Measurements on single and poly crystal diamond samples at CERN

1. Measurements on single and poly crystal diamond samples at CERN Luis Fernandez-Hernando Christoph Ilgner Alick Macpherson Alexander Oh Terry Pritchard Eleni Berdermann Peter Weilhammer

2. Diamond Characterization • Measurements performed on diamonds: • I-V curve. • First quality check of the samples, metallisations. • Collection distance vs time. • Study of the pumping. • Charge collection distance at 1 V/ µm. • Collection distance vs bias voltage. • Measurement of the charge collection distance at different electric fields. • Study of the radiation damage. • Study of the polarization. • I-T curve. • Find the thermo-stimulated current peak. Number of traps. • Depumping of diamonds.

3. Diamond Characterization The software gets the top value of the peak and deducts the average value of the base Those values are averaged over a certain time (usually 5 min) for calculating the collection distance

4. I-V curves Polycrystalline diamond I-V curves: CDS116 500 μm thick polycrystalline diamond CDS126 300 μm thick polycrystalline diamond

5. I-V curves Mono-crystalline diamond I-V curves: E6-sc-01 440 μm thick monocrystalline diamond CDS134 490 μm thick monocrystalline diamond

6. Pumping Pumping for an 360 μm thick polycrystalline CVD diamond at 1V/ μm. Pumping for a 500 thick polycrystalline CVD diamond at 1V/ μm. Pumping performed with a collimated 90Sr β-source.

7. Pumping Monocrystal diamond e6-sc-01 does not present pumping. The collection distance was bigger than the thickness. After a heating process that collection distance went to a more reasonable value.

8. Collection distance vs Bias Signal from CDS113 (500 µm). to a MIP vs time at different voltage steps. A polarization is present in each step.

9. Collection distance vs Bias Collection distance vs the electric field for CDS113 (500 µm). Each point represents the signal after a stabilization period of 4 hours.

10. Collection distance vs Bias Collection distance vs Electric field for e6-sc-01 (440 µm). Collection distance vs Bias CDS134 (490 µm).

11. Collection distance vs Bias CDS134, monocrystal diamond, presented polarization periods like any polycrystal. E6-sc-01 did not show polarization.

12. Radiation damage on polycrystalline samples CDS116 (500 µm). First irradiation of 1015 protons/cm2. Second irradiation of 2.8x1015 protons/cm2. Equivalent to 10 years of LHC at normal operation near the IP5. CDS126 (300 µm). First irradiation of 5x1014 protons/cm2. Second irradiation of 2.3x1015 protons/cm2.

13. Radiation damage The radiation affected the signal of the diamond and the evolution of the polarization and depolarization. The plot is of CDS126.

14. Radiation damage CDS 116 signal at 1 V/µm and leakage current after the first irradiation. CDS 126 signal at 1 V/µm and leakage current after the first irradiation.

15. Radiation damage CDS 116 signal at 1 V/µm and leakage current after the first irradiation and after a heating process that fully depumped the diamond. The dose necessary for pumping it has increased. CDS 126 signal at 1 V/µm and leakage current after the first irradiation and after a heating process that fully depumped the diamond.

16. Radiation damage CDS 116 signal at 1 V/µm and leakage current after the second irradiation. CDS 126 signal at 1 V/µm and leakage current after the second irradiation.

17. Some conclusions Diamond showed a signal degradation due to radiation damage of a 42% after a proton fluence equivalent to 10 years of normal operation of the LHC near the IP5. The leakage current from the diamonds decreased down to a 60% from its original value prior to irradiations. The most important effect of radiation damage on diamond is the creation of charge traps in its bulk. Due to this effect pumping periods increase considerably. The number of generated traps can be so important that in case the diamond is depumped those traps will suck the electron hole pairs generated by a passing particle masking the signal completely. After performing a TSC diamonds showed, after a pumping period, to have recovered the original collection distance values. New traps have been created, but those once filled do not interfere with the signal. Damage that made a decrease on the signal seemed to have disappeared.

18. TSC measurements Temperature vs time for the measurements. The rate is quite constant and reproducible. Current vs temperature for CDS126 after the first irradiation with the proton beam.

19. TSC measurements Current vs temperature for CDS115 after 2 hours of irradiation with the strontium source. Current vs temperature for e6-sc-01 after 2 hours of irradiation with the strontium source.

20. Some conclusions The similar temperatures at where the TSC peaks were produced, indicate that the charge traps in those diamonds are in similar energy levels. That could indicate that the kind of impurities is the same for all of them. The two polycrystalline diamonds measured were made from the same wafer, therefore this is expected. The monocrystal e6-sc-01, instead, did not show any hint about charge traps during the collection distance measurements, it did not pump neither polarized, yet a TSC peak is observed, also in a similar temperature range. That confirms the presence of traps, from impurities, in the crystal lattice. Impurities that may be similar to the polycrystalline ones. Nevertheless, the level of current achieved by the monocrystal is much less important than the ones achieved from the polycrystalline ones.