Lattice Strain Enhances Thermoelectric Properties in Sb₂Te₃/Te Heterostructure

Abstract

κ, κ e , κ L , and T are the Seebeck coefficient, electrical conductivity, total thermal conductivity, electrical thermal conductivity, lattice thermal conductivity, and absolute working temperature, respectively. [1,2] Since α, σ, and κ are strongly coupled with each other, a simple improvement in single parameter usually results in a deterioration of the others. The challenge of realizing superior TE properties lies in the improvement of ZT, that is, simultaneously increasing in power factor (PF = α 2 σ) and suppressing κ. Normally, α enhancement can be achieved by a carrier energy filtering effect, caused by band bending at the nanointerfaces between nanoparticle and TE host materials. [2-4] Meanwhile, reducing κ L by phonon scattering is an effective way to reduce κ while maintaining a high σ. Very recently, lattice strains regulated by annealing time have also been observed for remarkably decreasing κ without affecting the carrier mobility (µ). [3] Sb 2 Te 3 and its derivatives are considered to be one of the best p-type TE materials near room temperature. [5] Compared with its bulk counterparts, nanostructured Sb 2 Te 3 film provides promising possibilities for enhanced TE properties and potential applications in micro/nanoelectromechanical systems (MEMS/NEMS) TE device. [6] Experimentally, Sb 2 Te 3 has been prepared by various approaches such as physical vapor deposition (PVD), solid state reaction, and chemical synthesis method and so on. [1,7,8] The effect of substrate, annealing temperature, and thickness on PF as well as the strain-and grain size-dependent κ in Sb 2 Te 3 films was studied. [9-11] PF can be enhanced by introducing nanoscale metal/semimetals into

Bottom-Up (Cu, Ag, Au)/Al2O3/Bi2Te3 Assembled Thermoelectric Heterostructures

“…For a material with a single parabolic band, the Seebeck coefficient, DOS effective mass of carriers ( m *) and Lorenz number ( L ) can be written as [ 22 , 29 ] κ e = LTσ where e , m *, h , k B, L , and T are the electronic charge, effective mass, Planck’s constant, Boltzmann constant, Lorenz number, and absolute temperature, respectively. η is the reduced Fermi energy ( E F / k B T ), F i is the fermi integral of the order of x. Acoustic phonon scattering ( γ = −1/2) has been assumed as the main carrier scattering mechanism at room temperature.…”

“…The contact effect and other additional effect including heating effect of current and asymmetric effect of probing electrodes can be exclude in this current reversal method with four-probe configuration. The Seebeck coefficient was evaluated by a home-built system as reported in detail in our previous study [ 22 ].…”

“…The contact effect and other additional effect including heating effect of current and asymmetric effect of probing electrodes can be exclude in this current reversal method with four-probe configuration. The Seebeck coefficient was evaluated by a home-built system as reported in detail in our previous study [22]. The surface morphology, cross section, composition, and thickness of films were characterized by atomic force microscope (AFM, Multimode Nanoscope IIIa), scanning electron microscopy with energy dispersive spectrometer (SEM-EDS, Zeiss Ultra Plus) and surface profiler (KLA-Tencor P7).…”

“…The deposited Al2O3 layer allowed tunneling electrons to pass through, which would reduce the concentration of high-energy electrons in the film, and ultimately reduce the Seebeck coefficient. For a material with a single parabolic band, the Seebeck coefficient, DOS effective mass of carriers (m*) and Lorenz number (L) can be written as [22,29] 3/2…”

“…In addition, the corresponding electronic thermal conductivity calculated according to Equation ( 5) is given in Table 1. For a material with a single parabolic band, the Seebeck coefficient, DOS effective mass of carriers (m*) and Lorenz number (L) can be written as [22,29]…”