Thermochromic Properties of 3C-, 6H- and 4H-SiC Polytypes up to 500$^\circ$C

TL;DR

This study investigates the temperature-induced color changes in different SiC polytypes, revealing significant thermochromic effects in 3C-SiC up to 500°C, driven by bandgap shrinkage and demonstrating reversibility and stability.

Contribution

It provides the first detailed comparison of thermochromic properties across 3C, 4H, and 6H SiC polytypes up to 500°C, highlighting the pronounced effect in 3C-SiC due to its unique bandgap characteristics.

Findings

3C-SiC exhibits a color change from yellow to deep orange with ΔE up to 64.

Hexagonal polytypes show less pronounced color changes, ΔE < 20.

Thermochromic effect in 3C-SiC is reversible and stable up to 500°C.

Abstract

The thermochromic properties (color change with temperature) of n type doped SiC wafers of different polytypes (3C, 4H and 6H) have been investigated up to 500$^\circ$C under air. It was found that 3C-SiC color passes from bright yellow at room temperature to deep orangeat 500$^\circ$C leading to a color contrast ($\Delta$E) as high as 64. The hexagonal polytypes undergo also a color change upon heating but far less pronounced, with $\Delta$E values <20. All these semiconductors undergo band gap shrinkage upon heating which effect largely participated to the observed color change. This effect is very sensitive for 3C polytypesince its bandgap is already in the visible energy range at room temperature. The thermochromicity of 3C-SiC was found to be reversible thanks to its thermal stability and its resistance towards oxidation.