Characteristics of improved thin-film multijunction thermal converters

We fabricated thin-film MJTCs which consisted of a heater and thermocouple hot junctions on a dielectric membrane and cold junctions supported by a silicon frame. The sensitivity of the converter is higher in vacuum, 21.41 V/W, than in air, 5.82 V/W. The AC-DC transfer differences taken at 1 V and 40 Hz were 42.1 ppm in air and 11.8 ppm in vacuum. The AC-DC transfer differences were stabilized below 1 ppm in the frequency range from 1 kHz to 500 kHz. Studies to develop advanced converters with a thermal island structure under the heater to decrease the AC-DC transfer difference at low frequencies are under way. At the same time, new processes to optimize the skin effect and capacitive loss at high frequencies are being developed.