Effects of Stoichiometry on Structural, Morphological and Nanomechanical Properties of Bi2Se3 Thin Films Deposited on InP(111) Substrates by Pulsed Laser Deposition

Abstract

In the present study, the structural, morphological, compositional, nanomechanical, and surface wetting properties of Bi2Se3 thin films prepared using a stoichiometric Bi2Se3 target and a Se-rich Bi2Se5 target are investigated. The Bi2Se3 films were grown on InP(111) substrates by using pulsed laser deposition. X-ray diffraction results revealed that all the as-grown thin films exhibited were highly c-axis-oriented Bi2Se3 phase with slight shift in diffraction angles, presumably due to slight stoichiometry changes. The energy dispersive X-ray spectroscopy analyses indicated that the Se-rich target gives rise to a nearly stoichiometric Bi2Se3 films, while the stoichiometric target only resulted in Se-deficient and Bi-rich films. Atomic force microscopy images showed that the films’ surfaces mainly consist of triangular pyramids with step-and-terrace structures with average roughness, Ra, being ~2.41 nm and ~1.65 nm for films grown with Bi2Se3 and Bi2Se5 targets, respectively. The hardness (Young’s modulus) of the Bi2Se3 thin films grown from the Bi2Se3 and Bi2Se5 targets were 5.4 GPa (110.2 GPa) and 10.3 GPa (186.5 GPa), respectively. The contact angle measurements of water droplets gave the results that the contact angle (surface energy) of the Bi2Se3 films obtained from the Bi2Se3 and Bi2Se5 targets were 80° (21.4 mJ/m2) and 110° (11.9 mJ/m2), respectively.

Effects of Substrate Temperature on Nanomechanical Properties of Pulsed Laser Deposited Bi2Te3 Films

“…We found that the H and Ef values of the stoichiomectric Bi2Te3 films grown using the Bi2Te8 target are significantly larger those of the Te-deficient Bi2Te3 films grown using the Bi2Te3 target [23]. Similar beha have also been reported in the Bi2Se3 thin films [26]. Notably, for the present Bi2Te3 f C, and 300 • C, respectively.…”

“…We found that the H and E f values of the close stoichiomectric Bi 2 Te 3 films grown using the Bi 2 Te 8 target are significantly larger than those of the Te-deficient Bi 2 Te 3 films grown using the Bi 2 Te 3 target [23]. Similar behaviors have also been reported in the Bi 2 Se 3 thin films [26]. Notably, for the present Bi 2 Te 3 films, the intensity of the (006)-diffraction peak is dominantly higher than that of the (0015)-diffraction peak, whereas the Bi 2 Te 3 films in Ref.…”

Epitaxial Growth of the BiySb2–yTe3–xSex 3D Topological Insulator: Physical Vapor Deposition and Molecular Beam Epitaxy

“…The orthorhombic phases are formed or bismuth is aggregated in this condition. This problem is solved by increasing the flux of chalcogene-containing components or changing the source composition …”

“…This problem is solved by increasing the flux of chalcogenecontaining components or changing the source composition. 31 The influence of the substrate temperature on the surface relief is shown in Figure 2. The presence of quintuple layer (QL) steps, which are about 1.1 nm high, indicates the stepflow growth.…”

Additive Manufacturing of Thermoelectrics: Emerging Trends and Outlook

“…The choice of chemical dispersants and diluents is determined by the wettability of the filler material, governed by the chemical composition and microstructures. Wetting of non-oxide-based inorganic TE materials such as bismuth selenide (Bi 2 Se 3 ), bismuth telluride (Bi 2 Te 3 ), and lead telluride (PbTe) is a challenge as they tend to have low surface free energy, resulting in poor surface wettability and high contact angles. To obtain highly densified sintered structures, smaller sized TE particles can be used but these powders have higher surface area thus higher cohesive forces leading to poorer wettability, and hence dispersion difficulties .…”