Modulation of structural, electrical, optical and thermoelectric properties of MOCVD grown GdN thin films by nitrogen environment annealing process

Abstract

This manuscript demonstrated the effect of nitrogen annealing on the structural, optical, electrical and thermoelectric properties of MOCVD grown GdN thin films. After growth a representative sample was cut into pieces and annealed in nitrogen environment at various temperatures ranging from 300 to 500 °C. XRD data verified the formation of hexagonal structure of GdN with preferred orientation along C-axis. It was also observed that the crystalline size and intensity of (200) plane increased as the annealing temperature increased. This behavior indicates the improvement in the crystal structure because the nitrogen vacancy related defects compensated by the incoming nitrogen atoms during annealing. Raman spectroscopy and UV/Vis spectroscopy data also strengthened the XRD data that crystal structure improved significantly with annealing in nitrogen environment. Hall data demonstrated that carrier concentration of samples decreased by annealing due to decrease of nitrogen vacancy related donor defects. Room temperature Seebeck data showed that the values of Seebeck coefficient and power factor were found to be decreased with annealing temperature. The decreased in Seebeck coefficient is understandable because the conductivity of samples was found to be decreased with annealing temperature.