  We present ultra-thin silicon membrane thermocouple bolometers suitable for
fast and sensitive detection of low levels of thermal power and infrared
radiation at room temperature. The devices are based on 40 nm-thick strain
tuned single crystalline silicon membranes shaped into heater/absorber area and
narrow n- and p-doped beams, which operate as the thermocouple. The
electro-thermal characterization of the devices reveal noise equivalent power
of 13 pW/rtHz and thermal time constant of 2.5 ms. The high sensitivity of the
devices is due to the high Seebeck coefficient of 0.39 mV/K and reduction of
thermal conductivity of the Si beams from the bulk value. The bolometers
operate in the Johnson-Nyquist noise limit of the thermocouple, and the
performance improvement towards the operation close to the temperature
fluctuation limit is discussed.
