Ferroelectric and optical properties of Ba[sub 0.8]Sr[sub 0.2]TiO[sub 3] thin film (original) (raw)
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Ferroelectric and optical properties of Ba0.8Sr0.2TiO3 thin film
Journal of Applied Physics, 2002
Barium strontium titanate ͑Ba 0.8 Sr 0.2 TiO 3 ͒ thin films have been prepared on Pt/Ti/SiO 2 /Si substrates using a soft solution processing. X-ray diffraction and also micro-Raman spectroscopy showed that the Ba 0.8 Sr 0.2 TiO 3 thin films exhibited a tetragonal structure at room temperature. The presence of Raman active modes was clearly shown at the 299 and 725 cm Ϫ1 peaks. The tetragonal-to-cubic phase transition in the Ba 0.8 Sr 0.2 TiO 3 thin films is broadened, and suppressed at about 35°C, with a maximum dielectric constant of 948 ͑100 kHz͒. Electrical measurements for the prepared Ba 0.8 Sr 0.2 TiO 3 thin films showed a remnant polarization ͑P r ͒ of 6.5 C/cm 2 , a coercive field ͑E c ͒ of 41 kV/cm, and good insulating properties. The dispersion of the refractive index is interpreted in terms of a single electronic oscillator at 6.97 eV. The direct band gap energy ͑E g ͒ and the refractive index ͑n͒ are estimated to be 3.3 eV and n ϭ 2.27-2.10, respectively.
On the microstructure and optical properties of Ba0.5Sr0.5TiO3 films
Thin Solid Films, 1997
Thin films of Ba 1yx Sr x TiO 3 (xs0.5) were prepared on the (1 02) plane of sapphire substrates by pulsed laser deposition. Crystallographic # 1 studies show that the films are polycrystalline with a strong reflection from the (111) plane. Scanning electron micrographs reveal smooth surfaces. The index of refraction and the absorption coefficient were determined at room temperature in the wavelength range 382-800 nm from spectrophotometer measurements of the transmittance at normal incidence using the method devised by Swanepoel. The average value of the refractive index is found to be 2.06 in the visible spectrum; the higher values near the UV are associated with the fundamental band gap absorption. The dispersion of the refractive index is interpreted in terms of a single electronic oscillator at 7.16 eV. The direct band gap energy is found to be 3.96 eV. q 1997 Elsevier Science S.A.
Materials Chemistry and Physics, 2000
Ferroelectric thin films of barium strontium titanate (BST) have been deposited on silicon and quartz substrates by sol-gel technique through organic precursor route. Crystalline films were obtained by post deposition annealing at a temperature of 700 • C. X-ray diffraction (XRD) studies have been carried out to assess the crystallinity and phase formation. The surface features of the films, studied by optical microscopy reveal the grain growth pattern. The refractive index of the film has been estimated. Electrical characterisation of the films such as resistivity and C-V measurements in metal-ferroelectric-semiconductor (MFS) configuration have been carried out. The hysteresis behavior observed during the C-V measurements confirms the ferroelectric property of the films.
Structural and optical characterization of Ba0.8Sr0.2TiO3 PLD deposited films
Optical Materials, 2008
Structural and optical properties of Ba 0.8 Sr 0.2 TiO 3 (BST) ferroelectric thin films, deposited by the pulsed laser ablation (PLD) technique on Si/SiO 2 /Ti/Pt, Si/SrRuO 3 and Si substrates, were performed by X-ray diffraction, micro Raman, atomic force microscopy (AFM), and optical reflectometry measurements. Temperature dependences of the Raman spectrum, and room temperature refractive and extinction indices, and surface roughness were evaluated.
Electrical Properties of Crystalline Ba0.5Sr0.5TiO3 Thin Films
2001
Thin Ba0.5Sr0.5TiO3 (BST) films on p-type Si (100) using The Chemical Solution Deposition (CSD) method. X-ray diffraction (XRD), Scanning electron microscopy (SEM), C-V meter analysis measurement were employed to characterise the films. The growth condition to obtain enough quality epitaxial of Ba0.5Sr0.5TiO3 carried out by spin coating at 3000 rpm for 30 seconds, and then annealing at 900oC for 15 hours. The structure and crystallinity of thin films were investigated by XRD preffered orientation (100), (010); (110), (111), (200), surface analysis by SEM magnification x10000 thin films were heterogen and thickness film 1100 nm; electrical characterization Ba0.5Sr0.5TiO3 at MFS (Metal Ferroelectric Semiconductor) structure in room temperature (300 K) by carried out capacitance flat band (CFB) for frequency 10 KHz and 100 KHz were 206 pF and 187 pF, dielectric constant for frequency 10 KHz and 100 KHz were 132.67 and 117.22, dielectric loss minimum for frequency 10 KHz and 100 KHz were 5.37 % and 6.43 % respectively.
Thin Solid Films, 2001
. Polycrystalline Ba Sr TiO xs 0.4 and 0.8 thin films with a perovskite structure were prepared by the polymeric precursor x 1yx 3 method on a platinum-coated silicon substrate. High-quality thin films with uniform composition and thickness were successfully produced by dip-coating and spin-coating techniques. The resulting thin films prepared by dip and spin-coating showed a well-developed dense polycrystalline structure with uniform grain size distribution. The metal᎐BST-metal structure of the thin Ž . films displays good dielectric and ferroelectric properties. The ferroelectric nature to Ba Sr TiO xs 0.8 thin film, indicated x 1yx 3 by butterfly-shaped C᎐V curves and confirmed by the hysteresis curve, showed 2 P s 5.0 Crcm 2 and E s 20 kVrcm. The r c capacitance᎐frequency curve reveals that the dielectric constant may reach a value of up to 794 at 1 kHz. On the other hand, the Ž . Ba Sr TiO x s 0.4 thin films had paraelectric nature and dielectric constant and the dissipation factor at a frequency of 100 x 1yx 3 kHz were 680 and 0.01, respectively, for film annealed at 700ЊC. In addition, an examination of the film's I᎐V curve at room Ž . temperature revealed the presence of two conduction regions in the Ba Sr TiO xs 0.4 and 0.8 thin films, showing x 1yx 3
Applied Optics, 2006
The optical properties of barium strontium titanate ͑Ba 0.7 Sr 0.3 TiO 3 ; BST) thin films are described. The BST thin films were epitaxially grown upon MgO (001) substrates by pulsed laser deposition. The crystallographic properties of the BST thin films were examined by x-ray diffraction. The BST thin films were highly optically transparent in the visible region. The optical waveguide properties were characterized by a prism coupling technique. An inverse-WBK method was employed to determine the refractive-index profile along the thickness of the BST films. Optical losses were measured by a moving fiber method, and the optical losses were found to be 0.93 dB͞cm for the TE 0 mode and 1.29 dB͞cm for the TM 0 mode at 1550 nm. Electro-optic (E-O) properties were measured by a phase-modulation detection method at 632.8 nm, and the BST films exhibited a predominantly quadratic E-O effect with a quadratic E-O coefficient of 6.64 ϫ 10 Ϫ18 m 2 ͞V 2 .
Journal of Applied Physics, 2003
Polarized Raman spectra of heteroepitaxial (Ba 0.7 Sr 0.3 )TiO 3 thin film deposited on the ͑001͒MgO substrate have been studied in the broad temperature range from 30 to 1300 K. Our results show that the ferroelectric-paraelectric phase transition is markedly shifted to higher temperatures with respect to the bulk ceramics of the same composition. Because of the two-dimensional compressive stresses imposed on the film by the substrate, the symmetry of the paraelectric phase is found to be tetragonal well above the Curie temperature. Near the deposition temperature ͑1173 K͒, the thermoelastic compressive stresses vanish and Raman response suggests nearly cubic symmetry. Raman measurements below room temperature show clearly that the phase transition to the rhombohedral phase is completely suppressed and only one phase transition from the tetragonal to the monoclinic phase is revealed at ϳ150 K.
Effects of Li and Cu dopants on the crystal structure of Ba0.65Sr0.35TiO3 thin films
Ferroelectrics Letters Section, 2018
A barium strontium titanate Ba 0.65 Sr 0.35 TiO 3 and its lithium (Li) and copper (Cu) doped thin films have fabricated on quartz substrates based on sol-gel and spin-coating method. Chemical solution deposition with spin-coating technique deposited the thin films. The addition of Li and Cu dopants lead to the change of lattice constant and the change of grain size. From Scherrer's equation, it found that BLST and BCST thin films have larger and smaller grain size than that of BST, respectively. It also revealed that the crystal structures formed in a phase between cubic and tetragonal structure. Scanning electron microscopy was confirmed homogenous surfaces of thin film and energy dispersive x-ray was showed chemical composition according to the considered stoichiometry.
Applied Physics Letters, 1995
The primary objective of this research is to optimize the different deposition conditions to obtain high tunability and low dielectric loss of Barium Strontium Titanate (BST) thin films at microwave frequencies. Ba 0.5 Sr 0.5 TiO 3 thin films were deposited on Pt/TiO 2 /SiO 2 /Si substrates by pulsed laser deposition technique (PLD). Deposition conditions like temperature, oxygen pressure, substrate to target distance and laser energy are varied to obtain the objective. Deposition of the BST thin films on the Pt/TiO 2 /SiO 2 /Si substrates was carried out at temperatures of 450ºC, 550°C, 650ºC and oxygen pressures of 250mTorr and 450mTorr with laser fluence of 250 mJ/cm 2 and 450mJ/cm 2 at 10 pulses per second. The microstructural and phase analysis of the deposited BST films at different temperatures and different oxygen pressures were performed using X-ray diffraction (XRD) method. The diffraction patterns are attributed to cubic (perovskite) crystal system. Atomic force microscopy (AFM) was used to perform the surface analysis of the films deposited at different substrate to target distances, varied laser energies and oxygen pressures. The BST capacitor was fabricated using the Coplanar Waveguide Structure and the capacitance and dielectric constant were measured using the Vector Network Analyzer (VNA). Tunability of 3.1:1 and loss tangent of 0.0121 was achieved at 0.4-0.8 GHz.