Thermodynamic theory of growth of nanostructures

Colloidal Magnetic Heterostructured Nanocrystals with Asymmetric Topologies: Seeded-Growth Synthetic Routes and Formation Mechanisms

“…The synthesis is triggered at a suitable temperature, at which highly reactive "monomers, " the smallest building units (atomic species or clusters, or molecular fragments) with which the target material lattice may be constructed, are released upon conversion of the reactants and, above a critical supersaturation threshold, condense into a solid phase, thus initiating the nucleation of nanoparticles and sustaining their subsequent growth and crystallization (Ruckenstein and Djikaev, 2005;Erdemir et al, 2009;Gebauer and Colfen, 2011;Li et al, 2014). The organic stabilizers introduced into the liquid environment play several key roles during NC evolution: they can (i) form complexes with the monomers, thus dictating their actual chemical potential in the solution; (ii) dynamically adsorb onto/desorb from the surface of the growing NCs, guaranteeing controllable incorporation of monomers and steady growth; (iii) act as size-and shaperegulating agents; (iv) render the NCs highly soluble both in the synthesis environment and in other solvents of appropriate polarity after post-synthesis extraction and manipulation Jun et al, 2006;Kwon and Hyeon, 2008;Talapin et al, 2010).…”

“…This is illustrated in Figure 1. The sign of the total Gibbs free surface energy change function, ΔG S , that accompanies the heterogeneous deposition of a secondary material (2) over a primary preexisting substrate of a different composition/structure (1) will essentially dictate the growth mode of the former (Markov, 2003;Carbone and Cozzoli, 2010;Li et al, 2014):…”

“…As opposed, if the secondary material features higher-energy surfaces (i.e., γ 2 > γ 1 ) and/or is significantly latticemismatched (hence, γ 1,2 is high), then it will tend to deposit as an array of island-to-droplet-like domains as a means of minimizing of the overall interfacial area (hence, the interfacial misfit strain) shared with the seed substrate underneath (ΔG S < 0: Volmer-Weber mode in Figure 1B). The mean inter-domain distance would approximately scale with the extent of excess strain that has to be accommodated (Markov, 2003;Li et al, 2014). An evolutionary mixed-deposition regime could also be observed (Stranski-Krastanov mode in Figure 1C).…”

“…In other circumstances, the constituent atomic species of the connected materials may interdiffuse, accommodating variation in the chemical composition and/or crystal-lattice parameters across the heterojunction regions (Koo and Korgel, 2008;Yuhas et al, 2009). In the extreme cases of exceedingly large misfit, plastic relaxation may induce formation of interfacial defects, such as dislocations and stacking faults (Dunstan, 1997;Markov, 2003;Carbone and Cozzoli, 2010;Li et al, 2014). Experimental results (Casavola et al, , 2009Koo and Korgel, 2008;Deka et al, 2009;Yuhas et al, 2009;Liakakos et al, 2014) and thermodynamic modeling (Sadowski and Ramprasad, 2010;Xu et al, 2015) have indicated that the temperature and the particular chemical pathways underlying MHNC formation are decisive in determining whether either uniformly alloyed, graded, or abrupt interfaces may be attained.…”

Continuum modelling of semiconductor heteroepitaxy: an applied perspective

“…Continuum models are a possible solution to close both spatial and temporal gaps between simulations and experiments [53][54][55][56]. Based by definition on a coarse-grained description of the actual system, any continuum model of growth will necessarily rely on some simplifying assumptions.…”