Structure, Optical, and Photoelectric Properties of Lead-Sulfide Films Doped with Strontium and Barium
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OCRYSTALLINE, NANOCRYSTALLINE, POROUS, AND COMPOSITE SEMICONDUCTORS
Structure, Optical, and Photoelectric Properties of Lead-Sulfide Films Doped with Strontium and Barium L. N. Maskaevaa,b,*, E. V. Mostovshchikovac, V. I. Voroninc, E. E. Lekomtsevaa, P. S. Bogatovaa, and V. F. Markova,b a Ural
Federal University named after the First President of Russia B.N. Yeltsin, Yekaterinburg, 620002 Russia Ural Institute of State Fire Service, Emergency Ministry of Russia, Yekaterinburg, 620062 Russia c M.N. Mikheev Institute of Metal Physics, Ural Branch, Russian Academy of Sciences, Yekaterinburg, 620108 Russia *e-mail: [email protected] b
Received May 25, 2020; revised June 8, 2020; accepted June 8, 2020
Abstract—Evolution of the morphology, composition, structural characteristics (lattice constant, microstrains, texturing), and optical and photoelectric properties of PbS films produced by chemical bath deposition in the presence of ammonium iodide and strontium or barium chlorides at a concentration up to 5 mM is studied. According to the data of energy dispersive X-ray analysis, the content of strontium in the PbS films is 0.4–0.7 at %, whereas the content of barium is beyond the determination error. The size of the particles forming the films varies from ~200 to ~400 nm, and the size distribution of the particles is monomodal. The introduction of NH4I and SrCl2 or BaCl2 into the reactor retains the B1 cubic structure of lead sulfide, but gives rise to an unsteady change in the lattice parameter, which is due to the creation of vacancytype or interstitial ion defects. The introduction of salts of strontium or barium does not influence the band gap, but changes the intensities of the impurity absorption bands deep in the band gap or near the bottom of the conduction band. The dependences of the volt–watt sensitivity of the films on the content of salts of strontium and barium are of an extreme character and show maxima at 0.05 and 0.1 mM, respectively. Keywords: lead sulfide, thin films, crystal structure, strontium, barium, optical properties, photosensitivity DOI: 10.1134/S1063782620100231
1. INTRODUCTION Thin-film lead sulfide (PbS) occupies one of the most important places in the series of narrow-gap semiconductors (Eg = 0.41 eV at 300 K [1]) used for the production of detectors of infrared (IR) radiation [1, 2] in the range 0.4–3.2 μm. Due to the variety and specificity of its properties, this compound is extensively used for the production of mid-IR semiconductor lasers [2], chemical sensors [3, 4], fire detectors [5], converters of solar radiation [6], and quantum-dot semiconductors [7]. A widely used method of the production of lead sulfide in thin-film form is chemical bath deposition (CBD) from aqueous solutions [8–17]. This method is distinguished by its technological simplicity and by the possibility of controllably varying the electrical and photoelectric properties of films deposited by varying the conditions of their synthesis and the composition of the reaction mixture. The desired combination of optical and
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