Well-oriented zinc oxide nanorods arrays (ZnO NRsA) have been grown on seeded substrates. The morphology, chemical, and vibrational characteristics of the nanostructures were investigated. The dependency of the photocurrent of Au decorated ZnO NRsA on wavelength was evaluated by photogain response. Due to the induced surface plasmon excitation, selective response to green laser was observed. An analytical dispersion formalism was constructed to fit the experimental absorption spectrum of both ZnO NRsA and Au-decorated ZnO NRsA, over a wide spectrum range in order to evaluate the bandgap energy, subband tailing, dielectric constant and carrier effective mass and density, and nonlinear optical parameters. The proposed model exploits the Forouhi–Bloomer (FB) parameterization and Gaussian oscillator dispersion for the complex dielectric function of Au-decorated ZnO NRsA. Both the sharp variation in the optical absorption around the band edge and absorption behavior beyond the bandgap energy are covered well. It is surprising that the surface plasmon resonance (SPR) is included without introducing a new formalism. The photogain study on ZnO NRsA-Au 40nm heterostructure shows that the obtained ESPR from the dispersion model is in complete agreement with the selective green response of the heterostructure. Furthermore, the new model was satisfactorily tested on the optical absorption spectra of CuO thin films.
