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-Al2 O3-Al junctions and the surface morphology of the junction obtained by atom ic force microscopy (AFM). From the AFM micrographs, we find a self-correla tion length of our junction of about 0.4 mum, which corresponds to surface plasmon polarition (SPP) energies of about 2.0, 1.76, and 1.3 eV at 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 platfor m 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-A(2)O(3) interfaces. SPP modes at all three interfaces contribute to light emission via interfac e roughness in our system. (C) 2001 Elsevier Science B.V. All rights reserv ed.