Investigations of PbSe layers after anodic electrochemical etching by scanning electron microscopy

Abstract

Investigations of the morphology of the surface of PbSe/CaF2/Si(111) epitaxial structures after anodic electrochemical etching in a Norr electrolyte with anodizing current density of 2‐8 mA/cm2 and duration of 10‐20 min were performed. Two possible morphology types of PbSe nanostructured surficial porous layers were distinguished. Agglomerated nanoislands with 80‐400 nm lateral sizes and 70 nm average separating gaps were observed for the anodized films with initial flat terraced surface. It is shown that in this case it is possible to fabricate PbSe agglomerated nanoisland structures directly on silicon substrate. A double‐layered porous structure was obtained for epitaxial PbSe films with initial granular surface. Top porous layer with a thickness of 75‐100 nm presents a developed hierarchical porous network. Bottom layer is characterized with a presence of mesopores with 7‐18 nm diameter propagating into the layer. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Investigations of the pore formation in the lead selenide films using glacial acetic acid- and nitric acid-based electrolyte

“…The first batch of porous PbSe films was fabricated using the Norr electrolyte. We discussed these results in much detail in [ 8 ], and here, we will give only the basic overview. The principal result was that the modified anodized layer morphology strongly depended on the initial film surface state.…”

“…The average size of the synthesized mesopores was 22 nm, and their density on the surface was approximately 10 10 cm −2 . The thickness of the underlying unmodified PbSe film indicated that the thickness of the PbSe layer that was etched away was equal to the thickness of the fabricated porous layer, due to the stabilizing role of glacial acetic acid, in contrast to the Norr electrolyte treatment [ 8 ], when the thickness of a porous modified PbSe layer was typically an order of magnitude smaller than the removed layer thickness.…”

“…Current density was 2 to 8 mA·cm −2 , and treatment duration was 10 to 20 min, performed at room temperature. These film samples were further divided into two groups depending on the morphology type of their initial surface: the first group had a typical flat surface for MBE-grown PbX layers on CaF 2 /Si(111) with nanoterraces and dislocation exit pits with approximately 10 7 cm −2 density, while the second group had a peculiar granular surface (for details, see [ 8 ]). The second batch of PbSe films (containing 3% Sn, with flat initial surface) was anodized using a solution of 10 ml of nitric acid (HNO 3 ), 10 ml of glacial (undiluted) acetic acid (CH 3 COOH), and 40 ml of glycerol (first used by EH Tompkins and GL Johnson [ 11 ] for the electropolishing of lead selenide at high current densities), for which, by analogy with porous silicon, we reduced the current density (1 mA·cm −2 ) and processing temperature (20°C) with a duration of 10 min.…”