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We studied the strain introduced in a Si(111) substrate due to MeV ion implantation using extremely asymmetric x-ray diffraction and measured the rocking curves of asymmetrical 113 diffraction for the Si substrates implanted with a 1.5 MeV Au2+ ion at fluence values of 1×1013, 5×1013, and 1×1014/cm2. The measured curves consisted of a bulk peak and accompanying subpeak with an interference fringe. The positional relationship of the bulk peak to the subpeak and the intensity variation of those peaks with respect to the wavelengths of the x rays indicated that crystal lattices near the surface were strained; the lattice spacing of surface normal (111) planes near the surface was larger than that of the bulk. Detailed strain profiles along the depth direction were successfully estimated using a curve-fitting method based on Darwin’s dynamical diffraction theory. Comparing the shapes of resultant strain profiles, we found that a strain evolution rapidly occurred within a depth of ∼300 nm at fluence values between 1×1013 and 5×1013/cm2. This indicates that formation of the complex defects progressed near the surface when the fluence value went beyond a critical value between 1×1013 and 5×1013/cm2 and the defects brought a large strain to the substrate. [ABSTRACT FROM AUTHOR]

Snoring is the most common symptom of obstructive sleep apnoea (OSA). Several researchers have reported differences between the power spectra of non-OSA and OSA snorers. The traditional approach over the years has been to record snore sounds at a bandwidth of < 5 kHz. Narrowing of the upper airways during OSA events and the resulting upward shift of snore frequencies also lend support to the idea of examining snore sounds beyond 5 kHz. In this paper, we compute the power spectra of snores in three different bands defined as: low-frequency band (LFB: < 5 kHz); middle-frequency band (MFB: 5-10 kHz) and high-frequency band (HFB: 10-20 kHz). We illustrate that there is a significant difference between non-OSA snorers (Apnoea Hypopnoea Index (AHI) < 10) and OSA snorers (AHI > 10) in the region > 5 kHz. We then develop a feature to diagnose OSA based on the spectral differences in the high frequency region and evaluate its performance on a database of 20 subjects. Our results strongly suggest that the high-frequency region of the snore sounds carry information, hitherto disregarded, on the disease of sleep apnoea. [ABSTRACT FROM AUTHOR]

A novel technique for forming internal targets, named SCRIT (Self-Confining RI Ion Target), has been developed, which can make electron scattering off short-lived radioactive nuclei possible in an electron storage ring. SCRIT confines the ions of interest by utilizing the “ ion trapping” phenomenon in the electron storage ring. Approximately 107 stable 133Cs ions were trapped in a three-dimensional configuration along the electron beam axis at an electron beam current of 75mA. The angular distribution of the electrons scattered from the trapped 133Cs ions was successfully measured, and a collision luminosity of 1026/(cm2 s) was achieved. [ABSTRACT FROM AUTHOR]

We have established a novel method which make electron scattering off short-lived radioactive nuclei come into being. This novel method was named SCRIT (Self-Confining RI ion Target). It was based on the well known "ion trapping" phenomenon in electron storage rings. Stable nucleus, 133Cs, was used as target nucleus in the R&D experiment. The luminosity of interaction between stored electrons and Cs ions was about 1.02(0.06) × 1026cm-2s-1 at beam current around 80 mA. The angular distribution of elastically scattered electrons from trapped Cs ions was measured. And an online luminosity monitor was used to monitor the change of luminosity during the experiment. [ABSTRACT FROM AUTHOR]

We propose a novel interpretation and usage of Neural Network (NN) in modeling physiological signals, which are allowed to be nonlinear and/or nonstationary. The method consists of training a NN for the k-step prediction of a physiological signal, and then examining the connection-weight-space (CWS) of the NN to extract information about the signal generator mechanism. We define a novel feature, Normalized Vector Separation (γ ij ), to measure the separation of two arbitrary states “ i” and “ j” in the CWS and use it to track the state changes of the generating system. The performance of the method is examined via synthetic signals and clinical EEG. Synthetic data indicates that γ ij can track the system down to a SNR of 3.5 dB. Clinical data obtained from three patients undergoing carotid endarterectomy of the brain showed that EEG could be modeled (within a root-means-squared-error of 0.01) by the proposed method, and the blood perfusion state of the brain could be monitored via γ ij , with small NNs having no more than 21 connection weight altogether. [ABSTRACT FROM AUTHOR]

Abstract: We studied the effect of post-deposition annealing on a HfO2/Si interface of by extremely asymmetric X-ray diffraction. Comparing the rocking curves before annealing the sample with those of the annealed sample, it is found that an interfacial layer with a density of 3g/cm3 grows at the interface between the HfO2 layer and the substrate during post-deposition annealing. The wavelength dependency of the integrated intensities of the rocking curve for the as-deposited sample fluctuated with the observation position. This fluctuation was suppressed by annealing. From these results we concluded that the strain introduced into the substrate becomes homogeneous by annealing. Moreover, a quantitative estimation of the strain by curve fitting reveals the existence of compressive strain under the HfO2 layer. [Copyright &y& Elsevier]

A polycapillary X-ray lens is an effective optics to obtain a μm-size X-ray beam for micro-X-ray fluorescence spectrometry (μ-XRF). We developed a μ-XRF instrument using a polycapillary X-ray lens, which also enabled us to perform Grazing Exit μ-XRF (GE-μ-XRF). The evaluated diameter of the primary X-ray beam was 48 μm at the focal distance of the X-ray lens. Use of this instrument enabled two-dimensional mapping of the elemental distributions during growth of the plant “Quinoa”. The results of the mapping revealed elemental transition during growth. In addition, a small region of thin film was analyzed by GE-μ-XRF. We expect that GE-μ-XRF will become an effective method of estimating the film thickness of a small region. [Copyright &y& Elsevier]

Strain fields near InGaP surfaces due to bias sputtering are affected by the bias voltage used in this surface-cleaning treatment. Measured rocking curves of an InGaP113 reflection under grazing X-ray incidence conditions consisted of a main peak and broad sub peaks. The shape of the broad sub peaks was due to a compositional fluctuation near the subsurface. Changes in the main peak versus bias voltage curves indicate that bias sputtering introduces a tensile strain to the InGaP surface. Furthermore, changes in the sub peak versus supplied bias voltage curves indicate that excessive sputtering generates a heavy compositional fluctuation near the InGaP subsurface. In conclusion, based on the measured strain and compositional fluctuation, a heavy compositional fluctuation generally causes a large tensile strain near the InGaP surface. [Copyright &y& Elsevier]

We studied the affection of thin (i.e., 0.2–0.8 nm) Ni films on hydrogen-terminated Si(1 1 1) substrate surface by using strain-sensitive X-ray diffraction. It was reported that Ni deposition onto hydrogen-terminated Si surface apparently does not cause film growth, but rather diffuses into the Si crystal, creating an “Ni diffusion layer” up to Ni deposition 0.8 nm thick. Measured rocking curves of the Si 1 1 3 reflection and integrated intensities of the rocking curves for the substrate provide information about the evolution of the strain field introduced near the substrate surface during Ni diffusion into the substrate. Comparing the measured and calculated rocking curves indicates that compression of the {1 1 1} spacing of the Si occurs gradually up to an Ni thickness of 0.6 nm, and that above this thickness, strain relaxation occurs.We found that the slope of the integrated intensity of the rocking curve versus X-ray wavelength correlates to the strain field near the surface, in the same way that the shape of the rocking curves correlate to the strain field near the surface. Dynamical diffraction calculations indicate that measurement of the slope of the integrated intensity of the rocking curve versus X-ray wavelength is useful for strain analysis, because the dependence is not only sensitive to strain fields, but is also insensitive to the effect of absorption by the overlayer, which otherwise would cause deformation of the shape of the rocking curve. [Copyright &y& Elsevier]

Strain fields near InGaP or GaAs surfaces due to bias sputtering (Ar plasma-ion irradiation) for surface cleaning were measured by using a strain-sensitive X-ray diffraction technique. An extremely asymmetric InGaP or GaAs 1 1 3 reflection of the sample was measured to observe strain fields. We found that strain fields near InGaP or GaAs surfaces due to bias sputtering are affected by the bias voltage (Ar plasma-ion irradiation energy) used in this surface-cleaning treatment. By comparing measured 1 1 3 rocking curves and calculated ones based on the dynamical theory of X-rays, we estimated the thickness of a strained layer and a maximum strain at the surface. Resulting estimated parameters clearly show the bias sputtering to have two effects. One should be corresponding to the surface cleaning process of removing oxides on surfaces. The other is the lattice expansion, which is thought to be caused by compositional fluctuation near the surface or peening process of Ar ion. [Copyright &y& Elsevier]

We studied the effect of annealing in a hydrogen gas on the crystal structure of strontium bismuth tantalate (SBT) by means of X-ray diffraction measurements. The hydrogen reduction happens mainly in bismuth oxide layers followed by the decomposition of pseudo-perovskite layers. With increasing the annealing time and/or temperature, new crystalline products such as bismuth, strontium tantalate, and bismuth oxide, and an unidentified crystal are observed along with non-crystalline materials. Decomposition of SBT and recrystallization of the decomposed materials occur even from the initial stage of the hydrogen reduction process. [ABSTRACT FROM AUTHOR]

Abstract: Strain at surfaces and interfaces play an important role in the optical and electronic properties of materials. MeV ion-induced strain determination in single crystal silicon substrates and in Ag (nanoisland)/Si(111) at surface/interfaces has been carried out using transmission electron microscopy (TEM) and surface-sensitive X-ray diffraction. Irradiation has been carried out with 1.5MeV Au2+ ions at various fluences and impact angles. Selected area electron diffraction (SAED) and lattice imaging (using TEM) has been used to determine the strain at surface and interfaces. Preliminary results on the use of surface-sensitive asymmetric X-ray Bragg reflection method have been discussed. The TEM results directly indicate a contraction in the silicon lattice due to ion-induced effects. The nanoislands have shadowed the ion beam resulting in lesser strain beneath the island structures in silicon substrates. High-resolution lattice imaging has also been used to determine the strain in and around amorphization zones caused by the ion irradiation. [Copyright &y& Elsevier]

Abstract: Tailoring of nanostructures with energetic ion beams has become an active area of research leading to the fundamental understanding of ion–solid interactions at nanoscale regime and with possible applications in the near future. Rutherford backscattering spectrometry (RBS), high resolution transmission electron microscopy (HRTEM) and asymmetric X-ray Bragg-rocking curve experimental methods have been used to characterize ion-induced effects in nanostructures. The possibility of surface and sub-surface/interface alloying at nano-scale regime, ion-beam induced embedding, crater formation, sputtering yield variations for systems with isolated nanoislands, semi-continuous and continuous films of noble metals (Au, Ag) deposited on single crystalline silicon will be reviewed. MeV-ion induced changes in specified Au-nanoislands on silicon substrate are tracked as a function of ion fluence using ex situ TEM. Strain induced in the bulk silicon substrate surface due to 1.5MeV Au2+ and C2+ ion beam irradiation is determined by using HRTEM and asymmetric Bragg X-ray rocking curve methods. Preliminary results on 1.5MeV Au2+ ion-induced effects in nanoislands of Co deposited on silicon substrate will be discussed. [Copyright &y& Elsevier]

Surface structure of 6H-SiC(0 0 0 1)3×3 reconstruction has been studied by grazing incidence X-ray diffraction with synchrotron radiation. We compared the Patterson map obtained from experimental structure factors with calculated Patterson maps estimated from the models that had been proposed. As the result, the calculated Patterson maps of Kulakov et al.’s [Surf. Sci. 346 (1996) 49] and Starke and coworkers’ models [Phys. Rev. Lett. 80 (1998) 758; Phys. Rev. B 58 (1998) 10806; Surf. Rev. Lett. 6 (1999) 1129; Appl. Surf. Sci. 162–163 (2000) 9; Phys. Rev. B 62 (2000) 10335] are relatively in good agreement with experimental one. Therefore, we conclude that there is high possibility that either Kulakov et al.’s or Starke and coworkers’ models are reasonable as the actual 3×3 structure. [Copyright &y& Elsevier]

We have studied the crystal orientation of Ag thin films on a [formula] surface using grazing incidence X-ray diffraction with synchrotron radiation. After preparation of a [formula] surface, 50 ML Ag was deposited on the [formula] at the substrate temperature of 50–300 K. We found the [formula] structure at the interface. As for the Ag film, the Ag}111{ plane was mainly grown on the surface. The domain size of the Ag films strongly depends on the substrate temperature of the deposition. The domain size is found to be regulated by an original domain size of the [formula] surface before Ag deposition, which relates to the surface-structural phase transition. By scattering intensity measurements in the reciprocal lattice space, we found streaky scattering along the [formula] direction parallel to the surface. This scattering is thought to originate from the CTR (crystal truncation rod) scattering from a sidewall plane of the Ag {111} nanometer-scale crystals. [formula available in full text]. [ABSTRACT FROM AUTHOR]