Effect of working pressure and annealing temperature on microstructure and surface chemical composition of barium strontium titanate films grown by pulsed laser deposition

Abstract

Barium strontium titanate (BST, Ba 1−x Sr x TiO 3) thin films have been extensively used in many dielectric devices such as dynamic random access memories (DRAMs). To optimize its characteristics, a microstructural control is essential. In this paper, Ba 0.6 Sr 0.4 TiO 3 thin film has been deposited on the SiO 2 /Si substrate by the pulsed laser deposition (PLD) technique at three different oxygen working pressures of 100, 220 and 350 mTorr. Then the deposited thin films at 100 mTorr oxygen pressure were annealed for 50 min in oxygen ambient at three different temperatures: 650, 720 and 800 • C. The effect of oxygen working pressure during laser ablation and thermal treatment on the films was investigated by using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) analysis methods. X-ray photoelectron spectroscopy analysis was used to determine the surface chemical composition of the samples. The results indicate that the deposited BST film at low working pressure (100 mTorr) in PLD chamber shows a lower surface roughness than other working pressures (220 and 350 mTorr). The as-deposited films show an amorphous structure and would turn into polycrystalline structure at annealing temperature above 650 • C. Increase of temperature would cause the formation of cubic and perovskite phases, improvement in crystalline peaks and also result in the decomposition of BST at high temperature (above 800 • C). In addition, rising of temperature leads to the increase in size of grains and clusters. Therefore more roughness was found at higher temperatures as a result of a more heterogeneous growth and less tensions.

Influence of Alkaline and Alkaline Earth Metal Promoters on the Catalytic Performance of Pd–M/SiO2 (M = Na, Ca, or Ba) Catalysts in the Partial Hydrogenation of Soybean Oil-Derived Biodiesel for Oxidative Stability Improvement

“…To investigate the environment of the basic modifiers in the catalysts, the decomposition of high-resolution XPS spectra was performed (Figure A–C). For all three basic-modified catalysts, the characteristic peaks were shifted to BEs higher than those reported in the literature, − suggesting the relocation of electrons from the basic sites to the Pd atoms. ,, For Pd–Na/SiO 2 , the XPS spectrum of Na 1s was curve-fitted into three peaks, attributed to Na 2 O, NaOH, and NaNO 3 /NaNO 2 (Figure A), whereas a doublet assigned to Ca­(NO 3 ) 2 and BaCl 2 was clearly evident for Pd–Ca/SiO 2 and Pd–Ba/SiO 2 , respectively (Figure B and C). Here, the largest content was the basic compound corresponding to the basic precursor instead of the basic metal, despite the catalyst being reduced under a H 2 gas flow.…”

SrTiO3–TiO2 Heterostructured Nanotube Arrays for Ultrafast Ethanol Sensing

“…They show the bonding of Sr atoms in the SrTiO 3 perovskite structure. The Sr 3d 5 peaks are deconvoluted into four peaks, such as Sr-0 3d 5/2 (133.9 eV), Sr–O 3d 5/2 (134.4 eV), Sr-0 3d 3/2 (135.5 eV), and Sr-O 3d 3/2 (136.3 eV), which demonstrate the existence of perovskite and nonperovskite bonding in SrTiO 3 . , The intensity and area of nonperovskite bonding (Sr–OH, Sr–Sr, and Sr–O) of SrTiO 3 were the highest in S1 and minimum in the S3 sample, as shown in Figure b. The O 1s spectra were deconvoluted into three peaks related to the lattice oxygen (O L ), oxygen vacancies (O V ), and surface-chemisorbed oxygen (O C ) at 530.3, 531.7, and 533 eV, respectively, as shown in Figure c.…”

Characteristic Making of Ba0.4Sr0.6TiO3 Thin Film Nanoparticles

“…When a BST thin film is exposed to an electric field, it is generally assumed that there is a higher electric field density at the crest of a sharp valley than on a smoother surface. Therefore, grain growth can have a negative effect and lead to an increase in leakage currents [27].…”