Nanomorphology and performance of pure and doped lead selenide for infrared detector

Abstract

Lead selenide (PbSe) has been studied as a promising material for room temperature midwave infrared detection. We have investigated pure PbSe, as well as tin (Tn) and cadmium (Cd)-doped PbSe, nanocrystalline materials produced using physical vapor transport methods on glass and high-resistivity silicon substrates. The morphologies were investigated by scanning electron microscopy and energy-dispersive x-ray analysis. Pure PbSe layers consisted of nanocrystals that change into cubes and cuboids upon annealing. Cuboids generally grew in [100] orientation and ultimately developed in nanorods. Growth on silicon and glass substrates showed different morphologies of pure PbSe material. Parabolic and elongated morphologies resulted in nanowires on the top of thin layers of PbSe nanofilm, which acted as the substrate. Under low gradient annealing conditions (<20 K/cm), elongated morphologies grew into nanorods. Annealing of these samples resulted in coarse nanomorphologies with higher resistivity. In the case of Tn-doped PbSe, annealing dissolved a Tn-rich phase observed in as-grown films. Cd- and iodine-doped films produced through the addition of Cd selenide and Cd iodide, respectively, showed higher resistivity than similarly treated pure PbSe films. Annealing of as-grown materials in the presence of oxygen or iodine showed increased resistivity and significant changes in optical characteristics.