Template Epitaxial Growth of Thermoelectric Bi/BiSb Superlattice Nanowires by Charge-Controlled Pulse Electrodeposition

Abstract

Bi/BiSb superlattice nanowires ͑SLNWs͒ with a controllable and very small bilayer thickness and a sharp segment interface were grown by adopting a charge-controlled pulse electrodeposition. The deposition parameters were optimized to ensure an epitaxial growth of the SLNWs with a preferential orientation. The segment length and bilayer thickness of the SLNWs can be controlled simply by changing the modulating time, and the consistency of the segment length can be well maintained by our approach. The Bravais law in the electrodeposited nanowires is verified by the SLNW structure. Nanostructured thermoelectric materials can have dramatically higher efficiencies than their bulk counterparts. [1][2][3][4][5][6][7][8][9] The effectiveness of a thermoelectric material could be linked in an approximate way to the dimensionless thermoelectric figure of merit, ZT = S 2 T/, where S, , T, and are, respectively, the Seebeck coefficient, the electrical conductivity, the temperature, and the thermal conductivity.1 Compared to simple quantum wires, quantum dots, quantum wells, and two-dimensional superlattices, the quantum dot superlattices and superlattice nanowires ͑SLNWs͒ exhibit even greater advantages in the enhancement of the figure of merit ͑ZT͒. 3Because the heterogeneous interfaces between the nanodots can block the phonon conduction along the wire axis and thus reduce the lattice thermal conductivity, while the electrical conduction can be sustained and may benefit from the unusual electronic band structures, the SLNWs are especially attractive for thermoelectric applications.10 Recent studies further proved that the increased phonon scattering by grain boundaries would increase the ZT value. 2,8,9,11 The electron and phonon properties of SLNWs can be manipulated by many parameters, such as segment length, wire diameter, crystal orientation, bilayer thickness, and so on. [16][17][18][19][20][21][22][23][24][25] However, all these SLNWs are synthesized by modulating direct electrodeposition, the crystallinity is relatively not very high, and the interfaces between segments are not distinct. The pulsed electrodeposition, with various processing parameters and higher instantaneous current density, exhibits marked advantages over dc electrodeposition in controlling the deposited grain size, surface morphology, and preferred orientation, and proved to be a viable technological tool in materials engineering. 26,27 Bi is especially favorable for studying low dimensional systems and for low temperature thermoelectric applications due to its small electron effective mass and highly anisotropic Fermi surface.28 Calculations have proved that an unprecedented enhancement of the ZT value could be obtained in the Bi 1−x Sb x alloy nanowire system with the variation in x and the diameter of nanowires compared to pure Bi nanowires.29 Some promising work has been done on the Bi 1−x Sb x alloy 30-33 and other Bi-based 34,35 nanowire systems. As a result, the design and fabrication of SLNWs composed of Bi 1−x Sb x segment nanowires is...

Thermal Contraction of Electrodeposited Bi/BiSb Superlattice Nanowires

“…Figure 1d shows the HRTEM image of the region marked with a white rectangle in Fig. 1c , the clear and continue lattice fringes proved that the nanowire axis is along [110] direction, but no vacancies or dislocations were observed, as consistent with our previous observation [ 32 , 33 ].…”

“…We adopt the charge-controlled pulse electrodeposition to fabricate Bi/Bi 0.5 Sb 0.5 SLNWs in a two-electrode plating cell in which the AAM sputtered with a layer of Au film (about 200 nm in thickness) serves as the cathode, and a graphite plate serves as the counter electrode [ 32 , 33 ]. The AAM with the pore size of about 60 nm was prepared using the same procedures as in our previous reports [ 20 - 23 , 25 , 32 - 34 ].…”

Comprehensive Review on Thermoelectric Electrodeposits: Enhancing Thermoelectric Performance Through Nanoengineering

“…Weber et al (2008) electrodeposited high density nanowire arrays in AAO templates from the electrolyte of 50 mM Bi 3+ + 50 mM Sb 3+ in dimethyl sulfoxide. Dou et al (2009) synthesized Bi/BiSb multilayer nanowires by pulsed electrodeposition with small bilayer thickness. The electrolyte for the deposition contained a mixture of 80 mM SbCl 3 , 40 mM BiCl 3 , 0.24 M citric acid, 0.27 M tartaric acid, 1.2 M NaCl, 0.1 M glycerol and 1.0 M HCl.…”

Pulsed electrodeposition and unique properties of one-dimensional Bi-based nanostructures in porous alumina membranes

“…We adopt the charge-controlled pulse electrodeposition to fabricate Bi/Bi 0.5 Sb 0.5 superlattice nanowires in a two-electrode plating cell [37,38]. Briefly, the lower and higher pulse potentials are set by a computer-controlled pulse potential signal generator, the computer instantaneously integrates the current that the Real Time Current Acquisition System acquired to get the electric charge that passes during each time interval and subsequently monitors the pulse potential signal generator.…”