Fabrication and study of porous PbTe layers on silicon substrates

Abstract

Fabrication of porous PbTe layers on Si substrates using a developed technique based on anodic electrochemical etching of PbTe/CaF2/Si(111) heteroepitaxial structures in a Norr electrolyte with anodizing current density 2‐4 mA/cm2 is reported. The structural and morphological parameters of such layers are investigated with x‐ray reflectometry and diffractometry methods and with high‐resolution scanning electron microscopy. The influence of anodizing conditions on the parameters of the layers is discussed, as well as the morphological peculiarities of the anodized structures. The presence of cylindrical mesopores with diameter of 7‐26 nm inclined at the angle of ∼35° to the surface normal is shown. The value of the porosity for the near‐surface layer of lead telluride films is in the interval of 41‐68% and depends on the anodic electrochemical treatment conditions. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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

“…The anodic electrochemical etching under given parameters allowed us to succesfully obtain double-layered porous structure for PbSe films. Remarkably, the films showed a strongly modified unique morphology significantly distinct from PbTe films treated under similar conditions [11]. While the overall picture can be described as macroporous, it is quite possible that the underlaying modified layer is mesoporous, as the exits of the pores with 7-18 nm diameter are clearly seen on certain surface areas.…”

“…A vertical type electrochemical cell schematically shown in Fig. 1 was used, which allowed us to perform anodic electrochemical etching of heteroepitaxial multilayered PbSe/CaF 2 /Si(111) structures according to a technique that was previously elaborated and applied for the fabrication of porous PbTe layers [10,11]. Prefabricated teflon base of the cell consists of two main parts: upper unit (1) with a circular platinum cathode and lower unit (2) with flat metallic anode.…”

“…An interesting prospective possibility is to use porous PbX layers as elements of gas analyzers with the extension of already existing technology with a fabrication of high surface to volume ratio of nanostructured material. We have recently developed and reported a technique for the porous structure fabrication based on anodic electrochemical etching of lead telluride epitaxial layers on silicon substrates in a potassium hydroxide based solution [10,11]. The aim of the present work was to carry out anodic treatment for PbSe epitaxial layers under the same anodizing conditions as for PbTe and to compare the obtained results.…”

Abnormal conductivity behavior in porous lead telluride films

“…The conditions of the anodic electrochemical treatment for the particular studied samples are summarized in Table 1 . The results of the structural and morphological parameter investigations for the porous layers synthesized under these conditions are described in [ 6 , 7 ]. The surficial mesoporous nanostructured layer had a thickness ( d por ) up to 200 nm.…”

“…The porosity value, as determined with X-ray reflectometry method, was 41% to 52%. The experimental setup, measurement technique, and working formulas for determining the porosity of the samples by X-ray reflectometry are described in full detail in [ 6 , 7 ]. The effective conductivity type of the PbTe films after treatment did not change and remained n-type.…”