Nov 19 – 21, 2014
Europe/Zurich timezone

Investigation of the insulator layers for segmented silicon sensors before and after X-ray irradiation

Nov 21, 2014, 10:50 AM
500/1-001 - Main Auditorium (CERN)

500/1-001 - Main Auditorium


503-1-001 (Council Chamber) on 19th Nov ; 500-1-001(Main auditorium) on 20th in the morning and 4-3-006 (TH auditorium) in the afternoon; 500-1-001(Main auditorium) on 21st Nov.
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Ioannis Kopsalis (University of Hamburg)


For the proper simulation and understanding of segmented silicon sensors the surface boundary conditions and the charge density distribution in the SiO2 layer (and other insulator layers if present), as well as at the Si-SiO2 interface have to be known. It has been observed previously, that the boundary conditions on the sensor surface change with relative humidity, RH. A simulation example of time dependent surface potential of an AC coupled n+-p sensor with p-spray will be presented. We therefore have measured the surface conductivity of SiO2 at room temperature for RH values between 30 and 46 using a Gate Controlled Diode fabricated on n-type high-ohmic Si, and for RH = 50% using a MOSFET. For determining the effective oxide-charge density, Neff_ox, which is required for sensor simulations, as function of ionizing dose and biasing conditions, capacitance-voltage-frequency (C-V-f) measurements on MOS capacitors (MOS-C) irradiated up to SiO2 doses of 1GGy by 10 keV X-rays were performed previously. Large hysteresis effects were observed when the voltage was ramped from accumulation to deep inversion and back. We interpreted these shifts as evidence for field-enhanced injection of charges from the Si into the SiO2. Here we present C-V-f measurements on MOS-Cs fabricated on <100> and <111> high-ohmic Si, without irradiation and after X-ray irradiation to 1 GGy. In order to determine the time- and field-dependence of the injection of positive charges from the Si into SiO2, the MOS-Cs have been biased at different voltages in inversion for different time intervals.


The performance of segmented Si-sensors is influenced by the conditions at the sensor surface and at the Si-SiO2 interface.

Primary author

Ioannis Kopsalis (University of Hamburg)


Mr Dominik Brüske (University of Hamburg) Erika Garutti (Hamburg University (DE)) Jiaguo Zhang (Institute of Experimental Physics, University of Hamburg) Joern Schwandt (Hamburg University (DE)) Mr Khai Ton That (University of Hamburg) Prof. Robert Klanner (Hamburg University (DE))

Presentation materials