The temperature dependence of the absorption spectrum from the edge to the inset of the lattice vibrations can be described by indirect band-band transitions and excitations from a thermally occupied trap level, the existence of which has been proved in the second part of this paper by illumination a t low teinperatures changing the absorption and photoconductivity spectrum inportantly. -Free carrier absorption superimposed on the lattice spectrum has been found a t high temperatures. Its increase proportional to suggests scattering by charged centres. Their density is about 5 x 1O20 em+ surpassing impurities by a factor of 102. The effective mass of holes is estimated at 8 m, corresponding to a conductivity by hopping processes. The complicated lattice vibration spectrum is nearly independent of temperature between 4 and 13 pm indicating that there are no combination bands.
The rotation of the plane of polarisation and the ellipticity of the reflected light at both sides and the transmitted light through magnetically saturated evaporated layers (30 mti) of iron, cobalt and nickel are measured in the near I.R. and the visible spectrum (2"5 to 0"43 [~). The four measured magnetooptical angles are dependent one another according to the theory of VOlOT. They are found independent however each other. That can be explaned only by a magnetooptical term in the second equation of Maxwell too, if the layers are homogenous. This term is calculated and gives rise to a considerable portion of the magnetoopticM effects. The transmitted light gains a rotation and ellipticity not only in the interior of the metal but also on the surfaces. This surface-change surpasses that in the interior in the I.R. region. It Call be determined by extrapolating on the thickness zero or by calculating out of the measured Kerr-effect. Both methods agree well. This is a convincing prove that non-magnetical surface-layers are there not existing. The magnetooptical rotation of Nickel has a sharp peak at I V, the other magnetooptical constants, include the calculated magneticM terms show a more monotonous course with the wavelenght, also for the other metals. The optical constants are determined by measurements of intensity of the reflected light on both sides of the layer and of the transmitted light.
Der Temperaturgang der optischen und elektrischen Eigenschaften von rhomboedrischem BorJ o h a n n e s J a u m a n n und J o a c h im S c h n e l l II. Physikalisches Institut der Universität Köln(Z. Naturforschg. 20 a, 1639-1647 [1965] ; eingegangen am 5. September 1964)Ziel der Untersuchung war, eine Beziehung zwischen dem Absorptionsspektrum von rhombo edrischem grobkristallinen Bor und seinen elektrischen Eigenschaften im eigenleitenden Zustand zu suchen, wie sie vorher schon erfolgreich an Germanium 1 und Silicium 2 gefunden worden waren, weil dort freie Ladungsträger einen wesentlichen, mit der Wellenlänge stark wachsenden Anteil am Absorptionsspektrum haben. Bei Bor hat sich aber die Beteiligung freier Ladungsträger an der Absorption nicht überzeugend nachweisen lassen. Der langwellige Teil wird durch wenig tempera turabhängige, ziemlich scharfe Absorptionsbanden gebildet, die sicher einem Gitterschwingungsspektrum entstammen. An dem kurzwelligeren intensiven kontinuierlichen Untergrund, der mit der Temperatur stark wächst, sind sehr wahrscheinlich temperaturabhängige Kombinationsbanden der Gitterschwingungen und die Ausläufer der stark temperaturabhängigen Bandkante beteiligt, die auf eine mit wachsender Temperatur stark abnehmende Energielücke hinweist. Damit erklärt sich zwanglos die mit der Temperatur stark anwachsende und bei hohen Temperaturen, verglichen mit der Lage der Bandkante, viel zu hohe Aktivierungsenergie der Trägerzahl.Das gesinterte, grobkristalline (Korngröße 1/2 bis 1 mm), porenfreie Bor der Firma Starck, Goslar, hatte folgende spektralanalytisch festgestell ten Verunreinigungen in einer Konzentration von weniger als 10-3%: S i, Mn, Zn, Mg, Fe, Cu, Ca, Al, Bi. Die C-Konzentration war sicher nicht größer als 10~2%3. Das Aussehen der Borbrocken war dunkel grau glänzend. Drehkristallaufnahmen (wegen der groben Kristallstruktur wurde die Probe auch in der Längsachse verschoben) sind mit den von H o r n 4 an rhomboedrischem Bor gemessenen Netzebenenabständen verträglich. Es handelt sich um das von S a n d s und H o a r d 5 beschriebene "Rhombohedral Elemental Boron" mit einer Einheitszelle von 108 Atomen, a= 10,12 Ä, a = 6 5°2 8 /. Zum Dünnschlei 1 J. J a u m a n n u . R. K e s s l e r
The magnetical rotation of the plane of polarisation and the ellipticity of the reflected and transmitted light through magnetically saturated, evaporated layers of iron, cobalt and nickel (30 to 100 mtz ) are dependent one another according to the tShenomenological theory of W. VOIGT. The four measured magnetooptical angles are however independent each other. By comparison of other physical properties, except the magnetooptical ones, (f.e. magnetical saturation, optical absorption) measured respectively with transmitted and with reflected light, we try to prove, that the layers are homogenous at least near the glass-side. The linear increase of Faraday-rotation and optical absorption with the thickness of the layer supports this assumption. Then the independence can only be explaned by a magnetooptical term in the second equation of Maxwell also (precession of spin).The knowledge of the optical constants ist necessary for the comparison ot magnetooptical ones. They are find out by measurements of intensity only, using the transmitted light and the reflected light at both sides of the layer. By supernumerary kinds of determination the fonlt is estimated. The method of Drude is adapted to measurements of intensity and then applied on the glasside too. The results on this side agree with those of transmitted light, the air-side differs a little.
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