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Understanding the internal magnetization structure of an individual ferromagnetic nanoparticle (MNP) is crucial for deciphering its magnetic characteristics. Unfortunately, while certain techniques can measure the magnetic properties of an individual MNP, they fall short of accurately detecting the internal magnetization structure. In this work, micromagnetic simulations were employed to construct the internal magnetization structure of an individual CoFe2O4 (CFO) nanopyramid, and the energy jump behavior during the magnetization process was successfully explained, with simulation results aligning with dynamic cantilever magnetometry (DCM) experimental outcomes. Subsequently, the external stray field of the nanopyramid was simulated, and the stray field gradient map revealed distinct bright and dark regions corresponding to the reverse and forward saturation magnetizations of the CFO nanopyramid. This result is possible to be verified by magnetic force microscopy (MFM) measurements of individual CFO nanopyramids. The confidence in the accuracy of the simulated internal magnetization structure was significantly enhanced by independently verifying the micromagnetic simulation results through DCM and MFM experiments. Our work proposes a convenient and cost-effective method for studying the internal magnetization structure of individual MNPs. [ABSTRACT FROM AUTHOR]

The discovery of atom-like spin emitters associated with defects in two-dimensional (2D) wide-bandgap (WBG) semiconductors presents new opportunities for highly tunable and versatile qubits. So far, the study of such spin emitters has focused on defects in hexagonal boron nitride (hBN). However, hBN necessarily contains a high density of nuclear spins, which are expected to create a strong incoherent spin-bath that leads to poor coherence properties of spins hosted in the material. Therefore, identification of new qubit candidates in other 2DWBG materials is necessary. Given the time demands of ab initio methods, new approaches for rapid screening and calculations of identifying properties of suitable atom-like qubits are required. In this work, we present two new methods for rapid estimation of the zero-phonon line (ZPL), a key property of atomic qubits in WBG materials. First, the ZPL is calculated by exploiting Janak's theorem. For finite changes in occupation, we provide the leading-order estimate of the correction to the ZPL obtained using Janak's theorem, which is more rapid than the standard method (Δ SCF). Next, we demonstrate an approach to converging excited states that is faster for systems with small strain than the standard approach used in the Δ SCF method. We illustrate these methods using the case of the singly negatively charged calcium vacancy in SiS 2 , which we are the first to propose as a qubit candidate. This work has the potential to assist in accelerating the high-throughput search for quantum defects in materials, with applications in quantum sensing and quantum computing. [ABSTRACT FROM AUTHOR]

Inhomogeneous broadening of semiconductor nanostructures results from structural and chemical variations between different nanostructure entities. Inhomogeneous broadening can have profound impacts on the optical properties of a nanostructure array. In this work, various inhomogeneous broadening mechanisms in wurtzite InGaN/GaN dot-in-wire (DIW) structures were investigated, both experimentally and theoretically. Using lithographically defined nanostructures, the microscopic variations including random alloy fluctuations and atomic-scale thickness fluctuations can be isolated from macroscopic variations such as size, shape, and alloy nonuniformity. An epitaxial InGaN/GaN quantum well sample was patterned into an array of sparsely spaced dot-in-wire structures and measured by confocal microphotoluminescence (PL) at 10 K. Both static (photon energy) and dynamic (carrier lifetime) properties were measured. The PL measurement results were compared to a theoretical model based on the k-dot-p method under the effective mass approximation and including the excitonic effect and surface recombinations. Random alloy fluctuations, atomic-scale thickness fluctuations, and size variations of the quantum dots were separately analyzed. It was found that both the diameter variation and random alloys dominate the inhomogeneous broadening of photon energies, while the random alloys dominate the inhomogeneous broadening of decay rates. The piezoelectric field in InGaN materials plays a minor role in increasing the effect of random alloys but helps suppress the inhomogeneous broadening due to well-width fluctuations by keeping the electrons toward the center of the dots. [ABSTRACT FROM AUTHOR]

In this work, we report a simple method for solution-processed organic light emitting devices (OLEDs), where single-layer graphene acts as the anode and the hexa-peri-hexabenzocoronene exfoliating agent (HBC-6ImBr) provides surface modification. In SEM images, the PEDOT:PSS solution fully covered the graphene electrode after coating with HBC-6ImBr. The fabricated solution-processed OLEDs with a single-layer graphene anode showed outstanding brightness at 3182 cd/m² and current efficiency up to 6 cd/A which is comparable to that of indium tin oxide films, and the OLED device brightness performance increases six times compared to tri-layer graphene treated with UV-Ozone at the same driving voltage. This method can be used in a wide variety of solution-processed organic optoelectronics on surface-modified graphene anodes. [ABSTRACT FROM AUTHOR]

The structural and electrical properties of [Bi.sub.2][Mg.sub.2/3][Nb.sub.4/3][O.sub.7] (BMN) pyrochlore thin films are examined for various film thicknesses. The thickness dependence of leakage current characteristics is attributed to the copper diffusion into the BMN films.

The structural and optical properties of single crystal [Zn.sub.1-x][Mg.sub.x]O nanorods (0

The local field effects can be invoked by deriving the effective nondegenerate four-wave mixing (NDFM) susceptibility of graded metallic films with weak nonlinearity. Findings indicate that the presence of gradation in metallic films can yield a broad resonant plasmon band in the optical region.

ZnO epilayers grown under various Zn/O ratios by plasma-assisted molecular-beam epitaxy are investigated. The Zn/O flux ratio during growth has a strong influence on the quality of ZnO epilayer surfaces, crystal structures, and optical properties.

A detailed quantum chemical study of atomic layer deposition (ALD) was made. The growth mechanism of SiO2 on bare Si (100)-2*1 surface using SiC4 and H2O as precursors was made.

Research describing polymer light emitting diodes is presented. In particular methods for obtaining the optimal chemical structure of ionomers for increased efficiency are investigated.

Magnetic measurements were used to analyze the thermodynamics and kinetics of the magnetic conditions of the semiconductor-like compound polycrystalline La0.7Sr0.3Mn0.7Co0.3. The spontaneous magnetization of polycrystalline was observed to be a cluster-glass phase which can become a ferromagnetic condition under an outside magnetic field H. The defreezing temperature Tf for the cluster-glass phase and the merging temperature Tm for zero field cooled and field cooled magnetizations are linked to the field H by Hj=H0j(1-Tj/Tc)(sup nj), where H0j and nj are constants and j=f,m. The results are discussed.

Plasma-sheath resonances were observed in a capacitively coupled plasma reactor, which has a fairly low pressure discharge. Two different models were employed to resolve the resonances successfully, a uniform and a nonuniform plasma model. It was observed during further investigation and by applying the nonuniform plasma model that the plasma-sheath resonance coincides with the local plasma frequency at two planes within the discharge.

This study aims to investigate the influence of the sputtering pressure (PS) on Nb:TiO2-x films to enhance the bolometric properties. A decrease in the growth rate with the sputtering pressure was perceived in amorphous Nb:TiO2-x films. The incorporation of oxygen with PS was confirmed in an X-ray photo electron spectroscopy analysis. The electrical resistivity was increased with an increase in PS due to a decrease in the number of oxygen vacancies. The linear I-V characteristics confirmed the ohmic contact behavior between the Nb:TiO2-x layer and the electrode material. The present investigation finds that the sample with lower resistivity has good bolometric properties with low noise and high universal bolometric parameters. Finally, the Nb:TiO2-x sample deposited at a sputtering pressure of 2 mTorr shows better bolometric properties than other materials for infrared image sensor applications. [ABSTRACT FROM AUTHOR]

This study aims to investigate the influence of the sputtering pressure (PS) on Nb:TiO2-x films to enhance the bolometric properties. A decrease in the growth rate with the sputtering pressure was perceived in amorphous Nb:TiO2-x films. The incorporation of oxygen with PS was confirmed in an X-ray photo electron spectroscopy analysis. The electrical resistivity was increased with an increase in PS due to a decrease in the number of oxygen vacancies. The linear I-V characteristics confirmed the ohmic contact behavior between the Nb:TiO2-x layer and the electrode material. The present investigation finds that the sample with lower resistivity has good bolometric properties with low noise and high universal bolometric parameters. Finally, the Nb:TiO2-x sample deposited at a sputtering pressure of 2 mTorr shows better bolometric properties than other materials for infrared image sensor applications. [ABSTRACT FROM AUTHOR]

A study was conducted on the influence of magnetic field annealing on Fe73.5Cu1Mo3Si13.5B9 alloy ribbon giant magnetoimpedance. Giant magnetoimpedance and magnetic permeability were calculated as functions of the ac driving current frequency and external magnetic field. Results show a larger giant magnetoimpedance effect in the magnetic-field annealed state than in the nonfield annealed state.

The rate of hydrogen evolution from strained SixGe(1-x)(100)2x1:H surfaces grown on silicon(100) wafers via electron beam evaporation was investigated using angle resolved ultraviolet emission spectroscopy (ARUPS). The H-terminated samples, which underwent hydrogen adsorption and desorption at temperatures below the growth temperature, were found to have an ARUPS spectra characteristic of a single hydrogen-induced surface state/resonance due to the Si(Ge)-H bond.

Microstructural degradation of lattice-matched GaInAsP/InP heterointerface during Zn diffusion was investigated using high resolution transmission electron microscopy and Auger electron spectroscopy. The results showed that tensile stress was brought about by the diffusion-induced intermixing of In and Ga across the interface. The generationof paired dislocations with antiparallel Burgers vectors emanating from the intermixed interface effectively reduced interfacial strain.

Numerical simulations of polyalphaolefins-Al2O3 nanofluids containing cylindrical nanoparticles in a laminar pipe flow are performed by solving the Navier-Stokes equation with term of cylindrical nanoparticles, the general dynamic equation for cylindrical nanoparticles, and equation for nanoparticle orientation. The distributions of particle number and volume concentration, the friction factor, and heat transfer are obtained and analyzed. The results show that distributions of nanoparticle number and volume concentration are non-uniform across the section, with larger and smaller values in the region near the pipe center and near the wall, respectively. The non-uniformity becomes significant with the increase in the axial distance from the inlet. The friction factor decreases with increasing Reynolds number. The relationships between the friction factor and the nanoparticle volume concentration as well as particle aspect ratio are dependent on the Reynolds number. The Nusselt number of nanofluids, directly proportional to the Reynolds number, particle volume concentration, and particle aspect ratio, is higher near the pipe entrance than at the downstream locations. The rate of increase in Nusselt number at lower particle volume concentration is more than that at higher concentration. Finally, the expressions of friction factor and Nusselt number as a function of particle volume concentration, particle aspect ratio, and Reynolds number are derived based on the numerical data. [ABSTRACT FROM AUTHOR]

We propose and analyze a novel detector structure for pixel-level multispectral infrared imaging. More specifically, we investigate the device performance of a grating-integrated quantum dots-in-a-well photodetector under backside illumination. Our design uses 1-dimensional grating patterns fabricated directly on a semiconductor contact layer and, thus, adds a minimal amount of additional effort to conventional detector fabrication flows. We show that we can gain wide-range control of spectral response as well as large overall detection enhancement by adjusting grating parameters. For small grating periods, the spectral responsivity gradually changes with parameters. We explain this spectral tuning using the Fabry-Perot resonance and effective medium theory. For larger grating periods, the responsivity spectra get complicated due to increased diffraction into the active region, but we find that we can obtain large enhancement of the overall detector performance. In our design, the spectral tuning range can be larger than 1 lm, and, compared to the unpatterned detector, the detection enhancement can be greater than 92% and 148% for parallel and perpendicular polarizations. Our work can pave the way for practical, easy-to-fabricate detectors, which are highly useful for many infrared imaging applications. [ABSTRACT FROM AUTHOR]

A concentration of Manganese as high as 8% was successfully diluted into Zinc Oxide epitaxial films deposited by pulsed laser deposition. The films showed strong ferromagnetism with a large coercivity. Low temperature X-ray absorption spectroscopy measurements indicated that all the Manganese ions substitute for Zinc sites of the wurtzite lattice in the valency of +2. Photoluminescence measurements excluded the presence of Zinc vacancies, as well as Zn interstitials. All the magnetic moments measured were to ascribe to the formation of bound magnetic polarons, with no other contribution due to Manganese-secondary phases or Zinc vacancy-mediated double exchange interaction. [ABSTRACT FROM AUTHOR]

The correlation between the pairing symmetry and a metal-insulator transition near oxygen content for the Ce-optimal doped Pr(sub 1.85)Ce(sub 0.15)CuO(4+delta) electron superconductors is evaluated. It was seen that the superfluid density n(sub s) approximately equals lambda(sub ab)(super -2) increases from the underdoped to the optimal-doped region.

Calculation of in-plane penetration depth lambda-ab (T) on less-magnetic Pr1.85Ce0.15CuO3.97 c-axis aligned superconducting powder has been undertaken to eliminate the rare earth magnetic contribution. The results of this work are in good alignment with recent phase-sensitive research which suggests a d-wave nature for these electron-doped 214 cuprates.

Research into the impact of oxygen stoichiometric parameter y on the unusual Pr/Cu magnetic properties in high oxygen pressure annealed PrBa2Cu3O7-y cuprates is presented. The absence of metallic state for all samples investigated suggests that the superconducting state, if it exists, may only be found in a very narrow annealed pressure/temperature/time range.

Two types of giant magnetoresistance (GMR) multilayer bridge sensors with integrated permanent magnet biasing are demonstrated. The bridges were initialized by magnetizing the two types of permanent magnets in opposite directions.

Powder x-ray diffraction and magnetic susceptibility measurements were conducted on the Bi-doped Gd(sub 2-x)Bi(sub x)CuO4 system. The T'-(214) phase solubility region was retained in the narrow range of 0

Metastable filamentary superconductivity with Tc = 10.2 K was observed in SrPt2Ge2. This is the highest Tc reported outside the iron-based 122-layer compounds. The stable phase for this compound is a non-superconducting monoclinic LaPt2Ge2-type structure with lattice parameters a = 0.4401(4) nm, b = 0.4435(4) nm, c = 0.9764(10) nm, β = 90.5°-90°. Weak diamagnetic shielding signal indicates that superconductivity is not from the major monoclinic phase, but from the minor BaFe2As2-type body-center-tetragonal (122-bct) phase with a=0.44 nm, c=0.98 nm,β=90°. Investigation on the pseudoternary system Sr(Pd1-xPtx)2Ge2 suggests that the stable bct to monoclinic structure phase transition occurs near x = 0.15. For x<0.15 with bct phase, bulk Tc increases from 3.2 K for SrPd2Ge2 to 3.6 K for SrPd1.8Pt0.2Ge2. For x>0.15 with metastable filamentary bct phase, Tc increases from 7.5 K for x = 0.5 to 9.2 K for x = 0.7 and reaches a Tc maximum of 10.2 K for SrPt2Ge2. High Tc is due to a strong quasi-2D Pt-Ge-Pt 5dxz,yz-4p-5dxz,yz hybridization in the Pt-Ge layer with squeezed-along-c-axis PtGe4 tetrahedral crystal field and Pt-5d8 spin-orbital interaction in the metastable filamentary bct phase and is another example of multi-band (dxz/dyz/dxy) non-conventional s-wave superconductor. [ABSTRACT FROM AUTHOR]

Laser-excited N and R fluorescence lines of heavily doped ruby have been studied up to 26 GPa at low temperatures. While the intensity of the R lines at ambient pressure significantly decreases with decreasing temperature, the intensity of N lines originating from exchange-coupled Cr ion pairs is enhanced at low temperatures. The pressure induced wavelength shift of the N lines at 19 K is well fitted with an empirical formula similar to the equation for the R1 line, showing that the intense N line could be used as an alternative pressure scale at low temperatures. We also observe continuous increase in non-hydrostaticity with increasing pressure at low temperatures when silicone oil and 4:1 mixture of methanol and ethanol are used as pressure media. [ABSTRACT FROM AUTHOR]

Two new quaternary borocarbide phases have been discovered in the Y-Ru-B-C system, a (111) YRuBC phase of the LuNiBC structure, and a (1221) YRu(sub2)B(sub2)C phase of the LuNi(sub2)B(sub2)C type. Bulk superconductivity of 9.7 K was seen from transport and magnetic measurements for an annealed YRu(sub2)B(sub2)C sample.

We demonstrate the use of a highly effective biosensor array to fulfill the requirements of high intensity, reduced nonspecific adsorption (NSA), and low sample usage. The mixed self-assembled monolayers (SAMs), consisting of methyl-terminated and methoxy-(polyethylene glycol (PEG))-terminated silanes, were newly applied as the background layer to reduce the background NSA via wettability control. The surface was modified by a plasma process with a pattern mask. Gold nanoparticles (AuNPs) were grafted within pattern-modified regions to increase intensity and were modified with protein G variants with cysteine residues to immobilize the antibody proteins directly. The target protein samples were selectively dewetted by the high throughput wiping process, while retaining semi-contact with the substrate. The data revealed that the background NSA was significantly reduced by 78% with selective dewetting compared to the standard method. Furthermore, the peak intensity was improved 5 times by applying AuNPs as compared to that of a planar surface, and the protein requirement was significantly reduced versus the standard process. [ABSTRACT FROM AUTHOR]

The transport properties of armchair graphene nanoribbons with two structural nanoconstrictions are studied by atomistic simulations. With the appropriate geometry and size, the central region between the two constrictions can behave as a single tunneling quantum dot. Within the low energy range around the Dirac point, the conductance of the structure shows strong resonances that are related to the quasi-bound states localized in the dot. The quasi-bound states are associated with the standing waves confined by the two constrictions, and can be effectively modulated by the geometric parameters of the structure. [ABSTRACT FROM AUTHOR]

A Zr47.7Cu31Ni9Al12.3 bulk metallic glass was irradiated directly by KrF excimer laser pulses with wavelength 248 nm and duration 10 ns. Scanning electronic microscope photographs indicated that many ripples in micro-nano scale would be generated on the edge of the irradiated area under the action of the higher intensity laser pulse. Detailed observation demonstrated that the ripples exhibited fluidity and became closer and closer out from interior. Theoretical analysis revealed the formation mechanism of the ripples, including melting, subsequent propagation of capillary waves and final solidification. [ABSTRACT FROM AUTHOR]

The observation of enhanced terahertz (THz) wave generation from the large aperture photoconductive (PC) antenna excited by both a femtosecond pump beam and a collinearly propagating ZnTe-pregenerated THz wave is reported within this paper. An analysis based on both the calculated and experimental results demonstrated that the superposition acts as the main physical mechanism of this THz enhancement effect due to the dominant contribution from the rapid change in photoexcited carrier density. A prerequisite for the THz enhancement requires that the polarization of the applied bias and the ZnTe-pregenerated THz should be identical in order to have a constructive superposition. Therefore, this observation introduces the possibility of recycling the unused portion of the pump beam to further improve the THz radiation. The enhancement effect could be optimized by changing the thickness of ZnTe, which could affect the photoexcited-free-carrier absorption of THz in the PC antenna and the bandwidth of final enhanced THz radiation. [ABSTRACT FROM AUTHOR]

In this paper, we present a new type of concealed and buried chemical detection system by stimulating and enhancing spectroscopic signatures with multifrequency excitations, which includes a low frequency gradient dc electric field, a high frequency microwave field, and higher frequency infrared (IR) radiations. Each excitation frequency plays a unique role. The microwave, which can penetrate into the underground and/or pass through the dielectric covers with low attenuation, could effectively transform its energy into the concealed and buried chemicals and increases its evaporation rate from the sample source. Subsequently, a gradient dc electric field, generated by a Van De Graaff generator, not only serves as a vapor accelerator for efficiently expediting the transportation process of the vapor release from the concealed and buried chemicals but also acts as a vapor concentrator for increasing the chemical concentrations in the detection area, which enables the trace level chemical detection. Finally, the stimulated and enhanced vapors on the surface are detected by the IR spectroscopic fingerprints. Our theoretical and experimental results demonstrate that more than sixfold increase in detection signal can be achieved by using this proposed technology. The proposed technology can also be used for standoff detection of concealed and buried chemicals by adding the remote IR and/or thermal spectroscopic and imaging detection systems. [ABSTRACT FROM AUTHOR]

In situ high-resolution synchrotron x-ray diffraction, dielectric permittivity, hysteresis loop, and polarization current, were used to investigate phase transitions of (211)-cut 0.70Pb(Mg1/3Nb2/3)O3–0.30PbTiO3 single crystal before and after an electric (E) field poling. A rhombohedral (R)–tetragonal (T)–cubic transition sequence was observed upon zero-field heating in both unpoled and poled samples. Before the R–T transition takes place, an extra dielectric and polarization current anomalies near 365 K were observed in the poled sample due to a transition of polarization ordering. The direct piezoelectric coefficient d33 exhibits a rapid increase for poling at E=1.0–1.3 kV/cm, followed by an overpoling behavior. The increment of polarization ordering plays an important role while the high piezoelectric response builds up. [ABSTRACT FROM AUTHOR]

High-resolution synchrotron radiation diffraction results indicate that the room temperature tetragonal (T) phase in (93–92)%Pb(Zn1/3Nb2/3)O3–(7–8)%PbTiO3 [PZN–(7–8)%PT] single crystals is a metastable phase stabilized by the transformation-cum-cooling stress in the crystal. This is manifested by the “missing” (001)T diffractions when the diffractions were taken from (001) fractured surfaces. The stress relaxation in this case has caused the metastable (001)T domains in the surface layer to transform to the equilibrium rhombohedral phase. Temperature and particle size effects on the metastable domains have been examined and discussed. Based on the present finding, a new PZN–PT phase diagram showing extended rhombohedral+tetragonal region is proposed. [ABSTRACT FROM AUTHOR]

The in-plane aligned MnAs nanowires have been grown by molecular-beam epitaxy on GaAs(001) substrates at high growth temperature (≥450 °C). A discontinuous growth with break intervals (50 s’ interval per 10 s’ growth) was employed. The obtained nanowires were identified to be mainly type-B hexagonal MnAs. The influences of growth temperature and As4/Mn flux ratio on the nanowires’ morphology were investigated. Both high growth temperature and high As4/Mn flux ratio are necessary for the growth of uniaxially aligned MnAs nanowires with high aspect ratio. The magnetic anisotropy of the nanowires and their multimodal size distributions contribute to the large coercivity and special shape of the M-H loops along the magnetic easy axis, which is [1102]MnAs∥[110]GaAs. However, the longer growth time would lead to the both azimuthal alignments of the MnAs wires and the weakening of the magnetic anisotropy. [ABSTRACT FROM AUTHOR]

In this paper, we conduct a quantitative study on the physical mechanism of electrons dynamics near the nanostructured metal film surfaces, as well as the efficiency of generated terahertz radiation associated with different types of nanostructures. The simulation results show that although the oscillating motion of emitted electrons outside the metal surface may affect the terahertz generation efficiency to some extent, this efficiency is predominantly determined by the electric field magnitude inside the metal film associated with nanostructure enhanced plasmonic excitations. Due to the field enhancement effect of the nanostructure, an appropriately designed nanostructured surface could greatly enhance the strength of generated terahertz signal via the increased nonlinear interactions between the light and the nanostructures. [ABSTRACT FROM AUTHOR]

LaAlO3 is a promising candidate of gate dielectric for future very large scale integration devices. In this work, metal-oxide-semiconductor capacitors and transistors with LaAlO3 gate dielectric were fabricated and the electron mobility degradation mechanisms were studied. The LaAlO3 films were deposited by radio frequency magnetron sputtering. The LaAlO3 films were examined by x-ray diffraction, secondary ion mass spectroscopy, and x-ray photoelectron spectroscopy. The temperature dependence of metal-oxide-semiconductor field-effect transistors characteristics was studied from 11 K to 400 K. The rate of threshold voltage change with temperature (¿VT/¿T) is -1.51 mV/K. The electron mobility limited by surface roughness is proportional to Eeff-0.66 in the electric field of 0.93 MV/cm

The authors studied enhancement of photon-induced carrier density in silicon-on-insulator (SOI) by suppressing surface recombination. Through applying electric field at the top silicon surface or at the Si/SiO2 interface, either electrons or holes are depleted near the interface, reducing the possibility of recombination. We examined enhanced photon-induced carrier density depending on the thickness of the SOI layer and the polarity of the applied field. The results show that the enhanced carrier density is prominent for thin SOI and increases with applied voltage. The effective photon-induced carrier density is magnified by three times with surface bias simultaneously at the top and bottom interfaces of SOI. The corresponding plasma dispersion effect is also estimated. [ABSTRACT FROM AUTHOR]

This work examines possible luminescence mechanisms of silicon-rich nitride (SRN) films that were fabricated by atmospheric pressure chemical vapor deposition (APCVD). Under an ambient gas of either H2 or N2, two SRN films were deposited using the same precursors of Si and N. While photoluminescence (PL) measurements of both as-deposited specimens revealed an intense luminescence band (1.8–3.8 eV), which was observable by the naked eye, a detailed examination of the high energy band of the PL spectra over 2.8 eV yielded different results for those samples that were fabricated in different ambiences. To determine the reason for these differences, Fourier-transform infrared spectroscopy and x-ray photoelectron spectroscopy were conducted, suggesting unique chemical bonds and elemental ratio of nitrogen to silicon in SRN films. Further analysis involving plan-view high-resolution transmission electron microscopic observations of SRN films demonstrated the embedding of Si quantum dots (Si QDs), but with some differences depending on the deposition environment. Analyses of the results obtained suggest that the emission from SRN films that were deposited by APCVD is not only dominated by the quantum confinement effect of Si QDs, but also subordinately affected by the surface states around these Si QDs. [ABSTRACT FROM AUTHOR]

Several simulation studies reported that a hot spot exists in flip-chip solder bumps under accelerated electromigration. Yet, there are no experimental data to verify it. In this paper, the temperature distribution during electromigration in flip-chip SnAg3.5 solder bumps is directly inspected using infrared microscopy. Two clear hot spots are observed in the bump. One is located at the region with peak current density and the other one is at the bump edge under the current-feeding metallization on the chip side. Under a current stress of 1.06×104 A/cm2, the temperature in the two hot spots are 161.7 and 167.8 °C, respectively, which surpass the average bump temperature of 150.5 °C. In addition, the effect of under-bump-metallization (UBM) thickness on the hot spots is also examined. It indicates that the hot-spot temperature in the solder bump increases for the solder joints with a thinner UBM. Electromigration test indicates that these hot spots have significant influence on the initial failure location. [ABSTRACT FROM AUTHOR]

The relationship between the threshold current density and the critical line length in eutectic SnPb and SnAgCu electromigrations were examined using solder lines with the various lengths ranging from 100 to 1000 μm. When the electron wind-force was balanced by the back-stress gradient force, the net flux of electromigration is zero, at which the current density and line length are defined as the threshold current density and the critical length, respectively. It was found that in SnAgCu electromigration, the 1/L dependence on the threshold current density showed good agreement, whereas the threshold current densities of the eutectic SnPb deviated from the 1/L dependence. The balance between the electron wind-force and the back-stress gradient force was the main factor determining the threshold product of SnAgCu electromigration. On the other hand, in the case of eutectic SnPb, the chemical driving force is contributed as a back-flux force in addition to the back-stress gradient force. The existence of the chemical driving force was caused by the nonequilibrium Pb concentration inside the Pb-rich phases between the cathode and anode during the electromigration procedure. [ABSTRACT FROM AUTHOR]

From three dimensional whispering gallery cavities of GaAs photonic quantum ring fabricated in hyperboloid drum shape by chemically assisted ion beam etching with the central active region diameter of 0.9 μm, we have observed single mode lasing near 838 nm with a record low injection threshold of 300 nA (Jth=47.1 A/cm2) in continuous wave operation at room temperature. This indicates that the quantum ring lasing phenomena associated with the three dimensional whispering gallery modes continue to persist, even at the submicron range overcoming the conventional two dimensional whispering gallery mode limit. [ABSTRACT FROM AUTHOR]