Tuning Electrodeposition Conditions towards the Formation of Smooth Bi₂Se₃Thin Films

Abstract

Bismuth selenide (Bi 2 Se 3 ) is a semiconductor presenting two distinct crystalline phases with distinct bandgap and interesting optical, thermoelectric and topological electronic properties. In this work, thin films were grown by electrodeposition under constant potential onto silicon (100) substrate. It is shown that under an optimum set of deposition parameters, very smooth and thick films can be obtained. Such smoothness of the samples is highly desirable for future devices applications. Structural characterization of the samples indicates a majority of a metastable orthorhombic phase, while successively traces of rhombohedral and amorphous phases were detected. On the other hand, morphological characterization evidences the formation of compact, uniform and smooth layers. A full recrystallization to the rhombohedral structure can be achieved by using short time and low temperature thermal treatments.

Synthesis and Material Properties of Bi2Se3 Nanostructures Deposited by SILAR

“…Postsynthesis annealing at around 130–300 °C of Bi 2 Se 3 prepared by room-temperature deposition methods has been reported to result in a phase transformation from a mainly orthorhombic structure to the rhombohedral structure. , Since ambient annealing would further oxidize the selenides, the Bi 2 Se 3 [ x 90]/FTO samples were annealed in vacuum at 100 °C for 1 h. The XRD pattern was collected using a grazing incidence configuration for the annealed sample, as shown in Figure a. The five prominent peaks at 25.17°, 29.48°, 40.31°, 43.87°, and 48.12° matched the reference XRD pattern for rhombohedral Bi 2 Se 3 .…”

“…The group V–VI compounds such as Bi 2 Se 3 , Bi 2 Te 3 , and Sb 2 Te 3 have been traditionally investigated for thermoelectric conversion applications and recently have also been discovered to behave as 3D topological insulators (TIs). − These materials have a common rhombohedral crystal structure and a semimetallic bandgap of 0.105–0.335 eV. , In contrast, a second set of the same group V–VI compounds, Bi 2 S 3 , Sb 2 S 3 and Sb 2 Se 3 , have all been reported to exhibit semiconducting properties with bandgaps of around 1.1–1.76 eV. − This latter class of semiconductors has been shown to exhibit an orthorhombic crystal structure and has also demonstrated high radiation absorption coefficients, making them suitable for visible-light absorption in photonic devices and solar conversion technologies. Among these compounds, Bi 2 Se 3 appears unique since it has been reported to exhibit either a pure rhombohedral or a mixture of both rhombohedral and orthorhombic crystal structures, depending on the synthesis conditions. , The most commonly reported crystal structure for Bi 2 Se 3 is the rhombohedral phase (space group R- 3 m ), which exhibits a bulk bandgap of around 0.3–0.335 eV. , Formation of the alternative orthorhombic structure of Bi 2 Se 3 has only been shown to occur using fabrication techniques operating at close to room temperature, while techniques that require high temperature or some form of annealing during growth only produce the rhombohedral phase. This orthorhombic structure (space group Pnma ) has been reported to exist as a metastable phase under ambient conditions, and the bulk bandgap was estimated at 0.9 or 1.19 eV from two separate computational studies. ,, While doping, defect generation, size confinement, and variation of atomic composition in a compound material can promote tuning of its bandgap within a limited range, the ability to fabricate Bi 2 Se 3 with different crystal structures affords a wide range of properties and provides a unique opportunity to exploit this material in vastly different fields.…”

Comprehensive Review on Thermoelectric Electrodeposits: Enhancing Thermoelectric Performance Through Nanoengineering

“…Additionally, the deposited Bi 2 Se 3 had a bandgap of 1.25 eV (Tumelero et al, 2016). Souza et al (2017) synthesized Bi 2 Se 3 films by potentiostatic electrodeposition method in the electrolyte consisting of 1.5 mM SeO 2 , 0.5 mM Bi 2 O 3 and 1.0 M HClO 4 using silicon (100) as substrate. The deposited Bi 2 Se 3 films is compact with uniform and smooth morphology.…”

“…The as-deposited films had a dominant orthorhombic phase with mixture of rhombohedral and amorphous phases. However, pure rhombohedral structure was obtained after annealing (Souza et al, 2017).…”

Mathematical Modeling of the Electrodeposition Process of Bismuth-Selenium System

“…Халькогениды висмута являются одними из наиболее широко изученных слоистых материалов благодаря их хорошо известным термоэлектрическим свойствам [12], а также недавно обнаруженным свойствам топологических изоляторов [13]. Будучи важным халькогенидом n-типа, Bi 2 Se 3 обладает многими важными характеристиками, такими как высокая электропроводность [14], заметные термоэлектрические свойства [15], фоточувствительность [16] и фотопроводимость [17] [20].…”