Ruled gratings of 0.33–3.33-μm wavelength fabricated with SiO, SiO2, and In2O3-SnO2 are used to study the topographical effects of the surface on the twisted nematic (TN) alignments of liquid crystals (LC’s). The types of LC’s are Schiff base, azoxy, biphenyl, biphenyl ester, and phenyl cyclohexane. All of the LC’s, except the azoxy, used in this study take good homogeneous and TN alignments on all grating films of wavelength less than 0.8 μm. The azoxy takes homeotropic alignment on the SiO and SiO2 grating surfaces. The agreement between experimental results and Frank elasticity theory is fairly good. Topographical effects can take precedence over chemical effects between the LC and surface when chemical anchoring is weak. Making use of the calculated elastic deformation energy of LC’s on grating and rubbed surfaces, we estimate the anchoring energies of homogeneous and homeotropic alignments. The application of grating cells to optical display is limited by the occurence of tilt domains.
Effects of elemental additives on the densification, microstructure, strength, and thermal conductivity of hot-pressed Sic ceramics were investigated. The addition of Be, B, and A1 gave up to 98% of theoretical density, whereas other additives had only a slight effect on densification. The microstructure, flexural strength, and thermal conductivity of dense Sic ceramics varied considerably depending on the additive used. For example, Sic ceramics with added A1 had fine grains -2.3 pn in size and high flexural strength, =940 MNlm'. On the other hand, those with added Be or B had larger grains -5.1 and -4.2 p n in size and lower flexural strengths -400 and =290 MN/m2, respectively. Moreover, with added Be an extremely high thermal conductivity, =260 W/m K, was obtained; this value is much larger than those for Sic ceramics with B or A1 additions.
Elimination of stacking faults in Si epitaxial layer by heat treatment is investigated by observing repeated etch patterns. Two types of stacking faults are observed. One of them (about 70∼90%) is eliminated easily by heat treatment and the other (about 10∼30%) is stable and cannot be eliminated. Heat treatment at a temperature higher than 450°C is required to eliminate the faults in either atmosphere of O2, Ar and H2. In the temperature range higher than 600°C, the elimination is completed within a few minutes. Contrary to Mendelson's model, the observations on the initial stage of elimination process show that the elimination proceeds locally from the surface of growth layer to the substrate-growth interface.
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