Polycrystalline RuO2 thin films were grown by metal-organic chemical vapor deposition (MOCVD) on both SiO2/Si(001) and Pt/Ti/SiO2/Si(001) substrates. Films having a controllable and reproducible structural texture and phase purity were synthesized by carefully controlling deposition parameters. Moderate growth temperatures (∼350 °C) and low growth rates (<30 Å/min) produced highly (110)-textured RuO2 films. Highly (101)-textured RuO2 films were favored at slightly lower temperatures (∼300 °C) and much higher growth rates (>30 Å/min). The most conductive RuO3 films had resistivities of 34 to 40 µΩ−cm at 25 °C, an average grain size of 65 ± 15 nm, and a surface roughness (rms) of 3 to 10 nm. Both single-phase Ru and mixed Ru/RuO2 phase material were also fabricated at low temperatures (<350 °C) by using lower oxygen flow concentrations (<10%).

For growth temperatures in the range of 275°C to 425°C, highly conductive RuO2 thin films with either (110)- or (101)-textured orientations have been grown by metal-organic chemical vapor deposition (MOCVD) on both SiO2/Si(001) and Pt/Ti/SiO2/Si(001) substrates. Both the growth temperature and growth rate were used to control the type and degree of orientational texture of the RuO2 films. In the upper part of this growth temperature range (∼ 350°C) and at a low growth rate (< 3.0 nm/min.), the RuO2 films favored a (110)-textured orientation. In contrast, at the lower part of this growth temperature range (∼ 300°C) and at a high growth rate (> 3.0 nm/min.), the RuO2 films favored a (101)-textured orientation. In contrast, higher growth temperatures (> 425°C) always produced randomly-oriented polycrystalline films. For either of these low-temperature growth processes, the films produced were crack-free, well-adhered to the substrates, and had smooth, specular surfaces. Atomic force microscopy showed that the films had a dense microstructure with an average grain size of 50–80 nm and a rms. surface roughness of ∼ 3–10 nm. Four-probe electrical transport measurements showed that the films were highly conductive with resistivities of 34–40 μΩ-cm (at 25°C).

Pb(Zr0.5Ti0.5)O-3/RuO2 thin film heterostructures were successfully grown on SiO2/Si(001) substrates using metal-organic chemical vapor deposition with a maximum processing temperature of 525 degrees C. To form the heterostructures, (110)-textured RuO2 electrode layers were first deposited on SiO2/Si(001) substrates at temperatures as low as 350 degrees C at a typical grow rate of similar to 40 Angstrom/min.. The resistivity of the RuO2 films was 30-40 mu Omega-cm. Plan-view transmission electron microscopy (TEM) and atomic force microscopy (AFM) showed that typical RuO2 films had a grain size of 800-1000 Angstrom with surface roughness of 3-25 nm, respectively. Perovskite phase Pb(Zr0.5Ti0.5)O-3 (PZT) was then deposited at 525 degrees C. The as-deposited films exhibited a dense, randomly-oriented crystal structure with a grain size of similar to 800-1000 Angstrom. Using capacitors defined with Ag top electrodes, the film showed a remanent polarization of 21.5 mu C/cm(2) and a coercive field of 39.0 kV/cm. The capacitors showed little fatigue up to similar to 10(10) cycles. The as-deposited films exhibited high resistivity (10(12)-10(13) Omega-cm at 100 kV/cm). The current versus voltage characteristics show that the films have typical dielectric breakdown strengths of similar to 60 V/mu m with a sub-breakdown leakage current density of 5 x 10(-5) A/cm(2).

The phase transition and dielectric behavior of ferroelectric multilayers have been discussed. The coherent interaction between ultra-thin layers can be significantly strong, resulting in a broad diffuse phase transition. The thicknesses of layers and their spatial distributions hold the keys of enhancing dielectric properties in a broad temperature range.

We report the fabrication and characterization of a low temperature (200°C-400°C) thin film gas sensor constructed from a MOCVD-grown yttria-stabilized zirconia (YSZ) layer sandwiched between two platinum thin film electrodes. A reproducible gas-sensing response is produced by applying a cyclic voltage which generates voltammograms with gas-specific current peaks and shapes. Growth conditions are optimized for preparing YSZ films having dense microstructures, low leakage currents, and maximum ion conductivities. In particular, the effect of growth temperature on film morphology and texture is discussed and related to the electrical and gas-sensing properties of the thin film sensor device.

We have used temperature programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) to study the thermal chemistry of B2O3 deposited onto a graphite monolayer on the Pt(111) surface. The reaction produces CO which desorbs in the temperature range of 1050–1200 K. We also detected significant desorption of B2O2 although only for a narrow range of initial B2O3 coverages. XPS spectra of the B(1s) region recorded after annealing the B2O3/C layer to various temperatures indicate that B2O3 is not reduced prior to desorption. It was found that an initial B/C coverage ratio of at least 23 is required to completely remove the carbon layer indicating that B2O3 is reduced by carbon at temperatures above 1050 K according to the reaction: B2O3 + 3C → 2B + 3CO. Evidence for further reaction of B with excess B2O3 is presented to account for desorption of B2O2.