INFRARED PHOTOGRAPHY BASED ON VAPOR-DEPOSITED SILVER SULFIDE THIN-FILMS

Ag2S as a narrow band-gap semiconductor is appropriate for photoimagin g in the infrared (IR) region. Coevaporation of silver and sulfur from separate sources is used for preparing Ag2S thin films with different Ag/S ratios. The structure of the films is examined by transmission e lectron microscopy, electron diffraction, and x-ray diffraction. We fi nd that upon illumination latent-image centers or print-out silver spe cks are formed predominantly in the bulk of the Ag2S grains. Their gro wth in a stabilized physical developer becomes possible after appropri ate etching of the exposed Ag2S films. The photographic parameters of the films are related to the processing conditions, film thickness, an d Ag/S ratio. It is shown that after proper processing, Ag2S thin film s with stoichiometric composition or excess amount of silver can be su ccessfully used as either negative or positive high-resolution photogr aphic materials in the IR region. A maximum resolution of 1600 lines/m m has been achieved so far.