Effect of oxygen gas and annealing treatment for magnetically enhanced reactive ion etched (Ba{sub 0.65},Sr{sub 0.35})TiO{sub 3} thin films
- School of Physics and Electronic Technology, Hubei University, Wuhan 430062 (China) and Key Laboratory of Ferroelectric and Piezoelectric Materials and Devices of Hubei Province, Hubei University, Wuhan 430062 (China)
Sol-gel-derived (Ba{sub 0.65},Sr{sub 0.35})TiO{sub 3} (BST) thin films were etched in CF{sub 4}/Ar and CF{sub 4}/Ar/O{sub 2} plasmas using magnetically enhanced reactive ion etching technology. Experimental results show that adding appropriate O{sub 2} to CF{sub 4}/Ar can better the etching effects of BST films for the increase of etching rate and decrease of etched residues. The maximum etching rate is 8.47 nm/min when CF{sub 4}/Ar/O{sub 2} gas-mixing ratio is equal to 9/36/5. X-ray photoelectron spectroscopy (XPS) data confirm accumulation of reaction products on the etched surface due to low volatility of reaction products such as Ba and Sr fluorides, and these residues could be removed by annealing treatment. The exact peak positions and chemical shifts of the interested elements were deduced by fitting XPS narrow-scan spectra with symmetrical Gaussian-Lorentzian product function for Ba 3d, Sr 3d, and O 1s peaks, meanwhile asymmetrical Gaussian-Lorentzian sum function was used to fit Ti 2p doublet to adjust the multiple splitting and/or shake-up process of transition-metal Ti cations. Compared to the unetched counterparts, the etched Ba 3d{sub 5/2}, Ba 3d{sub 3/2}, Sr 3d{sub 5/2}, Sr 3d{sub 3/2}, Ti 2p{sub 3/2}, Ti 2p{sub 1/2}, and O 1s peaks shift towards higher binding energy regions by amounts of 1.31, 1.30, 0.60, 0.79, 0.09, 0.46, and 0.50 eV, respectively. While the etched Ti 2p{sub 3/2} and Ti 2p{sub 1/2} peaks have small chemical shifts for two reasons. One is that Ti fluoride (TiF{sub z}) is mostly removed from the etched surface because of its higher volatility in the process of thermal desorption. The other is that there is a shift compensation between TiF{sub z} and the etched BST matrix in which Ti{sup 4+} cations are partially reduced to form Ti{sup x+} (0<x<4) cations in the presence of adequate oxygen vacancies. The simulated formula of each BST surface is obtained to be (Ba{sub 0.65},Sr{sub 0.35})Ti{sub 0.97}O{sub 2.86}, (Ba{sub 0.70},Sr{sub 0.30})Ti{sub 0.24}O{sub 1.39}, and (Ba{sub 0.68},Sr{sub 0.32})Ti{sub 0.95}O{sub 2.74}, and then the average valence of Ti cations is estimated to be +3.84, +3.25, and +3.66 with respect to the electroneutrality principle, respectively. It is inferred that electrical properties of the etched BST film may be partially recovered by postannealed after etched.
- OSTI ID:
- 20884971
- Journal Information:
- Journal of Applied Physics, Vol. 101, Issue 1; Other Information: DOI: 10.1063/1.2402100; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ANNEALING
ARGON
BARIUM COMPOUNDS
BARIUM FLUORIDES
BINDING ENERGY
CARBON TETRAFLUORIDE
DESORPTION
ELECTRICAL PROPERTIES
ETCHING
MIXING RATIO
OXYGEN
SOL-GEL PROCESS
STRONTIUM FLUORIDES
STRONTIUM TITANATES
THIN FILMS
TITANIUM FLUORIDES
TITANIUM IONS
VACANCIES
X-RAY PHOTOELECTRON SPECTROSCOPY