Dec 3, 2024
8:00pm - 10:00pm
Hynes, Level 1, Hall A
Suman Abbas1,2,3,Bhawna Jarwal1,3,Thi-Thong Ho1,Suneesh Valiyaveettil1,Cheng-Rong Hsing4,Ta-Lei Chou3,Ching-Ming Wei1,Li-Chyong Chen3,Kuei-Hsien Chen1,3
Academia Sinica1,National Central University2,National Taiwan University3,Chang Gung University4
Suman Abbas1,2,3,Bhawna Jarwal1,3,Thi-Thong Ho1,Suneesh Valiyaveettil1,Cheng-Rong Hsing4,Ta-Lei Chou3,Ching-Ming Wei1,Li-Chyong Chen3,Kuei-Hsien Chen1,3
Academia Sinica1,National Central University2,National Taiwan University3,Chang Gung University4
Germanium Telluride (GeTe) has been extensively studied as a promising lead-free thermoelectric material in its rhombohedral and cubic phases. The rhombohedral to cubic phase transition at ~ 700 K made this material challenging for practical application. Additionally, due to the presence of multi-valence bands and strong anharmonic interactions, the high-temperature cubic phase demonstrates a higher power factor, and lower thermal conductivity, that leads to superior thermoelectric performance compared to its rhombohedral counterpart. In this work, a cubic phase of Ge<sub>0.9</sub>Sb<sub>0.1</sub>Te (GeSbTe) was first stabilized at room temperature. Then a simple and effective method was proposed to introduce Indium (In) into the GeSbTe structure. The impact of indium doping was thoroughly examined.It is demonstrated that through a two-step process (thermal evaporation and thermal annealing), indium was successfully and uniformly doped into Ge<sub>0.9-x</sub>Sb<sub>0.1</sub>Te-In<sub>x </sub>thin films. The gradual increase in doping amount (x= 0.02, 0.03, 0.04, and 0.05) indicated that the indium content can be controlled by adjusting the thickness of the evaporated indium layer. Indium doping had increased the effective mass and electron density in the GeSbTe films, reducing the overall p-type carrier concentration and significantly improving the Seebeck coefficient. Density functional theory (DFT) calculations revealed that indium acts as a resonant dopant in the room temperature cubic phase of GeSbTe. Additionally, due to point defect scattering, the presence of indium suppressed thermal conductivity. Overall, the zT for optimized sample increased to 1.95 at 575 K compared to a zT of 0.58 in pristine GeSbTe film. A higher average zT of 1.12 was achieved in the temperature range of 300-575 K, making GeTe-based materials suitable for near-room-temperature applications.