Study on the relation between surface roughness and the light emission spectrum of an Au±Al2O3±Al tunnel junction

We investigate the correlation between the light emission spectra of Au±Al2O3±Al junctions and the surface morphology of the junction obtained by atomic force microscopy (AFM). From the AFM micrographs, we ®nd a self-correlation length of our junction of about 0.4 mm, which corresponds to surface plasmon polarition (SPP) energies of about 2.0, 1.76, and 1.3 eVat the Au±air, Al±Al2O3, and Au±Al2O3 interfaces, respectively. This agrees well with spectrum peaks observed at 630 nm (2.0 eV) and 700 nm (1.77 eV). A platform region from 800 to 850 nm (1.48 eV) in the spectrum is proposed to result from the overlap of SPP modes at the Au±Al2O3 and Al±Al2O3 interfaces. SPP modes at all three interfaces contribute to light emission via interface roughness in our system. # 2001 Elsevier Science B.V. All rights reserved.