Investigating Coherent Zone-Folded Acoustic Phonons in Si/SiGe Superlattices by Transient Thermoreflectance Technique

AbstractIn this paper, we present a systematic study of coherent phonons in Si/SiGe superlattices with two different periods. The superlattice periodicity affects the acoustic properties of the structure. Transient thermoreflectance (TTR) technique is used to perform picosecond ultrasonics experiments and then, investigate coherent zone-folded acoustic phonons in different Si/SiGe superlattice structures. Several classes of coherent phonons are produced in the superlattice, whose generation mechanisms are different: Brillouin oscillations, coherent longitudinal-acoustic phonon Bragg reflection and impulsive stimulated Raman scattering (ISRS).

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Initial Process of the Ferroelectric B 2 Soft Mode of KDP Studied by the Impulsive Stimulated Raman Scattering with Heterodyne Detection

Ferroelectrics ◽

10.1080/00150190211577 ◽

2002 ◽

Vol 272 (1) ◽

pp. 57-62

Author(s):

Jun Kano, Yuhji Tsujimi ◽

Keith A. Nelson ◽

Toshirou Yagi

Keyword(s):

Raman Scattering ◽

Soft Mode ◽

Stimulated Raman Scattering ◽

Heterodyne Detection ◽

Impulsive Stimulated Raman Scattering ◽

Initial Process ◽

Stimulated Raman

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Vibrational relaxation of nascent diiodide ions studied by femtosecond transient resonance impulsive stimulated Raman scattering (TRISRS); experiment and simulation

Chemical Physics ◽

10.1016/0301-0104(94)00099-9 ◽

1994 ◽

Vol 183 (2-3) ◽

pp. 289-307 ◽

Cited By ~ 44

Author(s):

Uri Banin ◽

Ronnie Kosloff ◽

Sanford Ruhman

Keyword(s):

Raman Scattering ◽

Vibrational Relaxation ◽

Stimulated Raman Scattering ◽

Transient Resonance ◽

Experiment And Simulation ◽

Impulsive Stimulated Raman Scattering ◽

Stimulated Raman

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Guided Acoustic Phonon Modes in Layered Anisotropic Nanowires

Nondestructive Evaluation ◽

10.1115/imece2003-42956 ◽

2003 ◽

Author(s):

Osama M. Mukdadi ◽

Subhendu K. Datta ◽

Martin L. Dunn

Keyword(s):

Thermal Conductivity ◽

Acoustic Phonon ◽

Energy Transport ◽

Bulk Material ◽

Rectangular Cross Section ◽

Critical Role ◽

Acoustic Phonons ◽

Phonon Modes ◽

Low Velocity ◽

Analysis Technique

Acoustic phonons play a critical role in energy transport in nanostructures. The dispersion of acoustic phonons strongly influences thermal conductivity. Recent observations show lower values of thermal conductivity in finite dimensional nanostructures than in the bulk material. In this work, we will present results for guided acoustic phonon modes in (a) a bilayered GaAs-Nb nanowire of rectangular cross section and (b) a trapezoidal Si nanowire. The former has been used for phonon counting in a nanocalorimeter for measuring thermal conductivity and the latter is commonly used in MEMS applications. A semi-analytical finite element (SAFE) analysis technique has been used to investigate the effects of layering, anisotropy, and boundaries on the dispersion of modes of propagation. Many interesting features of group velocities are found that show confinements around the corners, in the low velocity layer, and coupling of the longitudinal and flexural modes. These would strongly influence thermal conductivity and might provide means of nondestrutive evaluation of mechanical properties.

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