Designer Ge/Si composite quantum dots with enhanced thermoelectric properties

Abstract

An otherwise random, self-assembly of Ge/Si composite quantum dots (CQDs) on Si was controlled by inserting a layer of Si, sub-dot stacks, and post-annealing to produce micron-scale-thick QD layers with desired QD morphology, interface density, and composition distribution. A heterostructure consisting of a deliberate insertion of Si between Ge sub-dots is shown to improve the epitaxial coherence of the Ge QDs by suppression of the Ge surface interdiffusion and coarsening. As compared to regular-QD materials, the thin-film-like multifold-CQD materials are found to exhibit both reduced cross-plane thermal conductivity and enhanced electrical conductivity, and 1.5 times higher ZT value by calculation, providing a promising building block for practical thermoelectric applications in micro- or nanoelectronics.

Tailoring thermal conductivity by engineering compositional gradients in Si1−x Ge x superlattices

“…2015, 8(9): 2833-2841 increases this value to 0.95 [7]. Additionally, the incorporation of a high interface density in epitaxial heterostructures has been recognized as an efficient approach to enhance boundary phonon scattering at low frequencies with a corresponding decrease in thermal conductivity [8][9][10][11][12][13][14][15][16][17]. SiGe planar superlattices (SLs) have thus emerged as potential candidates for both TE cooling of microelectronic devices and medium-temperature TE power generation [18,19].…”

Molecular Dynamics Calculation of Thermal Conductivity in a-SiO2 and an a-SiO2-Based Nanocomposite

“…The thermal conductivity in -SiO 2 should be taken into consideration, while studying the thermal properties of graphene layers or carbon nanotubes (in this case, -SiO 2 is used as a thermoinsulating substrate [2,3]). Recently, composites on the basis of the -SiO 2 matrix with Si or Ge nanocrystals have attracted attention; they are considered as promising materials for the development of novel thermoelectric converters [4][5][6]. The efficiency of thermoelectric conversion is known to be determined by the formula c ○ V.V.…”

Influence of the Localization of Ge Atoms within the Si(001)(4 × 2) Surface Layer on Semicore One-Electron States

“…Experimental and theoretical study of Ge on Si quantum dots is one of the exciting modern topics because of their great potentiality in producing thin-film solar cells, high figure-of-merit thermoelectric materials, and other thermo-and optoelectronic devices [1][2][3]. A number of parallel or sequential processes normally occur as soon as a heterojunction between a germanium quantum dot and reconstructed Si(001)(4ˆ2) surface is formed [4,5].…”