Optical Properties Of Defects Research Articles

Nickel related defects in diamond: the 2.51 eV band

Optical and magnetic properties of nickel related defects in as-grown diamond are reviewed. Published and new data on the problem of negatively charged substitutional nickel are presented and discussed. We show that the 2.51 eV absorption band occurs at the Ni s −, the spin–orbit and the Jahn–Teller interactions playing important roles in the optical properties of the defect.

Manifestation of intrinsic defects in optical properties of self-organized opal photonic crystals

Self-organized synthetic opals possessing a face centered cubic (fcc) lattice are promising for fabrication of a three-dimensional photonic crystal with a full photonic band gap in the visible. The fundamental limiting factor of this method is the large concentration of lattice defects and, especially, planar stacking faults, which are intrinsic to self-assembling growth of colloidal crystal. We have studied the influence of various types of defects on photonic band structure of synthetic opals by means of optical transmission, reflection and diffraction along different crystallographic directions. We found that in carefully chosen samples the stacking probability alpha can be as high as 0.8-0.9 revealing the strong preference of fcc packing sequence over the hexagonal close-packed (hcp). It is shown that scattering on plane stacking faults located perpendicular to the direction of growth results in a strong anisotropy of diffraction pattern as well as in appearance of a pronounced doublet structure in transmission and reflection spectra taken from the directions other than the direction of growth. This doublet is a direct manifestation of the coexistence of two crystallographic phases--pure fcc and strongly faulted. As a result the inhomogeneously broadened stop-bands overlap over a considerable amount of phase space. The latter, however, does not mean the depletion of the photonic density of states since large disordering results in filling of the partial gaps with both localized and extended states.

Structures and Optical Properties of Defects Correlated with Photo-Induced Refractive Index Changes in Ge-Doped SiO<sub>2</sub> Glass

Structures and Optical Properties of Defects Correlated with Photo-Induced Refractive Index Changes in Ge-Doped SiO<sub>2</sub> Glass

Characteristics of stacking faults in AlN thin films

We have investigated growth characteristics and atomic structure of defects in AlN thin films grown by the metalorganic chemical vapor deposition technique on the (101̄2) r plane of α-Al2O3. The AlN films were single crystal and exhibited the following epitaxial relationship: (112̄0)AlN∥(101̄2)sap with the in-plane alignment of [0001]AlN∥[1̄011]sap. Using high-resolution electron microscopy and multislice image simulation, the predominant defects in AlN thin films grown on the r plane of α-Al2O3 were found to be low-energy intrinsic stacking faults of type I1 lying in the basal plane. This fault, with a 1/6[202̄3] resultant displacement vector, can be formed by removing one (0002) plane and then shearing the remaining half-crystal by displacement of 1/3[101̄0]. The faults appear as a single face-centered-cubic stack ABC inserted into the normal …ABAB… hexagonal sequence. We discuss the possible role of these defects in optical properties of semiconductor devices.

Defects introduced in the electron irradiation of GaAs: Identification with the positron lifetime spectroscopy

We will show that positron lifetime spectroscopy provides information on the atomic structure of vacancy and ion-type defects in semiconductors. We will further demonstrate that positrons can be used to study electrical and optical properties of defects as well as their thermal stability in the heat treatments of the material. Especially, we will review information that positron experiments have provided on the point defects formed in 1–2 MeV electron irradiation of GaAs.

Gold Ion Irradiated Muscovite Mica: Infrared and Optical Properties of Defects and Metal Nanocrystals

Gold Ion Irradiated Muscovite Mica: Infrared and Optical Properties of Defects and Metal Nanocrystals

Optical properties of defects in ion implanted silicon carbide probed at λ=633 nm

The damage produced in silicon carbide single crystal by ion implantation was investigated by in situ optical transmittance and reflectance at 633 nm and by Rutherford backscattering channeling spectroscopy. Implantations were performed at room temperature with different ions (He, N, Ar, Kr, and Xe) in the fluence range 1011–2.5×1016 ions/cm 2. During irradiation a reduction of transmittance and a contemporary increase of reflectance occurred. RBS indicated a continuous accumulation of damage within a depth comparable with the ion range until the formation of an amorphous layer. A combination of optical and RBS data allowed to correlate the optical constant (n,k) to the damage produced during irradiation. Such a correlation was identical for every ion pointing out that the optical properties of the damaged material are independent of the energy density inside the single cascade.

Electrical and Optical Properties of Defects by Complementary Spectroscopies

ABSTRACTDeep levels in II-VI compounds were investigated by complementary junction and optical spectroscopy methods to assess the characteristics of the traps as well as the limits and the reliability of the techniques applied. The electrical properties have been investigated by current and capacitance transient spectroscopy, while the optical properties have been studied by cathodoluminescence. A critical and comparative analysis of the results obtained with the various methods allowed the determination of the parameters and the nature (majority or minority carrier trap) of most of the detected levels.

Electrical and Optical Properties of Defects in N-Type 4h-Sic

ABSTRACTSeveral n-type 4H-SiC samples grown by the physical vapor transport technique were studied using both thermal and optical admittance spectroscopy. The ionization energy ED for nitrogen donors in 4H-SiC was determined to be 0.053 eV and 0.10 eV below the conduction band. This agrees reasonably well with the values of 0.052 eV and 0.092 eV determined by IR absorption measurements. It is believed that EC-0.053 eV is the ionization energy of the nitrogen atom occupying the hexagonal site (h). The 0.10 eV activation energy has been attributed to the nitrogen atoms occupying the cubic sites(k).The optical admittance studies reveal five conductance peaks. One of these corresponds to the band-to-band transitions from which the bandgap of 3.41 eV was determined at 40K. The other four conductance peaks correspond to transitions from defect levels to the conduction band. These defects are located at EC-1.73 eV, EC-1.18 eV, EC-0.87 eV, and EC-0.72 eV.

Defects Introduced by Plasma Processing of Silicon

ABSTRACTThe electrical and optical properties of defects introduced by Reactive Ion Etching (RIE) in the near surface region of Si after dry etching with various gases and plasma conditions is studied with spreading Resistance (SR), photoluminescence (PL), and capacitance-voltage profiling (C-V). Plasma etching in chlorine and fluorine based gases produce donors at the surface in both n-type and p-type, Czochralski and float-zone silicon. Isochronal annealing reveals the presence of two distinct regions of dopant compensation. The surface damage region is confined to 1000 Å and survives heat treatment at 400°C, while the defect reaction region extends ≥ 1 μm in depth and recovers by 250°C. A comprehensive picture of the interstitial defect reactions in RIE silicon is completed. The interstitial defects, Ci and Bi, created in the ion damaged near surface region, undergo recombination enhanced diffusion caused by the presence of ultraviolet light in the plasma, resulting in the long range diffusion into the Si bulk. Subsequently, the interstitial atoms are trapped by the background impurities forming the defect pairs, CiOi, CSCi, or BiOi, which are observed experimentally. The depth of the diffusion-limited trapping and the probability of forming specific pairs depends on the relative concentrations of the reactants, oxygen, carbon or boron, present in the bulk material.

Optical Properties of Defects in Crystals (CdS) Plastically Deformed at 4.2-300 K

Optical Properties of Defects in Crystals (CdS) Plastically Deformed at 4.2-300 K

Electrical and optical properties of defects in silicon introduced by high-temperature electron irradiation.

2-MeV electron irradiation of Si at elevated temperature creates a dominant deep level at the energy E/sub c/-0.36 eV in addition to the oxygen vacancies. This level, which is less significant in room-temperature-irradiated Si, is found to be an efficient recombination center in the present situation. The optical cross section of this level measured by deep-level optical spectroscopy reveals a fine structure superimposed on the main transition. This fine structure is considered to be related to a new resonant phonon mode coupled with the above defect. The isochronal annealing behavior shows that this defect might be a kind of vacancy-oxygen complex. With the assumption of a V/sub 2/-O/sub 2/ complex structure, a calculation based on the Green's-function method of lattice dynamics indicates the existence of a defect-induced resonant phonon mode with energy of 10 meV, which is in good agreement with the experimental observation.

Optical properties of defects produced at annealing of neutron-induced clusters in silicon

Optical properties of defects produced at annealing of neutron-induced clusters in silicon

Colour, symmetry and imperfect crystals

Abstract This review is a discussion of colour introduced into normally transparent and colourless inorganic crystals by lattice defects and impurity ions. First (deliberately starting from the most elementary ideas) we outline the simple theory of processes which cause absorption and emission of light by isolated atoms. This is extended to the case of optically active agents in solids where both the static and dynamic effects of the crystalline electric field must be taken into account. There then follows a description of the optical properties of defects which have electronic configurations analogous to H and He atoms as well as H2 + and H2 molecules. It is shown that many aspects of the spectroscopy of such defects may be understood in terms of relatively unsophisticated models, based upon simple extension of the ideas of atomic and molecular spectroscopy. Some applications of colouration are reviewed briefly.