Chemically and Morphologically Stable HgTe Nanorods for Infrared Photodetector Applications

Abstract

We have developed the synthesis of HgTe branched nanorods that exhibit stable infrared (IR) photodetector performance on single-element detector (SED) substrates for more than a year without additional protective coating or packaging. For more than a year, we have been analyzing nanorod films using X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (TOF-SIMS), electron microscopy, and grazing incidence small-angle X-ray scattering (GISAXS). After deposition, the films become denser for about a month. The distance between nanorods noticeably decreases without a change in the nanorod size and then stabilizes. Heating of the films leads to similar densification. XPS and TOF-SIMS show that nanorods oxidize at both the film surface exposed to air and the underlying interface with the substrate. This oxidation is self-passivating and slows down enough to retain stable SED performance for more than a year. Tetrahedron-shaped colloidal quantum dots (CQDs) of HgTe were also synthesized and tested as IR photodetector materials for comparison. The CQDs also perform well but degrade after several months.