| CPC H01L 31/02005 (2013.01) [H01J 37/244 (2013.01); H01L 31/186 (2013.01)] | 20 Claims |

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1. A device comprising:
a detector;
a sensing pad electrically connected to the detector;
a ring structure over the sensing pad, wherein the ring structure comprises:
an upper conductive ring; and
a lower conductive ring between the upper conductive ring and the sensing pad;
a control circuit;
a first transistor interconnecting the upper conductive ring and the control circuit; and
a second transistor interconnecting the lower conductive ring and the control circuit.
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