Fabrication of Well-Aligned Al Nanowire Array Embedded in Si Matrix Using Limited Spinodal Decompositon

Abstract

The morphology of a phase-separated binary film during spinodal decomposition, whose evolution is limited on the growth surface, is studied. The temporal evolution of the Cahn-Hilliard equation without the elastic energy term under frozen bulk approximation is solved to investigate the possibility of well-aligned nanostructures. The model simulation showed that the well-aligned phase pattern on the top surface can be formed when surface diffusion length was optimized and film thickness was larger than a certain value. These simulation results highly agree with the experimental observation of phase-separated Al-Si films. An additional simulation study indicated that well-aligned nanowires can be prepared from the initial growth stage when an initial phase pattern given on the substrate matched the periodicity of the phase pattern of deposited films.

Ion-assisted phase separation in compound films: An alternate route to ordered nanostructures

“…Many of these metals have similar masses to each other, which points to the critical role of chemistry in these samples, as opposed to kinetics. Alternatively, in the regime of ion-assisted deposition of binary materials, a growing body of experimental evidence has documented the formation of 3D structures including vertically-organized alternating material layers [26] and laterally-organized nanowires [24]. These structures are consistent with numerical studies of phase separation during film growth [38] or at moving fronts more generally [39].…”

“…Motivated by a growing body of experimental [24][25][26][27] and numerical [24,28] evidence suggesting that phase separation plays an important role in pattern formation during the irradiation of two-component targets, and molecular dynamics simulations suggesting that existing theories neglecting this phenomenon may not explain the patterns [30], we have presented a generalization of the Bradley-Shipman theory of irradiated binary compounds [21,22] that admits the phase separation mechanism. We demonstrated that the resulting model readily admits the development of ordered patterns even for parameter values where the BS theory cannot.…”

“…irradiation are far below those needed for thermal segregation, but it is known that the ion beam induces an effective mobility in the target atoms that is many orders of magnitude higher than for an un-irradiated target [29]. Indeed, numerical phase-field simulations for irradiated GaSb exhibited structures qualitatively similar to those seen experimentally [28] (a pattern repeated in other irradiation regimes [24]), but so far phase separation during ion bombardment has not been explored analytically. This strongly motivates the development and exploration of a model incorporating phase separation.…”

“…This suggests the consideration of alternate physical mechanisms to explain the ordered structures in irradiated binary compounds. Here, based on a growing body of experimental [24][25][26][27] and numerical [24,28] evidence in a variety of irradiation regimes, we propose a generalization of the original BS theory that admits the process of phase separation. We find that our model admits a finite-wavelength bifurcation even when the assumptions of the BS theory are not fulfilled; in addition, it provides a clear experimental signature distinguishing it from the Bradley-Shipman mechanism.…”

Microstructure Map for Self-Organized Phase Separation during Film Deposition

“…Spinodal decomposition in thin films can certainly lead to periodical nanostructures [26][27][28]. During film deposition, spontaneous spinodal decomposition has been shown to lead to either LCMs [29] or VCMs [30]. However, a comprehensive model that can predict LCM and VCM microstructures observed in experiments as function of materials parameters and processing conditions seems still lacking.…”