Phase, nucleation and coalescence of HgI2 onto amorphous substrates

Abstract

Abstract Heterogeneous nucleation and further growth of HgI 2 onto glass were studied by the physical vapor deposition (PVD) method, with and without an argon atmosphere. Glass substrates 2″×2″ in area were used for nucleation and growth. Supersaturation strongly determined not only the nuclei population and size, but also the HgI 2 nucleation phase. A range of nucleation–growth temperatures between 303 and 333 K for the substrate, and a range of initial argon pressure between 1.3 and 2.6×10 4 Pa were found appropriate for nucleation and growth in the α (red) phase of HgI 2 . Other conditions, such as an argon pressure higher than 4×10 4 Pa, determined the nucleation and growth in the β (yellow) metastable phase. After a nucleation growth time of 30 min, clusters of about 0.5 μm for β-HgI 2 and 1 μm for α-HgI 2 and a minimum distance between the clusters of about 1 and 10 μm were, respectively, obtained. Coalescence was performed by annealing the clusters at a temperature between 303 and 333 K and from 5 min to 24 h, at an initial argon pressure of 10 4 Pa. They coalesced to form larger clusters, which, in the case of the β-phase also transformed to the α-stable phase. From the experimental nucleation–growth and further coalescence conditions, correlations between supersaturation conditions and phase were established. Also, considerations about interface free energies and nucleation phase were made. Future work will be conducted to diminish nuclei size and enlarge nuclei population, seeking for early stages of nucleation.