Study of Crystal Defects and Spectroscopy Characteristics of Ammonium Polyphosphate

Two kinds of commercial ammonium polyphosphate （APP） and three kinds of APP which were prepared in the laboratory were studied by X-ray diffraction （XRD）, Fourier transforms infrared spectroscopy （FTIR）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. In identification of the form Ⅱ crystal APP by XRD and FTIR, some discrepancies were discussed. It is pointed out that the absorbance of the FTIR spectra at 682 cm^-1 can exist not only in the form Ⅰ APP, but also in the form Ⅱ APP with the crystal lattice defects. The SEM images indicate that the form Ⅱ APP is of multilayer crystal structure. XRD and TEM can reveal the crystal lattice defects.

Crystal defects formed in electroformed nickel liners of shaped charges

Two types of electroformed nickel liners of shaped charges were prepared by electroforming technique. X-ray diffraction （XRD）, transmission electron microscopy （TEM）, electron backscattering diffraction （EBSD） technique and high resolution electron microscopy （HREM） have been employed to investigate the crystal defects formed in electroformed nickel liners of shaped charges. The result shows that （100） fiber texture which is parallel to the grown direction exists in the electroformed nickel prepared by using direct current electroforming without any additives, and （111） fiber texture exists in the electroformed nickel prepared by using direct current electroforming with additives. The deposits prepared by using direct current electroforming possess columnar grain with an average grain size of 30 μm in width and 170 μm in length. The deposits prepared with additives are composed of a colony structures with grain size of about 29 nm, and a lot of crystal defects such as twins, antiphase boundaries and stacking faults have been observed in the electroformed nickel.

CRYSTAL DEFECTS AND GRAIN INTERFACE STRUCTURE OF ION-NITRIDED LAYERS

Observation under high resolution electron microscope shows that the continuous bombing of high speed ions produces a great amount of vacant site defects.The assembly of vacancies forms vacant dish,and the collapase of vacant dish forms stacking fault tetrahedrons and oth- er crystal defects.The interfaces between phase ε(Fe_(2-3)N)and phase γ'(Fe_4N)are smooth, straight and coherent,and they have the orientation relationships of(11)//(0001)and [110]/[110] .

CRYSTAL DEFECTS IN PLASMA NITRIDED LAYER CATALYZED BY RARE EARTH

The microstructure of plasma nitrided layer catalyzed by rare-earth elementshas been studied with TEM. The results show that the grains of gamma ft-Fe_4N phase are refined byrare-earth elements and the plane defects in boundary are increased by rare-earth elements. Theaddition of rare-earth element increases the bombardment effect and the number of crystal defectssuch as vacancies, dislocation loops, twins and stacking faults in gamma ft -Fe_4N phase and canproduce the high-density dislocations in the ferrite of diffusion layer at a distance 0.08mm fromthe surface. The production of a number of crystal defects is one of important reasons whyrare-earth element accelerates the diffusion of nitrogen atoms during plasma-nitriding.

Design of Photonic Crystal Triplexer with Core-Shell Rod Defects

We investigate an optical compact triplexer based on two photonic crystal waveguides and resonant cavities. For performing wavelength selection, we use three core-shell rods as the resonant cavities. The core rods are created by introducing air holes in the center of the silicon rods. By varying the radii of the air holes, three specific wavelengths 1.31, 1.49 and 1.55μm can be obtained. This structure is designed and its performance is verified by the finite-difference time-domain method, which is highly suitable for photonic integrated circuits （PICs）. The average output transmission efficiency and quality factor are more than 98.85% and 560, respectively. The mean value of the crosstalk between output channels is about -36.49 dB. The present device is extremely compact with total size 96.24μm2, which is suitable for PICs and can be utilized in the fiber-to-the-home system.

Defects of (Tb_(0.3)Dy_(0.7))Fe_(1.95) Alloys with "One-Step" Directional Solidification Process

The main types of defect in the (Tb_(0.3)Dy_(0.7))Fe_(1.95) alloys with the 'one-step' directional solidification process were investigated. The effect of the dendrite, grain boundaries, twin boundaries, and REFe_3 precipitates on the magnetostrictive response of the (Tb_(0.3)Dy_(0.7))Fe_(1.95) alloys was analyzed respectively. The experiment results demonstrate that the dendrite, twin boundaries, and REFe_3 precipitates can be avoided by modifying alloying ingredient, solidification parameters and annealing technique. The dendritic growth front often leads to dendrite sheet, rare earth-rich phase, and twin boundaries. The lower proportion of rare earth, or slow solidification rate, results in the occurrence of REFe_3 precipitatates. It is vital for diminishing the defects to control the undercooling of solid-liquid interface at (2.4～5.1)×10~4 K·s·cm^(-2) so that the crystal grows in cellular growth front.

Molecular dynamics simulations of point defects in plutonium grain boundaries

A modified analytic embedded atom method （MAEAM） potential is constructed for fcc 5-Pu. Molecular dynamics （MD） simulations with the potential are performed to investigate the interactions between two symmetrical tilt grain boundaries （GBs） and point defects such as He atom, vacancy and self-interstitial atom （SIA） in Pu. The calculated results show that point defect formation energies are on average lower than those in the lattice but variations from site to site along the GBs are very remarkable. Both substitutional and interstitial He atoms are trapped at GBs. Interstitial He atom is more strongly bound at the GB core than the substitutional He atom. The binding energy of SIA at GB core is higher than those of He atom and vacancy. GB core can bind many He atoms and SIAs due mainly to the fact that it contains many vacancies. Compared with He atom and SIA, the vacancy far from GB core is difficult to diffuse into the core. The GBs can act as sinks and sources of He atoms and SIAs, which may be a reason for the swelling of Pu after a period of self-irradiation because of the higher concentration of vacancy in the bulk.

Optical and defect properties of S-doped and Al-doped GaSe crystals

S-doped and Al-doped GaSe crystals are promising materials for their applications in nonlinear frequency conversion devices. The optical and defect properties of pure, S-doped, and Al-doped GaSe crystals were studied by using photoluminescence（PL） and Fourier transform infrared spectroscopy（FT-IR）. The micro-topography of（0001） face of these samples was observed by using scanning electron microscope（SEM） to investigate the influence of the doped defects on the intralayer and interlayer chemical bondings. The doped S or Al atoms form the SSe^0 or AlGa^＋1） substitutional defects in the layer GaSe structure, and the positive center of AlGa-^＋1 could induce defect complexes. The incorporations of S and Al atoms can change the optical and mechanical properties of the GaSe crystal by influencing the chemical bonding of the layer structure. The study results may provide guidance for the crystal growth and further applications of S-doped and Al-doped GaSe crystals.

High-temperature annealing of(201)β-Ga_(2)O_(3) substrates for reducing structural defects after diamond sawing

A commercial epi-ready(201)β-Ga_(2)O_(3) wafer was investigated upon diamond sawing into pieces measuring 2.5×3 mm^(2).The defect structure and crystallinity in the cut samples has been studied by X-ray diffraction and a selective wet etching technique.The density of defects was estimated from the average value of etch pits calculated,including near-edge regions,and was obtained close to 109 cm^(-2).Blocks with lattice orientation deviated by angles of 1-3 arcmin,as well as non-stoichiometric fractions with a relative strain about(1.0-1.5)×10^(-4)in the[201]direction,were found.Crystal perfection was shown to decrease significantly towards the cutting lines of the samples.To reduce the number of structural defects and increase the crystal perfection of the samples via increasing defect motion mobility,the thermal annealing was employed.Polygonization and formation of a mosaic structure coupled with dislocation wall appearance upon 3 h of annealing at 1100℃ was observed.The fractions characterized by non-stoichiometry phases and the block deviation disappeared.The annealing for 11 h improved the homogeneity and perfection in the crystals.The average density of the etch pits dropped down significantly to 8×10^(6) cm^(-2).

Position Dependent Spontaneous Emission Spectra of a Λ-Type Atomic System Embedded in a Defective Photonic Crystal

We investigate the position dependent spontaneous emission spectra of a A-type three-level atom with one transition coupled to the free vacuum reservoir and the other one coupled to a double-band photonic band gap reservoir with a defect mode in the band gap. It is shown that, for the atom at the defect location, we have a two-peak spectrum with a wide dark line due to the strong coupling between the atom and the defect mode. While, when the atom is far from the defect location （or in the absence of the defect mode）, the spectrum has three peaks with two dark lines due to the coupling between the atom and the photonic band gap reservoir with the largest density of states near the band edges. On the other hand, we have a four-peak spectrum for the atom at the space in between. Moreover, the average spontaneous emission spectra of the atoms uniformly embedded in high dielectric or low dielectric regions are described. It is shown that the atoms embedded in high （low） dielectric regions far from the defect location, effectively couple to the modes of the lower （upper） photonic band. However, the atoms embedded in high dielectric or low dielectric regions at the defect location, are coupled mainly to the defect modes. While, the atoms uniformly embedded in high （low） dielectric regions with a normal distance from the defect location, are coupled to both of defect and lower （upper） photonic band modes.

High-precision X-ray characterization for basic materials in modern high-end integrated circuit

Semiconductor materials exemplify humanity's unwavering pursuit of enhanced performance,efficiency,and functionality in electronic devices.From its early iterations to the advanced variants of today,this field has undergone an extraordinary evolution.As the reliability requirements of integrated circuits continue to increase,the industry is placing greater emphasis on the crystal qualities.Consequently,conducting a range of characterization tests on the crystals has become necessary.This paper will examine the correlation between crystal quality,device performance,and production yield,emphasizing the significance of crystal characterization tests and the important role of high-precision synchrotron radiation X-ray topography characterization in semiconductor analysis.Finally,we will cover the specific applications of synchrotron radiation characterization in the development of semiconductor materials.

Study of Defect and Large Thermal Strain Nature in Organic Crystal of Rubidium Hydrogen Phthalate

Imperfections in the(001) plate of rubidium hydrogen phthalate(RAP, RbC8H5O4) crystals have been studied by means of X-ray topography. The main defects are the grown-in dislocations, inclusions, growth layers and the thermal strain lobes caused by heat. The large thermal strain nature was determined by an Inclusion Probed Method (IPM), which is due to the gradient of the interplanar spacing formed by atomic displacement to <110> directions.

Controllable synthesis of CdS nanospheres photoelectrode for photoelectrochemical water splitting

CdS nanospheres were grown on indium tin oxide(ITO)substrate using a hydrothermal method.The crystal structure,morphology and electronic structure of the samples synthesized were characterized in detail.The results confirm that the crystallinity,size,crystal defects of the CdS nanospheres and the film thickness of CdS photoelectrodes can be tuned by varying the precursor Cd2+concentration.Combined with charge transfer dynamics analysis,it can be found that proper particle size and film thickness,as well as fewer defects,will result in better charge separation efficiency of the prepared CdS/ITO photoelectrodes,thereby exhibiting better photoelectrochemical performance for water splitting.The optimized CdS/ITO photoelectrode synthesized with a Cd2+concentration of 0.14 mol⋅L1 gave a photocurrent density of 5.10 mA⋅cm^(-2)at potential of 1.23 V versus the reversible hydrogen electrode(RHE),under a simulated solar illumination of 100 mW⋅cm^(-2).

Tuning the electronic conductance of REH_(x)(RE=Nd,Ce,Pr)by structural deformation

Hydride ion(H-)conductors have drawn much attention due to their potential applications in hydrideion-based devices.Rare earth metal hydrides(REH_(x))have fast H-conduction which,unfortunately,is accompanied by detrimental electron conduction preventing their application as ion conductors.Here,REH_(x)(RE=Nd,Ce,and Pr)with varied grain sizes,rich grain boundaries,and defects have been prepared by ball milling and subsequent sintering.The electronic conductivity of the ball-milled REH_(x)samples can be reduced by 2-4 orders of magnitude compared with the non-ball-milled samples.The relationship of electron conduction and miscrostructures in REH_(x)is studied and discussed based on experimental data and previously-proposed classical and quantum theories.The H-conductivity of all REH_(x)is about 10^(-4)to 10^(-3)S cm^(-1)at room temperature,showing promise for the development of H-conductors and their applications in clean energy storage and conversion.

Low frequency damping capacities of commercial pure magnesium

The amplitude-dependent and temperature-dependent low frequency damping capacities of magnesium with 99.96% purity were studied by a dynamic mechanical analyzer. The pure magnesium alloys include CPM1 and CPM2 castings having textures of columnar grains which extraordinarily influence the damping behaviours. The commercial pure magnesium alloy CPM was re-melted to obtain equiaxed grains, which could remove the effect of texture orientation on the damping behaviours of these pure magnesium alloys. The results of strain amplitude-dependent damping spectrums of these pure magnesium alloys show that the pure magnesium with equiaxed grains possesses the highest damping capacity. In temperature-dependent damping plot for all these three pure magnesium alloys, there are two damping peaks P1 and P2 located at 80 and 230 °C, respectively. These two damping peaks are considered to be caused by the interaction between dislocation and point defects, and the movement of grain boundaries, respectively.

Investigation on Preparation and Anti-icing Performance of Superhydrophobic Surface on Aluminum Conductor

Aluminum is widely used in transmission lines, and the accumulation of ice on aluminum conductor may inflict serious damage such as tower collapse and power failure. In this study, super-hydrophobic surface （SHS） on alurninurn conductor with rnicro-nanostructure was fabricated using the preferential etching principle of crystal defects. The surface rnicrostructure and wettability were investigated by scanning electron microscope and contact angle measurement, respectively. The icing progress was observed with a self-made icing experiment platform at different environment temperature. The results showed that, due to jumping and rolling down of coalesced droplets from SHS of aluminum conductor at low temperature, the formation of icing on SHS could be delayed. Dynamic icing experiment indicated that SHS on aluminum conductor could restrain the formation of icing in certain temperature range, but could not exert influence on the accumulation of icing. This study offers new insight into understanding the anti-icing performance of actual aluminum conductor.

Roles of Te and Mn in the two phases of manganite with nominal composition La_(0.6)Sr_(0.1)Te_xMnO_3

Powder samples with nominal composition La0.6Sr0.1TexMnO3 （x = 0.00, 0.05, 0.10, 0.15, 0.20） were prepared using the sol-gel method with thermal treatment up to 1473 K. On the basis of powder X-ray diffraction （XRD）, thermogravimetric and magnetic measurements, it was found that almost all of the Te and a few of the Mn ions were lost from the samples when they were calcined at 1473 K. The reason for the Te loss and a quantitative phase analysis for the samples calcined at 1473 K are discussed in detail.

Three-dimensional photonic crystals containing designed defects achieved with two-photon photopolymerization

Two-photon photopolymerization （TPP） with femtosecond laser is a promising method to fabricate threedimensional （3D） photonic crystals （PCs）. Based on the TPP principle, the micro-fabrication system has been built. The 3D woodpile PCs with rod space of 2000 nm are fabricated easily and different defects are introduced in order to form the cross-waveguide and the micro-laser structure PCs. Simulation results of the optical field intensity distributions using finite-difference time domain （FDTD） method are given, which support the designs and implementation of the PC of two types in theory.

DIAMOND HETEROEPITAXY-NUCLEATION, INTERFACE STRUCTURE, FILM GROWTH

The present understanding of diamond heteroepitaxy by bias-enhanced chemical vapour deposition on technologically relevant substrate materials is briefly reviewed. First the early stages of diamond nucleation and the diamond film growth as well as influences of various deposition conditions are described. Then the results of microscopic investigations of the structure of interfaces and of grain boundaries are summarized.

Relation between EL2 Groupand EL6 Group in SI-GaAs

The annealing behavior for EL2 and EL6 groups as dominant deep levels in semi-insulating GaAs was presented using Photo Induced Transient Spectroscopy measurement (PITS). During rapid thermal annealing, a relation was identified between EL2 group at 0.79 and 0.82 eV and EL6 group at 0.24, 0.27 and 0.82 eV below the conduction band. It is found that they may be close in structure, and belong to the EL2 and EL6 groups, respectively. In rapidly annealed samples, the quantity of all defects in the EL2 group increases, while that in the EL6 group decreases. However, by furnace annealing at 950°C for 5 h, some of the defects in the EL2 group break up, and the quantity of all defects in the EL6 group increases. It is suggested that the EL2 group and EL6 group are related in their microscopy structures. The relation between the two groups and origins was also discussed.