CVT is popular for single crystals growth due to its simplicity and efficiency. For lamellar structures this approach could be successfully applied. For the CVT, open tube and close tube (most typical setup) systems are possible to use. The mass transfer sometimes is named gas flow crystallization and it takes place in the presence of a carrier substance (transport agent). A temperature gradient is used in order to distinguish the volatilization and crystallization regions in the tube (ampule). This method allows to control the growth quality of single crystals.
A large number of promising materials were obtained via CVT. For instance, transitional metals dichalcogenides MX2 (M = a transitional metal, X = O, S, Se, Te) are often grown by chemical transport reactions.
Some difficulties may appear due to dependence on the sign of the enthalpy change (ΔH) associated with the chemical transport reaction. It means, that in contrast to physical vapor transport methods, CVT does not always proceed with mass transfer from the hot to the cold region. From another point, close tube CVT processes are especially suitable for growing bulk crystals, providing no specific requirements to control chemical composition and size of the crystals during growth. The mass-transport yield typically is very high. However, traces of a transport agent in some cases cannot be avoided.
