Microstructural and phase evolution in Nb–Si intermetallic thin films deposited using the pulsed laser ablation technique

The present study investigated alloy films of Nb_62.5Si_37.5 and Nb_33.7Si_66.3, corresponding to Nb₅Si₃ and NbSi₂ intermetallics. Both types of films were deposited using laser ablation technique on NaCl and Si [100] single crystal substrates at room temperature, as well as on Si substrates at elevated temperatures of 600 °C and 700 °C. Amorphization occurred during the quenching of vapor plasma on NaCl and Si substrates at room temperature. The amorphous phase in the Nb_62.5Si_37.5 thin foil remained stable up to 400 °C and fully crystallized between 700 and 800 °C, with SAD studies revealing the hexagonal Nb₅Si₃ metastable phase. In contrast, the Nb_33.7Si_66.3 thin foil began crystallizing around 400 °C and fully crystallized at 600 °C. Columnar microstructures were observed in both alloy films deposited at elevated temperatures. FFTs from high-resolution images confirmed the presence of both hexagonal Nb₅Si₃ and NbSi₂ phases. However, grains with the hexagonal Nb₅Si₃ metastable phase dominated in the Nb_62.5Si_37.5 alloy film; while, grains with the hexagonal NbSi₂ phase were more prevalent in the Nb_33.7Si_66.3 alloy film.