The term photonic crystals appears because of the analogy between electron waves in crystals and the light waves in artificial periodic dielectric structures. During the recent years the investigation of one-, two-and three-dimensional periodic structures has attracted a widespread attention of the world optics community because of great potentiality of such structures in advanced applied optical fields. The interest in periodic structures has been stimulated by the fast development of semiconductor technology that now allows the fabrication of artificial structures, whose period is comparable with the wavelength of light in the visible and infrared ranges.

http://ieeexplore.ieee.org/iel5/6354/16969/00781867.pdf

Photonic crystals

We present a comprehensive and up-to-date compilation of band parameters for all of the nitrogen-containing III–V semiconductors that have been investigated to date. The two main classes are: (1) “conventional” nitrides (wurtzite and zinc-blende GaN, InN, and AlN, along with their alloys) and (2) “dilute” nitrides (zinc-blende ternaries and quaternaries in which a relatively small fraction of N is added to a host III–V material, e.g., GaAsN and GaInAsN). As in our more general review of III–V semiconductor band parameters [I. Vurgaftman et al., J. Appl. Phys. 89, 5815 (2001)], complete and consistent parameter sets are recommended on the basis of a thorough and critical review of the existing literature. We tabulate the direct and indirect energy gaps, spin-orbit and crystal-field splittings, alloy bowing parameters, electron and hole effective masses, deformation potentials, elastic constants, piezoelectric and spontaneous polarization coefficients, as well as heterostructure band offsets. Temperature an...

Band parameters for nitrogen-containing semiconductors

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Principles Of Optics Electromagnetic Theory Of Propagation Interference And Diffraction Of Light

The last decade of research in the physical sciences has seen a dramatic increase in the study of nanoscale materials. Today, "nanoscience" has emerged as a multidisciplinary effort, wherein obtaining a fundamental understanding of the optical, electrical, magnetic, and mechanical properties of nanostructures promises to deliver the next generation of functional materials for a wide range of applications. While this range of efforts is extremely broad, much of the work has focused on "hard" materials, such as Buckyballs, carbon nanotubes, metals, semiconductors, and organic or inorganic dielectrics. Meanwhile, the soft materials of current interest typically include conducting or emissive polymers for "plastic electronics" applications. Despite the continued interest in these established areas of nanoscience, new classes of soft nanomaterials are being developed from more traditional polymeric constructs. Specifically, nanostructured hydrogels are emerging as a promising group of materials for multiple biotechnology applications as the need for advanced materials in the post-genomic era grows. This review will present some of the recent advances in the marriage between water-swellable networks and nanoscience.

Soft nanotechnology with soft nanoparticles.

CdSe and CdTe nanocrystals are linked to nanostructured TiO2 films using 3-mercaptopropionic acid as a linker molecule for establishing the mechanistic aspects of interfacial charge transfer processes. Both these quantum dots are energetically capable of sensitizing TiO2 films and generating photocurrents in quantum dot solar cells. These two semiconductor nanocrystals exhibit markedly different external quantum efficiencies (∼70% for CdSe and ∼0.1% for CdTe at 555 nm). Although CdTe with a more favorable conduction band energy (ECB = −1.0 V vs NHE) is capable of injecting electrons into TiO2 faster than CdSe (ECB = −0.6 V vs NHE), hole scavenging by a sulfide redox couple remains a major bottleneck. The sulfide ions dissolved in aqueous solutions are capable of scavenging photogenerated holes in photoirradiated CdSe system but not in CdTe. The anodic corrosion and exchange of Te with S dominate the charge transfer at the CdTe interface. Factors that dictate the efficiency and photostability of CdSe and C...

Quantum dot sensitized solar cells. A tale of two semiconductor nanocrystals: CdSe and CdTe.

We have synthesized semiconductor and metal nanoparticles (NPs) in the constrained geometry of polymer microgels. We used electrostatically driven attraction between the ionic groups of the microgels and the precursor cations in the bulk liquid medium to introduce the cations in the interior of the microgel. In the second step, the cations in the microgel interior reacted with the anion (to obtain semiconductor NPs) or they were treated with a reducing agent (to obtain metal NPs). Good control over the size and the concentration of the NPs in the microgel particles was achieved by changing the composition of the corresponding microgel. The doped microgel spheres were heated at pH 4 above the volume-transition temperature of the polymer to expel the water from the microsphere interior; then the polymer was encapsulated with a hydrophobic polymeric shell. Hybrid core–shell particles were used as the building blocks of the nanostructured material with properties of a photonic crystal.

From Hybrid Microgels to Photonic Crystals

Tuneable complementary metamaterial structures based on graphene for single and multiple transparency windows

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We have studied the effect of rapid thermal annealing (RTA) on GaInNAs/GaAs quantum wells (QWs) grown by molecular-beam epitaxy using a dc plasma as the N source. It was found that RTA at low temperature (LT, 650 degrees C) and high temperature (HT, 900 degrees C) could both improve the QW quality significantly. To clarify the mechanism of quality improvement by RTA, a magnetic field perpendicular to the path of the N plasma flux was applied during the growth of the GaInNAs layers for the sake of comparison. It was found that LT-RTA mainly removed dislocations at interfaces related to the ion bombardment, whereas, HT-RTA further removed dislocations originating from the growth. LT-RTA caused only a slight blueshift of photoluminescence peak wavelength, probably due to defect-assisted interdiffusion of In-Ga at the QW interfaces. The blueshift caused by HT-RTA, on the other hand, was much larger. It is suggested that this is due to the fast defect-assisted diffusion of N-As at the QW interfaces. As defects are removed by annealing, the diffusion of In-Ga at interfaces would be predominant. (C) 2000 American Institute of Physics. [S0003- 6951(00)01535-7].

Effect of rapid thermal annealing on GaInNAs/GaAs quantum wells grown by plasma-assisted molecular-beam epitaxy

We have investigated the optical transitions in Ga1-yInyNxAs1-x/GaAs single and multiple quantum wells using photovoltaic measurements at room temperature. From a theoretical fit to the experimental data, the conduction band offset Q(c), electron effective mass m(e)*, and band gap energy E-g were estimated. It was found that the Q(c) is dependent on the indium concentration, but independent on the nitrogen concentration over the range x=(0-1)%. The m(e)* of GaInNAs is much greater than that of InGaAs with the same concentration of indium, and increases as the nitrogen concentration increases up to 1%. Our experimental results for the m(e)* and E-g of GaInNAs are quantitatively explained by the two-band model based on the strong interaction of the conduction band minimum with the localized N states. (C) 2001 American Institute of Physics.

Conduction band offset and electron effective mass in GaInNAs/GaAs quantum-well structures with low nitrogen concentration

We report the combination of microsphere self-organization to form a photonic crystal, providing spectrally and angularly dependent electromagnetic structural resonances; with nanocrystal growth in situ on microsphere surfaces, providing optical functionalization with spectral control achieved through the quantum size effect. We demonstrate this material system using CdS nanocrystals coating the surfaces of poly(methyl methacrylate)–poly(methacrylic acid) (PMMA–PMAA) micrometer spheres. The in situ synthesis of the CdS nanocrystals on the surface of the PMMA/PMAA microspheres preserves the propensity of the hybrid microspheres to form ordered colloid arrays. Luminescence from surface states ensures that light is emitted at energies significantly below the absorption edge of the emitting species. Transmission and photoluminescence measurements reveal the interaction of the photonic stop band with photoluminescence from the nanocrystals.

/pdf/photonic-pseudo-gap-based-modification-of-photoluminescence-2ul6oqjgce.pdf

Yuankun Lin

Papers

From Hybrid Microgels to Photonic Crystals

Tuneable complementary metamaterial structures based on graphene for single and multiple transparency windows

Effect of rapid thermal annealing on GaInNAs/GaAs quantum wells grown by plasma-assisted molecular-beam epitaxy

Conduction band offset and electron effective mass in GaInNAs/GaAs quantum-well structures with low nitrogen concentration

Photonic pseudo-gap-based modification of photoluminescence from CdS nanocrystal satellites around polymer microspheres in a photonic crystal