Study of photoresistor fabrication based on mercury chalcogenides applying various ligand exchanges

Colloidal quantum dots (CQDs) of mercury telluride have attracted a lot of attention in the last decade because of their unique properties. Mercury telluride-based CQDs are promising candidates for use in various fields of engineering and science, due to the incomparable combination of the large radius of the Boron exciton (30 nm) and the band gap (0 eV) for bulk material. This ensures the spectral rearrangement of the properties of the CQDs from the near to far IR range. On the basis of this material the photodetectors, lasers and telecommunication devices are being under active development. Mercury sulfide CQDs are a material that has been little investigated, and based on our research, interesting results have been obtained.

Photosensitive thin films are created from sols of coloidal quantum dots of mercury chalcogenides for the use in photodevices. The ligand exchange procedure strongly affects the photoelectric properties of thin films, but it has an additional impact on their properties.

In order to optimize the fabrication of photoresistors the several additional aspects were studied like morphology and thicknesses of created films. HgTe and HgS CQDs were applied on glass substrates and interdigitated electrodes by dip-coating and spin-coating methods applying layer-by-layer deposition technique. The surface morphology and roughness of the obtained films were studied using atomic force microscope. Film thicknesses were also determined depending on various ligand exchange (ethandithiol, sulfide, thiocyanate, iodide). Photosensitive films were created by applying layers of colloidal quantum dots of mercury chalcogenides to golden electrodes and their volt-ampere characteristics were determined.

As part of the work, measurements were made of both - dark volt-ampere characteristics (VAC) and light VAC when illuminated with a laser at 980 nm, for thin films of mercury chalcogenides. After replacing the original shells with I^-, S^2-, SCN^- and ethandithiol-1,2, the results obtained were analyzed.