Photo‐Induced Electron Spin Resonance (Photo‐ESR) in β‐Rhombohedral Boron

Abstract

Photo-induced ESR has been investigated in the temperature range 150 to 300 K using nearly homogeneous optical excitation (hv N 1.3 eV). The relaxation of the photo-ESR shows, similarly to that of photoconductivity, two components which are approximately described by a logarithmical function of time, decay rate being enhanced with increasing temperature. The time and temperature dependences of the photo-ESR as well as the relationship between the photo-ESR and photoconductivity are interpreted on the basis of a model, with traps for electrons having various values of emptying energy continuously distributed in a certain energy range and two kinds of localized valence states.Photo-induzierte ESR wird zwischen 150 und 300 K mit nahezu homogener optischer Anregung (hv 1,3 eV) untersucht. Die Relaxation der Photo-ESR zeigt, ahnlich wie die der Photoleitung, zwei Komponenten, die durch eine logarithmische Zeitabhangigkeit niiherungsweise beschrieben werden konnen und deren Abklingrate mit steigender Temperatnr groBer wird. Die Zeit-und Temperaturabhangigkeit der Photo-ESR ebenso wie die Zusammenhange zwischen Photo-ESR und Photoleitung werden durch ein Model1 mit Elektronenhaftstellen unterschiedlicher Befreiungsenergie interpretiert, die kontinuierlich uber ein bestimmtes Energieintervall verteilt sind, und zwei Arten von lokalisierten Valenzzustanden.

Correlation between structural defects and electronic properties of icosahedral boron-rich solids

“…That assumption easily explains the ESR results. The density of paramagnetic centres (about 10 15 cm −3 [35]) is very low compared with the defect concentration (about 10 20 cm −3 ) and can only be appreciably enhanced by heating or optical excitation [36,37]. Moreover, it is consistent with the charge transport in β-rhombohedral boron preferably due to hopping processes but with a certain contribution of delocalized carriers (see [1]).…”

On the diffusion of free carriers in β-rhombohedral boron

“…Ref. [15]) are definitely disproved. Accordingly, our experimental result is also not compatible with the theoretical hypothesis of bipolaron transport (see Refs.…”

Structural Defects of Some Icosahedral Boron-Rich Solids and Their Correlation with the Electronic Properties

“…The density of paramagnetic centers [about 10 cm\ (31)] is very low compared with the defect concentration (about 10 cm\) and can be appreciably enhanced only by heating or optical excitation (32,33). Moreover, it is consistent with the charge transport in -rhombohedral boron preferably due to hopping processes but with a certain contribution of delocalized carriers [see (34)].…”