The compositional homogeneity of the metal particle during vapor-liquid-solid growth of nanowires

The vapor-liquid-solid (VLS) mechanism is probably the most versatile method to fabricate semiconductor nanowires and several investigations assume a compositionally homogeneous catalyst particle. In this investigation we address the compositional homogeneity of the catalyst particle during growth of nanowires. Using diffusion calculations, we show that the particle is indeed homogeneous during VLS growth, but can have a strong concentration gradient during vapor-solid-solid growth, that is, growth with a solid particle. We also show that the response to a concentration change is extremely fast, meaning that if the concentration at the surface of the particle changes, the entire particle reaches this new concentration effectively instantaneously.