�ber Zusammenh�nge zwischen Elektronenspinresonanz, elektrischer Leitf�higkeit und Photoleitung bei reinem und dotiertem Bor

Abstract

The conductivity mechanism in pure and doped, fl-rhombohedral, polycrystalline boron between 1.5 ~ and 900 ~ is clarified by measurements of electrical conductivity, photoconductivity, electron paramagnetic resonance and thermoelectric effect. The semiconductor behaviour of boron between 1.5 and 900 ~ is similar to that of doped and compensated germanium and silicon at helium temperatures concerning the temperature-independent number of carriers and the thermally activated conduction process at low and high carrier concentrations. The paramagnetic centres are nearly localized electrons at 1.5 ~ and nearly free electrons at 900 ~ with a continuous transition between these two extreme kinds of behaviour. Mobilities of charge carriers in carbon doped boron over a range from 1016 cm -3 to 1020 cm -3 and 77 ~ to 900 ~ were measured for the first time and were found to obey an exponential law.

Crystallography, semiconductivity, thermoelectricity, and other properties of boron and its compounds, especially B6O

“…The possible high mobility (10e100 cm 2 /V$sec. at 300 K) crystals are stoichiometric B 6 O, B 6 P, B 6 As and possibly B 6 S and B 12 C 3 .…”

“…The temperature variation of the s of b-B with 8.5 atom% C from [6] has been published [14, see their Fig …”

“…It is also noted that Weintraub [1, page 182] said in 1909 that the maximum solubility of carbon in b-boron is close to 8%. The carbon-doped boron remains p-type in the doping process up to 8.5 atom% carbon [6]. Just where in the lattice the 9 carbon atoms per rhombohedral unit cell are located has been unclear, until now.…”

“…At the very lowest carbon concentrations this assumption may no longer be valid. The open squares are from two highly-doped samples [6] with electrical conductivities of s ¼ 4 Â 10 À2 S/cm and 8 Â 10 À3 S/cm but unspecified carbon content. These points fit the solid line in Fig.…”

Mössbauer Effect Studies of 57Co and 57Fe in β‐Rhombohedral Boron

“…It is thus of interest to investigate, which places inside the unit cell an element like Co or Fe would occupy if incorporated as an impurity in the concentration range of less than 1 at yo. Some information of this type is available from EPR measurements [3]. However, these results are not fully conclusive and cannot be used to judge the quality of a source of 57C0 in B for the Mossbauer spectroscopy.…”