Electrical and Structural Characterization of Thin Pb0.5S0.5 Films Deposited with Different Thicknesses

Pb0.5S0. 5 alloy has been prepared successfully by the method of quenching for elements melt. The Pb0.5S0. 5 thin films of 200, 400, 600, 800 and 1000 nm thickness have been prepared from the prepared alloys by thermal evaporation technique onto glass substrate at room temperatures. The X-ray diffraction study shows that the prepared films are cubic polycrystalline structure with strong peaks at (200) and (111) planes, the intensity of the peaks increases with increasing film thickness. The grain size increases with increasing film thickness and their values varied between 35 and 59 nm. The D.C conductivity has been displayed two stages of conductivity through the whole temperature range. D.C conductivity have increased from 0.50×10-2 to 1.86×10-2 (Ω.cm)-1 as film thickness increased. All prepared films have two activation energies, where these values decrease with increasing thickness. The maximum value of activation energy was 0.177eV at 200nm thickness, and then decreased to 0.067 eV in thermal range 413-493K. Hall Effect results have been shown that all prepared thin Pb0.5S0. 5films were p-type material. The carrier concentration increases with increasing thickness, and it varies from 0.079×1019 cm-3 to 9.55×1019 cm-3 for thickness from 200 to 1000nm. The Hall mobility has been decreased from 3.99 to 0.098 (cm2/V.sec) as thickness increased from 200 to 1000nm. The drift velocity of these films decreases with increasing this films thickness. Introduction Semiconductor materials are always in focus due to their outstanding electronic and optical properties [1]. Lead salts and their alloys have a number of interesting physical properties as well as numerous potential applications. Lead chalcogenides (PbS, PbSe and PbTe) exhibit some unusual and unique properties such as high dielectric constant, narrow energy gap and high mobility [2]. The most remarkable feature of this group of compound semiconductors is the relative stability of the lattice over a wide range of stoichiometry [2]. As an important IV-VI group semiconductor, lead sulphide (PbS) is an important direct narrow band gap semiconductor material (≈ 0.41 eV at room temperature) [1], a relative cut-off wavelength of 3 μm [2] and high absorption coefficient continuously increasing the infrared through the visible region [3]. PbS thin films have been used as ideal selective surfaces for photo thermal conversion application. It is important as electronic and optoelectronic devices, in infrared photography, photoconductive cells, photovoltaic cells, contact less thermometers [3], including light-emitting diodes, single electron transistors, field effect transistors, Pb2+ion-selective sensors, IR detector, photography and solar absorption [1, 3]. In addition PbS has been utilized as photo resistance, diode single electron transistors, field effect transistors, Pb2+ion-selective sensors, IR detector, photography and solar absorption [1,3]. In addition PbS has been utilized as photo resistance, diode lasers, humidity and temperature sensors, decorative and solar control coatings [1]. Laser diodes based on lead chalcogenides and their alloys act as an important source of tunable radiations in mid infrared wavelength region. They are widely utilized in advance measuring systems to detect hydrocarbon pollutants in atmosphere, high resolution spectroscopy, trace gas analysis and optical fiber communication analysis and optical fiber communication systems over long distances [4,5]. This material has been studied by various deposition techniques such as electrodeposition, spray pyrolysis, photo accelerated, chemical deposition, microwave heating, chemical bath deposition (CBD), and vacuum evaporation [6-9].