Effect of morphological structure on photosensitivity of chemically deposited PbS thin films

Abstract

Chemically deposited PbS thin films have been prepared for use as infrared detectors. A systematic and elaborate study using scanning electron microscopy shows that the structure and crystallite size are related to the photosensitivity. Both the role of chemical oxidant influencing the type of conductivity and morphological details such as crystallite size distribution have been investigated. It is observed that in the absence of oxidant the average size of crystallites is about 0.9 pm. This decreases to 0.3 pm for the concentration of oxidant imparting maximum photosensitivity and further reduces to 0.2 pm or less at higher concentrations. A good photosensitive film is electronically p-type and has a more uniform crystallite size distribution with relatively loose compact structure. Annealing of the films at 393 K under vacuum (5 x Torr) for 4-5 h affects the electronic properties considerably but does not cause any appreciable change in the structure except in smoothing the grain boundaries to a certain extent. A qualitative explanation in terms of rate of chemical reaction is offered for the morphological parameters observed in these experiments. It is also suggested that the photocharacteristics could be viewed partly as a support for barrier modulation but having its origin in the physical nature of the films.

Structural characterization of chemically deposited PbS thin films

“…The components were added in the mentioned order (a change may provide a different product at the end), to obtain a final dark solution. The variant C was used in a previous work as a seeding process in order to provide nucleation centers and improve the adherence between film and substrate [1,5].…”

“…Polycrystalline PbS thin films are currently attracting interest mainly due to their potential as infrared detector materials [1,2]. These films can be obtained by several methods [3,4], but chemical bath deposition (CBD) is mostly used due to its low cost and the quality of the obtained films.…”

“…The manufacture of advanced electronic devices with desired physical properties requires the availability of semiconductors films with controllable compositions, grain sizes and orientations. Indeed, the photosensitivity of the PbS polycrystalline thin film has a strong dependence with their structural and morphological characteristics [1,5].…”

Influence of a polymeric solution buffer layer on the chemical bath deposition of polycrystalline PbS films

“…Polycrystalline PbS thin films are currently attracting general interest, mainly due to their potential as infrared detector materials [1][2][3]. These films can be obtained by several methods [4,5], but chemical bath deposition (CBD) is just one of the more utilized due to its low cost and the quality of the obtained films.…”

“…The manufacture of advanced electronic devices with desired physical properties requires the availability of growth semiconductors films with controllable compositions, sizes, shapes and orientations. Indeed, it is known that photosensitive response of the PbS films depends on its structural characteristics [1,6]. Oriented crystallization of nanoparticles was observed in the growth of PbS nanocrystals mediated by surfactant polymer templates [7][8][9][10].…”