Evidence of electronic cooling from resonance states of nanocrystalline graphite (NCG) field emitters

We have performed an experiment in which a 5mmx5mm silicon chip coated with 100nm of Ta and 100nm of NCG is placed on a thermally insulating acrylic cantilever pair. The temperature of the chip is measured with a thermistor that is glued to the bottom of the chip with silver paint. On an adjacent cantilever pair, a reference chip/thermistor is placed to monitor possible temperature changes in the vacuum chamber during the experiment. By placing the anode directly onto the NCG film, a resistance of about 140 Omega was measured and the change in temperature was recorded at different currents. From that control run, it was established that the effective resistance of the film was kOmega in the range and the cause of the heating. The small decrease in temperature around 10 muA is believed to be caused by a cooling effect since it also coincides with the onset of saturation in the I-V curve.