Effect of Substrate Temperature on the Growth of Molybdenum Trioxide Thin Films
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URFACE AND THIN FILMS
Effect of Substrate Temperature on the Growth of Molybdenum Trioxide Thin Films Divya Dixita and K. V. Madhuria,* a
Thin Film Research Laboratory, Division of Physics, Department of Science and Humanities, Vignan’s Foundation for Science, Technology and Research (Deemed to be University), Vadlamudi, Guntur, Andhra Pradesh, 522213 India *e-mail: [email protected] Received September 24, 2019; revised December 21, 2019; accepted January 8, 2020
Abstract—Molybdenum oxide is one of the most important inorganic material, which exhibits several phases, such as MoO3, MoO2, Mo4O11, Mo5O14, etc. Among them, molybdenum trioxide (MoO3) can crystallize in various phases, such as orthorhombic, monoclinic etc., which makes it useful for possible applications in chemical, electrical and electrochemical industries. In this work, MoO3 films were obtained by pulsed laser deposition by varying the substrate temperature from room temperature to 400°C. The thin films were deposited on fine cleaned glass substrates coated with fluorine tin oxide under a pressure of 10–5 mbar. X-ray diffraction patterns display two polymorphic phases of MoO3 (α and β), but no other phases are observed, and the structure changes from orthorhombic to monoclinic. The substrate temperature strongly influences the structure and surface topography. Morphological studies show the surface homogeneity, crack-free, layered structure and crystallinity of the films. The band gap of the obtained MoO3 thin films increases from 3.0 to 3.39 eV with increasing substrate temperature from room temperature to 400°C. DOI: 10.1134/S1063774520050065
INTRODUCTION Transition metal oxides have attracted much attention of researchers due to their highly fascinating features. In these oxides, the metal and oxygen atoms are bonded either with an ionic, or covalent, or metal bond. The very surprising properties of transition metal oxides are clearly related to their partially filled d-orbital and multiple oxidation states [1]. The combination of these oxides with thin film technology dramatically reduces the size of the electronic device for various technical and methodological applications and, hence, leads to miniaturization. Among the transition metal oxides, molybdenum trioxide (MoO3) has absolutely impressive characteristics, such as high stability, wider band gap, two-dimensional layered structure, diverse morphology, and it also has chromogenic properties [2, 3]. Due to changes in the physical as well as chemical structure, which leads to a change in optical, electrical and magnetic properties, they can be useful in public applications in diverse fields. Hence, thin MoO3 film has received more attention in recent years because of their important applications in gas sensors, photocatalysis [4–6], electro, photo, gasochromic display devices [7], smart windows, optical switching devices, optical recording, optoelectronics, energy-efficient window technology, high-density memory devices, bulk heterojunction solar cells, heterogeneous catalysis and positive an
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