Surface measurements with gamma radiated ATLAS12A samples Matthew Domingo, Mike Shumko, Hartmut F.-W. Sadrozinski, Vitaliy Fadeyev, Zachary Galloway, Zhijun Liang SCIPP, UCSC 1

Electrical tests of ATLAS12A mini sensors UCSC status Samples ◦ ATLAS12A samples radiated with gamma at BNL ◦ Samples have not been annealed yet ◦ 4 fluences :10 Mrad, 3Mrad, 1Mrad, 300krad, 100krad ◦ Zones : BZ3C and BZ3F This talk focus on the following measurements ◦ R(interstrip) ◦ C(interstrip) 2

Inter-strip resistance The inter-strip resistance setup as follow ◦ BZ3C sensors ◦ Measured at -10 °C, 0 °C, 15 °C 3 Measure nA current for G Ω level resistance Relative low S/N Do a careful job in grouding to reduce the noise

R_INT in different temperature Higher resistance in low temperature Higher resistance with higher bias voltage. -10°C 0°C 15°C Bias voltage (V) Fluence=10Mrad Bias voltage (V) -10°C 0°C 15°C Fluence=1Mrad Fluence-10°C0°C15°C 10 Mrad62.6 G Ω /cm5.3G Ω /cm0.64G Ω /cm 1 MRad136.5G Ω /cm35.0G Ω /cm8.8 G Ω /cm Biased voltage=-1000V R_INT( Ω /cm)

R_INT Vs fluences 100kRad 1M Rad 10Mrad R_INT( Ω /cm) Bias voltage (V) Higher bias voltage dependence as fluence increases T=15°C1M Rad 10Mrad T=-10°C Bias voltage (V) R_INT( Ω /cm)

Inter-strip capacitance C(interstrip) Measurements setups BZ3C sensors, Measured in -10 °C, before annealed ◦ 5 probe methods:  Middle strip connected to to LCR meters low side  First neighbor strips connected to LCR meters high side.  The Second neighbor strips grounded ◦ 3 probe methods:  Similar to 5 probe methods  Except that the 2 nd neighbor strips are not connected 6

Bias Voltage dependence Inter-strip capacitance shows a stronger bias voltage dependence at low frequency (i.e. 100kHz) 7 Bias voltage(V) Inter-strip capacitance ( pF/cm) 100 kHz 1 MHz

Inter-strip capacitance VS Fluence Main result: Less impact by radiation in high frequency region  With 300V biased voltage, Inter-strip capacitance vary by ~50% as fluence increases  With 1000V biased voltage, Inter-strip capacitance variation is within uncertainty Inter-strip capacitance ( pF/cm) Fluence [Rad] 8 Fluence [Rad] Inter-strip capacitance ( pF/cm) Biased voltage=1000V Biased voltage=300V

Summary ATLAS12A mini sensors irradiated by gamma beam are measured. Inter-strip capacitance in irradiated samples ◦ Increased by one order of magnitude at low frequency (100k) ◦ Increased by 50 % at high frequency ◦ ATLAS Specification < 0.8 pF/cm at 100kHz ◦ meet ATLAS specification with high biased voltage Inter-strip resistance ◦ ATLAS Specification R_INT>10*R(bias) ◦ According to Specification interstrip resistance is sufficient when bias voltage is high 9

Next steps Starting on laser-based dynamic PTP study ◦ Aim to report the results in next meeting Will work on sensors performance after annealing, 10