Microwave characterization of nanostructured ferroelectric Ba_0.6Sr_0.4TiO₃thin films fabricated by pulsed laser deposition

Abstract

A series of nanostructured ferroelectric thin films of barium strontium titanate were fabricated using a pulsed laser deposition system with real-time in situ process control. Pulsed laser deposition parameters were controlled during the growth of nanostructured thin films for use in the development of high frequency tunable microwave devices. The thin films were all grown at the same substrate temperature and laser beam energy density, but the chamber oxygen partial pressure (COPP) was varied systematically from 19 mTorr through 1000 Torr. Structural and electromagnetic characterization was performed using atomic force microscopy and evanescent microwave microscopy, respectively. Atomic force microscopy showed a linear increase in grain size with increases in the ambient oxygen pressure from 38 to 150 mTorr and from 300 mTorr to 1000 Torr. The correlation of the microwave properties with the epitaxial film microstructure can be attributed to stresses and polarizability in the film. Microwave characterization showed that a COPP of 75 mTorr yielded the most desirable film in terms of tunability and loss tangent over a wide frequency range.

Microwave Properties of Bi1.5Zn1.0Nb1.5O7/Ba0.6Sr0.4TiO3 Hetero Layered Films Directly Sputtered on Si up to 50 GHz

“…The losses presently obtained on our BST‐based films could be ascribed to different Ba/(Ba+Sr) ratios or (Ba+Sr)/Ti ratios, deposition conditions, lack of post annealing, and too high deposition temperature . Other factors such as oxygen nonstoichiometry, and sputtering pressure range could also be considered . Moreover, The sudden decrease in tan δ for BZN/BST film was undoubtedly ascribed to the presence of low loss BZN phase in BST, which is similar to that observed in the case of BST doped with other dielectrics .…”

Giant Enhancement of Polarization and Strong Improvement of Retention in Epitaxial Ba0.6Sr0.4TiO3‐Based Nanocomposites

“…The c / a values obtained for the composite films are significantly larger than the plain BSTO ( x = 0) films studied here and compared to literature BSTO films . The highest value achieved was 1.033(7) for the x = 0.75 film of thickness 1000 nm.…”

Synthesis of Epitaxial Metal Oxide Nanocrystals via a Phase Separation Approach

“…As the chamber oxygen pressure increases, the collision probability increases and as a consequence creates a slower plume, which allows more time for larger sized nanostructures to grow. 34 Size and internanostructure distance analysis of these SEM images reveals that the mean lateral size and inter-nanostructure distance increases (80 to 180 nm and 15 to 160 nm) with increasing oxygen partial pressure, from 10 to 400 mTorr (shown in Figure 2D). An analogous dependence on laser pulse frequency was also found, where increasing the pulse rate from 5 to 20 Hz for a fixed oxy-gen partial pressure and temperature reduced the internanocrystal distance as well as the mean lateral size.…”