The exciton-phonon coupling in high-quality cubic phase zinc telluride (ZnTe) nanorods (NRs) is investigated by resonant micro-Raman spectroscopy near the direct bandgap of ZnTe. The scattering cross section of longitudinal optical (LO) phonon is enhanced significantly in the resonant process, where the enhancement factor of LO modes is much higher than that of the transverse optical (TO) modes, indicating a dominant Fröhlich electron-phonon interaction mechanism. Up to fifth-order LO phonons are observed by resonant Raman scattering at room temperature. The Huang-Rhys factor of individual NRs-and thus the exciton-LO coupling strengths-is evaluated, showing increasing with the NR diameter. Surface optical (SO) phonon and its high-order overtones are observed between nLO and (n − 1)LO + TO for the first time, whose positions are consistent with a dielectric continuum model. Strong acoustic phonon-exciton coupling induces a high-frequency shoulder above each nLO peaks with two maxima located around 14 cm −1 and 32 cm −1 , which are assigned to transverse acoustic and longitudinal acoustic phonons, respectively. The resonant multiphonon scattering process involving acoustic and LO phonons is discussed based on an exciton-intermediated cascade model, where a scattering sequence of acoustic phonon followed by LO phonons is favorable. These results advance the understanding of electron-phonon coupling and exciton scattering in quasi-one-dimensional systems, especially in the scarcely documented ZnTe compound, facilitating the development and optimization of NR-based optoelectronic devices.

No abstract

No abstract

Highly oriented boron carbonitride (BCN) nanostructures consisting of nanotubes and nanofibers have been synthesized by bias-assisted hot-filament chemical vapor deposition from the source gases of B2H6, CH4, N2, and H2. It is found that the B concentration of the BCN nanostructures increases with increasing B2H6 in the gas mixture, and the highest B concentration is 45 at. %. Photoluminescence spectrum shows that the BCN nanostructures, identified as B0.34C0.42N0.24, are semiconductors with a band gap energy of around 1.0 eV.

A progressively complex anti-counterfeiting platform with large information density, high security and low-error decoding is achieved by utilizing plasmonic nanopillar arrays fabricated using two-photon photolithography. Multiplex molecular information hidden under the same physical features are read out in the form of fluorescence, SERS, and their signal intensities.

Boron carbonitride (BCN) films with various compositions have been prepared by bias-assisted hot filament chemical vapor deposition. The three elements of B, C, and N are chemically bonded with each other and an atomic-level BCN hybrid has been formed in the films. The deposited films are composed of turbostratic structural regions ranging from a few to a few tens of nanometers. Besides, there exist some amorphous domains in the films. Boron atoms have been confirmed to be incorporated into the films with a concentration up to 70 at. %. The interplanar spacing of 3.49 Å is found to be independent of the film composition in this range. These films show a blueshift in photoluminescence peak with increasing B content. These findings show that the electronic structure of BCN compounds can be controlled by changing compositions and the BCN compounds are blue-light emitting materials.

Hydrogenated amorphous silicon carbide (a-Si 1Ϫx C x :H) films have been deposited using an electron cyclotron resonance chemical vapor deposition system. The effects of varying the microwave power from 100 to 1000 W on the deposition rate, optical band gap, film composition, and disorder were studied using various techniques such as Rutherford backscattering spectrometry, spectrophotometry, Fourier-transform infrared absorption, and Raman scattering. Samples deposited at 100 W are found to have a carbon fraction ͑x͒ of 0.49 which is close to that of stoichiometric SiC, whereas samples deposited at higher microwave powers are carbon rich with x which are nearly independent of the microwave power. The optical gaps of the films deposited at higher microwave powers were noted to be related to the strength of the C-H n bond in the films. The photoluminescence ͑PL͒ peak emission energy and bandwidth of these films were investigated at different excitation energies (E ex ) and correlated to their optical band gaps and Urbach tail widths.Using an E ex of 3.41 eV, the PL peak energy was found to range from 2.44 to 2.79 eV, with the lowest value corresponded to an intermediate microwave power of 600 W. At increasing optical gap, the PL peak energy was found to be blueshifted, accompanied by a narrowing of the bandwidth. Similar blueshift was also observed at increasing E ex , but in this case accompanied by a broadening of the bandwidth. These results can be explained using a PL model for amorphous semiconductors based on tail-to-tail states radiative recombination. A linear relation between the full width at half maximum of the PL spectra and the Urbach energy was also observed, suggesting the broadening of the band tail states as the main factor that contributes to the shape of the PL spectra observed.

No abstract