Energy filtering enhancement of thermoelectric performance of nanocrystalline Cr-Si composites

TL;DR

This study demonstrates that nanocrystalline Cr-Si composite films exhibit enhanced thermoelectric performance due to energy filtering effects at nanograin interfaces, which scatter charge carriers selectively.

Contribution

It introduces a new type of heterogeneous nanocrystalline/amorphous composite material where energy filtering improves thermoelectric efficiency.

Findings

Nanocrystalline Cr-Si films show increased thermopower.

Energy filtering at nanograin interfaces enhances thermoelectric performance.

Partially crystallized films with dispersed nanocrystals are effective thermoelectric materials.

Abstract

We report on thermoelectric properties of nanocrystalline Cr$_{\rm 1-x}$Si$_{\rm x}$ composite films. As-deposited amorphous films were transformed into a nanocrystalline state with average grain size of 10--20~nm by annealing during in-situ thermopower and electrical resistivity measurements. The partially crystallized films, i.e. the films consisting of crystalline grains dispersed in the amorphous matrix, are a new type of the heterogeneous material where the nanocrystalline phase plays the role of scattering centers giving rise to a large contribution to the thermopower. We show that the thermopower enhancement is related to the energy dependent scattering (energy filtering) of the charge carriers on the nanograin interfaces.