Sketch of our SSIOD optical setup (top view). The optical diode protects the laser from backreflected light. With the telescope one can change the spot sizes on the detectors. The complete optical setup is positioned outside the UHV.
A one-dimensional PSD (top) and a two segment photodiode (bottom) in comparison. The one-dimensional PSD delivers continuous information about the center of intensity of the light spot through the two photocurrents out of terminals A and B, while a split photodiode gives the intensity difference of the parts of the spot on the two different segments.
Sketches for the illustration of the calculation of the bending radius from the spot deflections.
-shaped sample after several experiments. The is deformed as illustrated by the distorted reflection of the camera. The current density at the inner part of the was high enough to flash away the milky phase which is still present at the outer part, while the edges of the sample are still covered with the native silicon oxide.
Old and new samples and their clamping in comparison. The -shaped samples are complicated to produce and to clean, whereas strips can be easily applied and show superior properties.
The dependence of the ratio of the spring constants of the braid and the strip sample on the sample thickness . For the braid is much softer than the silicon sample. The plot is calculated from Eq. (5) using , (source: WebElements [http://www.webelements.com/] ), , , , and .
Cross section through the UHV chamber, showing the combination of high resolution low energy electron diffration and surface stress measurement.
Photos of the two sample designs at . In contrast to the old sample, the new strip sample shows a uniform temperature distribution. The arrows indicate the laser spot positions. (The slightly different colors of the samples are caused by the automatic white balances of the used CCD cameras.)
Temperature distribution profiles over the strip sample for various sample temperatures. The temperature is homogenuous within less than over a usable length of . (The position corresponds to the center of the sapphire ball, the clamp that connects to the wire starts at ).
Comparison of the thermal behavior at of the old clamp (upper curve) and the new point-contact version with the sapphire ball (lower curve): A long-term thermal drift is still inevitable because of the slow thermalization of the sample holder but the large stick-slip effects of the old design have been eliminated.
Comparison of a measurement done with the setup as described in the text to an old one. Germanium grows in a layer-by-layer mode on silicon for about three wetting layers and a linear film stress of about exhibits due to the 4.2% lattice mismatch. Then the film roughens into hut and later into dome clusters which can relieve stress due to their three dimensional shape (Ref. 56). The lower temperature of the new measurement causes an earlier onset of the roughening. On the upper right, histograms of the signals are shown, that were calculated from the linear parts of the curves after a line subtraction. The Gaussian distribution shows the pure statistical nature of the noises.
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