Dopant Induced Stabilization of Silicon Cluster at Finite Temperature

TL;DR

This study demonstrates that doping silicon clusters with titanium can significantly enhance their thermal stability, allowing them to withstand higher temperatures before fragmenting, as shown through first-principles simulations.

Contribution

The paper introduces a method to stabilize silicon clusters at high temperatures by doping with titanium, extending their stability beyond natural limits.

Findings

Ti doping stabilizes Si16 clusters up to 2600 K.

Melting occurs in two steps: surface melting at 600 K and cage destruction at 2250 K.

Doped clusters exhibit a higher melting point than pure silicon clusters.

Abstract

With the advances in miniaturization, understanding and controlling properties of significant technological systems like silicon in nano regime assumes considerable importance. It turns out that small silicon clusters in the size range of 15-20 atoms are unstable upon heating and in fact fragment in the temperature range of 1200 K to 1500 K. In the present work we demonstrate that it is possible to stabilize such clusters by introducing appropriate dopant (in this case Ti). Specifically, by using the first principle density functional simulations we show that Ti doped Si$_{16}$, having the Frank-Kasper geometry, remains stable till 2200 K and fragments only above 2600 K. The observed melting transition is a two step process. The first step is initiated by the surface melting around 600 K. The second step is the destruction of the cage which occurs around 2250 K giving rise to a peak in the heat capacity curve.