Electron spin resonance doped samples

A. Shengelaya, S. Reich, Y. Tsabba, and K. A. Muller, Electron spin resonance and magnetic susceptibility suggest superconductivity in Na doped WO3 samples, Eur. Phys. J. B 12(1), 13-15 (1999). 

Recently, both polycrystalline and microcrystalline ( 200 A crystallite size) Si films have been investigated by ESR (Hasegawa ft a/., 1981b, 1983b). A dangling bond resonance in microcrystalline silicon films is observed at g = 2.0049. The spin density of this resonance is typically between 10 and 10 spins cm. In P-doped samples a conduction-electron spin-resonance signal is observed at = 1.997. 

The electropolymerization of fluorene (Fig. 26) produces a polymer with a conductivity of 10 S cm. By functionalizing carbon 9 of the five-membered ring, substituted fluorenes have also been oxidized to form polymers of 9-methylfluorene, 9,9 -dimethylfluorene, and 9-phenylfluorene. These polymers gave comparable voltammograms, which seems to indicate that the substituents are not directly involved in the polymerizations. The doped polymers contained tetrafluoroborate anions, but their conductivities were very low [382,383]. The samples were analyzed by elemental analysis, infrared spectroscopy, electron spin resonance, and scanning electron microscopy. 

The electron spin resonance (ESR) spectra of the V ion-implanted T1O2 catalysts were measured before and after calcination of the samples in O2 at around 723 to 823 K, respectively. Distinct and characteristic reticular ions were detected only after calcination at around 723 to 823 K. When a shift in the absorption band toward visible light regions by the V ion-implantation was observed, the presence of the reticular ions could be detected by ESR measurements. No such V ions having the same local stmcture or shifts in the absorption band could be observed with Ti02 catalysts chemically doped with V ions. 

Another important feature to note regarding the bipolaron levels in particular is that they are either empty (p-type doping) or fiilly occupied (n-type doping), and thus spinless. An important reason why a model different from that of conventional semiconductors was sought for CPs is that in highly doped CP samples, which had high intrinsic conductivity, there was no evidence for unpaired electrons from experiments such as electron spin resonance (esr) measurements, or correlation of conductivity with esr absorption, but rather, spinless charge carriers were indicated [16]. 

---