Influence of the humidity on the IV curves A.Chilingarov Lancaster University UK-Valencia Cluster Meeting RAL,

A.Chilingarov, Influence of the humidity on the IV curves 2 Examples of the IV curves measured in the QA. Each plot contains the data for 4 detectors with consecutive numbers. All currents are corrected to 20 o C. Note the flattening of the curves at high bias values with humidity.

A.Chilingarov, Influence of the humidity on the IV curves 3 Recollect our earlier reports that in a typical detector the current increases and the inter-strip capacitance decreases after bias application. (The plots are for U=150V.) The stabilisation time decreases rapidly with the ambient humidity. According to Rainer Richter, MPI, these effects can be explained by a charging of the insulation layer covering the detector surface, which in turn depletes the electron accu- mulation layer at the Si-SiO 2 interface.

A.Chilingarov, Influence of the humidity on the IV curves 4 The same effect can explain the flattening of the IV curves at high voltages. This is probably due to the surface charging completed already during the measurement. (In our case the IV from 5 to 500V takes ~13min.) The reason for a decrease of the maximum current with humidity (detectors w21-54 and w21-17) is less clear.

A.Chilingarov, Influence of the humidity on the IV curves 5 Four w21 detectors from the same batch, tested at low humidity during the QA, were recently re-measured at high humidity. The results clearly confirm the above mentioned trend.

A.Chilingarov, Influence of the humidity on the IV curves 6 Conclusions 1.The IV curves measured for the same detector become more flat at high bias values as the ambient humidity increases. This can be understood from the same model which explains the long-term stabilisation effects reported earlier. 2.The current at maximum bias voltage (500V) also changes with humidity. However the nature of this dependence is less clear. 3.All the above effects should be taken into account when comparing the IV measurements at different stages of the module production.