Speaker
Description
The present work reports a series of experiments aimed at the fabrication and investigation of photosensitive thin films operating in the 3-5 μm spectral range based on mercury chalcogenide colloidal quantum dots (CQDs), namely mercury telluride (HgTe) and mercury selenide (HgSe). Particular attention was devoted to the effect of ligand exchange on the structural and electrophysical properties of the resulting photoresistive devices.
Thin CQD films were fabricated via spin-coating under an inert argon atmosphere. The morphology and thickness of the deposited layers were characterized using atomic force microscopy (AFM). Photoresistive structures were prepared by sequential deposition of CQDs onto gold interdigitated electrodes followed by layer-by-layer ligand exchange. Their electrophysical characteristics were subsequently investigated.
Colloidal quantum dots are semiconductor nanocrystals whose surfaces are passivated by an organic monolayer composed of coordinating ligands. Due to quantum confinement effects, the optical properties of CQDs strongly depend on the size of the semiconductor core.
HgTe CQDs have attracted significant attention over the past decade owing to their unique physical properties. The combination of a large exciton Bohr radius (~30 nm), a near-zero bulk bandgap, and spectral tunability in the infrared region makes these materials highly promising for laser and photodetector applications. In contrast, HgSe CQD-based materials remain relatively underexplored, although their photoresponse extends into the 3-5 μm spectral range. In this study, thin films based on mercury chalcogenide CQDs and photoresistors fabricated from these materials were investigated.
Photosensitive thin films were synthesized from HgTe and HgSe CQD solutions using wet-chemistry approaches. The composition and thickness of the ligand shell were found to strongly affect the photoelectrical properties of the films.
Within this work, photosensitive HgTe and HgSe CQD thin films were fabricated on oxidized silicon substrates by layer-by-layer spin-coating performed both in an inert argon atmosphere and under ambient conditions. AFM characterization was employed to analyze surface morphology, roughness, and film thickness as a function of different ligand-exchange procedures. Ethane-1,2-dithiol and iodide ligands were selected as ligand-exchange agents. Photoresistors were fabricated by depositing CQD layers onto gold interdigitated electrodes formed on oxidized silicon substrates.
The fabricated photoresistors were investigated under different illumination conditions (980 nm irradiation and blackbody source illumination). Current-voltage (I-V) characteristics of mercury chalcogenide CQD thin films were measured and analyzed following ligand exchange with iodide ions and ethane-1,2-dithiol.
