Phonon reflection at a sapphire-vacuum interface?
نویسندگان
چکیده
Theoretical and experimental studies have been conducted of the transmission of phonons in sapphire and their reflection at a crystal-vacuum interface. The effects of crystal anisotropy on the reflection process, not previously noted in the literature, are discussed in detail. The heat-pulse technique has been used to obtain high-resolution timeof-flight spectra as a function of the angle of incidence in accurately known crystallographic directions. The agreement with predictions from numerical calculations is excellent. The relevance of these observations to studies of the anomalous transmission of energy through a crystal-liquid helium interface is also discussed.
منابع مشابه
Diffuse reflection of phonons and the anomalous Kapitza resistance
High-resolution time-of-flight phonon-reflection spectra in sapphire crystals are analyzed with the aid of detailed numerical calculations. It is argued that spectra from vacuum interfaces may be understood if about half the incident phonons are assumed to be reflected specularly, the remainder diffusely. A simple model of the effect on spectra of diffuse scattering is presented and compared to...
متن کاملSaturation Effects in the Phonon Reflection at a Quartz-Liquid Helium Interface*
The reflection coefficient of longitudinal 25-GHz phonons at a quartz-liquid 4He interface was measured for various phonon intensities. For thoroughly cleaned quartz surfaces a reflection coefficient of I independent of the incident intensity was found. When the sample was covered with a thin hydrocarbon film, however, the reflection coefficient dropped by typically 5-10% when the phonon intens...
متن کاملNanomechanical probing of the layer/substrate interface of an exfoliated InSe sheet on sapphire
Van der Waals (vdW) layered crystals and heterostructures have attracted substantial interest for potential applications in a wide range of emerging technologies. An important, but often overlooked, consideration in the development of implementable devices is phonon transport through the structure interfaces. Here we report on the interface properties of exfoliated InSe on a sapphire substrate....
متن کاملEffect of reactor pressure on the electrical and structural properties of InN epilayers grown by high-pressure chemical vapor deposition
The influence of super-atmospheric reactor pressures (2.5–18.5 bar) on the electrical and structural properties of InN epilayers deposited on GaN/sapphire (0001) templates by high-pressure chemical vapor deposition has been studied. The epilayers were analyzed by Raman, x-ray diffraction (XRD), and Fourier transform infrared reflectance spectrometry to determine the structural properties as wel...
متن کاملInfrared reflection of GaN and AlGaN thin film heterostructures with AlN buffer layers
Infrared reflection spectroscopy is applied to state-of-the-art thin film heterostructures of group-III nitrides on sapphire and Si substrates. The individual layers of GaN and AlGaN and the AlN buffer layer are identified by their phonon frequencies. Under non-perpendicular incidence of the light, A1~LO! phonon modes are observed in the wurtzite system. The presence of the very thin AlN buffer...
متن کامل