Thermal stability of ZnO/ZnCdO/ZnO double heterostructures grown by pulsed laser deposition

The thermal stability of ZnO / Zn 1 − x Cd x O / ZnO double heterostructures grown by pulsed-laser deposition was studied by annealing them for 30 min in air at temperatures from 620 to 970 °C. In photoluminescence spectroscopy measurements on the as-grown samples emission with energies between 3.122 and 3.044 eV were observed, corresponding approximately to Cd-contents between 2.7% and 3.6%. Due to the annealing a monotonic blue-shift of the Zn 1 − x Cd x O - related luminescence was found with increasing annealing temperature. The shift was small for annealing temperatures of up to 720 °C, thus a stability of the heterostructures up to this temperature was concluded. The underlying diffusion process was investigated to determine the diffusion coefficient for the different annealing temperatures. The temperature dependence of the diffusion coefficient shows an activation enthalpy in the range between 2.1 and 3.5 eV, depending on the growth conditions. ► ZnCdO that exhibits a bandgap in violet spectral range was investigated. ► We studied the thermal stability of ZnO/ZnCdO/ZnO heterostructures under annealing. ► A blue-shift of the ZnCdO luminescence due to the annealing was observed. ► The shift is explained and modeled assuming a diffusion process. ► We determined the diffusion coefficients and activation enthalpies.