the characterisation of x-ray light sources as encountered in synchrotron experiments. Since diamond exhibits a low absorption to low energy x-ray photons, these devices allow beam position monitoring with very little beam attenuation at photon energies as low as 2 keV. We present here diamond based new devices for four different applications, including (i) semitransparent beam intensity and (ii) position monitors with high position resolution (< 2 µm), (iii) beam profile monitors with 20 µm pitch resolution, and (iv) ultra-fast diamond detectors (response time…
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ABSTRACT In small beam dosimetry, the detector has to be as close as possible to tissue equivalence and exhibit a small detection volume compared to the size of the irradiation field, because of the lack of lateral electronic equilibrium.... more
ABSTRACT In small beam dosimetry, the detector has to be as close as possible to tissue equivalence and exhibit a small detection volume compared to the size of the irradiation field, because of the lack of lateral electronic equilibrium. Characteristics of single crystal diamond (tissue equivalent material Z = 6, high density) make it an ideal candidate to fulfil most of small beam dosimetry requirements.Material and methodsWe developed a single crystal diamond dosimeter (SCDDo) with a small detection volume of 0.165 mm3. Basic SCDDo behaviours in large field were checked successfully: repeatability, dose linearity, dose rate dependence, energy dependence and long term stability. SCDDo lateral dose profile, depth dose curve and output factor (OF) measurements up to 6 × 6mm2 were performed for small photon beams with a micro-MLC m3 (BrainLab) attached to a Varian Clinac 2100C linear accelerator. These measurements were compared to different commercial detectors: a shielded silicon diode (Sun Nuclear EDGE), an unshielded silicon diode (PTW 60017), a PinPoint ionisation chamber (PTW 31014) and two natural diamond detectors (PTW 60003).ResultsIn small field dosimetry, SCDDo presents an excellent spatial resolution. Low energy dependence (1.2% between 6 MV and 18 MV photon beam) and dose rate dependence less than 1% from 0.53 to 2.64 Gy min−1 explain the good agreement between the SCDDo and the other detectors in depth dose curve measurements. OF values obtained with the SCDDo from 2 × 2 cm2 to 10 × 10 cm2 field sizes, show no significant differences as expected for these file sizes compared to the other devices. For the critical field size of 0.6 × 0.6 cm2, SCDDo exhibits the best result compared to the PinPoint ionisation chamber and to the EDGE diode that are known to respectively underestimate and overestimate OF values in small beam.Conclusion To our knowledge, this is the first study demonstrating the feasibility of diamond dosimeter for field size less than 1 × 1 cm2.
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ABSTRACT Synthetic diamond materials are currently attracting attention for applications such as thin films supercapacitors or medical implantable electrodes where chemically stable materials featuring high double layer capacitance as... more
ABSTRACT Synthetic diamond materials are currently attracting attention for applications such as thin films supercapacitors or medical implantable electrodes where chemically stable materials featuring high double layer capacitance as well as low electrochemical impedance are sought. Those properties may be reached with high aspect ratio diamond provided that current collection is done efficiently through the diamond layer. In this paper, we introduce a very novel material, namely SPDia™, based on boron-doped diamond grown on a highly porous polypyrrole scaffold prepared by chemical vapour deposition. This composite was first characterised by SEM and Raman spectroscopy to cheque the diamond crystallinity and the structural evolution of the polypyrrole during the CVD process. Then cyclic voltammetry and electrochemical impedance spectroscopy were performed to assess its electrochemical reactivity. It was found to exhibit remarkable properties, that include a large double layer capacitance with values reaching up to 3 mF cm−2 in aqueous LiClO4 and a low electrochemical impedance, thus highly competitive with respect to other nanostructured diamond materials as recently reported.
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ABSTRACT Diamond films are considered as superior dielectric in comparison to Si3N4 for MEMS applications. The present paper provides a detail characterization study of electrical properties of undoped microcrystalline diamond films... more
ABSTRACT Diamond films are considered as superior dielectric in comparison to Si3N4 for MEMS applications. The present paper provides a detail characterization study of electrical properties of undoped microcrystalline diamond films involving dc and charge/discharge transient analysis over a wide temperature range. The aim of the study is to provide a better insight on the physical mechanisms responsible for the charge injection and collection processes under different operation conditions applicable to MEMS capacitive switches.
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ABSTRACT This paper presents the electrical assessment and modeling of the discharge process in RF MEMS capacitive switches with nanocrystalline diamond dielectric film. The assessment is performed by taking into account the detailed dc... more
ABSTRACT This paper presents the electrical assessment and modeling of the discharge process in RF MEMS capacitive switches with nanocrystalline diamond dielectric film. The assessment is performed by taking into account the detailed dc electrical characterization of the dielectric film at different temperatures with the aid of metal–insulator–metal (MIM) capacitors fabricated on the same die. The model assumes screening of trapped charges through carriers that are injected from the bottom electrode, transported through grain boundaries and redistributed across the diamond film surface through the sp2 state of non-diamond carbon. Simulated data and experimental results are found to be in excellent agreement, clearly indicating that nanocrystalline diamond can be considered as a MEMS dielectric with predictable discharging process.
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ABSTRACTThis paper deals with a LT transport study in B-doped diamond. To understand the electrical transport in heavily B-doped diamond and the influence of disorder onto the electrical transport, we have prepared nanocrystalline and... more
ABSTRACTThis paper deals with a LT transport study in B-doped diamond. To understand the electrical transport in heavily B-doped diamond and the influence of disorder onto the electrical transport, we have prepared nanocrystalline and epitaxial B-doped diamond films at CEA Saclay. The transport properties of these layers have been studied at the Institute of Physics Czech Academy of Sciences in Prague. It has been found that our B-doped nanocrystalline diamond exhibits also the SC transition, similarly as the original Russian work done on HPHT polycrystals or single crystal diamond. Additionally, the properties of (111) epitaxial films are discussed.
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ABSTRACT In the framework of nuclear waste management, minor actinides could be incinerated in subcritical reactors driven by an accelerator coupled to a spallation target. For safety reason, this so-called Accelerator-Driven System (ADS)... more
ABSTRACT In the framework of nuclear waste management, minor actinides could be incinerated in subcritical reactors driven by an accelerator coupled to a spallation target. For safety reason, this so-called Accelerator-Driven System (ADS) requires on-line and robust core reactivity monitoring. In such a system, a simple proportional relationship exists between the reactivity and the ratio of the beam current to the thermal power of the reactor core. This relationship is planned to be exploited as a relative reactivity indicator by the measurement of both the beam current delivered by the accelerator and the core neutron flux. The GUINEVERE experiment facility, which is being built at SCK-CEN in Mol (Belgium), will be devoted to the study of such reactivity measurement techniques. This zero power experiment will consist of the coupling of a subcritical fast core to an external source of 14-MeV neutrons originating from fusion reactions between a deuteron beam and a tritium target. In this case, the target evolution over time and target inhomogeneities preclude from using the beam current for reliable reactivity monitoring and therefore the external neutron source intensity must be monitored directly. This paper presents the systems envisioned to achieve such a monitoring and the results of test experiments.
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We have fabricated Silicon-On-Diamond (SOD) substrates on which, for the first time, we integrated n and p Fully Depleted MOSFETs high-K/metal gate down to 200 nm gate length. The devices show excellent electrical characteristics and a... more
We have fabricated Silicon-On-Diamond (SOD) substrates on which, for the first time, we integrated n and p Fully Depleted MOSFETs high-K/metal gate down to 200 nm gate length. The devices show excellent electrical characteristics and a 57% improvement of the thermal resistance compared to the co-processed one on standard SOI.
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ABSTRACTDue to its radiation harness, single crystal CVD diamond is a remarkable material for the construction of detectors used in hadron physics and for medical therapy. In this work, single crystal CVD diamond plates were grown in a... more
ABSTRACTDue to its radiation harness, single crystal CVD diamond is a remarkable material for the construction of detectors used in hadron physics and for medical therapy. In this work, single crystal CVD diamond plates were grown in a microwave plasma reactor, using home design substrate holder and a relatively high pressure. Optical Emission Spectroscopy was employed during the MW-PECVD growth to characterize excited species present in the plasma and to detect the presence of residual gases such as nitrogen which is unsuitable for detector's applications.The samples were characterized using various methods such as Raman spectroscopy, photoluminescence (PL), photocurrent spectroscopy, Raman mapping, birefringence microscopy, optical microscopy and also AFM. The best sample, exhibits a FWHM for the 1332 cm−1 Raman peak about 1.6 cm−1. Room temperature PL spectra showed no N–related luminescence, confirming the high quality of the grown single crystal diamond.
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The chemical stability of three heterosubstrates (Si, 3C-SiC and iridium) has been studied using the same MPCVD reactor during the successive steps of BEN process. An in situ sequential approach allows a monitoring of the chemical... more
The chemical stability of three heterosubstrates (Si, 3C-SiC and iridium) has been studied using the same MPCVD reactor during the successive steps of BEN process. An in situ sequential approach allows a monitoring of the chemical modifications induced by interactions between plasma and surfaces. Contrary to silicon, 3C-SiC and iridium underwent weak surface evolutions during BEN. This leads to favourable conditions for the interface formation in agreement with the better Highly Oriented Diamond films reported in the literature. A short description of the nucleation pathways identified for each heterosubstrate is also presented.