PbSe

Several LED chips have been mounted together on the same thermoelectric cooler shown in Fig. 13.56b. This nondispersive IR analyzer utilizes sample and reference PbSe photoresistors as detecting elements. The LED emission (4.3 xm for CO2 and 4.7 xm for CO detection) is focused onto a sample photodetector by a concave mirror. 

Molten Pb reacts with the chalcogens to give PbS, PbSe and PbTe. 

The lead compounds PbS, PbSe, PbTe are narrow-gap semiconductors that have been widely investigated for infrared detectors, diode lasers, and thermo-photovoltaic energy converters. Their photoconductive effect has been utilized in photoelectric cells, e.g., PbS in photographic exposure meters. Integrated photonic devices have been fabricated by their heteroepitaxial growth on Si or III-V semiconductors. 

Aqueous electrolytes proposed in the literature for cathodic electrodeposition of lead selenide are generally composed of dissolved selenous anhydride and a lead salt, such as nitrate or acetate. Polycrystalline PbSe films have been prepared by conventional electrosynthesis from ordinary acidic solutions of this kind on polycrystalline Pt, Au, Ti, and Sn02/glass electrodes. The main problem with these applications was the PbSe dendritic growth. Better controlled deposition has been achieved by using EDTA in order to prevent PbSeOs precipitation, and also acetic acid to prevent lead salt hydrolysis. 

Being isomorphous, PbSe and PbTe form solid solutions in the whole range of compositions. Cathodic electrodeposition of the PbSe Tei-x ternary (0 < x < 1)... 

Within the scope of applications in electronics, electrooptics, and photovoltaics, several metal sulfides and selenides, mostly binaries such as CdS, CdSe, Bi2S3, Bi2Sc3, PbS, PbSe, Ag2S, TlSe, M0S2, ZnSe, ZnS, and SnS2, but also the ternaries... 

MoUn AN, Dikusar Al (1995) Electrochemical deposition of PbSe thin films from aqueous solutions. Thin Solid Films 265 3-9... 

Streltsov EA, Osipovich NP, Ivashkevich LS, Lyakhov AS, Sviridov VV (1998) Electrochemical deposition of PbSe Films. Electrochim Acta 43 869-873... 

Li KW, Meng XT, Liang X, Wang H, Yan H (2006) Electrodeposition and characterization of PbSe films on indium tin oxide glass substrates. J Solid State Electrochem 10 48-53... 

In fact, different techniques revealed cadmium segregation and decrease of the Pb/Se ratio near the InP/PbSe interface, indicating that during the first steps of deposition a CdSe layer is formed on InP prior to the PbSe growth. It was suggested that selective adsorption of Cd(0) on the InP surface gives rise to an epitaxial CdSe monolayer, which facilitates an ordered PbSe growth on account of the small lattice mismatch (0.7%) at the CdSe/(rock salt)PbSe interface. Importantly, it was found... 

Similar to PbSe, the controlled growth of lead telluride, PbTe, on (111) InP was demonstrated from aqueous, acidic solutions of Pb(II) and Cd(II) nitrate salts and tellurite, at room temperature [13]. The poor epitaxy observed, due to the presence of polycrystalline material, was attributed to the existence of a large lattice mismatch between PbTe and InP (9%) compared to the PbSe/InP system (4.4%). The characterization techniques revealed the absence of planar defects in the PbTe structure, like stacking faults or microtwins, in contrast to II-VI chalcogenides like CdSe. This was related to electronic and structural anomalies. 

Fig. 4.6 Layer sequence and X-ray diffraction (CuK ) of 8f period 4PbTe/4PbSe superfattice. Buffer layer is a fO-cycfe PbSe. Angle of incidence is 1°. The (111) diifraction peak (So), along with both first-order satellite peaks, and one second-order peak, are evident and indicative of the formation of a superlattice. (The XRD diagram is reprinted with permission from [76], Copyright 2009, American Chemical Society)...

Rajeshwar and co-workers performed photocatalytic underpotential deposition of Cd and Pb onto the surface of Se-modified Ti02 particles to prepare CdSe/Ti02 and PbSe/Ti02 composites [97, 98]. The Se-modified Ti02 particles were prepared themselves by UV illumination of titania particles in a Se(fV)-containing aqueous solution. The photocatalytic UPD of Cd and Pb on the bare Ti02 surface was found... 

Cachet H, Cortes R, Froment M, Mamin G (1999) Epitaxial growth of electrodeposited cadmium selenide on (111) gallium arsenide. Philos Mag Lett 79/10 837-840 Muthuvel M, Stickney JL (2006) CdTe Electrodeposition on InP(lOO) via Electrochemical Atomic Layer Epitaxy (EC-ALE) Studies Using UHV-EC. Langmuir 22 5504-5508 Streltsov EA, Osipovich NP, Ivashkevich LS, Lyakhov AS (1999) Effect of Cd(ll) on electrodeposition of textured PbSe. Electrochim Acta 44 2645-2652 Beaunier L, Cachet H, Cortes R, Froment M (2000) Electrodeposition of PbSe epitaxial films on (111) InP. Electrochem Commun 2 508-510... 

---