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Notes: A kinetic model is developed to study the process of phase separation that occurs when a polymer-dispersed liquid-crystal diffraction grating is produced by a process of photopolymerization. We find that the type of system produced depends sensitively on the rate of polymerization and on whether the spatially periodic illumination used to produce the grating is followed by a period of uniform illumination. While the average liquid-crystal concentration is always increased in the region of least irradiation, in some cases small inclusions of liquid-crystal form by spinodal decomposition at the minima in the irradiating intensity, while in others they form at the maxima. The simplest version of the theory combines the Flory-Huggins and Hillert models of phase separation. In some circumstances it must be augmented by including the effects of interdiffusion of polymer molecules having different degrees of polymerization. © 1996 American Institute of Physics.

Notes: The properties of interface traps in metal–silicon nitride (deposited by jet vapor deposition technique) –silicon (MNS) capacitors have been studied in some detail. In comparison with those in metal–oxide–Si capacitors, the interface traps in our MNS capacitors exhibit the following major differences: (i) ∼2 orders of magnitude higher time constants; (ii) no evidence of two distinguishable defects following irradiation as revealed by the ac conductance measurement; and (iii) absence of latent generation of interface traps following irradiation. On the other hand, the interface-trap transformation process following irradiation is qualitatively similar in silicon nitride and thermal oxide devices. © 1996 American Institute of Physics.

Notes: Co2ScSn crystallizes with the cubic L21 Heusler structure and is an itinerant ferromagnet with Tc=238 K. X-ray diffraction measurements show that Co2−xSc1+xSn retains the L21 crystal structure with an essentially unchanged lattice constant for 0≤x≤0.15. However, Tc determined from the magnetization measurements decreases monotonically with increasing Sc concentration from 238 K for x=0 to 40 K for x=0.11, and then remains at 40 K from x=0.11 to 0.14. The electronic specific heat coefficient γ is enhanced from 13 mJ/mole-K2 for Co2ScSn (x=0) to 30 mJ/mole-K2 for x=0.13 (Co1.87Sc1.13Sn). In addition, the C/T versus T2 plot shows a leveling-off behavior at low temperatures for the x=0.13 sample. The γ enhancement and level-off behavior observed when a system approaches a magnetic instability are discussed in terms of the self-consistent renormalization theory of spin fluctuations for weak itinerant ferromagnets and nearly magnetic systems. © 1996 American Institute of Physics.

Notes: Three kinds of textures, i.e., (200), (111), and (220) of TiN films prepared by filtered arc deposition have been continuously observed with varying film thickness and bombarding energy of the deposited particles. The evolution of the texture from (200) to (111), then to (220) is discussed on the basis of the so-called overall energy which consists of the surface energy, the strain energy, and the stopping energy of the films. © 1996 American Institute of Physics.

Notes: The evolution of surface morphologies of films prepared by ion-based deposition techniques has been investigated by atomic force microscopy. Two deposition processes, filtered arc deposition (FAD) and ion-beam-assisted deposition, where low-energy (〈100 eV) ion irradiation and high-energy (several tens of keV) ion-beam bombardment concurrent with film growth were involved, respectively, have been employed to prepare TiN and Al films. Comparative studies on the effect of energetic ions on the development of topography have been performed between the low-ion-energy regime and high-ion-energy regime. In addition, the relationship between topography and mechanical properties of thin films has been revealed, by involving thin films prepared by thermal evaporation deposition (TED), where almost all depositing particles are neutral. In the images of the TED TiN and Al films, a large number of porous and deep boundaries between columnar grains was observed, suggesting a very rough and loose surface. In contrast, the FAD films exhibited much denser surface morphologies, although still columnar. The root-mean-square roughness of the FAD films was less than 1 A(ring). Hardness test and optical parameter measurement indicated that the FAD films were much harder and, in the case of optical films, much more transparent than the TED films, which was considered to arise from the denser surface morphologies rather than crystallization of the films. The high density and super smoothness of the FAD films, and the resultant mechanical and optical properties superior to those of the TED films, were attributed to the enhancement of surface migration of the deposited adatoms in the FAD process, which could provide intensive low-energy ion irradiation during film growth. As for topography modification by high-energy ion-beam bombardment concurrent with film growth, in addition to the increase of surface diffusion due to elastic collision and thermal spikes, physical sputtering must be considered while explaining the development of the film topography. Both surface migration enhancement and sputtering played important roles in the case of high-energy heavy-ion-beam bombardment, under which condition surface morphology characterized by dense columns with larger dimension and deep clean boundaries was formed. However, under high-energy light-ion-beam bombardment, the sputtering was dominant, and the variation of sputtering coefficient with position on the surface of growing film led to the formation of cones. © 1996 American Institute of Physics.

Notes: Time-resolved emission spectrum from the plasma produced by 1.06 μm, 10 ns pulsed-laser irradiation of titanium alloy targets in air at a flux of 9.3×109 W cm−2 was analyzed in the wavelength range of 2000–8800 A(ring). From the evolutions of the specific spectrum lines of N II, Ti I, and Fe I, the velocities of N+ ions and the excited neutral Ti and Fe atoms have been obtained using a time-of-flight diagnostic method. The electron temperatures were deduced using the relative emission intensities of N II and Fe I isolated spectrum lines, and an electron number density was determined from the Stark-broadened line of the N II line at wavelength λ=3995 A(ring). © 1996 American Institute of Physics.

Notes: We have measured χ(T) for oxygen-annealed YBa2Cu3Ox samples and observed a glass-like behavior at low magnetic fields which can be explained in terms of a Josephson weak link effect. The glass transition temperature Tg depends on the oxygen annealing temperature and sample pellet pressure. Tg disappears when a sample was powdered after receiving an oxygen anneal, indicating that the Josephson weak link effect occurs between intergranular boundaries. In addition, Tc shifts from 93 K for the air-sintered samples to 90 K for the oxygen-annealed materials. Under vacuum annealing, Tg disappears and Tc first shifts back to 93 K. Prolonged vacuum annealing or vacuum annealing at higher temperatures depresses Tc to below 90 K. The temperature dependence of the specific heat shows a single anomaly for samples sintered in air or annealed under high vacuum. But a double-peak specific heat anomaly occurs for the oxygen-annealed samples. © 1996 American Institute of Physics.

Notes: Two wire monitors have been developed and installed in the Advanced Photon Source (APS) storage ring insertion device (ID) front ends to directly detect synchrotron radiation exiting the storage ring vacuum chamber that is missteered by ±5 mm. Each wire monitor employs four in-vacuum tungsten wires positioned above and below the normal x-ray orbit. The temperature change of the wire under x-ray irradiation causes a resistance change that is detected by a local high-sensitivity low-noise signal processing electronics unit with four independent channels. The four outputs of the local unit are linked to a central VME wire resistance measurement and interlock module via 4–20 mA current loops. The central VME module can accept inputs from up to eight wire monitors and has a heartbeat that feeds a MPS summation module. In this paper, an overview of the wire monitor signal processing and data acquisition system design is presented together with recent commissioning results. © 1996 American Institute of Physics.

Notes: A missteered beam safety monitor (MBSM) has been designed to protect the accelerator ring of the Advanced Photon Source against incursions of the missteered synchrotron radiation. When the orbit of the particle beam in the accelerator shifts out of its safety limits, the photon beam from the bending magnet will pass through the square apertures on the cooled mask of the MBSM and will heat up a very thin tungsten wire (0.025 mm in diameter) behind the mask. Acting as a resistance thermometer, the electrical resistance of the tungsten wire increases proportionally with temperature rise. As soon as the electrical resistance of the tungsten wire reaches a preset point, a signal is triggered immediately to dump the particle beam in the accelerator. The tungsten wire is inclined to the photon beam at 4.5 degrees in the vertical direction to prevent it from being overheated by the high power photon beam. Detailed mechanical design and thermal analysis are presented. © 1996 American Institute of Physics.

Notes: The possibility that ion sputtering could be used to modify the growth mode of Ge on GaAs(110) was investigated by scanning tunneling microscopy. Analysis shows that the nucleation density was significantly increased following vacancy island creation by ion sputtering. The Ge/GaAs(110) structures were thermodynamically stable because of energy gained by saturating dangling bonds at steps. Accordingly, a uniform film could be obtained at a smaller thickness compared to conventional growth. © 1996 American Institute of Physics.