1. Effects of annealing on charge collection in heavily irradiated silicon micro-strip detectors
G. Kramberger, V. Cindro, I. Mandić,
M. Mikuž, M. Milovanović, M. Zavrtanik

2. Motivation
Long-term annealing does not seem to be as harmful as at lower fluencies (measured by Liverpool, USCS, IJS)
New method used to investigate CCE – Edge-TCT (see previous talk)
Multiplication effects
τeff changes. What is the effect?
Electric field changes.
The difference between forward and reverse bias

3. Experimental Setup Detector: Setup:
Manufacturer: Micron (RD50 Micron run)
Type: FZ Si, p-type micro-strip, VFD≈16V
Irradiation fluence: 5x1015 neutrons/cm2 (by TRIGA)
Setup:
Peltier cooler (-20 ÷ 60 oC)
Power supply: Keithley 2410
Wide band amplifier: MITEQ AM-1309 (10kHz-1Ghz)
Osciloscope: LeCroy 950 WavePro (1Ghz)
IR Laser: ALDS, λ=1060nm
Positioning system: Newport M-ILS100PP

4. Experimental Setup

5. Annealing process Sample always annealed in the setup
absolute charge measurement (conservative estimation of precision: 10-20%)
constant laboratory temperature: 21 oC
stable position/laser (the same spots in the detector were illuminated for all annealing steps)
sample temperature stabilized to less than 1°C
Annealing at 60°C up to cumulative time of min.
After each annealing step, voltage scans up to 800V were performed

6. Charge (reverse bias) Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

7. How can we be sure that this is not an artifact of the setup?
The laser stability can be verified in forward direction
Multiplication can be clearly seen in induced current pulse shapes

8. Charge 400V (forward bias) Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

9. What can we see?
Annealing process does not seem to influence charge collection efficiency
The efficience of the detector is best at its centre
There is no peak in the electric field!

10. <Q> vs. Bias for all annealing times Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

11. E-TCT Measurements, Reverse Bias Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

12. E-TCT Measurements, Reverse Bias Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

13. E-TCT Measurements, Reverse Bias Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

14. E-TCT Measurements, Reverse Bias Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

15. E-TCT Measurements, Reverse Bias Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

16. E-TCT Measurements, Reverse Bias Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

17. E-TCT Measurements, Reverse Bias Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

18. E-TCT Measurements, Reverse Bias Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

19. E-TCT Measurements, Reverse Bias Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

20. <Q> vs. Ileak for all annealing times Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

21. The increase of second peak amplitude Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C

22. Conclusion
Charge collection efficiency increases with long-term annealing for highly irradiated (Φ≥5x1015) micro-strip detectors when reversely biased.
No effect of annealing in forward bias
no peak of electric field
Changes in trapping time and electric field due to multiplication effects
Increase in Ileak.

23. Ileak vs. Voltage for all annealing times Detector: Micron, FZ-Si p-type micro-strip, Φ=5x1015 cm-2, T=-20°C