Atomic dynamics of tin nanoparticles embedded into porous glass

Lattice dynamics in Sn nanoislands and cluster-assembled films

“…(i) The decrease in intensity of high-energy modes (15 and 18 meV) was observed before in various nanoscale systems 12,13,16,19,[21][22][23][24][25] , an effect which was found to originate from phonon scattering. From the TEM study, it was concluded that a single Sn island is composed of many Sn crystallites.…”

“…The phonon density of states (PDOS) of low dimensional systems is expected to be modified due to the restriction of phonon propagation [7][8][9][10][11] . Previously, clear differences between the phonon density of states of bulk and that of nanostructures have been observed, with as most commonly observed anomalies in the phonon spectra of nanostructures: an enhancement of low-energy modes, appearance of high-energy modes above the cut-off energy of the bulk material and a broadening of the PDOS features [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] . For thin films, the broadening of features in the PDOS was attributed to phonon damping 13,19,27,28 and the enhancement of low-energy phonon modes due to the appearance of surface modes 14,19,27 .…”

“…In some nanocrystalline structures an enhancement of high-energy modes above the cut-off energy was observed which was attributed to surface oxides 12,16 , grain boundary atoms 9,21 or to changes in the inter-atomic force constants 11,18,26 . Another type of nanostructure that was studied is isolated nanoparticles 7,8,10,17,20,22,25 for which also an enhancement of low-and high-energy phonon modes as well as a broadening of the PDOS features was observed. The enhancement of low-energy phonon modes was attributed to grain boundary atoms 22 and/or surface atoms 7,8,10,20 or to a weakening of the chemical bonds for surface layer atoms 25 .…”

“…Another type of nanostructure that was studied is isolated nanoparticles 7,8,10,17,20,22,25 for which also an enhancement of low-and high-energy phonon modes as well as a broadening of the PDOS features was observed. The enhancement of low-energy phonon modes was attributed to grain boundary atoms 22 and/or surface atoms 7,8,10,20 or to a weakening of the chemical bonds for surface layer atoms 25 . The enhancement of high-energy modes is due to the contribution of surface oxides or matrix atoms 20,25 or changes in the inter-atomic force constants 10 .…”

“…The enhancement of low-energy phonon modes was attributed to grain boundary atoms 22 and/or surface atoms 7,8,10,20 or to a weakening of the chemical bonds for surface layer atoms 25 . The enhancement of high-energy modes is due to the contribution of surface oxides or matrix atoms 20,25 or changes in the inter-atomic force constants 10 . Notwithstanding the vast amount of work on Fe nanostructures, phonons remain poorly understood in many other nanomaterials.…”