Tuning the plasmon resonance of metallic tin nanocrystals in Si-based materials

The optical properties of metallic tin nanoparticles embedded in silicon-based host materials were studied. Thin films containing the nanoparticles were produced using RF magnetron sputtering followed by ex situ heat treatment. Transmission electron microscopy was used to determine the nanoparticle shape and size distribution; spherical, metallic tin nanoparticles were always found. The presence of a localized surface plasmon resonance in the nanoparticles was observed when SiO2 and amorphous silicon were the host materials. Optical spectroscopy revealed that the localized surface plasmon resonance is at approximately 5.5 eV for tin nanoparticles in SiO2, and at approximately 2.5 eV in amorphous silicon. The size of the tin nanoparticles in SiO2 can be varied by changing the tin content of the films; this was used to tune the localized surface plasmon resonance.Comment: 14 pages, 7 figure

Light emission from silicon with tin-containing nanocrystals

Tin-containing nanocrystals, embedded in silicon, have been fabricated by growing an epitaxial layer of Si_{1-x-y}Sn_{x}C_{y}, where x = 1.6 % and y = 0.04 %, followed by annealing at various temperatures ranging from 650 to 900 degrees C. The nanocrystal density and average diameters are determined by scanning transmission-electron microscopy to ~ 10^{17} cm^{-3} and ~ 5 nm, respectively. Photoluminescence spectroscopy demonstrates that the light emission is very pronounced for samples annealed at 725 degrees C, and Rutherford back-scattering spectrometry shows that the nanocrystals are predominantly in the diamond-structured phase at this particular annealing temperature. The origin of the light emission is discussed.Comment: 5 pages, 3 figures, submitted to AIP Advance

Ion-Beam-Induced Atomic Mixing in Ge, Si, and SiGe, Studied by Means of Isotope Multilayer Structures

Crystalline and preamorphized isotope multilayers are utilized to investigate the dependence of ion beam mixing in silicon (Si), germanium (Ge), and silicon germanium (SiGe) on the atomic structure of the sample, temperature, ion flux, and electrical doping by the implanted ions. The magnitude of mixing is determined by secondary ion mass spectrometry. Rutherford backscattering spectrometry in channeling geometry, Raman spectroscopy, and transmission electron microscopy provide information about the structural state after ion irradiation. Different temperature regimes with characteristic mixing properties are identified. A disparity in atomic mixing of Si and Ge becomes evident while SiGe shows an intermediate behavior. Overall, atomic mixing increases with temperature, and it is stronger in the amorphous than in the crystalline state. Ion-beam-induced mixing in Ge shows no dependence on doping by the implanted ions. In contrast, a doping effect is found in Si at higher temperature. Molecular dynamics simulations clearly show that ion beam mixing in Ge is mainly determined by the thermal spike mechanism. In the case of Si thermal spike, mixing prevails at low temperature whereas ion beam-induced enhanced self-diffusion dominates the atomic mixing at high temperature. The latter process is attributed to highly mobile Si di-interstitials formed under irradiation and during damage annealing

Anomalous behavior of electrically active defects near EC−0.5 eV in MOCVD, as-grown GaN

The present work reports on a distinct and very reproducible bistable-like behavior of two defects at around EC − 0.5 eV in MOCVD-grown GaN. The kinetics of the thermally activated transformation between the two states are analyzed in an Arrhenius model, yielding an energy barrier of 0.4 ± 0.1 eV, and a frequency factor of 106±1 s−1. Depth profiles suggest that the charge state of the defects determines the observed amplitude variation. Relevant models for the observed behavior, and their shortcomings are discussed: (i) passivating properties of hydrogen, and (ii) bistable defect component(s). A proper explanation of the experimental observations represents, however, a further challenge

Activation Volume for Phosphorus Diffusion in Silicon and Si0.93Ge0.07

The hydrostatic pressure dependence of the diffusivity of P in compressively strained Si0.93Ge0.07 and unalloyed Si has been measured. In both cases the diffusivity is almost independent of pressure, characterized by an activation volume V* of (+0.09±0.11) times the atomic volume Omega for the unalloyed Si, and (+0.01±0.06) Omega for Si0.93Ge0.07. The results are used in conjunction with the reported effect of biaxial strain on diffusion normal to the surface to test the prediction for an interstitialcy-based mechanism of Aziz's phenomenological thermodynamic treatment of diffusion under uniform nonhydrostatic stress states. The prediction agrees well with measured behavior, lending additional credence to the interstitial-based mechanism and supporting the nonhydrostatic thermodynamic treatment.Engineering and Applied Science