Growth of Bi 2 Se 3 Films by Chemical Bath Deposition at Room Temperature
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Growth of Bi2Se3 Films by Chemical Bath Deposition at Room Temperature Sovannary Phok, Fatima Subait Al Wahshi, Shifaa Mohsen Al Baity and Saeed Ali Abdulla Yalyali. National Energy and Water Research Center, Abu Dhabi Water and Electricity Authority, Po. Box 54111, Abu Dhabi, United Arab Emirates.
ABSTRACT Bismuth selenide (BixSey) films are deposited onto glass substrate using chemical bath deposition at room temperature. The reacting bath contained bismuth nitrate, triethanolamine and sodium selenosulfate as selenium (Se) source. Ammonium hydroxide is used to adjust the pH of the bath. The films deposited in solutions containing Se source solution of 10 ml and 15 ml are characterized by surface morphological, compositional and structural, properties. The optimum deposition time is about 3 hours for both solutions. Films deposited up to 24 hours in bath with 10 ml Se source solution had thickness ranging up to 232 nm. The deposition rate is found to increase up to 61 nm/h for 3-hour deposition. In the case of bath with 15 ml Se source solution, the film thickness ranged from 45 nm to 632 nm for 1-hour to 24-hour deposition, respectively; with a deposition rate increasing up to 123 nm/h for 3-hour deposition. Film roughness of about 6.6 nm to 22.8 nm is measured by atomic force microscope for films deposited in bath containing 10 mL Se source and 15 ml of Se source, respectively. Crack free layers are observed with randomly large plate-like particles on top of the layer for some films. The films with typical composition of Bi21.8Se78.2 are found to be rich in Se when deposited for 6 hours, whereas the composition of a film deposited in the same bath (10 mL Se source) for 3 hours is found at Bi60.3Se39.6. Additionally, structural analysis performed by x-ray diffraction (XRD) did not reveal well-defined XRD patterns, which indicates that BixSey films were constituted mostly of nanocrystalline grains.
INTRODUCTION In the past decade, a new field has emerged in condensed matter physics. Topological insulators (TIs) including tetradymite compounds show unique electrical properties and topological surface states for applications in thermoelectric devices, spintronics, quantum computing [1], optoelectronics and sensor microdevices. Unlike the quantum Hall systems, the topological insulators can be doped into magnets and superconductors. A topological insulator, like an ordinary insulator, has a bulk energy gap separating the highest occupied electronic band from the lowest empty band. The surface or edge in two dimensions of a topological insulator, however, necessarily has gapless electronic states [2], that are reminiscent of edge states in the quantum Hall effect. Recently, experimental investigations have demonstrated that bismuthbased chalcogenides, in particular the tetradymite Bi2Se3 phase are topological insulators [2] that can be also converted into a topological superconductor by doping with copper [3]. The negative Hall effect RH [4-7] is clearly indicating that the native Bi2Se3 phase is always an n-type sem
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