1. Diamond Sensors Laboratory 3D micro-structuring of diamond for radiation detector applications B.Caylar, M.Pomorski, P.Bergonzo Diamond Sensors Laboratory CEA-LIST, Gif-Sur-Yvette, France José Alvarez Laboratoire de génie électrique de Paris (LGEP), Gif-sur-Yvette, France Alexander Oh University of Manchester, School of Physics and Astronomy, Manchester, United Kingdom Thorsten Wengler CERN, Geneva, Switzerland

2. Diamond Sensors Laboratory  Advantages 1 :  Higher electric field for a given applied bias voltage  Shorter drift path thus drift time  Lower probability of trapping 2 Context – Why using 3D electrodes? [1] J.Morse, C.J. Kenney, E.M. Westbrook et al. / Nuclear Instruments and Methods in Physics Research Section A, 524 (2004) 236. 2D Electrodes 3D Electrodes Ionizing particle

3. Diamond Sensors Laboratory 3 Context – Why using 3D electrodes?  Planar  3D  Analytically calculated currents generated by a MIP

4. Diamond Sensors Laboratory 4  NIEL induces bulk defects  When flux increases :  Defects number increases  Carrier lifetime reduction  CCE decreases [2] Michal Pomorski – PhD debate, Frankfurt University 07/08/2008 before irradiation after 1.2 x 10 14 20MeV n.cm -2 after 1.97 x 10 14 20MeV n.cm -2 Signal decrease Context – Why using 3D electrodes?

5. Diamond Sensors Laboratory 5  3D geometry is faster : 8ns vs 208ps.  3D geometry makes the detector more radiation hard Context – Why using 3D electrodes?  Planar  3D

6. Diamond Sensors Laboratory Burried electrodes  Laser setup & Fabrication  Structural characterization  Electrical characterization pc-CVD Detector (e6 detector grade)  Electrical characterization  Characterization under alpha particles sc-CVD Detector (e6 electronic grade)  Optical characterization  Electrical characterization  Transient current measurements Conclusion 6 Outline

7. Diamond Sensors Laboratory BURRIED ELECTRODES LASER SETUP & FRABRICATION 7

8. Diamond Sensors Laboratory 8 Burried electrodes – Laser setup  Tunable parameters  Scan velocity 1-1000 µm/s  Laser power 0-160µJ/pulse  Repetition rate 1-30 Hz Sample holder Nitrogen laser λ = 337nm τ = 3ns XYZ Motorized stage Webcam 20x Lens

9. Diamond Sensors Laboratory 9 Burried electrodes – Fabrication XYZ Motorized stage  Photoluminescence during laser processing Translation Graphitization

10. Diamond Sensors Laboratory 10 BURRIED ELECTRODES STRUCTURAL CHARACTERIZATION

11. Diamond Sensors Laboratory 11  Clean surface (Where graphitization starts)  Cracked Surface (Where graphitization ends)  Tilted sample 150 µm  Optical grade sc-CVD sample Structural characterization – Optical microscopy 10µm diameter 20-100 µm diameter 700µm depth

12. Diamond Sensors Laboratory 12 Structural characterization – 2D Raman mapping  2D Raman depth mapping obtained by integrating diamond peak  No micro-channel  Micro-channel with cracks 1000 CCD cts 0 CCD cts 1000 CCD cts 0 CCD cts 10µm Depth

13. Diamond Sensors Laboratory 13 Structural characterization – SEM imaging  Channel’s clean side after laser processing  Channel’s clean side after H 2 plasma H 2 Plasma

14. Diamond Sensors Laboratory 14 BURRIED ELECTRODES ELECTRICAL CHARACTERIZATION

15. Diamond Sensors Laboratory 15 Electrical characterization – I(V) measurements  Graphite’s channel resitivity [3] T.Ohana, T.Nakamura, A.Goto et al. / Diamond and Related Materials, 12 (2003) 2011 ρ (average) = 5.7x10 -1 Ω.cm R (500µm) ~ 2kΩ Match with nanocrystalline graphite given in literature 3 A

16. Diamond Sensors Laboratory 16 PC-CVD DETECTOR ELECTRICAL CHARACTERIZATION E6 detector grade 10 x 10 x 0.7 mm 3 Sample courtesy Alexander Oh

17. Diamond Sensors Laboratory 17 Electrical characterization – Device leakage current A  Comparison between planar and 3D geometry  Planar  3D

18. Diamond Sensors Laboratory 18 PC-CVD DETECTOR CHARACTERIZATION UNDER ALPHA PARTICLES

19. Diamond Sensors Laboratory 19 α Al front contact Al back contact Am-241 Source 5.486MeV R V bias = ±500V Characterization under alpha particles – Experimental setup FCSA Fast Charge Sensitive Amplifier M.Ciobanu, GSI, Germany Signal Scope Collimator

20. Diamond Sensors Laboratory 20 Characterization under alpha particles - Results  Polarization study – Holes drift (pc-CVD sample)  Planar  3D

21. Diamond Sensors Laboratory 21 Characterization under alpha particles - Results  Polarization study – Electrons drift (pc-CVD sample)  Planar  3D

22. Diamond Sensors Laboratory 22 Characterization under alpha particles - Results  Holes drift (pc-CVD sample) α α Amplitude has been normalized with the signal of a sc-CVD « e6 electronic grade » diamond

23. Diamond Sensors Laboratory 23 Characterization under alpha particles - Results  Electrons drift (pc-CVD sample) α α Amplitude has been normalized with the signal of a sc-CVD « e6 electronic grade » diamond

24. Diamond Sensors Laboratory 24 Characterization under alpha particles - Analysis α α Low CCE High CCE  Electric field simulation  3D Geometry but pseudo–3D detector 700µm 200µm HV +500V V/µm 5 4.5 4 3.5 3 2.5 2 1.5 1 0.5 0

25. Diamond Sensors Laboratory 25 SC-CVD DETECTOR E6 electronic grade - oriented 3 x 3 x 0.3 mm 3 Sample courtesy Eleni Berdermann

26. Diamond Sensors Laboratory 26 SC-CVD DETECTOR OPTICAL CHARACTERIZATION

27. Diamond Sensors Laboratory 27  Bulk strain mapping after graphitization  Micro structured sc-CVD diamond observed with crossed polarizers Test areas Detector area Detector’s optical characterization – Optical microscopy

28. Diamond Sensors Laboratory 28 Detector’s optical characterization – Optical microscopy  Detector after metallization

29. Diamond Sensors Laboratory 29 SC-CVD DETECTOR ELECTRICAL CHARACTERIZATION

30. Diamond Sensors Laboratory 30 Electrical characterization – Device leakage current  sc-CVD sample after plasma O2 etching  HV on cracked surface  HV on clean surface

31. Diamond Sensors Laboratory 31 SC-CVD DETECTOR TRANSIENT CURRENT MEASUREMENTS

32. Diamond Sensors Laboratory 32 2D Zone HV +100V Electrical characterization – Setup and methods 2D Zone Signal Scope Ampli  Transient current measurements 300µm Ultra-Fast 40 dB, 2 GHz Broadband Amplifier

33. Diamond Sensors Laboratory Signal 3D ~500mV Electrons drift Mixed e/h drift Signal 2D ~100mV Signal 2D ~80mV Holes drift 33 Transient current measurements - Results  Without collimator  Alphas’ injection on cracked side  Alphas’ injection on clean side 1 ns

34. Diamond Sensors Laboratory 34 Transient current measurements - Results  With collimator 1 ns Mixed e/h drift  Alphas’ injection on cracked side

35. Diamond Sensors Laboratory V/µm 35 Transient current measurements - Analysis  Electric field simulation 3 2.5 2 1.5 1 0.5 0 300µm +100 V α α Planar+3D signal Planar signal only

36. Diamond Sensors Laboratory 36 Transient current measurements - Results  Experimental results  Selection of relevant events Amplitude ratio = 6

37. Diamond Sensors Laboratory Amplitude ratio = 23.8  2GHz low pass filter 37 Transient current measurements - Results  Analytically calculated signals  Theoritical response Amplitude ratio = 22

38. Diamond Sensors Laboratory Amplitude’s ratio = 6.2 38 Transient current measurements - Results  Analytically calculated signals  350 MHz low pass filter  Ampli + device bandwith ~350MHz  R device ~ 520 Ω  12 channels connected  R channel ~ 6 kΩ

39. Diamond Sensors Laboratory 39 Conclusion Conductive graphitic structures has been achieved on both pc- and sc-CVD sample These structures are suitable for detectors applications Two dectetors using 3D-geometry electrodes has been produced A real improvement between planar and 3D geometry has ben observed  Higher signal  Faster response  « Polarization effect » decrease on pc-CVD detector But real 3D detector hasn’t been achieved yet…

40. Diamond Sensors Laboratory 40 Thanks for your attention !