Properties of Chemical Bath Deposited and sensitized PbSe thin films for IR detection

PbSe thin films of one-micron thickness were deposited on SiO2/Si wafers using chemical bath deposition method for IR detector applications. To sensitize the PbSe films for efficient midwave IR detection in the spectral range from 3 to 5 mu m, oxidation at 460 degrees C and subsequent iodization at 350 degrees C were performed. The x-ray diffraction for as-grown PbSe shows polycrystalline face-centered cubic NaCl type structure while Pb3O2(SeO3) oxide peak develops as a function of oxidation time. The existence of Se-rich structure may lead to p-type conduction. Scanning electron microscope and cross-sectional energy dispersive x-ray depth profile measurements after oxidation show the top layer of the film contains primarily Pb-Se-oxide while film at the bottom layer was PbSe. After sensitization, polytype trigonal 12R PbI2, Pb3O2I2 and PbSe were confirmed. The top layer of the sensitized PbSe film was found to be converted to primarily PbI2 while the bottom layer remained PbSe. However, during sensitization without oxidation, little PbSe remained because most of the PbSe was converted into PbI2. Also, the presence of metallic Pb nano-crystals with 10 nm diameter was detected in the sensitized film.