IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Dielectrics Tuesday Sessions
       Session DI-TuA

Paper DI-TuA3
Substitutional Effects of the Dielectric Constant in Ta@sub 2@O@sub 5@

Tuesday, October 30, 2001, 2:40 pm, Room 130

Session: High K Dielectrics III
Presenter: K. Larsson, Uppsala University, Sweden
Authors: K. Larsson, Uppsala University, Sweden
J. Westlinder, Uppsala University, Sweden
H.-O. Blom, Uppsala University, Sweden
J. Olsson, Uppsala University, Sweden
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Tantalum pentoxide (Ta@sub 2@O@sub 5@) is considered to be a promising candidate as a dielectric material. The reported dielectric constant (@epsilon@? for Ta@sub 2@O@sub 5@ ranges between 20-40. Depending on annealing temperature, process temperature and process method, the Ta@sub 2@O@sub 5@ films have crystallised into different phases. Since @epsilon@ is greatly dependent of phase of Ta@sub 2@O@sub 5@ as well as dependent of various solutions of additives (e.g., Ti, Zr, Nb), it is of a large interest to study and compare different phases and solutions separately. The purpose with the present study has been to theoretically investigate the substitutional effect of various additives (Ti, Zr, Hf, V, Nb, Sn) in the @beta@-phase of Ta@sub 2@O@sub 5@ on the dielectric constant. The ionic, as well as the electronic, part of the dielectric function have then been calculated for mono-crystalline materials, using the first principle Density Functional Theory. In addition, the electronic part of @epsilon@ has also been calculated for a polycrystalline material as well. In the present study, an atomic substitution of 12 % of Ta with Ti, Zr, Hf, V, Nb and Sn, respectively, has been performed with a maintained ideal stoichiometry. For the situation with a Ti solution, the substitutions of 8 and 13 atom% were also used. As a general result, dielectric constants very similar to experimentally obtained values have been theoretically calculated in the present investigation.