Mo/Au Transition-Edge Sensors: effect of sensor size and absorber stem position on parameters and noise.

The basic transition parameters and excess noise of Mo/Au-based TES X-ray detectors without banks and with Au absorber are analysed as a function of TES dimensions and absorber stems position. We show the effect of the absorber stems and TES dimensions on these parameters. We observe that the logarithmic derivatives of R(T) are reduced and develop non-monotonous behaviour versus bias as stems are placed on the Mo/Au sensor area, progressively disturbing the current flow inside the TES. TESs with outer tangent stems display higher excess noise but also higher figures of merit because of their higher a and b values. We find that both longer and narrower TESs have higher excess noise, so that a trade-off is required for TES performance optimization. We discuss some hints for that. The possible origins of the experimental excess noise of these devices are also explored and discussed.