Electric dipole centres and colour centres in natural sodalite

Abstract

SynopsisExperiments on an electric dipole centre, exhibiting multiple relaxation, in the natural mineral sodalite, are described. The concentration of the dipole centres is reduced upon X irradiation, whereas simultaneously colour centres and paramagnetic centres arise. Thermal bleaching restores the original concentrations. The interrelationships between these centres are established.A model is proposed in which the dipole centre is ascribed to an interstitial monovalent metal ion (say a Na + ion) acting as a charge compensator for an A13÷ ion, substituted for a Si 4+ ion. This A1-Na complex may be destroyed by X rays, yielding an electron trapped at the sodium ion and a hole trapped at a nonbridging oxygen ion, adjacent to the A13÷ ion, to which both the optical and paramagnetic properties of the X ray induced centres are attributed.

Local Heating in Nanoscale Conductors

“…The effective local temperature, resulting from the equilibrium between local heating and heat dissipation into the electrodes, is plotted in Fig. 4 at T e = 0 K. Values of the local temperature for the gold contact are in good agreement with experimental results [6] and previous theoretical estimates. [1] It is evident from Fig.…”

“…Indeed, such an effect has recently been observed in several atomic-scale structures. [4,5,6] Apart from its fundamental importance in solid state physics, the problem has thus gained renewed interest due to its possible impact on nanoscale electronics. At this length scale, all atoms of the junction and corresponding vibrational modes need to be treated explicitely, and the electronic distribution calculated selfconsistently with the correct scattering boundary conditions.…”

Mechanisms of TL for production of the 230°C peak in natural sodalite

“…The EPR spectra show lines at g ¼2.01132, g¼2.0008 lines and 11 hyperfine lines superimposed on the g¼2.0008 signal. The observed intense EPR line at g¼2.01132 has been attributed to the [AlO 4 ] 0 (this center corresponds to a hole trapped at a non-bridging oxygen ion adjacent to the Al 3 + ion) defect following the works of Hassib et al [13], Van den Brom et al [14] and Annersten and Hassib [15]. The eleven EPR lines with a hyperfine coupling constant of 3.5 G is associated with an O À ion in an intermediate position with respect to two adjacent Al nuclei (I ¼5/2), one in a lattice site and one replacing a Si 4 + of the crystal structure breaking the usual alternation of aluminum and silicon that occurs in the perfect lattice, this group of eleven hyperfine lines (centered at g¼2.0008) was also observed by Annersten and Hassib [15] on an irradiated blue sodalite crystal.…”

“…A trivalent Al 3 + ion easily replaces a Si 4 + in the ionic crystal scheme of the sodalite lattice [14]. The principle of ionic charge neutrality in an ionic crystal may require a charge compensating monovalent cation in an interstitial site.…”

Atomic Dimer Shuttling and Two-Level Conductance Fluctuations in Nb Nanowires

“…It has been predicted theoretically and shown experimentally [1][2][3][4][5][6]13] that indeed the structural and transport properties of NWs are correlated with each other, and that precisely at conductance jumps between neighboring plateaus fluctuations may occur in the form of random telegraph noise (RTN), involving high and low-conductance states (HG and LG, respectively), whose origin remains unknown [14,15]. However, short of direct imaging of the NW structure during elongation and simultaneous conductance measurements [16], evidence for the aforementioned close correlation between the structural and transport characteristics is lacking.…”