Stoichiometry Controlled, Single‐Crystalline Bi₂Te₃ Nanowires for Transport in the Basal Plane

Abstract

Thermoelectric Bi2Te3 based bulk materials are widely used for solid‐state refrigeration and power‐generation at room temperature. For low‐dimensional and nanostructured thermoelectric materials an increase of the thermoelectric figure of merit ZT is predicted due to quantum confinement and phonon scattering at interfaces. Therefore, the fabrication of Bi2Te3 nanowires, thin films, and nanostructured bulk materials has become an important and active field of research. Stoichiometric Bi2Te3 nanowires with diameters of 50–80 nm and a length of 56 μm are grown by a potential‐pulsed electrochemical deposition in a nanostructured Al2O3 matrix. By transmission electron microscopy (TEM), dark‐field images together with electron diffraction reveal single‐crystalline wires, no grain boundaries can be detected. The stoichiometry control of the wires by high‐accuracy, quantitative enegy‐dispersive X‐ray spectroscopy (EDX) in the TEM instrument is of paramount importance for successfully implementing the growth technology. Combined electron diffraction and EDX spectroscopy in the TEM unambiguously prove the correct crystal structure and stoichiometry of the Bi2Te3 nanowires. X‐ray and electron diffraction reveal growth along the [110] and [210] directions and the c axis of the Bi2Te3 structure lies perpendicular to the wire axis. For the first time single crystalline, stoichiometric Bi2Te3 nanowires are grown that allow transport in the basal plane without being affected by grain boundaries.

Electrodeposition of stoichiometric bismuth telluride Bi2Te3 using a piperidinium ionic liquid binary mixture

“…The figure 8 shows the evolution of A 2 peak current density with the for films electrodeposited in aqueous media [44]. This orientation is suitable for thermoelectric devices configuration since cleavage planes are perpendicular to the surface [45].…”

From thermoelectric bulk to nanomaterials: Current progress for Bi2Te3 and CoSb3

“…Series of binary nanowires were prepared by applying different reduction potentials, yielding different chemical compositions . Near stoichiometric single crystalline nanowires were obtained, allowing favorable transport along the basal plane of the rhombohedral structure . More recently, quasi single‐crystalline p‐type Bi 15 Sb 29 Te 56 and n‐type Bi 38 Te 55 Se 7 nanowires were grown with the same technique and will be presented in this work .…”

“…Bi 2 Te 3 ‐based nanowires, thin films, and nanostructured bulk materials as well as CoSb 3 ‐based thin films were prepared to study excitations and thermoelectric properties affected by dimensionality and nanostructuring. Advanced synthesis methods include potential‐pulsed electrodeposition , molecular beam epitaxy (MBE) , and spark plasma sintering (SPS) .…”

“…(iii) Bi 2 Te 3 materials have a layered rhombohedral crystal structure yielding a strong effect of texture on transport properties . Conventional and high‐energy X‐ray diffraction and electron diffraction in the TEM turned out to be of key importance to control the texture in nanowires , thin films , and nanostructured bulk .…”

Fabrication of alumina films with laminated structures by ac anodization

“…These products have been utilized in a variety of promising applications such as magnetic recording media [9–16, 33, 34], thermoelectric materials [17, 18], optical materials [20–22, 48, 49], sensors [23–25, 35], energy storage [25, 26, 36, 37, 50], photocatalysis [27, 51, 52], photovoltaic devices [28, 29] and biomaterials [53–56]. …”