Showing papers by "Hong Jin Fan published in 2002"
TL;DR: In this article, a systematic Brillouin study has been carried out on acoustic modes in porous silicon films prepared from p-type Si(100), where a surface Rayleigh mode and two bulk acoustic modes, transverse and longitudinal, were observed.
Abstract: A systematic Brillouin study has been carried out on acoustic modes in porous silicon films prepared from p-type Si(100). A surface Rayleigh mode and two bulk acoustic modes, transverse and longitudinal, were observed. Results are presented for the dependence of the phase velocities of these three modes on sample porosity and film thickness. The phonon velocities, especially those of the bulk modes, increase sharply with decreasing film thickness below \ensuremath{\sim}10 \ensuremath{\mu}m. This thickness dependence is attributed to the presence of a transition layer between the porous silicon film and crystalline Si substrate. Its influence on the film bulk modes increases with decreasing thickness. Elastic constants and Young's modulus of porous Si are estimated for different porosities from the phase velocities of the two bulk acoustic modes and are compared with the corresponding data obtained by other techniques.
33 citations
TL;DR: In this paper, Brillouin scattering has been performed on the relaxor ferroelectric Pb(Ni1/3Nb2/3)O3 (PNN) from 80 to 450 K across its Curie temperature.
Abstract: Brillouin scattering has been performed on the relaxor ferroelectric Pb(Ni1/3Nb2/3)O3 (PNN) from 80 to 450 K across its Curie temperature. A diffuse phase transition from the paraelectric to ferroelectric phase, associated with a broad phonon frequency dip and a damping maximum, is observed around 200 K. A relaxation mode in the form of a broad Rayleigh wing, whose frequency is strongly temperature dependent above 190 K, is observed and analyzed based on a modified superparaelectric model. Dielectric studies of PNN have also been carried out at several measurement frequencies. The relation between the measurement frequency and the dielectric maximum temperature was analyzed on a modified Vogel–Fulcher model.
22 citations
TL;DR: In this article, the authors performed Brillouin scattering to probe acoustic waves in porous silicon films that have been chemically modified with either 1-decene, decyl aldehyde, undecylenic acid, or ethyl diacetylenate.
Abstract: Brillouin scattering has been performed to probe acoustic waves in porous silicon films that have been chemically modified with either 1-decene, decyl aldehyde, undecylenic acid, or ethyl undecylenate. The shift in the frequencies of acoustic modes in the passivated porous silicon samples, relative to those in freshly prepared porous silicon, is different for different chemical modifiers. The magnitude of the frequency shift is qualitatively correlated with the change, caused by the passivation, in the average densities and elastic constants of the samples.
6 citations