Thermoelectric properties of monolayer MSe sub(2) (M = Zr, Hf): low lattice thermal conductivity and a promising figure of merit

• Published in: Nanotechnology 2016-09, Vol.27 (37), p.375703-375709
• Main Authors: Ding, Guangqian, Gao, G Y, Huang, Zhishuo, Zhang, Wenxu, Yao, Kailun
• Format: Article
• Language: English
• Subjects: Boltzmann transport equation; Figure of merit; Heat transfer; Lattices; Mathematical analysis; Monolayers; Thermal conductivity; Thermoelectricity
• ISSN: 0957-4484; 1361-6528
• DOI: 10.1088/0957-4484/27/37/375703

Monolayer transition-metal dichalcogenides (TMDCs) MX sub(2) (M = Mo, W, Zr, Hf, etc; X = S, Se, Te) have become well-known in recent times for their promising applications in thermoelectrics and field effect transistors. In this work, we perform a systematic study on the thermoelectric properties of monolayer ZrSe sub(2) and HfSe sub(2) using first-principles calculations combined with Boltzmann transport equations. Our results point to a competitive thermoelectric figure of merit (close to 1 at optimal doping) in both monolayer ZrSe sub(2) and HfSe sub(2), which is markedly higher than previous explored monolayer TMDCs such as MoS sub(2) and MoSe sub(2). We also reveal that the higher figure of merits arise mainly from their low lattice thermal conductivity, and this is partly due to the strong coupling of acoustic modes with low frequency optical modes. It is found that the figure of merits can be better optimized in n-type than in p-type. In particular, the performance of HfSe sub(2) is superior to ZrSe sub(2) at a higher temperature. Our results suggest that monolayer ZrSe sub(2) and HfSe sub(2) with lower lattice thermal conductivity than usual monolayer TMDCs are promising candidates for thermoelectric applications.