Study of radiation damage in silicon detectors for high ... - F9
Study of radiation damage in silicon detectors for high ... - F9
Study of radiation damage in silicon detectors for high ... - F9
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6. Inuence <strong>of</strong> Bias Voltage 93Figure 6.3: Comparison time development <strong>of</strong> N eff <strong>for</strong> a sample biased (D2A) and unbiased(S3A) after ir<strong>radiation</strong>. Both samples were biased dur<strong>in</strong>g ir<strong>radiation</strong> and keptat15 C.B had 66mm 2 active area and those marked S 33 mm 2 active area. All diodes were300 m thick.Diodes D2A and S3A were used to determ<strong>in</strong>e the orig<strong>in</strong> <strong>of</strong> the dierence betweenbiased and unbiased samples. It could orig<strong>in</strong>ate <strong>in</strong> bias dependent creation rates or be aconsequence <strong>of</strong> defect reactions be<strong>in</strong>g aected by the electric eld. To dist<strong>in</strong>guish thesetwo scenaria, D2A was biased dur<strong>in</strong>g and after ir<strong>radiation</strong>, while diode S3A was biaseddur<strong>in</strong>g and unbiased after ir<strong>radiation</strong>. Time development <strong>of</strong> N eff at 15 dur<strong>in</strong>g the rstfew days after ir<strong>radiation</strong> is shown <strong>in</strong> gure 6.3. The diode unbiased after ir<strong>radiation</strong>exhibits alower N eff than the biased one 38 .At later stages <strong>of</strong> anneal<strong>in</strong>g we can also compare those two samples with theirpartners, unbiased dur<strong>in</strong>g ir<strong>radiation</strong> (gure 6.4). While diode D2B was unbiased bothdur<strong>in</strong>g and after the ir<strong>radiation</strong>, diode S3B was biased with 200 V after the ir<strong>radiation</strong>.Comparison <strong>of</strong> N eff <strong>for</strong> all four samples at the plateau shows that both samples, unbiasedafter the ir<strong>radiation</strong> (S3A and D2B), annealed to an equal N eff . It also agrees well withthe m<strong>in</strong>imal N eff <strong>of</strong> the U3 samples (g. 6.2). Plateau <strong>of</strong> the D2A sample is about twotimes <strong>high</strong>er and agrees well with biased samples B3, I3 and D3 (g. 6.2). The plateau38The dierence at the end <strong>of</strong> ir<strong>radiation</strong> can be expla<strong>in</strong>ed by anneal<strong>in</strong>g dur<strong>in</strong>g ir<strong>radiation</strong>, s<strong>in</strong>ce their<strong>radiation</strong> time was 39 m<strong>in</strong>utes <strong>for</strong> diode D2A and 6.5 hours <strong>for</strong> S3A. This dierence however becomesirrelevant after a few days <strong>of</strong> anneal<strong>in</strong>g.