The cathodic electrolysis of propylene carbonate containing lithium perchlorate was studied by means of an in-situ quartz crystal microbalance technique. A lithium compound was deposited at about +1.5 V vs. Li/Li+ and dissolved at about +4.0 V vs. Li/Li+. In constant potential electrolysis at +0.9 V vs. Li/Li+, the deposition process was divided into two stages. In the first stage, in which lithium carbonate was most probably deposited, an electrode reaction of ferrocene which was added to the solution was gradually retarded. In the second stage, in which some chemical reaction proceeded dominantly, the electrode reaction of ferrocene was almost completely blocked. A cathodic charge of +3.0 mC cm−2 was necessary for almost complete blocking.
This note reports on the observation of the appearance of singularity in the equal-thickness fringes at the outcrop of a dislocation in silicon observed with a plane-wave of X-rays and proposes a method of determining directly the magnitude and sense of the Burgers vector from the number of the extra half lines of the fringes.In this note we will report on the change of the equal-thickness fringe pattern near a dislocation with the incident direction in topographs of a silicon crystal, when a plane wave of X-rays is used. We propose another method of determining the magnitude and sense of the Burgers vector of a dislocation, which is more direct and simpler than previous ones: comparison of the observed and calculated intensity profiles obtained with the double-crystal arrangement (Bonse, 1962), the section topograph (Epelboin, 1974) or the counting of the extra half lines at the dislocation outcrop in the moir6 pattern (Chikawa, 1967;Lang, 1968;Hart, 1972).(~02) diffraction topographs with Mo K~ were taken with the double-crystal arrangement of parallel setting, in which asymmetric diffraction was used for the first crystal so that the angular spread of the beam incident on the second or specimen crystal was estimated to be 0-46", much smaller than the angular range of the symmetric diffraction, 2.3". The source-monocromator, monochromator-specimen and specimen-photographic plate distances were 35, 20 and 1 ,,-1.5 cm respectively. The apparent focal size was 0.1 x 0.1 mm, and Mo g0t 2 was excluded by a 4 mm wide slit placed in front of the specimen. The instrumental resolution in the vertical and horizontal directions was estimated at 1.8 and 0"6 #m respectively. The exposure time was 0"5 ,--1.0 h with a rotating-anode X-ray tube operated at 40 kV and 7 mA. The specimen was a silicon wafer about 500 #m thick with the surface (1]1) prepared from a single crystal grown along [111] by the floating-zone method.A series of (~02) diffraction topographs was taken at several angular positions on both sides of the diffraction peak from a part near the circumference of the specimen, the wedge angle of which was about 8 ° on the average. In Fig. 1 of the glancing angle of the incident wave from the Bragg angle, and finally two half-line fringes spring out from the outcrop on either the left or the right for 50<0 or 50>0, respectively. It is presumed that the number of the excess fringes is represented as d n = h. b, where h is the diffraction vector and b the Burgers vector.In Fig. 2 are reproduced the calculated intensity distributions of the diffracted wave on the incident plane within the crystal. The calculations were made at the angular positions corresponding to those of Fig. 1, using Takagi's (1969) equations. The relation between the calculated and observed patterns corresponds to that of the calculated intensity distribution within a crystal and the observed section topograph from a wedge crystal with a spherical wave (Hattori,
We have carried out pseudopotential calculations of the effect of mixing in semiconductor superlattices between bulk states derived from the conduction band minimum at thecentreof the bulk Brillouinzoneand thoseoftheXminimaat thezone edges. Wepresent a systematic account of (i) the strength of this coupling in GaAh4I.4~ superlattices as a function of the layer widths, (ii) the variation as a function of layer width of the magnitude of the energy gap that occurs when the levels derived from different bulk valleys cross, (iii) the changeoftheoscillatorstrengthofthe transitionacross thesuperlattice gapasafunction of the separation of the interacting levels, and (iv) the magnitude of the effect of strain on valley mixing.
An analytical interpretation is presented of extra half‐line equal‐thickness fringes observed at a dislocation outcrop in X‐ray and electron micrographs of wedge‐shaped crystals taken at off‐Bragg conditions. Extra fringes arc well explained as the interference of two wavefields deduced from Takagi's equations for dynamical diffraction in distorted crystals. Theoretical discussions given in the present paper confirm the experimentally obtained rule of Δn = h. b (h is the diffracting vector and b the Burgers vector of a dislocation), which determines the extra number of fringes, Δn, at the dislocation outcrop. When h. b≠ integer, it is predicted that a discontinuous shift will occur in the position of equal‐thickness fringes along the topographic image of a dislocation.
Crystal moiré fringes in monolithic bi‐crystals of silicon have been observed with a highly parallel X‐ray beam obtained from an asymmetric diffraction. An appreciable improvement in fringe visibility has been achieved over the scanning method utilizing a slit‐collimated X‐ray beam. This is explained to be due to a high contrast of the standing wave reproduced outside the crystal and a weak intensity of the beams carrying no moiré information. A discussion is also given on the spatial coherence of the X‐ray beam obtained from the asymmetric Bragg‐case diffraction of a single crystal.
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