Changhong Yang

Dielectric and ferroelectric properties of (Na0.8K0.2)0.5Bi0.5TiO3 thin films prepared by metalorganic solution deposition

(Na0.8K0.2)0.5Bi0.5TiO3 thin films have been prepared on Pt∕TiO2∕SiO2∕Si and p-type Si substrates using a metalorganic solution deposition method. The films annealed at 700 °C crystallize well and present perovskite phase. The films exhibit a well-defined hysteresis loop at an applied voltage of 4 V, with a remanent polarization of 4.7μC∕cm2 and a coercive field of 38kV∕cm. The films also show fatigue-free response up to 1.5×1010 switching cycles. The relaxor behavior of the films is confirmed by the frequency-dependence of capacitance-temperature relation. The capacitance-voltage curves show that the films are polarization-type switching and the memory window is about 2.5 V at ±4V applied dc bias voltages. The changes of dielectric constant and dissipation factor with frequency are also investigated briefly.

Ferroelectric properties of 0.87Na0.5Bi0.5TiO3–0.13PbTiO3 thin film prepared by metalorganic solution deposition

0.87Na0.5Bi0.5TiO3–0.13PbTiO3 thin film has been prepared by metalorganic solution deposition on Pt∕TiO2∕SiO2∕Si and SiO2∕Si substrates. The film shows good switching endurance under bipolar stressing up to 3×1010 switching cycles with a remanent polarization 2Pr of about 3μC∕cm2 and a coercive field Ec of approximate 56kV∕cm. The high frequency C–V curve is indicative of good film/substrate interface characteristics. The film could be used in storage capacitors, CMOS integrated devices, and insulation gate field-effect transistors.

PREPARATION AND CHARACTERISTICS OF Sm-DOPED Bi2Ti2O7 THIN FILMS

Crack-free Sm-doped Bi2Ti2O7 (Sm:Bi2Ti2O7) thin films with a strong (111) orientation have been prepared on p-Si(111) by chemical solution deposition (CSD). The structural properties and crystallizations were studied by X-ray diffraction. The surface morphology and quality were examined using atomic force microscopy (AFM). The dielectric constant and loss factor at different frequencies were also evaluated at room temperature. Their insulation was studied, too. The films exhibit better insulating property than does the pure Bi2Ti2O7.

STRUCTURE AND CHARACTERIZATION OF ZnO THIN FILM PREPARED BY SPIN COATING

ZnO thin films were prepared on silica glass substrates by a sol–gel spin coating technique. The thickness of the films was about 200 nm. At 370 nm in the ultraviolet region, there is a sharp absorption edge that corresponds to the ZnO intrinsic band gap of 3.30 eV. The structural properties of the films were examined by X-ray diffraction, which demonstrates that the ZnO films were c-axis oriented. From the infrared spectrum, we conclude that ZnO was deposited on silica glass substrates through a high temperature process at 700°C.

GROWTH AND ELECTRICAL PROPERTIES OF (Bi, Nd)4Ti3O12 THIN FILMS

Neodymium-doped Bi4Ti3O12 (Bi3.15Nd0.85Ti3O12) thin films have been synthesized by metalorganic solution decomposition and deposited on SiO2/p-Si(111) substrate by spin coating. The structural characteristic and crystallization of the films were examined by X-ray diffraction and atomic force microscope. The insulating property, dielectric constant and dissipation loss were found to be dependent on the annealing temperature. Nonhysteretic C–V curves at various frequencies were also collected. The films in the ON and OFF states were relatively stable.

PREPARATION AND ELECTRICAL PROPERTIES OF LEAD-FREE Bi0.5(Na0.4K0.6)0.5TiO3 THIN FILMS

Lead-free Bi0.5(Na0.4K0.6)0.5TiO3 films have been synthesized by a chemical solution deposition method and deposited on p-Si(111) substrate by spin coating. Powder of the precursor solution heated at 650°C was studied by infrared scattering spectroscopy. The structural characteristics and crystallization of the films were examined by X-ray diffraction. The surface morphology and quality were studied using atomic force microscopy. The films exhibit good insulating properties and resistance to breakdown. The clockwise hysteresis curve is referred to as polarization type switching and the memory window is about 1.5 V.