Luminescence Excitation Spectroscopy of InAs/InGaAs/GaAs Quantum-Dot Arrays in the Temperature Range between 20 and 300 K

Optics and Spectroscopy - Evolution of photoluminescence (PL) and PL excitation spectra in structures containing InAs/InGaAs/GaAs quantum-dot (QD) arrays is investigated in detail as a function of...     

Optical Properties of Three-Dimensional InGaP(As) Islands Formed by Substitution of Fifth-Group Elements

Optics and Spectroscopy - The optical properties of three-dimensional quantum-size InGaPAs islands, which are formed by substitution of phosphorous by arsenic in an InGaPAs layer deposited on GaAs...     

Thermoelectric energy conversion in layered structures with strained Ge quantum dots grown on Si surfaces

The efficiency of the energy conversion devices depends in many ways on the materials used and various emerging cost-effective nanomaterials have promised huge potentials in highly efficient energy conversion. Here we show that thermoelectric voltage can be enhanced by a factor of 3 using layer-cake growth of Ge quantum dots through thermal oxidation of SiGe layers stacked in SiO₂/Si₃N₄ multilayer structure. The key to achieving this behavior has been to strain the Ge/Si interface by Ge dots migrating to Si substrate. Calculations taking into account the carrier trapping in the dot with a quantum transmission into the neighboring dot show satisfactory agreement with experiments above ≈200 K. The results may be of interest for improving the functionality of thermoelectric devices based on Ge/Si.     

Ultrasonic engine based on traveling waves in a plate

Velocity dispersion curves and phase relationships between the surface displacement components are calculated in the case of waves propagating in XZ-, YZ-, and ZY-cut LiNbO₃ plates. The dispersion curves agree with experimental frequency dependences of the excitation efficiency for various modes in the plates. The displacements of ZnS microparticles placed on the surface of the plates qualitatively agree with the analytical phase relationships between the displacement components. Results obtained indicate that the plate may be used as an ultrasonic engine capable of transferring microparticles in various physical and industrial processes.