Impact of low dose electron irradiation on the chargecollection of n + p silicon strip sensors

Christian Henkel
Feb 2014

Thesis Type:

In this work, the charge collection of two different $\mathrm{n^{+}p}$ silicon strip sensors has been studied, using the ALiBaVa (\textbf{A} \textbf{Li}verpool, \textbf{Ba}rcelona, \textbf{Va}lencia) read-out system.\\
In the beginning the two sensors were both completely unirradiated. One of them is a float zone produced FZ200-Y sensor having a p-spray strip isolation, the other is a magnetic Czochralski produced MCz200-P sensor with p-stop isolation. Most of the measurements were performed under radiation with a 100\,MBq $^{90}$Sr-source as provider for MIPs (\textbf{m}inimum \textbf{i}onizing \textbf{p}articles), irradiating a spot of $\approx$2\,mm in diameter on the sensor surface with a dose rate of about $2.1\,\mathrm{\frac{Gy}{h}}$.\\
Long term measurements up to days of duration under constant environmental conditions were performed to study the charge collection properties of the two sensors.\\
The results show changes in the charge collection in strong connection to the charge sharing for both sensors: While the charge sharing is low for an unirradiated sensor, it rises already significantly after an irradiation duration by $\upbeta$-particles of one day, accompanied by a decrease of the whole collected cluster charge. The temperature treatment of a sensor by annealing at 60\textdegree C and 80\textdegree C shows that the observed changes can only be recovered partially.\\
The observations can be explained by radiation induced positive charges in the $\mathrm{SiO_2}$ field oxide and are supported by TCAD simulations.

The work of this bachelor thesis led to the following publications:

R. Klanner et al.
"Impact of Low-Dose Electron Irradiation on the Charge Collection of n^+p Silicon Strip Sensors"
PoS TIPP2014 (2014) 040