Toward Reduced Interface Contact Resistance: Controllable Surface Energy of Sb₂Te₃ Films via Tuning the Crystallization and Orientation

Abstract

The electrical contact resistance between a metal and semiconductor is one of the keys to improving the output performance of thin-film thermoelectric devices. Herein, we reduced the interface contact resistance by controlling the surface energy of a Sb 2 Te 3 semiconductor via tuning of the crystallization and orientation, preparing an intrinsically compact and flat Sb 2 Te 3 film with high surface energy and low roughness, which can give rise to a low average specific contact resistivity (8.2 × 10 −6 Ω cm 2 ) with a Ni/Cu metal. The improvement in interface electrical properties is due to the increase in the surface energy and decrease in the surface roughness of the semiconductor surface, which lead to a transformation from three-dimensional island-shaped nucleation to two-dimensional layered nucleation for surface-attached metal films, forming a longitudinally tight connection contact with a low resistance. This approach allows the resistivity to become close to the fundamental theoretically calculated limit. Our work provides a new idea for reducing the contact resistivity of thin-film thermoelectric devices, which is conducive to supporting the development of thermoelectric semiconductor planarization.

Structural Defects and Ferromagnetic Signature of V-Doped Sb2Te3 Thin Films Grown on SrTiO3(001) Produced by RF-Magnetron Sputtering

“…This result indicates that Sb 2 Te 3 grows faster in the lateral direction during the crystal growth on the SrTiO 3 (001) substrate. The surface free energy of Sb 2 Te 3 (0.03–0.07 J/m 2 ) 12 is much lower than that of the SrTiO 3 (1.09 J/m 2 ), 13 also justifying the lateral growth of Sb 2 Te 3 on the SrTiO 3 substrate.…”

“…This result indicates that Sb 2 Te 3 grows faster in the lateral direction during the crystal growth on the SrTiO 3 (001) substrate. The surface free energy of Sb 2 Te 3 (0.03−0.07 J/m 2 ) 12 is much lower than that of the SrTiO 3 (1.09 J/m 2 ), 13 also justifying the lateral growth of Sb 2 Te 3 on the SrTiO 3 substrate. Figure 3a shows a cross-sectional HREM image of the Vdoped Sb 2 Te 3 thin film sputtered for 120 s. As seen, there exists a thin amorphous layer between the Sb 2 Te 3 and the SrTiO 3 substrate.…”

“…It is presumed that the amorphous layer is formed to relax the lattice strain between the single-crystal substrate and the Sb 2 Te 3 film. Once the strain is relaxed, the (0001) atomic plane, which is a low-index atomic plane with low surface free energy, 12 preferentially grows on the amorphous layer, and hence, the c axis tends to orient perpendicular to the film plane. The FFT pattern shown in Figure 3 a was obtained from the Sb 2 Te 3 film.…”

Soldering Pressure Effect on Lifetime of Thermoelectric Modules under Thermal Cycling

“…It can be influenced by various factors, including the crystallinity of the metal layer, surface cleanliness and roughness of the substrate, and the deposition technique. 32,33 Figure 3a illustrates the calculation method for determining the contact resistivity of the module, specifically for the N-type samples at a soldering pressure of 50 N (data 3). Figure 3b,c shows the measured contact resistivity of P-type and N-type bismuth telluride TE joints assembled with different soldering pressures (15,25,35, and 50 N).…”

Localized Surface Doping Induced Ultralow Contact Resistance between Metal and (Bi,Sb)2Te3 Thermoelectric Films

“…TLM is a common method for calculating the ρ c of the thin-film interface between a metal and a semiconductor, and ρ c can be extracted from the linear fitting curve of TLM. 33,34 It is noted that for the TLM model, the bulk resistance of the contact metal is very small and thus can be ignored. In specific measurements, the probe is in contact with two adjacent electrodes, and the total resistance R T that varies with the distance between the two electrode contacts is tested.…”