Reaction kinetics of CuGaSe₂ formation from a GaSe/CuSe bilayer precursor film

The reaction pathway and kinetics of CuGaSe₂ formation were investigated by monitoring the phase evolution of temperature ramp annealed or isothermally soaked bilayer glass/GaSe/CuSe precursor film using time-resolved, in situ high-temperature X-ray diffraction. Bilayer GaSe/CuSe precursor films were deposited on alkali-free thin glass substrates in a migration-enhanced epitaxial deposition system. The initial CuSe phase begins to transform to β-Cu_2-xSe at around 230 °C, followed by CuGaSe₂ formation accompanied by a decrease in the β-Cu_2-xSe peak intensity at around 260 °C. Both the parabolic and Avrami diffusion-controlled reaction models represented the experimental data very well over the entire temperature range (280-370 °C) of the set of isothermal experiments with estimated activation energies of 115(±16) and 124(±19) kJ/mol, respectively. Transmission electron microscopy-energy-dispersive X-ray spectrometry (TEM-EDS) analysis suggests that CuGaSe₂ forms at the interface of the initial GaSe and CuSe layers.