Design of a thin-plate based tunable high-quality narrow passband filter for elastic transverse waves propagate in metals

For the elastic SV (transverse) waves in metals, a high-quality narrow passband filter that consists of aligned parallel thin plates with small gaps is designed. In order to obtain a good performance, the thin plates should be constituted by materials with a smaller mass density and Young’s modulus, such as polymethylmethacrylate (PMMA), compared to the embedded materials in which the elastic SV waves propagate. Both the theoretical model and the full numerical simulation show that the transmission spectrum of the designed filter demonstrates several peaks with flawless transmission within 0 KHz ∼20 KHz frequency range. The peaks can be readily tuned by manipulating the geometrical parameters of the plates. Therefore, the current design works well for both low and high frequencies with a controllable size. Even for low frequencies on the order of kilohertz, the size of this filter can be still limited to the order of centimeters, which significantly benefits the real applications. The investigation also finds that the same filter is valid when using different metals and the reason behind this is explained theoretically. Additionally, the effect of bonding conditions of interfaces between thin plates and the base material is investigated using a spring model

Synthesis and Characterizations of Bare CdS Nanocrystals Using Chemical Precipitation Method for Photoluminescence Application

Bare cadmium sulfide (CdS) nanocrystals were successfully synthesized by the thermolysis of a single-source organometallic precursor, cadmium chloride hemipentahydrate (CdCl2⋅2.5H2O) with thiourea in ethanol. The microstructure of the CdS samples was characterized using XRD, TEM, and Raman spectroscopy. The XRD's results showed that there was a transformation from cubic to hexagonal crystalline phase when higher mass of CdCl2⋅2.5H2O was used. Further experimental with different Cd2+ source showed ion Cl− originated from CdCl2⋅2.5H2O attributed to this crystalline phase transformation. The UV-Visible analysis indicated that quantum confinement effect took place when compared to the bulk CdS. However, the photoluminescence experiments revealed that the red-light emission was observed in all samples. This finding could be ascribed to deep trap defects that were due to sulfur vacancies as suggested by XPS and also the fact that the bare CdS nanoparticles are in contact with each other as shown in the TEM images

Effect of deposition temperature on surface acoustic wave velocity of aluminum nitride films determined by Brillouin spectroscopy

3 pages, 4 figures.-- PACS: 78.35.+c; 68.35.Iv; 78.66.FdBrillouin spectroscopy has been used to study the effect of the deposition temperature on the surface acoustic wave (SAW) propagation velocity of aluminum nitride (AlN) films. The results show a dependence of the SAW propagation velocity on the growth temperature of AlN films. The highest value of acoustic velocity was obtained for the film elaborated without heating. Structural characterization of the AlN films synthesized at various deposition temperatures was carried out by x-ray diffraction. These analyses pointed out that the deposition temperature influences the standard deviation of (002) AlN film preferred orientation. The growth temperature clearly influences the acoustical and crystalline properties of AlN thin films.This work was partially supported by the Spanish Ministery of Education and Science (Project No. MAT-2003- 01880), the autonomous community of Madrid (Project No. 07N/0077/2002), and by a bilateral cooperation between CNRS and CSIC within the frame of the Picasso program common project Assouar/Jiménez (France) and Acción Integrada 2004FR0008 (Spain).Peer reviewe

Domains Inversion in LiNbO3 Using Electron Beam Irradiation for Phononic Crystals

International audienc

Solar blind metal-semiconductor-metal ultraviolet photodetectors using quasi-alloy of BGaN/GaN superlattices

Large internal gains that can be obtained in wide band gap semiconductors-based (GaN and ZnO types) Schottky and/or metal-semiconductor- metal photodetectors are generally accompanied by large dark current and time response. We show that, using quasi-alloy of BGaN/GaN superlattices as the active layer, the dark current can be lowered while maintaining high internal gain (up to 3 10 4) for optical power in the nW range and low time response (few tens of ns) for optical power in the W range. Furthermore, the boron incorporation allows the tuning of the cutoff wavelength