T. P. Alexander

Piezoelectric properties of sol-gel derived ZnO thin films

Abstract ZnO films exhibit a wide range of interesting material properties. Recently, ZnO films have been studied for sensing applications based on their piezoelectric and pyroelectric behaviors. Reported literature values of piezoelectric and pyroelectric coefficients of ZnO films are in the range of 11–12 pm/V and 1.0–1.4 nC/cm2-K Respectively. In this study, the piezoelectric properties of sol-gel derived ZnO thin films were measured. These films were prepared on platinized Si wafers and fired to temperatures ranging from 550°C to 750°C. Multiple spincoating was performed with an intermediate firing at 400°C between coatings to obtain films up to 6000 A thick. Top Pt electrodes were sputtered to form monolithic capacitors. XRD indicated that the films consisted of crystalline wurtzite at firing temperature as low as 400°C, and that the c-axis orientation increased with increasing firing temperature. A dielectric constant of 10 was obtained, while piezoelectric characterization indicated d33 values as l...

Dielectric and ferroelectric properties of sol-gel derived BiFeO3 films

Abstract There has been a lot of interest on ferroelectric (FE) films especially for non-volatile memories and ultra high density DRAM applications. These films such as PZT and (Ba,Sr)TiO3 are crystalline perovskite. BiFeO3 is an interesting antiferromagnetic material which belongs to the perovskite crystal structure. Sol-gel derived BiFeO3 films have been prepared on platinized Si substrates and their electrical and magnetic properties were obtained. XRD indicated that the films were crystalline perovskite when fired at 400°C and above. Dielectric constant of up to 100 was also obtained; however, the films tend to exhibit low resistivities especially in films fired to higher temperatures. The hysteretic loops obtained indicated a remanent polarization and coercive field of 5.5 μC/cm2 and 180 kV/cm respectively.

Dielectric properties of sol-gel derived ZnO thin films

Sol-gel derived ZnO thin films were prepared on platinized Si wafers and fired to temperatures ranging from 550C to 700C. Multiple spincoating was performed with an intermediate firing at 400C between coatings to obtain films up to 6000 A thick. Top Pt electrodes were sputtered to form monolithic capacitors. Dielectric characterization indicated dielectric constants as large as 24, twice the highest value reported previously. The leakage currents decreased with increasing firing temperature. XRD indicated that the films consisted of crystalline wurtzite films at firing temperatures as low as 400C and that the c-axis orientation increased with increasing firing temperature. Piezoelectric characterization indicated d/sub 33/ values as large as 17 pm/V, which is larger than any previously reported value for ZnO films.

Pyroelectric properties of various sol-gel derived PLZT thin films

Abstract Pyroelectric IR imaging, especially based on monolithic technology integrated with semiconductors, is receiving increased attention for the next generation of room temperature uncooled IR cameras. In the present work, sol-gel derived PZT, including PbTiO3, PLT 28, PLZT 9/65/35, and PZT 53/47, films were prepared on platinized Si substrates. Their pyroelectric properties were determined, and are discussed with respect to film microstructures, processing, and chemistries. Pyroelectric coefficients as large as 7.7×10−8 C/cm2-K, were obtained for PZT 53/47 films.

Dielectric characterization of sol-gel derived sn doped ZrTiO4 thin films

Abstract High-quality thin film dielectric materials are critical for the next generation of integrated microwave devices. Much recent attention has been focused on ZrTiO4 and Sn doped ZrTiO4 films for applications in these devices. Sol-gel derived Sn doped ZrTiO4 thin films were prepared on Si and platinized Si wafers and fired to temperatures ranging from 550°C to 700°C. Multiple spincoating was performed to obtain films up to 0.5μm thick, with intermediate firings at 400°C between coatings. The ZrTiO4 films exhibited a dielectric constant of about 32 with low leakage currents of 2×10−9 A. These films were crystalline when fired to 700°C or above. The addition of Sn lowered the dielectric constant but also improved the dissipation factor.

Optical waveguide losses of PZT thin films with various Zr/Ti stoichiometries

Abstract Sol-gel derived PZT thin films were spincoated on Corning 7059 glass substrates and fired to temperatures ranging from 500C to 600C for 30 min. The PZT compositions consisted of PZT x/y where x/y = 0/100, 20/80, 35/65, 53/47, 65/35, 80/20 and 100/0. Only single coated films were used since multiple coatings led to higher losses. XRD was used to characterize the phase assembly of the fired films and indicated that films with higher Zr contents contained proportionally more pyrochlore; while films with higher Ti contents have higher perovskite contents. UV-VIS spectroscopy was utilized to obtain the transmission and optical properties(refractive index and extinction coefficient) via the envelope method. Waveguide losses were measured using prism coupling at the 633 nm HeNe laser wavelength. The waveguide losses in the PZT films ranged from 1.3 to 2.0 dB/cm. The surface texture or morphology of the films significantly affected the optical losses as striated films gave losses of 2.7 to 3.3 dB/cm. The...

Dielectric properties of organic-inorganic hybrids: PDMS-based systems

Organic-inorganic hybrids, with tailorable properties via control of their chemistries, offer great potential for many optical, electrical and mechanical applications. PDMS-based materials have been fabricated, having low optical losses of < 0.15 dB/cm but the dielectric properties of these hybrids have rarely been explored or reported. In the present study, the dielectric properties of PDMS:SiO{sub 2}:TiO{sub 2} films are explored as a function of composition and curing temperature using an impedance analyzer. Dielectric spectroscopy was also performed to investigate the dielectric relaxation and dispersion behaviors. Results indicate that {var_epsilon}{sub r} at 1 MHz ranges from 3 to 5. Residual hydroxyl and alkoxy species in the films contribute to the overall polarizabilities especially at low frequencies (< 100 kHz).

Sol-gel derived RuO2-PZT-RuO2 ferroelectric capacitors

Abstract There has been a lot of attention on novel oxide electrodes, e. g., RuO2, LaSrCoO3, YBCO, for contacts to ferroelectric capacitors. Such devices were reported to yield fatigue-free behaviors which are crucial for implementation in ferroelectric memory technology. Typical Pt/PZT/Pt capacitors fatigue as fast as after 104 cycles. In this study, sol-gel techniques are used to prepare both conducting RuO2 and PZT 53/47 thin films. Conductivity of the RuO2 films ranged was measured as 5 × 10−4 Ω-cm. Oxidized Si and platinized Si wafers were used as the substrates; Si/ SiO2/RuO2/PZT/RuO2 and Si/SiO2/Pt/RuO2/PZT/RuO2/Pt and Si/SiO2/Pt/PZT/Pt capacitors were obtained. The effect of RuO2 electrode on microstructure, ferroelectric properties and leakage characteristics will be discussed.

Effect of PbO content on the properties of sol-gel derived PZT films

Abstract The PbO content of lead zirconate titanate(PZT) films has been widely recognized as affecting not only the phase assembly and microstructure but also the dielectric and ferroelectric properties. Excess PbO has often been incorporated in PbO-based films to optimize the film properties by compensating for PbO loss either through volatilization or diffusion into the substrates. Sol-gel derived PZT 53/47 films with various PbO contents, i.e., Pbx Zr0.53 Ti0.47O3 (x = 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.05, 1.10, 1.25 and 1.5) were prepared on platinized Si wafers and fired to temperatures ranging from 550C to 700C under oxygen. Multiple spincoating with an intermediate firing of 400C between coatings was performed to obtain films up to 0.5μm thick. After the final crystallization firing, top Pt electrodes were sputtered to form monolithic capacitors. These capacitors were subjected to dielectric and ferroelectric characterization using an impedance analyzer and a Radiant Technologies RT66A Ferroelectric ...

Optical properties of Au and Pt-doped PLT 28 films

Metal colloid-doped oxides yield potentially interesting non-linear optical properties especially third order non-linearity which is expected to be enhanced in oxide matrices with high values of dielectric constant or refractive index. La-doped PbTiO/sub 3/ (i.e. PLT 28) films, incorporated with 0.05 to 2 mole % Au and Pt, were obtained using sol-gel deposition techniques. The films were spincoated on Corning 7059 glass substrates and fired at 400/spl deg/C-600/spl deg/C. The films were then subjected to optical characterization, namely transmission and absorbance spectroscopy. PLT films doped with Au appeared bluish which turned deeper with higher Au concentration or higher firing temperatures. Additionally, the absorbance peak (near 650 nm) shifted to shorter wavelengths with higher metal colloid contents but shifted to longer wavelengths at higher firing temperatures. The waveguiding loss in the Pt-doped films ranged from 2-3 dB/cm.