Microcalorimeter arrays for high resolution soft X-ray spectroscopy

We have produced monolithic silicon detector arrays comprising 36 one-square-millimeter microcalorimeter pixels capable of achieving a resolution of ∼8 eV FWHM for soft X-rays. Each silicon pixel is suspended by silicon beams that provide a weak link to a ∼60 mK heat sink. The thermometer element of each pixel is an ion-implanted thermistor. X-ray thermalization is achieved in a 1 μm absorbing layer of MOCVD-grown HgTe. The HgTe is grown on thin Si substrates that are individually attached to the array elements using epoxy. We have determined that the value of the conductance of the link between absorber and thermometer critically affects device performance. We have performed preliminary investigations using arrays with small suspended absorber isolators etched in the center of each pixel. When an absorber is attached to the center of an absorber isolator, the beams supporting that isolator provide the thermal link to the rest of the pixel.