Measurements on single and poly crystal diamond samples

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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
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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.

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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
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I-V curves
Polycrystalline diamond I-V curves
CDS116 500 µm thick polycrystalline diamond
CDS126 300 µm thick polycrystalline diamond
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I-V curves
Mono-crystalline diamond I-V curves
E6-sc-01 440 µm thick monocrystalline diamond
CDS134 490 µm thick monocrystalline diamond
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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 ß-source.
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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.
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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.
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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.
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Collection distance vs Bias
Collection distance vs Electric field for
e6-sc-01 (440 µm).
Collection distance vs Bias CDS134 (490 µm).
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Collection distance vs Bias
CDS134, monocrystal diamond, presented
polarization periods like any polycrystal.
E6-sc-01 did not show polarization.
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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.
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Radiation damage
The radiation affected the signal of the diamond
and the evolution of the polarization and
depolarization. The plot is of CDS126.
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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.
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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.
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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.
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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.
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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.
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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.
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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.