NORMAL-STATE TUNNEL JUNCTION AS A TUNABLE QUASI-MONOCHROMATIC PHONON SOURCE

The frequency distribution of the acoustic phonons emitted from a bias ed metal-insulator-metal normal-state tunnel junction has been studied . Electrons tunneling across the insulating layer form an excited popu lation with a range of energies up to similar to eV(B) above the Fermi level and then relax, producing a phonon spectrum with a frequency cu toff at the same characteristic value. Normal-state tunnel junctions m ade from aluminum have been produced and phonon spectra determined by using the stress-tuned splitting of boron accepters in silicon as a sp ectrometer. It has been shown that, in the range similar to 1-4 meV (s imilar to 250-1000 GHa), the second differential of the signal with re spect to junction bias (partial derivative(2)P/partial derivative V-B( 2)) is quasimonochromatic, having a spectrum of an approximately Gauss ian form with the peak: occurring at an energy of eV(B) and a half wid th of similar to 6kT(e).