When a focused laser beam is irradiated onto a target, electrons and cations are emitted from the target to form a plume (plasma). This phenomenon is referred to as laser ablation (LA). The thin film deposition method using laser ablation is referred to as pulsed laser deposition (PLD). Recombination of electrons and cations usually occurs in the plume before they arrive at a substrate to form a thin film. However, previous reports show that applying a magnetic field to the plume suppresses recombination and enhances electron-impact excitation. The flux of electrons and cations can therefore be controlled by an external magnetic field during PLD. Charged cations can separate from neutral particles or heavy clusters such as droplets. This principle has been used to obtain droplet-free thin films. Applying a magnetic field to the plume also causes ohmic heating and suppression of adiabatic expansion. The electron temperature in a plume with magnetic field application is therefore higher than that in a plume without magnetic field application. This principle has been used to lower crystallization temperatures, improve crystallinity, and enhance thin film properties. Because application of a magnetic field suppresses recombination and enhances electron-impact excitation, several cations exist in the plume. These then rush to the substrates. This principle produces changes the growth mode, which in turn brings about changes in the thin film morphology. Furthermore, this principle leads to phase separation control. The impingement of cations reportedly brings about lowering of the activation energy for diffusion, which leads to phase separation by spinodal decomposition. A thin film with a spontaneous superlattice structure forms when compositional wave propagation occurs in one direction, but when a cross-linked microstructure is obtained the compositional wave direction of propagation is random. This review presents the influence of application of a magnetic field during deposition.
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