Aging of nano-morphology, resistivity, and far-infrared absorption in gold-black

Abstract

Gold black is a highly porous, extremely fragile, infrared-absorbing film used primarily as a coating for bolometers. Long term stability of its absorbance is a significant practical concern. This paper reports on the aging of morphological, electrical, and optical properties of gold black samples prepared with different initial porosities. An observed two-fold decrease in electrical resistance after 90 days at room-temperature is correlated with an increase in nano-crystalline grain size. Much larger resistance drops were observed after isothermal annealing at temperatures up to 100 °C. Aging and annealing tended to improve the far-infrared absorption. Samples with the highest initial porosity have the fastest structural relaxation.