Abnormal conductivity behavior in porous lead telluride films
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NANO EXPRESS
Open Access
Abnormal conductivity behavior in porous lead telluride films Sergey P Zimin1*, Egor S Gorlachev1,2 and Fedor O Skok1
Abstract: We report the experimental observation of the novel phenomenon of the resistivity decrease in porous PbTe layers during the pore formation process. Investigations were performed on the n-PbTe films with 2.3-μm thickness, which were near the point of the conductivity-type inversion at room temperature. Anodic electrochemical treatment for the porous layers with 41% to 52% porosity fabrication was performed using a KOHbased Norr electrolyte solution. For the porous lead telluride layers, the resistivity value at 300 K decreased 2.5 to 3 times. For the explanation of the observed phenomenon, a physical model is proposed which takes into account the Pb/Te ratio change during the anodic treatment. Keywords: Porous semiconductors, Porosity, Lead telluride, Electrical conductivity PACS: 81.05.Rm, 71.20.Nr, 72.60. + g
Background One of the most urgent problems in the field of a new porous semiconductor material synthesis is the systematic study of the change of the electrical conductivity during the pore formation. In the classical cases, the processes of the pore formation result in the resistivity increase, which is due to the additional charge carrier scattering at the pores, the processes of the charge carrier depletion in the areas around the pores, quantum size effects, oxidation processes, etc. [1,2]. Recently, we have demonstrated that the formation of a porous lead telluride (PbTe) layer using anodic electrochemical treatment method is accompanied by the changes of the ratio between metal and chalcogen atoms [3]. This process is in strong degree determined by the anodic treatment conditions and by the initial material Pb/Te ratio. Secondary ion mass spectrometry investigations have shown that, in most cases, the tendency of the increase of the metal concentration with respect to chalcogen takes place. It is well known that, in lead chalcogenides, the concentration of the charge carriers is defined by a deviation from stoichiometry, with the abundance of lead resulting in the increase of the concentration of electrons. Under these conditions, theoretically, there are possibilities of an * Correspondence: [email protected] 1 Microelectronics Department, Yaroslavl State University, Sovetskaya Street 14, Yaroslavl 150000, Russia Full list of author information is available at the end of the article
abnormal conductivity behavior when porous lead telluride would demonstrate a conductivity increase in comparison with an initial state. The aim of this work was to confirm experimentally the phenomenon of the PbTe resistivity reduction after anodic electrochemical treatment.
Methods Monocrystalline (111)-oriented n-PbTe films with 2.3-μm thickness (dinit) were grown on СaF2/Si(111) substrates using molecular beam epitaxy in ETH, Zürich [4]. The typical thickness of the calcium fluoride (CaF2) buffer insulating layer was 2 to 4 nm. The silicon substrate resistivity w
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