Dynamics of vibrations in a mixed amorphous-nanocrystalline Si system

2019-11-26 02:14:30

NC Si CM phonon phonons

责任者: van der Voort, M.;Muskens, O.L.;Akimov, A.V.;Pevtsov, A.B.;Dijkhuis, J.I. 单位: Fac. of Phys. & Astron., Utrecht Univ., Netherlands 来源出处: Physical Review B (Condensed Matter and Materials Physics)(Phys. Rev, B, Condens, Matter Mater. Phys. (USA)),2001/07/15,64(4):045203-1 摘要: We present results of pulsed Raman and phonon-induced luminescence experiments on a mixed amorphous-nanocrystalline silicon system (a-nc-Si:H). With these experiments, the decay and transport of nonequilibrium phonons in a-nc-Si:H was examined and compared with the behavior of phonons of the same frequencies in a-Si:H and c-Si. From the Raman measurements, we find that in the spectral region of the TO vibrations in the crystallites (505-520 cm-1), phonons have shorter decay times than the TO phonons in a-Si:H, but longer than in c-Si. In addition, the lifetimes increase with decreasing frequency, from less than 10 ns at 515 cm-1 to ~30 ns at 505 cm-1. We further show that phonons with a frequency of ~150 cm-1 in a-nc-Si:H have longer lifetimes than in a-Si:H (τ<10 ns). Finally, the diffusion of 29-cm-1 phonons through the a-nc-Si:H and a-Si:H material was examined in phonon-induced luminescence experiments. Transport through the a-nc-Si:H film appears to be much slower than through the a-Si:H layer. We explain these results as effects of phonon confinement, and relate them to the extremely long phonon lifetimes found in Raman experiments on a-Si(:H) 关键词: amorphous semiconductors;elemental semiconductors;hydrogen;luminescence;nanostructured materials;phonon spectra;Raman spectra;semiconductor thin films;silicon;vibrational modes;mixed amorphous-nanocrystalline system;Si;vibrations dynamics;pulsed Raman spectra;phonon-induced luminescence spectra;a/nc-Si:H;phonon transport;nonequilibrium phonons;a-Si:H;c-Si;TO vibrations;crystallites;phonon decay time;phonon frequency;film;phonon confinement;phonon lifetime;phonon diffusion;10 to 30 ns;Si:H