Comparison of BST film microwave tunable devices based on (100) and (111) MgO substrates

Author

Noda, Minoru ; Yamada, Tomoaki ; Seki, Kousuke ; Kamo, Takafumi ; Yamashita, Kaoru ; Funakubo, Horoshi ; Okuyama, Masanori

Author_Institution

Grad. Sch. of Sci. & Technol., Kyoto Inst. of Technol., Kyoto, Japan

Volume

57

Issue

10

fYear

2010

fDate

10/1/2010 12:00:00 AM

Firstpage

2221

Lastpage

2227

Abstract

We have increased the figure-of-merit (FOM) of a (Ba,Sr)TiO₃ (BST) film microwave tunable device by approximately three times for MgO(111) compared with a MgO(100) substrate at a frequency range of 20 GHz. Differences in permittivity and tunability in a BST film may be closely related to the difference in the film strain. The ratio of calculated permittivities of BST(100) and BST(111) films nearly corresponds to that of the FOM in the microwave range, which was rather unexpected because a higher permittivity leads to both larger tunability and dielectric loss in ferroelectrics. From a series of results, it is suggested that there are additional influences of orientation (other than the direct influence of strain itself) on the tunable properties in BST films especially in the high-frequency region.

Keywords

dielectric losses; ferroelectric devices; ferroelectric thin films; magnesium compounds; microwave devices; permittivity; strontium compounds; tuning; (100) substrate; (111) substrate; BST film microwave tunable devices; BaSrTiO₃-MgO; MgO; dielectric loss; ferroelectrics; film strain; frequency 20 GHz; permittivity; tunability; Capacitors; Dielectric losses; Films; Permittivity; Strain; Substrates;

fLanguage

English

Journal_Title

Ultrasonics, Ferroelectrics, and Frequency Control, IEEE Transactions on

Publisher

ieee

ISSN

0885-3010

Type

jour

DOI

10.1109/TUFFC.2010.1681

Filename

5587402