FABRICATION, CHARACTERIZATION OF A 3D DIAMOND DETECTOR Benoît CAYLAR On behalf of the 3D Diamond Detector Collaboration

At the beginning, a small collaboration between Manchester, CEA-LIST and CERN  CEA-LIST  CERN  The University of Manchester Growing in 2011  ETH Zürich  LGEP-Paris  Ohio State University 2 3D DIAMOND DETECTOR COLLABORATION 3D diamond activities has started in 2010… 13 th Vienna Conference on Instrumentation |

3 3D DIAMOND DETECTOR COLLABORATION 13 th Vienna Conference on Instrumentation | The 3D Diamond Detector Collaboration » M. Ahmed » J. Alvarez » F. Bachmair » L. Bäni » P. Bergonzo » B. Caylar » I. Haughton » D. Hits » H. Kagan » R. Kass » L. Li » A. Oh » S. Phan » M. Pomorski » D. Smith » D. Tromson » V. Tyzhnevyi » C. da Via » R. Wallny » S. Watts » T. Wengler » D. Whitehead

Planar geometry 4 CONTEXT What is a 3D detector ? 13 th Vienna Conference on Instrumentation | » S.I. Parker et al., NIM. A 395 (1997) µm 50µm  Higher electric field for a given applied bias voltage  Shorter drift path  Lower probability of trapping 3D geometry

5 CONTEXT TCAD Simulation 13 th Vienna Conference on Instrumentation |  Electrostatic Potential +40V  Absolute Electric Field  Electrons density Z=250 (25,25) MIP 100µm Electron cloud generated by a MIP drifting under Electric field 0,6 ns

6 CONTEXT Quick overview of existing solid state 3D detectors 13 th Vienna Conference on Instrumentation | Solid state 3D detectors have already been produce in several sensing materials  Silicon » High energy physics : radiation hard trackers » Looking for being installed in part of ATLAS-IBL  CdTe/CdZnTe » For medical applications : X-ray detectors, Gamma Camera  GaAs » For medical applications : X-ray detectors, Gamma Camera But there is at least one interesting candidate left…

7 CONTEXT Diamond as sensing material 13 th Vienna Conference on Instrumentation | Advantages  Large band gap : 5,48 eV » High resistivity: low leakage current.  Low dielectric constant : 5,7 » Low capacitance : low noise  High breakdown field : 10 7 V/m » Operation at high voltage  Large thermal conductivity : > 1800 W.cm -1.K -1 » Operation without cooling  High displacement energy : 43 eV » Radiation hard Limits  High energy required to create an e-h pair » Low signal  Only small area available » Single crystal : 5x5 mm² » Poly-crystalline sample : 10x10 mm²  Expensive Diamond is already used at LHC

8 BURIED ELECTRODES Fs-laser setup and fabrication 13 th Vienna Conference on Instrumentation | Electrodes are processed using laser-induced graphitization of diamond bulk  Wavelength : 800nm  Repetition rate : 1kHz  Pulse length : 100fs  Spot size : 10µm

9 BURIED ELECTRODES Structural characterization 13 th Vienna Conference on Instrumentation |  Femtosecond laser » Diameter : 5µm » Pitch < 35µm Laser process improvement over the past two years 100µm  YAG Laser » Hollow, conical shape » Diameter : 100µm » Pitch : 300µm  UV Laser + x10 Lens » Diameter : 75µm » Pitch : 200µm  UV Laser + x20 Lens » Diameter : 20µm » Pitch : 150µm 100µm Dec 2010 Feb 2011 Jun 2011 Apr 2012

10 BURIED ELECTRODES Structural characterization 13 th Vienna Conference on Instrumentation |  Resistance distribution in the mapping area 1µm Electrode mapping using Conductive probe AFM  AFM mapping  Resistance mapping 200 kΩ ρ ~ 1 Ω.cm R

11 3D DIAMOND DETECTOR Batch 1 – April th Vienna Conference on Instrumentation | Optical microscopy » Graphitization process wasn’t optimized – 70% success rate Optical microscopy – Crossed polarizers (Surface)Optical microscopy – Crossed polarizers (In Bulk)Optical microscopy – 45° Tilt 50µm 125µm Rectangular unit cell

th Vienna Conference on Instrumentation | D DIAMOND DETECTOR Characterization using protons micro-beam Ion Beam Induce Current (IBIC) Zagreb  4.5 MeV Protons  Spot size : 1µm  Ion by ion hits  Penetration depth : 100µm  Readout electronic : Charge Sensitive Amplifier Diamond sample Proton µ-beam

th Vienna Conference on Instrumentation | D DIAMOND DETECTOR Characterization using protons micro-beam IBIC mapping – Batch 1 Single crystal sample  HV = +1V » The inefficient area is due to a broken strip » All connected columns are active

th Vienna Conference on Instrumentation | D DIAMOND DETECTOR Characterization using protons micro-beam IBIC mapping – Increasing positive bias  +1V  +40V  +100V  +5V » CCE is non uniform » Probably due to bad contact quality or electrodes non uniformity

th Vienna Conference on Instrumentation | D DIAMOND DETECTOR Characterization using protons micro-beam IBIC mapping – Charge Collection efficiency spectra 100% CCE

16 3D DIAMOND DETECTOR Batch 2 – August th Vienna Conference on Instrumentation | Batch 2 improvements  Sc + PcCVD samples  100% Graphitization rate  Ti/Pt/Au contacts  Three structures on one diamond sample » Face centered cubic cell 100µm with buried electrodes ( A ) » Analog metallized structure without buried electrodes ( B ) » 2D Geometry classical pattern (Strip) ( C ) (A)(A) (B)(B)(C)(C)

17 3D DIAMOND DETECTOR Batch 2 – August th Vienna Conference on Instrumentation | Test beam CERN  SPS H6 line » 120 GeV Protons » Spill every 40sec » k triggers per spill  Silicon telescope » Two X and two Y planes in front of diamond » Two X and two Y planes in back of diamond » 3,6k evenets recorded per spill » Scintillator triggered  Diamond pumped » Before the start of first measurement » After changing bias voltage polarity » C. Colledani et al., Nuclear Instruments and Methods in Physics Research A 372 ( 1996)

18 3D DIAMOND DETECTOR Batch 2 – August th Vienna Conference on Instrumentation | Fiducial cuts defined by requiring hits in  Exactly one cluster in each silicon plane  Exactly one cluster in diamond  Cuts for analysis

MIPs spectra measured on single crystal sample  3D area collects same amount of charges as strip detector although weaker electric field  Low charge collection in the « 3D without columns » area » Prove buried electrodes contribution in charge collection 19 3D DIAMOND DETECTOR Test CERN SPS 13 th Vienna Conference on Instrumentation |  Strip detector +500V  No buried electrodes +25V  3D Diamond detector +25V Mean 1068 Mean 451 Mean 990

MIPs spectra measured on single crystal sample 20 3D DIAMOND DETECTOR Test CERN SPS 13 th Vienna Conference on Instrumentation | Strip detector 3D diamond

21 CONCLUSION 3D diamond detector works ! 13 th Vienna Conference on Instrumentation | Conclusion  Real progress has been achieved in the last three years  This work demonstrates the feasibility of fabrication of 3D diamond detectors  CVD diamond detectors with laser-processed burried electrodes were investigated with micro-focused ion beam and in CERN test beams.  A lot of work is ahead to make this technology available for high luminosity experiments Thanks for your attention !

th Vienna Conference on Instrumentation | Spare slides

23 BURIED ELECTRODES Why is femtosecond laser so much better ? 13 th Vienna Conference on Instrumentation | A two-step process  Producing a graphitic seed at the surface » Excitation of a large number of valence electrons via multi-photon absorption » Energy barrier decreases » Phase transition Diamond- Graphite  Propagation of laser supported graphitic wave No heat accumulation T.V. Kononenko et Al – Rus’nanotech (2010)

24 BURIED ELECTRODES Structural characterization 13 th Vienna Conference on Instrumentation | Raman Analysis EHT = 5kVWD = 4.9mmInLens detector  Diamond  Electrode  Border