ABSTRACT

In order to compete with traditional techniques of converting heat into electrical power (vapor compression techniques, for example), the figure of merit, ZT, which characterizes a thermoelectric material, should reach values well above 3 for the current ~1.5 to 2. A renewed interest in thermoelectrics started in the 1990s, when new strategies were proposed to enhance ZT (Kanatzidis 2010; Lan et al. 2010; Alam and Ramakrishna 2013; Martín-González et al. 2013; Leadley et al. 2014; Mouis et al. 2014). One method to enhance ZT is to reduce lattice thermal conductivity. This is achieved by using different approaches, such as phonon scattering using mass fluctuations in mixed crystals, and grain boundary scattering or interface scattering in thin films or multilayers. Low dimensional materials show advantages towards enhancing ZT. They are used either to enhance the power factor or to reduce the lattice thermal conductivity. Lowdimensional materials currently investigated are thin films and superlattices, as well as semiconductor nanowires. (Hicks and Dresselhaus 1993; Venkatasubramanian et al. 2001; Boukai et al. 2008; Hochbaum et al. 2008; Donadio and Galli 2010; Chen et al. 2012; Neophytou et al. 2013).