Morphological surface analysis of spin gapless CoFeMnSᵢ semiconductor thin films grown by pulsed laser deposition

CoFeMnSi spin gapless semiconductor thin films were grown on a (100) oriented MgO substrate by pulsed laser deposition. In this work, we explored the dependence of CoFeMnSi thin film’s surface morphology on different parameters of growth process. It was shown that an island-like CoFeMnSi thin film with an average grain diameter of D50% = 16.48 nm and roughness parameters R_a = 1.29 nm, R_z = 13.06 nm grows on a (100) oriented MgO substrate if a laser pulse frequency is 1–2 Hz and a pulse energy is 150 mJ. Reducing the frequency of laser pulses to 0.5 Hz with the same pulse energy led to a change in the film growth mechanism to a mixed growth. The film initially grows in the layer-by-layer mode and then 3D islands gradually form. Roughness parameters of the films deposited in this mode decrease to R_a = 0.61 nm and R_z = 11.51 nm. It became possible to implement layer-by-layer film deposition mode by introducing time pauses of 1–2 minutes between the depositions of each CoFeMnSi atomic layer. We found out that the layer-by-layer grown films had solid structure, defects and irregularities of their surface microrelief were smoothed out. The roughness parameters of the samples grown in the layer-by-layer mode decreased to R_a = 0.31 nm and R_z = 4.60 nm. The production of CoFeMnSi thin films with high quality of surface opens up opportunities for fabrication of CoFeMnSi-based heterostructures. With the selected technological parameters of growth process we fabricated MgO/CoFeMnSi/Co thin film with average surface roughness of R_a = 0.17 nm using selected above technological parameters of growth process. The results of this work can be used in fabrication of multilayer structures based on CoFeMnSi and their application in spintronic devices.