Realizing optically and/or electrically tunable plasmonic resonances in the visible to ultraviolet (UV) spectral region is particularly important for reconfigurable photonic device applications. Ultrathin layered group-III chalcogenides, such as GaS, GaSe, GaTe, Sb2S3, are particularly intriguing 2D materials that are revealing exotic phase-change properties with great promise for application in next generation reconfigurable electronics and optoelectronic devices.
In this contribution, we present experimental and calculated results obtained on low-loss layered phase-change semiconducting materials of GaS, GaSe, GaTe, Sb2S3, which shows in addition to the conventional amorphous to crystalline phase transition (like the GST family), order-order (polytypes), metal-to-insulator transitions that can be triggered electrically, optically and via plasmonic coupling with alternative phase-change plasmonic metals.
Transparent conducting metal oxides (TCO) are unusual semiconducting materials displaying transparency to visible light. TCO materials are used for electrostatic shielding, antistatic screens, transparent heating devices, solar cells and even organic light emitting diodes. However, most TCOs are n-type, while p-type TCOs are scarce. SrCu2O2 is a leading candidate as a p-type transparent conductive oxide. In this paper, we report theoretical calculations and experimental studies on the vibrational, optical and microstructural properties of both bulk and thin films of polycrystalline undoped SrCu2O2 obtained by pulsed laser deposition (PLD). Barium doping of the SrCu2O2 by substitution of Sr atoms is also reported. The simulated crystal structures of both SrCu2O2 and BaCu2O2 materials, obtained through a state-of-the-art implementation of the Density functional theory, are compared with experimental X-ray diffraction data of undoped and Ba-doped SrCu2O2 bulk materials. Raman spectra of both SCO and BCO materials are simulated from the derivatives of the dielectric susceptibility and a symmetry analysis of the optical phonon eigenvectors at the Brillouin zone center is proposed. Good agreement with Raman scattering experimental results is demonstrated.
ZnO nanostructures were synthesised by Metal Organic Chemical Vapor Deposition growth on Si (100) and c-Al2O3
substrates coated with a 5nm thick layer of Au. The Au coated substrates were annealed in air prior to deposition of
ZnO so as to promote formation of Au nanodroplets. The development of the nanodroplets was studied as a function
of annealing duration and temperature. Under optimised conditions, a relatively homogeneous distribution of regular
Au nanodroplets was obtained. Using the Au nanodroplets as a catalyst, MOCVD growth of ZnO nanostructures was
studied. Scanning electron microscopy revealed nanostructures with various forms including commonly observed
structures such as nanorods, nanoneedles and nanotubes. Some novel nanostructures were also observed, however,
which resembled twist pastries and bevelled-multifaceted table legs.
GaN-based optoelectronic devices are plagued by a tendency to non-radiative transitions linked to defects in the active layers. This problem has its origin in (1) intrinsic factors such as GaN's relatively low exciton binding energy (~24meV) and (2) extrinsic factors including the poor availability of native substrates good enough to significantly suppress the defect density. Indeed, the quality and availability of large-area bulk GaN substrates is currently considered a key problem for the continuing development of improved GaN-based devices. Since development of bulk GaN substrates of suitable quality has proven very difficult, a considerable amount of effort is also being directed towards the development of alternative substrates which offer advantages compared to those in widespread use (c-sapphire and 6H SiC). ZnO is promising as a substrate material for GaN because it has the same wurtzite structure and a relatively small lattice mismatch (~1.8%). In this paper, we discuss use of ZnO thin films as templates for GaN based LED.
Conference Committee Involvement (1)
Oxide-based Materials and Devices VI
8 February 2015 | San Francisco, California, United States
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