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The temperature dependence of the isotope effect for the diffusion of Na+ in NaCl
iv
ABSTRACTS OF PAPERS TO APPEAR IN
J. F. Dairymple and W. E. Spear, Carnegie Laboratory of Physics, University of Dundee, Dundee, Scotland. The unique structural property which links these two molecular solids is the eight membered puckered ring molecule The molecular orbitals and the energy level schemes that have been proposed are briefly discussed. Electron and hole transport in Sa and Sea is compared on the basis of the available drift mobility data It is concluded that in both crystals holes propagate in a band with a lattice mobility of about •iO cm 2 sec 1 V1. The same applies to electrons in Sea, but the intermolecular electron hopping transport in Sa presents an interesting anomaly, unexpected in view of the structural and electronic similarity of these solids. On the optical side, new reflectivity results for Sea are presented, together with the optical constants between 2 and 14 eV obtained by a Kramers—Krönig analysis. The spectral features of
J. PHYS. CHEM. SOLIDS
VoL 10, No.6
additional optical phonon scattering for the energy relaxation. Due to the non-Maxwellian distribution only a smaller amount of this optical phonon scattering gives agreement withthe experimental data. Received 7 July 1971
5.
THE TEMPERATURE DEPENDENCE OF THE ISOTOPE EFFECT FOR THE DIFFUSION OF Na~IN NaCI S. J. Rothman, N.L. Peterson, A. L. Laskar, and L. C. Robinson, Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439
The isotope effect for the diffusion of Na~ in Harshaw NaC1 crystals has been measured in
E 2 cures for Sa and Sea are discussed and the comparison suggests that in Sea a higher lying band (possibly formed from ci and 8 orbitals) overlaps the eleätron hopping level, whereas in Sa it does not. This model also explains the transport problem. Received 1 October1971.
4.
IMPURITY SCATTERING OF WARM HOLES IN GERMANIUM AND SILICON Guido R. Tschulena Battelle Institute e,V. D 6 Frankfurt/Main 90, Germany.
the temperature range 589—796°C. The diffusion coefficients of Na~in NaC1 are given by D
77 exp
(.
2.04 ±0.02 eV 2/sec kT ) cm The isotope effect, fAk, decreases as the temperature increases, indicating a vacancy pair contribution to the self-diffusion of Na~in NaC1. This contribution reaches 30 45 per cent near the melting point. The temperature dependence of fAk and D suggests fAk is <0.2 for Na~diffusion by means of of vacancy pairs. This implies that, if Ak for ditfusion by vacancy pairs is greater than 0.8, f pairs is~0.25, and hence the ration CF jumps by pairs to Na~jumps by pairs must be less than 0.1. Also, a large entropy for Na~diffusion by vacancy =
—
Warm hole mobility, namely that of the coefficient i3 = (~— /.~)/~ E2 is strongly affected by the pairs is inthcated. number of impurities. We measured this value for relative pure p-type germanium and silicon for different orientations and found no anisotropy contrary Received 5 October 1q71. to that observed in previous experiments for relatively impure samples. In addition a comparison is given between .experimental and theoretical ,~-values. 6. THE ELECTRICAL CONDUCTIVITY In the case of p-type silicor~it is sufficient OF SEMICONDUCTORS INVOLVING to take into account acoustic phonon ani ionisel INCLUSION S OF ANOTHER PHASE impurity scattering to achieve agreement between Carl Wagner, measured and calculated /3 -values. In the case Max-Planck-Institut f~irbiophysikalische of p-type germanium we had to take into account Chemie, G6ttingen, Germany
ABSTRACTS OF PAPERS TO APPEAR IN
J. F. Dairymple and W. E. Spear, Carnegie Laboratory of Physics, University of Dundee, Dundee, Scotland. The unique structural property which links these two molecular solids is the eight membered puckered ring molecule The molecular orbitals and the energy level schemes that have been proposed are briefly discussed. Electron and hole transport in Sa and Sea is compared on the basis of the available drift mobility data It is concluded that in both crystals holes propagate in a band with a lattice mobility of about •iO cm 2 sec 1 V1. The same applies to electrons in Sea, but the intermolecular electron hopping transport in Sa presents an interesting anomaly, unexpected in view of the structural and electronic similarity of these solids. On the optical side, new reflectivity results for Sea are presented, together with the optical constants between 2 and 14 eV obtained by a Kramers—Krönig analysis. The spectral features of
J. PHYS. CHEM. SOLIDS
VoL 10, No.6
additional optical phonon scattering for the energy relaxation. Due to the non-Maxwellian distribution only a smaller amount of this optical phonon scattering gives agreement withthe experimental data. Received 7 July 1971
5.
THE TEMPERATURE DEPENDENCE OF THE ISOTOPE EFFECT FOR THE DIFFUSION OF Na~IN NaCI S. J. Rothman, N.L. Peterson, A. L. Laskar, and L. C. Robinson, Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439
The isotope effect for the diffusion of Na~ in Harshaw NaC1 crystals has been measured in
E 2 cures for Sa and Sea are discussed and the comparison suggests that in Sea a higher lying band (possibly formed from ci and 8 orbitals) overlaps the eleätron hopping level, whereas in Sa it does not. This model also explains the transport problem. Received 1 October1971.
4.
IMPURITY SCATTERING OF WARM HOLES IN GERMANIUM AND SILICON Guido R. Tschulena Battelle Institute e,V. D 6 Frankfurt/Main 90, Germany.
the temperature range 589—796°C. The diffusion coefficients of Na~in NaC1 are given by D
77 exp
(.
2.04 ±0.02 eV 2/sec kT ) cm The isotope effect, fAk, decreases as the temperature increases, indicating a vacancy pair contribution to the self-diffusion of Na~in NaC1. This contribution reaches 30 45 per cent near the melting point. The temperature dependence of fAk and D suggests fAk is <0.2 for Na~diffusion by means of of vacancy pairs. This implies that, if Ak for ditfusion by vacancy pairs is greater than 0.8, f pairs is~0.25, and hence the ration CF jumps by pairs to Na~jumps by pairs must be less than 0.1. Also, a large entropy for Na~diffusion by vacancy =
—
Warm hole mobility, namely that of the coefficient i3 = (~— /.~)/~ E2 is strongly affected by the pairs is inthcated. number of impurities. We measured this value for relative pure p-type germanium and silicon for different orientations and found no anisotropy contrary Received 5 October 1q71. to that observed in previous experiments for relatively impure samples. In addition a comparison is given between .experimental and theoretical ,~-values. 6. THE ELECTRICAL CONDUCTIVITY In the case of p-type silicor~it is sufficient OF SEMICONDUCTORS INVOLVING to take into account acoustic phonon ani ionisel INCLUSION S OF ANOTHER PHASE impurity scattering to achieve agreement between Carl Wagner, measured and calculated /3 -values. In the case Max-Planck-Institut f~irbiophysikalische of p-type germanium we had to take into account Chemie, G6ttingen, Germany