Characterization of SC CVD diamond detectors for heavy ions spectroscopy

Size: px

Start display at page:

Download "Characterization of SC CVD diamond detectors for heavy ions spectroscopy"

Tobias Curtis
5 years ago
Views:

1 Characterization of SC CVD diamond detectors for heavy ions spectroscopy Characterization of SC CVD diamond detectors for heavy and ions MIPsspectroscopy timing and MIPs timing Michal Pomorski and GSI group* *E.Berdermann, M. Ciobanu, W. Hartmann, B. Lommel, A. Martemiyanov, P. Moritz, M. Rebisz, B. Voss.

2 ABOUT SAMPLES SC CVD diamonds producer e6 SC-E x 3.5 x.48 mm 3 ; Cr(5 nm) Au (1 nm) BDS-5 5 x 5 x.325 mm 3 ; Cr(5 nm) Au (1 nm) BDS 7 5 x 5 x.318 mm 3 ; Cr(5 nm) Au (1 nm) BDS 9 5 x 5 x.32 mm 3 ; Al(1nm) guard ring BDS 1 5 x 5 x.3 mm 3 ; Al(1nm) guard ring BDS 14 5 x 5 x.49 mm 3 ; Al(1nm) guard ring Cleaning and oxidation before metallisation: If metallised before Aqua Regia H 2 SO 4 + KNO 3 boiling ~3 min rinse with ultra-pure water ultrasonic bath dry with N 2 Metallisation sputtering or evaporation at Target Laboratory of GSI Bettina Lommel talk Cr(5nm)Au(1nm) ; Ti(3nm)Pt(5nm)Au(1nm); Al(1 nm) annealing 5C for 1min Ar

3 OUTLINE Current-Voltage characteristics and surfaces influence Charge collection properties and stability Energy resolution Timing properties Summary

4 CURRENT-VOLTAGE CHARACTERISTICS Zoo of I-V characteristics bulk + surface current screened box, no light + N 2 flow dark current [A] BDS BDS 7 BDS BDS 1 BDS 9 SC-E6-4 breakdown HI LO 6517 V-source DIAMOND top electrode bottom electrode A HI LO 6517 Picoammeter E [V/µm] - not reproducible I-V for various samples - asymmetry

5 HI LO CURRENT-VOLTAGE CHARACTERISTICS bulk current screened box, no light + N 2 flow DIAMOND guarded electrode 6517 V-source top electrode guard ring electrode A HI LO 6517 Picoammeter no difference in I-V for: various metallisation (Al,Cr,Ti) (2 samples tested) guarded electrode mainly bulk leakage current (3 samples tested) dark current [A] BDS 1 1 nm Al no - guard guarded E [V/µm] dark current [A] BDS 14 1nm Al 5 Cr - 1 Au E [V/µm]

6 CURRENT-VOLTAGE CHARACTERISTICS AFM pictures of both diamond (BDS14) surfaces BDS14_7.bmp profile substrate side (?) 15 Z [nm] 1 5 roughness rms 5.6 [nm] path lenght [nm] BDS14_12o.bmp profile growth side (?) Z [nm] roughness rms 1.4 [nm] path lenght [nm]

CURRENT-VOLTAGE CHARACTERISTICS Asymmetry

7 CURRENT-VOLTAGE CHARACTERISTICS Asymmetry in I-V characteristic is present due to surface damage (polishing?)... scratches pop up after samples annealing... damaged surface substrate side(?) leakage current I a E I I b a >>I b Annealed in 6C, 3min growth side(?)

8 CURRENT-VOLTAGE CHARACTERISTICS dark current [A] 1-8 SC-E6-4 February May Cr;Au Long term stability bias [V]

9 CHARGE COLLECTION Vacuum 1-6 mbar CVD DD - Use of an α-source 241 Am (5.486 MeV) for charge injection - α-particle range in diamond ~12µm - detector thickness >3µm, induced charge mainly motion of one type of carriers GND e or h drift ~3 µm GND HV +/- α 239 Pu/ 241 Am/ 244 Cm Signal readout Charge sensitive electronics GND - Choosing the HV +/- drift of or - presented geometry +HV drift, -HV - drift - detector coupled to classical spectroscopy front-end electronic pramp HV MA TFA discr. ADC TDC camac PC DAQ GG

10 CHARGE COLLECTION Saturation to ~ 68.6 [fc] for both and drift. CCE=1% at low electric field <.3 V/mm collected charge [fc] E [V/µm] SC-E6-4 collected charge [fc] E[V/µm] BDS [fc] e-h Average energy for e-h pair creation 12.8 ev/e-h collected charge [fc] E[V/µm] BDS 1 collected charge [fc] E [V/µm] BDS 14

11 [a.u.] 4x1 4 3x1 4 2x1 4 1x1 4 1 SC-E Energy [MeV] SC-E6-4 E ~.8 V/µm 3 start SC-E6-4 E~.8 V/µm ADC channel [a.u.] after ~ 5h after ~ 12h 1 events in each spectrum DETECTION STABILITY Time of spectrum collecting > 12h 1.2x1 4 1.x1 4 8.x1 3 6.x1 3 4.x1 3 2.x x x1 4 1.x1 4 8.x1 3 6.x1 3 4.x1 3 2.x1 3 BDS 9 BDS 9 E~.8 V/µm collected charge [fc] BDS 9 E~.8 V/µm Collected charge [fc] 1.6x x x1 4 1.x1 4 8.x1 3 6.x1 3 4.x1 3 2.x x1 4 1.x1 4 8.x1 3 6.x1 3 4.x1 3 2.x1 3 BDS 14 BDS 14 E~.8 V/µm collected charge [fc] BDS 14 E~.8 V/µm collected charge [fc]

12 DETECTION STABILITY 5x1 3 4x1 3 BDS BDS 1 E~.8 V/µm 5 events 3x1 3 2x1 3 1x1 3 6x1 3 5x1 3 4x1 3 3x1 3 2x1 3 1x1 3 BDS 1 E~.8 V/µm collected charge [fc] 7% BDS 1 E~.8 V/µm collected charge [fc] release of previously trapped collected charge [fc] Indication of presence for : regions with 1% efficiency main peak region with lower efficiency 93%, quite uniform density of trapping centres shifted peak

13 Diamond resolution close to silicon detectors: FWHM = 17 kev (5.486 MeV) (sc-e6-4 ) measured with not dedicated CS electronics silicon e~3.6 ev/e-h; diamond e~12.8 ev/e-h We are close to statistical limits (Fano factor?) ENERGY RESOLUTION 4.x x1 4 3.x x1 4 2.x x1 4 1.x1 4 5.x Pu E/E =.31% FWHM=17keV 241 Am 244 Cm Energy [MeV] SC-E6-4 E ~.8 V/µm 6 3 3K Silicon detector HV -1V FWHM ~13 kev Ε/Ε =,23 % 1.6x x x1 4 1.x1 4 8.x1 3 6.x1 3 BDS 14 E~.8 V/µm Main peak E/E=.32% 241 Am 4.x Energy [MeV] 2.x collected charge [fq]

14 TIMING PROPERTIES Air CVD DD Time of Flight Technique Low impedance of 5 Ω voltage amplifier DBA II, bandwidth 2.3 GHz (3dB), gain 44dB Digital Scope bandwidth 3GHz, GS/s GND e or h drift ~3 µm GND HV +/- α 241 Am Signal readout BB electronic GND Voltage Amplifier Digital scope 5Ω GND

15 TIMING PROPERTIES output signal [V].1.5 E=1.23 V/µm Average signals from 5 single shots BDS 9 drift output signal [V] V/µm BDS 1 drift output signal [V] electronics oscillation 2GHz due to 5ohm mismatching SC-E6-4 sample thick.= 393[µm] drift. E=.3 V/µm. 1.x1-8 2.x1-8 3.x1-8 time [s].. 9.x x x1-8 time [s].12 V/µm.. 1.x1-8 2.x1-8 3.x1-8 time [s] output signal [V] V/µm. 1.x1-8 2.x1-8 time [s] BDS 9 drift,12 V/µm output signal [V] V/µm. 1.x1-8 2.x1-8 3.x1-8 time [s] BDS 1 drift.12 V/µm output signal [V] x1-8 2.x1-8 3.x1-8 time [s] SC-E6-4 drift sample thickness: 393µm

16 TIMING PROPERTIES electron drift signals Assuming uniform internal electric field (flat top of BB signals) and CCE=1% v ( E) = dr d t tr d detector thickness t tr transition time FWHM of BB signals error standard deviation of signals at FWHM output signal [V] t tr t tr E~1[V/µm].2.1..E+ 2.5E-9 5.E-9 7.5E-9 1.E-8 time [s]

17 TIMING PROPERTIES Drift velocities for and drift velocity [µm/ns] BDS E in <1> [V/µm] drift velocity [µm/ns] SC-E E in <1> [V/µm] drift velocity [µm/ns] BDS E in <1> [V/µm] drift velocity [µm/ns] BDS Ein <1>[V/µm] drift velocity [µm/ns] BDS E in <1> [V/µm] drift velocity [µm/ns] BDS E in <1> [V/µm]

18 V TIMING PROPERTIES µ E dr = v dr β 1/ β sat v β 1 1+ E sat 1 + µ E V = µ E µ 2 fits:.3 1 V/µm µ 1 3 V/µm v sat drift velocity [µm/ns] tested SC Diamonds from E6 3K mi ± vsat ± E in <1> [V/µm] Holes µ 2332 [cm 2 /Vs] V sat 14 [µm/ns] µ 14-31[cm 2 /Vs] V sat 19 [µm/ns]

19 SUMMARY Current voltage characteristics huge difference in leakage current for various samples no difference for guarded samples mainly bulk leakage Asymmetry in I-V probably due to damaged surface as a result of samples polishing requires overgrowth after polishing No difference for various metallisation proposal to use light elements e.g. Al

20 SUMMARY charge collection, stability, and E CCE ~ 1% at low E <.3V/µ for and most of tested samples all samples spectroscopic grade some of them resolution close to silicon detectors perfect behavior for drift no trapping (or negligible) most of them stable as well for drift

21 SUMMARY Timing properties - flat top of BB signals for all tested samples uniform internal electric field no internal space charge -common behavior --> drift velocity > drift velocity in <1> - intrinsic limit for timing application with CSA electronic drift of 1ns / 1 µm (optimistic E=2.8V/µm) - uniform rise time of ~16 ps (limited by electronics) jitter - 26 ps for BB electronic

R3B Heavy Ion Tracking

R3B Heavy Ion Tracking Roman Gernhäuser, TU-München High Rate Diamond Detectors for Heavy Ion Tracking and TOF material investigations detector concept (a reminder) electronics development prototype production