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

Abstract

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 �-Cu2-xSe at around 230 �C, followed by CuGaSe2 formation accompanied by a decrease in the �-Cu2-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 to 370 �C) of the set of isothermal experiments with estimated activation energies of 115 (�16) and 124 (�19) kJ/mol, respectively. TEM-EDS analysis suggests that CuGaSe2 forms at the interface of the initial GaSe and CuSe layers.