Investigation of Ti/Pd Bilayer for Single Photon Detection

Transition-edge sensor (TES) microcalorimeters are promising for application in the field of quantum information and quantum computation thanks to their outstanding single photon detection capabilities. Good energy resolution and photon number discrimination at visible and near-infrared wavelengths make them extensively used as single photon detectors. In this work we report details on the fabrication of Pd/Ti TESs deposited by e-beam evaporation on silicon nitride substrates. We use Pd as alternative to Au layer thanks to its stronger influence on the Ti layer, that allows to obtain the same temperature reduction with thinner layers. The transition temperatures T_c of the devices range from 83 to 110 mK with a transition width DeltaT_c=0.5 mK. Thermal and electric characteristics of Pd/Ti TESs at different temperatures and its capability as single photon sensor are reported.