Reaction diffusion in Ta/GaAs contacts

Exploration of growth conditions of TaAs Weyl semimetal thin film using pulsed laser deposition

“…101) and (600) reflections of Ta 5 As 4 , respectively, while the expected TaAs phase was not detected. According to the phase diagram, [28,33] the appearance of the Ta 5 As 4 phase is due to the heavy loss of the As component during the growth process.…”

“…We have already found that the As component can evaporate from the GaAs substrate during heating, and we now investigate the formation mechanism of the TaAs thin films. As early as 1993, Han et al reported that the ternary Ta-Ga-As phase could be formed at the interface between Ta and GaAs 047103-3 thin films due to the diffusion of As components at 850 • C-950 • C. [28] Subsequently, Li et al also found that the TaAs 2 phase annealed at 550 • C, and the TaAs, TaAs 2 , and Cu 3 Ga phases annealed at 600 • C were built in the Cu/Ta/GaAs multilayer films because of the percolation of As components. [37] Therefore, we realize that the As component in the GaAs substrate is unstable, and can penetrate to the neighboring Ta layer at high temperature.…”

“…In addition, the Ta-As binary system has complicated phase diagrams, including Ta 3 As, Ta 2 As, Ta 5 As 4 , TaAs, and TaAs 2 phases, which makes it difficult to synthesize the pure TaAs phase, especially in TaAs film. [28,29] In this work, to explore the optimal growth conditions of the TaAs films by PLD, Ta-As films were grown on various substrates using TaAs targets with different As contents, and their crystalline structures were subsequently characterized. The results reveal that the polycrystalline TaAs films can only be achieved on GaAs substrates, which is likely to provide an effective As-rich atmosphere for TaAs, while the Ta 5 As 4 phase prefers to nucleate on other substrates without the As element.…”