Academic Thesis

Basic information

Name Nakamura Osamu
Belonging department
Occupation name
researchmap researcher code B000300963
researchmap agency Okayama University of Science

Title

Dielectric function analysis of superstoichiometric samarium dihydride films

Bibliography Type

Author

M. Sakai, T.Nanbo,Y.Tanji, O.Nakamura, M.Endo, H.Tajima

Summary

We have carried out an experimental study to reveal the dielectric function of SmHx(x=2.28,2.42,2.56,2.57) films based on room-temperature reflectivity for photon energies ranging from 0.05 to 6.5 eV. The derivation of the dielectric functions has been carried out using model dielectric functions as well as Kramers–Kronig analysis. It is inferred from our analysis that when the H/Sm value is increased from 2.28 to 2.57, (i) the interband transition band located in the ultraviolet region shows a redshift of about 1 eV, (ii) the relatively weak transition band located in the near-infrared region shows a reduction in intensity, and (iii) the unperturbed plasma frequency of free carriers decreases slightly. The behaviors (i), (ii), and (iii) caused by the H/Sm value change are thoroughly approximately the same as those observed for YHx, suggesting that these trends are characteristic of H–M systems showing a metal-insulator transition. It was also confirmed from our structural analysis that these changes in the dielectric function are achieved without a change in the lattice constant. The origin of this constancy in the lattice constant in our samples with different H/Sm values is discussed by assessing the T- and O-site hydrogen concentrations. The hydrogen incorporation effect is also observed in the magnitude of the unperturbed plasma frequency, about 1.7 eV, which is unexpectedly small compared to conventional metals. This characteristic can possibly be attributed to mass enhancement of mobile carriers; we obtained an effective mass of about 10m0 (where m0 is the free electron mass) when the carrier density estimated from the Hall coefficient value is used.

Dielectric function analysis of superstoichiometric samarium dihydride films

Magazine(name)

Journal of Applied Physics

Publisher

Volume

105

Number Of Pages

StartingPage

083512

EndingPage

Date of Issue

2009/00

Referee

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Invited

Not exist

Language

English

Thesis Type

Research papers (academic journals)

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