TY - JOUR
T1 - Voltage tunable epitaxial Pb x Sr(1- x )TiO3 films on sapphire by MOCVD
T2 - Nanostructure and microwave properties
AU - Dey, Sandwip
AU - Wang, C. G.
AU - Cao, W.
AU - Bhaskar, S.
AU - Li, Jian
AU - Subramanyam, G.
N1 - Funding Information:
SKD would like to acknowledge support of Dr Deborah Van Vechten of the Office of Naval Research, Dr. Stuart A. Wolf of the Defense Science Office at Defense Advanced Research Projects Agency (DARPA), and the Frequency Agile Materials for Electronics (FAME) program at DARPA (contract number N00014-00-1-0471).
PY - 2006/1
Y1 - 2006/1
N2 - Frequency and phase agile microwave components such as tunable filters and phase shifters will require ferroelectric thin films that exhibit a nonlinear dependence of dielectric permittivity (εr ) with dc electric bias, as well as a high material (Δεr/tan δ) and device (or K-factor in phase shift/dB) figure of merits (FOM). Therefore, voltage tunable (Pb0.3Sr0.7)TiO3 (PST) thin films (90-150 nm) on (0001) sapphire were deposited by metal-organic chemical vapor deposition at rates of 10-15 nm/min. The as-deposited epitaxial PST films were characterized by Rutherford backscattering spectroscopy, X-ray methods, field emission scanning electron microscope, high resolution transmission electron microscopy, Raman spectroscopy, and electrical methods (7-17 GHz) using coplanar waveguide test structures. The epitaxial relationships were as follows: out-of-plane alignment of [111] PST//[0001] sapphire, and orthogonal in-plane alignments of [11̄0] PST//[ 101̄0] sapphire and [ 1̄1̄2] PST//[12̄10] sapphire. The material FOM and device FOM (or K-factor) at 12 GHz were determined to be 632 and ̃ 13 degrees/dB, respectively. The results are discussed in light of the nanostructure and stress in epi-PST films. Finally, a rational basis for the selection of PST composition, substrate, and process parameters is provided for the fabrication of optimized coplanar waveguide (CPW) phase shifters with very high material and device FOMs.
AB - Frequency and phase agile microwave components such as tunable filters and phase shifters will require ferroelectric thin films that exhibit a nonlinear dependence of dielectric permittivity (εr ) with dc electric bias, as well as a high material (Δεr/tan δ) and device (or K-factor in phase shift/dB) figure of merits (FOM). Therefore, voltage tunable (Pb0.3Sr0.7)TiO3 (PST) thin films (90-150 nm) on (0001) sapphire were deposited by metal-organic chemical vapor deposition at rates of 10-15 nm/min. The as-deposited epitaxial PST films were characterized by Rutherford backscattering spectroscopy, X-ray methods, field emission scanning electron microscope, high resolution transmission electron microscopy, Raman spectroscopy, and electrical methods (7-17 GHz) using coplanar waveguide test structures. The epitaxial relationships were as follows: out-of-plane alignment of [111] PST//[0001] sapphire, and orthogonal in-plane alignments of [11̄0] PST//[ 101̄0] sapphire and [ 1̄1̄2] PST//[12̄10] sapphire. The material FOM and device FOM (or K-factor) at 12 GHz were determined to be 632 and ̃ 13 degrees/dB, respectively. The results are discussed in light of the nanostructure and stress in epi-PST films. Finally, a rational basis for the selection of PST composition, substrate, and process parameters is provided for the fabrication of optimized coplanar waveguide (CPW) phase shifters with very high material and device FOMs.
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U2 - 10.1007/s10853-005-5926-4
DO - 10.1007/s10853-005-5926-4
M3 - Article
AN - SCOPUS:32944459018
SN - 0022-2461
VL - 41
SP - 77
EP - 86
JO - Journal of Materials Science
JF - Journal of Materials Science
IS - 1
ER -