Transient current induced in thin film diamonds by swift heavy ions
Résumé
Single crystal diamond is a suitable material for the next generation particle detectors because of the superior electrical properties and the high radiation tolerance. In order to investigate charge transport properties of diamond particle detectors, transient currents generated in diamonds by single swift heavy ions (26 MeV O$^{5+}$ and 45 MeV Si$^{7+}$) were investigated. Two dimensional maps of transient currents by single ion hits are also measured. In the case of 50 $\mu$m-thick diamond, both the signal height and the collected charge are reduced by the subsequent ion hits and the charge collection time is extended. These results are thought to be attributable to the polarization effect in diamond and it appears only when the transient current is dominated by hole current. In the case of 6 $\mu$m-thick diamond membrane, an "island" structure is found in the 2D map of transient currents. Signals in the islands showed different applied bias dependence from signals in other
regions, indicating different crystal quality. The instability of signals resulting from the polarization effect was also observed in the 6 $\mu$m-thick diamond membrane. Simulation study of transient currents based on the Shockley-Ramo theorem clarifies that the polarization appears only in the irradiated region and both the electric field and the hole lifetime are reduced by the polarization effect
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