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2 Aug 1999

Volume 75, Issue 5, pp. 597-739

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Can lead nonstoichiometry influence ferroelectric properties of Pb(Zr,Ti)O3 thin films?

S. Aggarwal, S. Madhukar, B. Nagaraj, I. G. Jenkins, R. Ramesh, L. Boyer, and J. T. Evans

Appl. Phys. Lett. 75, 716 (1999); http://dx.doi.org/10.1063/1.124492 (3 pages) | Cited 25 times

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In this letter, we report on the influence of lead content on thin-film ferroelectric properties of lead niobium zirconate titanate. These films were prepared by the sol-gel technique and deposited on (La,Sr)CoO3 electrodes. It was determined that 7% excess lead in the sol was required to obtain nominally stoichiometric films. Lead deficiency in the film results in lead vacancies and excess lead is accommodated by forming octahedral site vacancies. Further amounts of lead in the sol leads to second phase PbO, which then coexists with the perovskite phase. The charged vacancies are compensated by mobile holes, which can interact with domains during switching. Under applied field and short pulse widths, the films with larger number of holes exhibited poor switching. Significant polarization relaxation was measured for films with excess lead, which is attributed to interaction of ionic defects with domains. Our results indicate that lead excess leads to poor reliability properties,whereas lead deficiency suppresses the polarization of the capacitors. © 1999 American Institute of Physics.
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77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
61.66.Bi Elemental solids
61.66.Dk Alloys
77.55.-g Dielectric thin films
77.80.Dj Domain structure; hysteresis
61.72.J- Point defects and defect clusters
77.22.Ej Polarization and depolarization

Ferroelectricity of YMnO3 thin films prepared via solution

Hiroya Kitahata, Kiyoharu Tadanaga, Tsutomu Minami, Norifumi Fujimura, and Taichiro Ito

Appl. Phys. Lett. 75, 719 (1999); http://dx.doi.org/10.1063/1.124493 (3 pages) | Cited 33 times

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We have observed the ferroelectricity at room temperature in YMnO3 thin films prepared via solution. Precursor films of YMnO3 on Pt/sapphire or Y2O3/Si substrates were heat treated in vacuum or in air for controlling the crystallinity. X-ray diffraction measurements indicated that each film was a single phase of hexagonal YMnO3. While the film heat treated in air indicated an insufficient crystallinity, the film heat treated in vacuum showed a high crystallinity with a c-axis preferred orientation. The leakage current of the film heat treated in vacuum was at least three orders of magnitude lower than that heat treated in air. The ferroelectricity of the film heat treated in vacuum was confirmed in the capacitance–voltage measurement at room temperature due to its high crystallinity with the c-axis preferred orientation and the small leakage current. © 1999 American Institute of Physics.
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77.80.-e Ferroelectricity and antiferroelectricity
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates

Metal/ferroelectric/insulator/semiconductor structure of Pt/SrBi2Ta2O9/YMnO3/Si using YMnO3 as the buffer layer

Kyu-Jeong Choi, Woong-Chul Shin, Jung-Hwan Yang, and Soon-Gil Yoon

Appl. Phys. Lett. 75, 722 (1999); http://dx.doi.org/10.1063/1.124255 (3 pages) | Cited 25 times

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The ferroelectric SrBi2Ta2O9 (SBT) and YMnO3 buffer layers for the metal/ferroelectric/ insulator/semiconductor (MFIS) structure were deposited using pulsed-laser ablation and metalorganic chemical vapor deposition, respectively. Memory windows of the MFIS structure were in the range of 0.3–1.5 V when the gate voltage varied from 2 to 6 V. There were no reactions between ferroelectric SBT and Si in the MFIS structure annealed at 900 °C. The YMnO3 buffer layer plays an important role in alleviating the interdiffusion between elements of SBT and Si. The proposed MFIS structure of Pt/200 nm–SBT/25 nm–YMnO3/Si is attractive for nondestructive read-out ferroelectric random access memory applications. © 1999 American Institute of Physics.
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85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
73.40.Qv Metal-insulator-semiconductor structures (including semiconductor-to-insulator)
81.15.Fg Pulsed laser ablation deposition
81.15.Gh Chemical vapor deposition (including plasma-enhanced CVD, MOCVD, ALD, etc.)
61.72.Cc Kinetics of defect formation and annealing
85.30.Tv Field effect devices

Low-temperature anodic oxidation of silicon using a wave resonance plasma source

S. Uchikoga, D. F. Lai, J. Robertson, W. I. Milne, N. Hatzopoulos, R. A. Yankov, and M. Weiler

Appl. Phys. Lett. 75, 725 (1999); http://dx.doi.org/10.1063/1.124494 (3 pages) | Cited 3 times

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A rf wave resonance plasma (WARP) source has been used to plasma oxidize Si at temperatures below 100 °C. Oxidation under positive substrate bias in constant current mode gives an oxidation rate of 1–8 nm/min for current densities of 0.4–5.5 mA/cm2. This corresponds to an ionic (O−) current of about 10% of the total current, which is 2–5 times higher than previously reported, due to the high plasma density of 1012–1013 cm−3 achieved by the WARP source. The breakdown field of ∼10 MV/cm and the etch rate of 60 nm/min of the oxide are independent of the oxidation rate and similar to those of the thermal oxide. Results from capacitance–voltage measurements, Fourier transform infrared absorbance spectroscopy, null ellipsometry, and Rutherford backscattering spectroscopy suggest that the oxide grown at low rates (<2 nm/min) is very close to stoichiometric SiO2 while the oxide grown at high rates (>3 nm/min) is Si rich (35%–40% atomic Si). © 1999 American Institute of Physics.
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81.65.Mq Oxidation
81.05.Cy Elemental semiconductors
52.77.Bn Etching and cleaning
52.77.Dq Plasma-based ion implantation and deposition
78.30.Am Elemental semiconductors and insulators
78.66.Db Elemental semiconductors and insulators
82.45.-h Electrochemistry and electrophoresis
61.66.Bi Elemental solids
61.66.Dk Alloys
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