Ultrashort Pulse Laser Annealing of Amorphous Atomic Layer Deposited MoS2 Films

Thin films of molybendum disulfide grown via thermal atomic layer deposition at low temperatures, suitable for temperature sensible substrates, can be amorphous. To avoid a high temperature post treatment of the whole sample, which can cause thermal degradation of the substrate or other layers, a ultrashort pulse (usp) laser-induced transformation to crystalline layers is one of the most promising routes. In this paper we report the crystallization of amorphous MoS2 layers processed with ultrashort laser pulses. The amorphous MoS2 films were deposited by atomic layer deposition (ALD) and exposed to picosecond laser pulses (λ=532 nm). The crystallization and the influence of the processing parameters on the film morphology were analyzed in detail by Raman spectroscopy and scanning electron microscopy. Furthermore, a transition of amorphous MoS2 by laser annealing to self-organized patterns is demonstrated and a possible process mechanism for the ultrashort pulse laser annealing is discussed. Finally, the usp laser annealed films were compared to thermally and continuous wave (cw) laser annealed samples.