Synthesis and Characterization of Iron-Doped Lead Sulfide Thin Films

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reported that semiconductor-doped glasses have extraordinary optical properties.[1] Optical, electronic, and magnetic properties of quantum dots can be controlled by changing their size, shape, surface characteristics, and crystal structure.[2] Thin films as semiconductors are commonly used in various industrial applications.[3] Since film form materials acquire and present new effects that are not originally observable in bulk form samples, in recent years, researchers are focused to study the physical properties of thin films. When the dimensions of the film are thin enough to be compared with the de Broglie wavelength of the electron, the optical and electrical properties of the materials are considerably affected by the film size.[4,5] Traditionally, researchers are interested in the optical absorption of the nano size semiconductors.[6] In another study, the growth of cobalt-doped nanostructured CuO thin films using the successive ionic layer adsorption and reaction (SILAR) method is presented.[7] Lead sulfide (PbS) is a narrow band gap IV–VI semiconductor material widely examined for technological applications such as optoelectronic,[8,9] photovoltaic devices,[10] infrared detector,[11–13] and solar control coatings.[14] The grain size and growth conditions greatly affect the optical and electrical properties of this material. The band gap (Eg) of PbS can be varied significantly by changing the grain size, and there are reports of opening the band gap to as high as 2.5 eV from its bulk value of 0.41 eV by decreasing the grain size to the order of 2 nm.[5] Changing the applied YASIR GU¨LEN, Assistant Professor, is with the Department of Physics, Faculty of Arts and Sciences, Marmara University, Istanbul 34722, Turkey. Contact e-mail: [email protected] Manuscript submitted February 25, 2015. Article published online July 22, 2015 4698—VOLUME 46A, OCTOBER 2015

temperature and pressure or the nanocrystal size affects and changes the band gap of lead sulfide. Band gap tunable lead sulfide nanocrystals ranging from 0.6 to 1.7 eV have been synthesized.[15] PbS thin films can be synthesized by several chemical deposition techniques such as chemical bath,[6] electro,[16] photo chemical,[17] and SILAR method.[18,19] Ultrasounds lead to an increase of crystallites size and strain. PbS obtained from static baths were formed from near spherical grains with average size of 183 nm; on the other hand, in ultrasonic baths cubical particles of 257 nm were formed.[20] In another study, PbS thin films were deposited on glass substrates by using chemical bath technique at different solution temperatures and various deposition times. X-ray diffraction showed that the thicknesses of the obtained thin films were between 600 and 1000 nm. Band gap of thin films was reported to be 2.30 to 1.96 eV, respectively. It was observed that transmission of the films was decreasing as the thickness of the films was increasing.[21] Because of its extraordinary third-order nonlinear optical properties PbS quantum dots may be useful in optical devices.[22] Comparing w

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