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1 Diamond particle detectors for high energy physics

G. Chiodini

Istituto Nazionale di Fisica Nucleare Via Arnesano 73100, Lecce - Italy gabriele.chiodini@le.infn.it, tel. 0832-297460

Abstract

In this last decade, synthetic poly crystal diamond features:

reproducible high quality, high radiation tolerance, and wafer size availability, making diamond an attractive sensor material in harsh radiation environment, like in the next generation of high luminosity collider experiments.

Nevertheless, to make diamond sensors a viable and alternative solution to advanced radiation hard silicon sensors, the technological effort and costs must be affordable and a state-of-the-art low noise electronics must be used to cope with the low intrinsic signal.

Introduction

In the nineties, a systematic R&D program started to investigate the radiation detection properties of artificial diamond produced by Chemical Vapor Deposition (CVD) techniques. The main goal was to prove the expected radiation hardness as required by vertex detectors placed near the interaction region for Large Hadron Collider (LHC) experiments at CERN.

Nevertheless, the modest and not uniform Charge Collection Efficiency (CCE) of poly crystal CVD diamond (pCVDD) jeopardizes the stringent requirements for tracking application on minimum ionizing particle detection efficiency and track spatial resolution. This is related to the charge trapping centers associated to the small size grain boundaries which also modify the effective response due to charge trapping dynamics.

Anyway, it was soon clear that CVD diamond could be used as radiation and nuclear sensors with unique features (see Table 1) in several scientific and technical fields [1]. Diamond sensors were successfully employed where the signal is not a concern but radiation tolerance and fast response are mandatory. These applications are mainly heavy ions detection (see GSI experiments at Darmstadt in Germany) and beam or X-ray monitoring (intense synchrotron light, FEL, and inertial fusion sources).

Since 1995, the CERN RD42 collaboration worked closely with De Beer Industrial Diamonds in UK (now named Element Six Ltd.) to improve Charge Collection Distance (CCD) and uniformity response of industrial poly crystal CVD diamond, reaching in about 10 years the goal to have more than 7000 electrons of collected charge signal across an entire free standing 4-inch diameter wafer [2]. The Element Six Ltd.

is almost the unique worldwide detector grade diamond supplier, producing the highest quality CVD diamond, with the exclusive distributor being Diamond Detector Ltd. in UK.

Another industrial supplier is Diamond Materials in Germany and several scientific groups all around the world are engaged in diamond production and research as well.

Property Diamond (Si) Comment Density [g/cm3] 3.52 (2.33)

Atomic number 6 (14) Tissue eq.

Band gap[eV] 5.5 (1.12) Solar blind Displ. [eV/atom] 43 (13-20) Rad-hard Dielectric constant 5.7 (11.9) Low noise

Resistivity [Ωcm] >1011 (2x105) No dark I Thermal [W/cmK] 24 (1.5) Room T Breakdown [V/cm] 107(3x105)

Saturated ve [km/s] 270 (100) Fast signal Energy/e-h [eV] 13 (3.6)

MIP[e-h/µm] 36 (89) Low signal Rad. length[cm] 12.2 (9.4) Less M.S.

Table 1: CVD Diamond outstanding properties compared with silicon material, the main competitor. In the last column comments on benefits or disadvantages.

In 2002, un-doped and ultra-pure single-crystal diamond was also produced by omoepitaxy from a seed of special oriented HPHT (High Pressure High Temperature) single crystal diamond. The single crystal CVD diamond (sCVDD) has exceptional charge collection properties and features very good energy resolution and tracking capability [3]. Real devices for alpha, gamma and neutron spectroscopy (like in fusion and fission reactors [4]), and pixelated beam monitoring (like the CMS Pixel Luminosity Telescope monitor upgrade [5]) are already envisioned in the next years.

The sCVD diamond is almost insensitive to polarization phenomena and has a uniform response, this is more and more true for pCVD diamond of increasing quality. These phenomena are less important in tracking applications, where minimum ionizing particle are detected, and their effects are mitigated by exposure to 1-10 kGray of X or beta rays (“pumping” or “priming”). They are instead crucial in radiation dosimeters, where the current response to the exposed radiation dose must be linear, fast, reproducible, and stable in time [6]. The sCVDD radiation dosimeters are already on the market and compete with natural gems, which must be carefully selected from thousands samples.

Anyway, due to its limited size, no more than 5 mm by 5 mm, and high cost, detector grade single crystal diamonds are confined to small area applications. Several methods are being developed to overcome the size limitations, for example

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bonding of cloned wafers into large mono-crystalline mosaics [7] and hetero-epitaxial CVD diamond growth on iridium substrates [8]. When such technological developments will be available, in a cost effective manner, the diamond sensor fields will strongly benefit. In the meantime, high quality poly crystal diamond is the only available practical solution where high performance and large size are necessary.

Two complementary and paradigmatic applications where single crystal diamond perform well, and likely better than silicon sensors, but inadequate for the small size, are: an ultra radiation hard pixel diamond vertex detector for the next generation of collider experiment and a pixelated radiation dosimeter for Intensity Modulated Radiation Therapy (IMRT).

How high quality poly crystal diamond can be made suitable for IMRT application is described in the up-to-date reference [9] and it consists in operating the detector in photovoltaic regime, named zero-bias operation. The radiation hardness of high quality poly crystal diamond was clearly established by RD42 collaboration [10,11], but to adequately profit of these results in tracking systems at extremely high radiation level an appropriate low noise readout electronics must be developed [12].

Fabrication processes

Diamond detectors are realized from high quality free- standing thick diamond film after surface metallization and interconnection to readout electronics.

Diamond film can be synthesized on a crystalline substrate from several DC plasma, arc-discharge and CVD techniques in an atmosphere of Hydrogen and Methane. Diamond plate produced by microwave-plasma-enhanced- CVD process [Figure 1] show excellent electronic properties and high chemical purity. In contrast, they have not a homogeneous crystal structure, which is a common feature in natural and HPHT material. The recipe for growing high quality diamonds uses low pressure and fairly low power with growth rates of ~ 1m/hour.

Figure 1: Cartoon of a diamond film growth in a microwave- plasma-enhanced CVD reactor chamber.

A linear gradient in thermal and electric properties of those diamond samples is clearly observed and it is attributed to the

“conically” shaped single crystal diamond grains developed during the growth process. In fact, on the seed side the diamond nucleation centers sit above a hetero structure with a significant lattice mismatch. During the growth process the different grains extend vertically and horizontally but several of them are stopped by neighbor grains, which instead

increase in size up to 10% the film thickness on the growth side.

The “as grown” diamond material homogeneity is improved by lapping and polishing the seed surface after substrate removal. In fact, the lapping process removes small size grain crystal and the polishing process reduces the surface roughness up to about few nm. Instead, the growth side is usually polished but not lapped. Typically, from a few mm thick sample we are left with 300-500 um thick sample.

The metallization process is relatively simple with respect to semiconductor devices and is often realized by research laboratories. Nevertheless, the electric contact response, reproducibility, and stability in time are a concern.

Metallization process is performed after careful diamond surface cleaning with ultrasounds and acid bathes, followed by boiling with NH4OH+H2O2 and rinsing with de-ionized water.

Usually, a carbide forming metal layer (chromium or titanium) is vacuum deposited by evaporation or sputtering on the cleaned surface, followed by the deposition of a stable contact metal (gold, aluminum or tungsten). The sputtering process provides enough kinetic energy to the atoms of the first metal to penetrate in the diamond surface and produce a carbide layer. Otherwise, a post-deposition thermal annealing at high temperature is required. The carbide layer realizes an ohmic contact between the diamond sensor and the metal contact which manifests in a linear I-V characteristics in the typical operation range from 100 to 1000 V. Ohmic contacts are desirable in MIP detection due to the fast response and both carrier collections.

Working principle

The diamond detector is a solid state detector working like a ionization chamber. The diamond band gap is about 5.5 eV and it can be classified as an insulator material. Nevertheless, diamond has very good charge transport properties and can be classified as a large gap semiconductor. A negligible intrinsic carrier densitiy, even at room temperature, allows to operate the intrinsic diamond as a detector, without any doping. The diamond detector can work with both electric field polarity and charge carriers. In fact, there is no p-n junction and bulk depletion is not needed, like in traditional semiconductor detectors.

Bulk and surface dark current of diamond sensors are less than 1 nA/cm2 for a typical electric field of 1V/m. The charge collection is very fast, about 270µm/ns in velocity saturation regime, and count rates above 100 MHz have been reached.

The average energy loss E0 by ionizing radiation necessary to create one e-h pair in diamond is about 13 eV and the average number of electron–hole pairs qMIP released by a minimum ionizing particle in diamond is about 36e-h/µm. This corresponds to a signal about two times less than silicon. Nevertheless, the negligible dark current and the low electric capacitance, due to two time less dielectric constant value with respect to silicon, allow for a good signal- to-noise ratio.

In a parallel-plate detector of thickness D, assumed equal to electrode spacing, when an electron–hole pair is created by an ionizing particle, an electric current I=e(ve+vh)/D is induced in the external circuit, where ve(h) are the electron and

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holes drift velocity. The charge dQ induced in the time interval dt is given by dQ=Idt= e(dxe+dxh)/D=edx/D where dx is the separation distance between electrons and holes drifting in opposite directions along the electric field lines.

The charge carrier lifetimes τe(h) are limited by the presence of trapping defects like impurities and/or grain boundaries. Consequently, the charge collection efficiency is strongly correlated with crystal quality. The main parameter used to assess the quality of CVD diamond as particle detector is the Charge Collection Distance (CCD). The CCD is defined as the average distance electrons and holes move apart before being trapped.

An ionizing radiation penetrating a distance L inside the material bulk will generate locally a total charge Q0. The electron-hole separation distribution has an exponential shape CCD-1e-x/CCD with mean given by the CCD. Integrating the induced charge formula from L to 0 (from L to D ) for electrons (for holes) the total collected charge formula is obtained: Qc=Q0CCD/D[(1-e-L/CCD)+(1-e-(D-L)/CCD)]. For the special case where L=0 (alpha particles or UV photon above the band-gap) only one carrier drifts to the opposite electrode and the induced charge is given by Qc=Q0CCD/D[1-e-D/CCD] with CCD=ve(h)τe(h). Similarly, if a relativistic ionizing particle generates a charge Qg=qMIPD=Q0 across all detector thickness, the induced charge is given by the same formula but with CCD= 1/2(veτe+vhτeh). The ratio Qc/Q0 is the Charge Collection Efficiency.

The CCD can be assumed uniform along the bulk only for very thinned poly crystal or single crystal samples and it is always a function of the electric field. For thick samples or very low CCD, the charge collection formula can be approximated with the linear expression Qc~Q0CCD/D.

Polarization, pumping, and trapping-detrapping

Large energy gap materials are plugged by polarization effects due to surface or bulk charge trapping, which cause signal degradation and counting rate decrease with time due to the build-up of space charge [13].

The build-up of space charge in the bulk lowers the local electrical field, which increases near the electrodes. On the contrary, the build-up of space charge near the surface, due to low quality contact or damaged surface, lowers the local electric field near the surface itself. Polarization effects manifest also as asymmetric response with respect to high voltage bias. Moreover, pulses are registered for sometime at zero bias due to the residual internal electric field after switch- off.

Polarization can cause track-to-track correlation and lateral electric field components in not uniform samples. These phenomena could worsen the spatial resolution in tracking system when traditional position finding algorithm based on charge sharing between adjacent strips or pixels are used.

A traditional method to improve CCD and reduce polarization in diamond detector is by “pumping” with penetrating radiation, like β and X ray sources. The pumping dose vary from 1 to 10 Gray, according to the material quality.

The pumped state is slowly decaying in time but could last for months. This “priming” mechanism is erased by thermal

annealing and fluorescent light. However, blue light in some cases was observed to improve the diamond response.

Surface polarization phenomena should be avoided by careful surface polishing and cleaning and high quality metal electrode vacuum deposition. Bulk polarization is intrinsically present for finite CCD, because the high voltage bias introduces and asymmetry. In fact, opposite sign charge carriers drift apart in opposite directions and are trapped in different position, creating a net space charge. De-trapping and recombination effects re-establish the equilibrium condition in time scale ranging from microseconds to seconds, causing delayed or unstable dynamic response and changing the rise and decay times of the device.

Nevertheless, for increasing diamond material quality, polarization and pumping effects are less and less important, and in detector grade single crystal diamond are even absent.

Radiation hardness

The RD42 collaboration irradiated poly crystal and single crystal CVD diamonds up to fluences of 1.8x1016 protons/cm2 with 24 GeV at CERN PS. The samples were equipped with micro-strip and pixel front-end electronics and beam tested after irradiation for charge collection efficiency and spatial resolution [10,11]. In this work the measured charge collection distance as a function of the total fluences φ is fitted with a universal phenomenological curve given by CCD=CCD0/(1+kφCCD0) described by the damage parameter k~10-18µm-1cm2. The poly crystal sensors had about 7800 e- average signal prior to irradiation with 1 V/µm bias field.

After the full irradiation the sensor was operated at 2 V/µm and they had about 2500 e- average signal.

The single crystal data points, with initial CCD0=470 µm, overlap with poly crystal curve, with initial CCD0=215 µm, if they are shifted by about 3.8x1015 protons/cm2. In poly crystal diamond the initial trapping is likely localized on grain boundary and radiation damage induces bulk trapping similar to single crystal ones, making its response more uniform after irradiation. This means that the initial advantage of employing single crystal becomes less relevant to very high irradiation doses.

Charge trapping and related phenomena, like charge losses and polarization, are the only important radiation damage effects in diamond. Instead, for silicon material, other detrimental radiation damage effects, such as dark current increase and space charge accumulation, must be cured to avoid thermal runaway and depletion voltage above breakdown voltage.

Figure 2: Silicon detector with planar and 3D geometry where the charge drift before collection is respectively equal and much less than the distance along with the charge is created by ionizing particle.

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The so called 3D Silicon detectors [14] are the only realistic competitor to diamond for ultra-radiation hard applications. In these devices the ohmic and junction implants are realized vertically in the active region and not in the surface as in planar geometry (see Figure 2). In the 3 D geometry the collection distance is reduced, this lowers the depletion voltage and mitigates the charge trapping induced by radiation.

In silicon the radiation damage usually scales with the Non Ionizing Energy Loss (NIEL hypothesis) due to permanent lattice damage. At low energy NIEL is dominated by elastic interaction and at high energy by inelastic interactions [15]. At high energy inelastic interactions in diamond are much less than in silicon but elastic interactions at low energy (below 30 MeV) are similar for the two materials. In reference [15] the much higher radiation hardness of diamond with respect to silicon is questioned below that kinetic energie also with experimental data. This can have an impact on the total radiation damage because low energy particles are always present near the interaction point.

Front-end electronics

The electric signal induced on the external circuit by the charge carrier drift could be amplified by a Charge Sensitive Amplifier (CVA) or by a Fast Voltage Amplifier (FVA). A simplified electrical schema of the two readout chains is shown in Figure 3.

The CSA is generally followed by a shaper optimized to minimize the noise and to increase the count rate. In ideal condition the input signal is given by the voltage drop on the input capacitance due to the collected charge: SCSA =Qc/Cinp. The input noise is given by the first transistor channel trasconduttance NCSA= (4kT0.7/gmfCSA)1/2 where fCSA is the bandwidth.

The FVA is usually realized by a cascade of two RF amplifiers terminated at the input by a 50 Ω resistor Rinp. In ideal condition the input signal is given by Qcve(h)/DRinp and the input noise by the input resistance thermal noise NVFA=(4kTRinpfVFA)1/2 where fVFA is the bandwidth.

The relative signal-to-noise ratio for the two configurations can be written as:

(SCSA/NCSA)/(SFVA/NVFA) ~ 1.2D/ve(h)(gm/RinpfFVA/fCSA)1/2/Cinp. Typically, D/ve(h)=3ns, Cinp =1pF, (Rinp/gm)1/2=0.5Rinp=25Ω, (fFVA/fCSA)1/2=10 and the charge sensitive amplifier is one order of magnitude favourite with respect to the fast voltage amplifier [16].

The drawback of the charge sensitive amplifier is the limited counting rate (fFVA >> fCSA) or the timing resolution for time-of-flight applications. The timing resolution is limited by the electronic noise and the finite signal slope. In fact, the time jitter is given by the formula σT=Nout/(dV/dT)thr where Nout is the noise at the output and (dV/dT)thr is the output signal slew rate at the discriminator threshold. Time resolution could be improved by minimizing the signal-to-noise ratio and with a fast rise time.

For these applications broadband amplifiers with no less than 2 GHz bandwidth are required. On the market there are several choices such as GaAs and new SiGe bipolar transistors with noise figure of less than 2 dB at frequencies above 1 GHz

(referred to 50 Ω input thermal noise). Packaging is also important and a high frequency printed circuit board must integrate electronics, diamond sensor, and high voltage bias tee to preserve the performances. In fact, the signal rise-time is less than 100 ps, due to the high mobility of charge carriers in diamond. The pulse fall-time is determined by the R-C time constant of the diamond electrodes capacitance C and the input resistance R of the preamplifier, which is about 10 pF x 50 Ω = 500 psec. Moreover, pulse amplitudes are also very low and for a MIP the input signal is less than hundred microvolt.

Finally, broadband amplifiers reproduce the induced signal allowing to study the internal electric field and charge transport parameters. For example, using a short-range 241Am alpha source only one carrier at the time drifts to the opposite electrode and diamond sensor homogeneity can be probed.

The induced signal from single crystal diamond is typically trapezoidal with a flat-top. In contrast, the induced signal in poly crystal diamond is triangular with fluctuating amplitude, thus demonstrating the inhomogeneous occurrence of random charge losses and recombination.

Figure 3: Electronic chains to measure diamond signal with very high signal-to-noise ratio (AC coupled charge sensitive amplifier + shaper) and fast induce signal (input resistor terminated multi stage wide band amplifier). The passive HV bias tee is also showed.

Applications

Pad detectors are used when position information is not required, as in radiation monitoring and radiotherapy. Micro- strips and pixels detectors are necessary for tracks and primary and secondary vertex reconstruction.

Radiation monitoring

Diamond, being a low Z material, is particularly promising in high gamma environment, for example in presence of intense neutron fluxes, and in dosimetry, because of its tissue equivalence, avoiding to introduce correction factors. It can be used for beta and alpha monitoring, but also for neutron monitoring. Thermal neutrons can be detected using converters, like 10B or 6Li, and fast neutrons using reactions on carbons 12C, which generate alpha particles.

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Intensity Modulated Radiation Therapy

In radiotherapy, the proven linearity over three dose decades and radiation hardness make diamond a very actractive material. Very promising is poly crystal diamond in null-bias operation [9]. If a Schottky barrier at the metal- diamond interfaces is created, than an active region is established, due to the built-in electric field. In this condition the charge carriers do not cross the diamond bulk and the dinamic response is unaffected by trapping mechanism at defects. Stability in dynamic response is crucial for clinical radiotherapy such as Intensity Modulated Radiation Therapy (IMRT) where several beam profiles modulated in time must be reconstructed within large area and with a 0.5% precision.

Beam monitoring

Traditionally, the use of PIN diodes for beam monitoring is complicated and requires a large effort due to the large increase of the dark current with radiation and temperature.

Use of polycrystalline diamond for beam condition monitoring (BCM) or beam loss monitoring (BLM) were pioneered by the BaBar and Belle collaborations. Later the CDF collaboration commissioned the largest diamond system to improve the beam abort system and protect the CDF silicon tracker from beam accidents.

All four experiment at LHC installed beam monitoring based on diamond detectors. In particular, the ATLAS collaboration developed a novel system based on poly crystal diamonds operated at twice the nominal voltage and using a two stage amplifier chain for improving time resolution. Their system is capable to provide bunch-to-bunch monitoring, online luminosity monitoring, measure the daily and integrated dose received by the tracking system, and protect the tracking system by aborting the beam on large current spikes.

These applications demonstrate that poly crystal diamond is by now a mature detector material for radiation monitoring purposes in high radiation environments.

Tracking and vertexing

Silicon micro-strip detectors are the most common detectors in modern particle physics experiments. Diamond micro-strip detectors were successfully demonstrated during the years by the RD42 collaboration and are described carefully in their progress reports. Uniform response and high efficiency were obtained from diamond micro-strip detectors of large size (2×4cm2) from diamond wafer. The one side metalized micro-strips with 50 m pitch were wired bonded to multichannel readout chip such as VA2 electronics.

Anyway, micro-strip detectors have limited pattern recognition capability and a potential large noise due to the large electrical capacitance. Pixel detectors are best suitable to be placed where high density of particles are present and radiation damage is intense. In order to use the same readout electronics developed for silicon, diamond pixel detectors were constructed with lithographic metallization masks having pitch equal to the silicon pixel detectors built by the two major LHC experiments: CMS and ATLAS.

The first diamond pixel prototypes [17] with CMS geometry (125 µm x 125 µm) were metalized by chromium–

gold process and a passivation layer was applied to define small openings where Indium bumps are evaporated by a

metal mask. In fact, the interconnection between the extremely packed pixels and electronic channels could not be realized by wire bonding and therefore bump-bonding with flip-chip techniques must be used. Small blobs of Indium are deposited on each pixel and electronic channel input. Mechanical and electrical connections are realized heating or pressing together sensor and electronic chip. Careful control of bump-bonding conditions are necessary to get a high yield of contacts.

Similar techniques were used with the first pixel prototypes [17] with ATLAS geometry (50 µm x 400 µm).

The most advance and recent diamond pixel prototypes were assembled with standard ATLAS pixel electronics (FE- I3) using Ti-W metallization and IZM PbSn (solder) bump- bonding. An entire ATLAS module, made of high quality poly crystal diamond and equipped with 16 front-end chips, showed more than 97% of working channels and a global threshold setting as low as 1500 e-. In addition, single crystal diamond sensor was bump-bonded to single chip showing almost ideal performance. All these prototypes, after calibration in the laboratory with radioactive source, were fully characterized in high-energy particle beams before and after irradiation showing very good results in term of efficiency and in-time spatial resolution [10,11].

Diamond offers quite a few advantages over silicon:

excellent thermal conductivity, room temperature operation, much less cooling required, low leakage current, fast charge collection time, low inter-pixel electric capacitance (the dominant contribution in planar geometry). This must be compared with the 3D silicon sensor where low temperature cooling is required to avoid thermal runaway and radiation damage, and the inter-electrode electric capacitance is high (the dominant contribution in 3D geometry).

The negligible leakage current (negligible shot noise) and the smaller detector capacitance (smaller white noise and 1/f noise) contributions could offset the disadvantage of the smaller signal size if the effective threshold of the pixel readout electronics is equal or less than 1000 e-. Likely, a dedicated analog-digital front-end must be designed to match the features of this material. The need to have a negligible analog-to-digital cross talk, small pixel pitch, sophisticated pixel-level and chip-level functionality, push for a design with modern high density CMOS processes (130 nm or below) or even next generation electronics based on 3D vertical scale integration [12].

Conclusions

CVD diamond materials can be competitive with other semiconductor and insulator materials such as Silicon or CdTe/CdZnTe. Unique diamond properties are: ultra radiation hardness, room temperature operation, and tissue equivalence.

In this decade the CERN RD42 collaboration together with Element Six have produced poly and single crystal CVD diamond sensors suitable for high energy application where unprecedented radiation reliance is required. CVD diamonds can be operated after fluences up to 18x1015proton/cm2. Single crystal CVD diamond has reached almost ideal charge collection properties, but only poly crystal can be manufactured at wafer size as needed for large coverage application like in a tracking system.

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Poly crystal diamonds were successfully used in beam monitoring providing bunch-to-bunch separation and online luminosity with time of flight information. Many additional and more sophisticated applications are also planned (see Table 2).

Exp. Application # ch cm2 FE Year

Babar BCM 12 12 DC 2002

CDF BCM 13 16 DC 2006

ATLAS BCM 8 7.7 MIP 2008

ATLAS BLM 12 32 DC 2008

CMS BCM 32 7.7 MIP/DC 2009

CMS PLT 200 k 30 Pixel 2012

ATLAS DCM 730 k 90 Pixel 2013

Table 2: Diamond detector built and proposed for beam monitoring and luminosity measurements (PLT and DCM).

Several poly crystal diamond strip and hybrid pixel detectors were produced, including a full ATLAS pixel module, and very good performance as tracking device were shown in test beam also after heavy irradiation. Nevertheless, for tracking application in high radiation environments, in order to take advantage of diamond benefit with respect to 3D Silicon sensor, a next generation of low threshold pixel front- end electronics must be pursued.

Acknowledgments

The author would like to thank the organizing committee for the invitation to the workshop. Many thanks to Pasquale d’Angelo, Mauro Dinardo, Luigi Moroni, Roberto Perrino, and Stefania Spagnolo for their help to correct this review talk and to work with me on diamond detectors. Special thanks to Giuseppe Fiore and Carlo Pinto for they invaluable technical skill to setup diamond pixel laboratory at INFN Lecce and Università of Salento.

I acknowledge the support of INFN Technology and Interdisciplinary National Scientific Committee (CSN5) through the experiment DIAPIX (DIAmond PIXel).

References

1. Berdermann E. for the NoRDHDia, “Advanced Diamond Particle Detectors” Nuclear Physics News, Vol. 19, No. 2 (2009), 25-31.

2. Adam W. et al. for RD42 collaboration, “The development of diamond tracking detectors for the LHC” NIM A, 514 (2003), 79-86.

3. Kakan H. for RD42 collaboration, “Diamond radiation detectors may be forever” NIMA, 546 (2005), 222-227.

4. Almaviva S. et al., “Thermal and fast neutron detection in chemical vapor deposition single-crystal diamond detectors” Journal of Applied Physics, 103 (2008), 054501_1-054501_6.

5. Bartz E., Doroshenko J., Halyo V., Harrop B.,b D.A. Hits D.A., Macpherson A., Marlow D., Perera L., Schnetzera S., and Stone R., “A CMS Luminosity Monitor Using Single-Crystal CVD Diamond Pixel Detectors” JINST, 4 (2009) P04015.

6. Balducci A., Garino Y., Lo Giudice A., Manfredotti C., Marinelli M., Pucella G., Verona-Rinati G., “Radiological

X-ray dosimetry with single crystal CVD diamond detector” Diamond & Related Materials, 15 (2006), 797- 801.

7. Chayahara A., Mokuno Y., Umezawa H., Shikata S., and Fujimori N., “Fabrication of 1 Inch Mosaic Crystal Diamond Wafers” Applied Physics Express, 3 (2010), 051301_1-051301_3.

8. Gsell S. et al., “A route to diamond wafers by epitaxial deposition on silicon via iridium/yttria-stabilized zirconia buffer layers” Applied Physics Letters, 84 (2014), 4541- 4543.

9. Bruzzi M., De Angelis C., Scaringella M., Talamonti C., Viscomi D., Bucciolini M., “Zero-bias operation of polycrystalline chemically vapour deposited diamond films for Intensity Modulated Radiation Therapy” Diamond &

Related Materials, 20 (2011), 84-92.

10.RD42 Collaboration, Status Report, “Development of Diamond Tracking Detectors for High Luminosity Experiments at the LHC” CERN/LHCC 2008-005.

11.Cristinziani M. for the RD42 Collaboration, “Diamond prototypes for the ATLAS SLHC pixel detector” NIM A, 623 (2010), 174-176.

12.Re V. “3D vertical integration technologies for advanced semiconductor radiation sensors and readout electronics”.

Invited talk at this workshop.

13.Manfredotti C., “CVD diamond detectors for nuclear and dosimetric applications” Diamond & Related Materials 14 (2005), 531-540.

14.Tuovinen E., “Recent advances in the development of semiconductor detectors for SLHC” NIM A, 623 (2010), pp. 171-173.

15.W. de Boer W., J. Bol1, A. Furgeri1, S. Muller, C. Sander, E. Berdermann, M. Pomorski, M. Huhtinen, “Radiation hardness of diamond and silicon sensors compared” Phys.

Stat. Sol. 204 (2007), pp. 3004-3010.

16.Caragheorgheopol A. “SC diamond detector fron-end electronics for MIP’s timing” Talk given at NoRHDia2 Workshop GSI, 30.08-01.09 (2005).

17.RD42 Collaboration and the ATLAS pixel group, “CVD diamond pixel detectors for LHC experiments” Nuclear Physics B (Proc. Suppl.), 78 (1999), pp. 497-504.

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