| タイトル | Surface Phonons and Surface Plasmons in Quantum Dots and Metal Colloids |
| 著者（英） | Ueda, A.; Tung, Y. S.; Zuhr, R.; Mu, R.; White, C. W.; Henderson, D. O.; Zhu, Jane G. |
| 著者所属（英） | Fisk Univ. |
| 発行日 | 1997-02-01 |
| 言語 | eng |
| 内容記述 | Nanophase materials have attracted considerable attention form the scientific and technological communities, The intense interest in this class of materials originates from the fact that reduction of matter to the nanometer scale often results in a manifestation of material properties that are unique from the bulk. The technological implication of nanophase materials has already had an impact in the areas of catalysis, optical devices for telecommunications, lasers based on quantum well structures, high density optical memory, optical computing and ultrafast all-optical switching devices. Nanophase materials are also ideal candidates for investigating cross-over phenomena, whereby a metal cluster, for example, undergoes a transition from having physical properties that can be described by molecular physics to those which can be understood in terms of band structure theory of the bulk. Nanophase materials also open the opportunity to study the basic physics and chemistry that govern the transformation of very small clusters to subcritical nuclei to critical nuclei and consequently to the crystal growth process itself.In the course of the transition, quantum size effects are often observed and are expressed in the optical properties of the nanophase materials. As an example, semiconductor nanocrystals with particle sizes smaller than their excitonic radii (quantum dots, QD's) show blueshifts in their bands gaps as a result of quantum confinement. The photon spectra of QD's exhibit surface modes that arise from a break-down of the cyclic boundary conditions for the bulk material and lead to a resonance that falls between the bulk longitudinal and transverse optical photon frequencies. Metal nanocrystals, on the other hand, show collective-ti&d&, surface plasmons, in the visible to the ultraviolet part of the spectrum and are responsible for some of the beautiful colors of metal doped glasses. Such optical properties of metal nanocrystals and quantum dots can be used as probes to interrogate cross-over phenomena to gain understanding of how the properties of nanophase material evolve as a function of size. Along this line, we have investigated the optical spectra of gold nanocrystals embedded in dielectric matrices and report on the development of the surface plasmon absorption (53 O nm) for different annealing environments. Surface phonon spectra for GaAs nanocrystals buried in sapphire and silica matrices are also reported and shown to agree with Froelichs theory of surface phonons. |
| NASA分類 | Nonmetallic Materials |
| レポートNO | URC97177 |
| 権利 | No Copyright |
| URI | https://repository.exst.jaxa.jp/dspace/handle/a-is/339475 |
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