Sökning: "Band gaps"

Visar resultat 1 - 5 av 36 avhandlingar innehållade orden Band gaps.

  1. 1. Numerical Studies of Energy Gaps in Photonic Crystals

    Författare :Andreas Rung; Carl-Gustaf Ribbing; Norbert Kaiser; Uppsala universitet; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Materials science; photonic crystals; polaritonic; periodic structures; Reststrahlen; band structure; energy gap; Materialvetenskap; Materials science; Teknisk materialvetenskap;

    Sammanfattning : The concept of photonic crystals was born in the late 1980's when two important letters were published that showed the possibility to control light propagation by a periodic structure. A photonic crystals consists of two or more materials with different dielectric functions periodically arranged on the length scale of light. LÄS MER

  3. 2. Magnetism in Band Gap Engineered Sputtered MgxZn(1-x)O Thin Films

    Författare :Sreekanth Mahadeva; K Venkat Rao; Lyubov Belova; Mark Fox; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; Magnetron co-sputtering; MgO; MgxZn 1-x O; MnxMg 1-x O; thin films; Room-temperature ferromagnetism; band gap engineering; and intrinsic defects;

    Sammanfattning : This dissertation presents a comprehensive study of the intrinsic room temperature ferromagnetism, RTFM, in technologically important thin films of ZnO, MgO, Mg@ZnO, the so-called d0–magnets that do not contain any intrinsic magnetic elements. We also present the first report on magnetism in Mn doped MgO films fabricated by dc magnetron sputtering. LÄS MER

  4. 3. 3D Magnetic Photonic Crystals : Synthesis and Characterization

    Författare :Mei Fang; K.Venkat Rao; Lyubov Belova; Rajeev Ahuja; KTH; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; magnetic photonic crystals; photonic band gaps; Fe3O4 nanoparticles; silica; Optical physics; Optisk fysik; Materials science; Teknisk materialvetenskap;

    Sammanfattning : This thesis presents the synthesis methods and the characterizations of magnetic Fe3O4 nanoparticles, silica spheres with Fe3O4 nanoparticles embedded, and three dimensional magnetic photonic crystals (MPCs) prepared from the spheres. The structure, material composition, magnetic and optical properties, photonic band gaps (PBGs), as well as how these properties depend on the concentration of the magnetic nanoparticles, are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), superconducting quantum interference device (SQUID), Faraday rotation (FR) and optical spectrophotometers. LÄS MER

  5. 4. First Principles Studies of Functional Materials Based on Graphene and Organometallics

    Författare :Sumanta Bhandary; Biplab Sanyal; Olle Eriksson; Stefano Sanvito; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Graphene; Magnetism; Organometallics; Density functional theory; Electron correlation; Spin switching; Nanoribbons; Exchange interaction; Edge functionalization; Band gap; Physics with spec. in Atomic; Molecular and Condensed Matter Physics; Fysik med inriktning mot atom- molekyl- och kondenserande materiens fysik;

    Sammanfattning : Graphene is foreseen to be the basis of future electronics owing to its ultra thin structure, extremely high charge carrier mobility,  high thermal conductivity etc., which are expected to overcome the size limitation and heat dissipation problem in silicon based transistors. LÄS MER

  7. 5. Theoretical study of electronic structure and optical properties of semiconductor nanostructures

    Författare :Martin Persson; Fasta tillståndets fysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; nanowire superlattices; nanostructures; band structure; wavefunctions; III-V materials; optical properties; Halvledarfysik; Semiconductory physics; Fysicumarkivet A:2004:Persson; Tight-binding theory; nanocrystals; nanowires;

    Sammanfattning : In this thesis, the electronic structure and optical properties of semiconductor nanostructures are studied theoretically. Three types of nanostructures have been studied, silicon nanocrystals, free-standing III-V nanowires and free-standing GaAs/AlGaAs nanowire superlattices. LÄS MER