R. Pascual

Crystallization of sputtered lead zirconate titanate films by rapid thermal processing

A rapid thermal annealing (RTA) technique has been employed to process lead zirconate titanate (PZT) films prepared by reactive magnetron sputtering. The films were fabricated by dc sputtering a multielement metal target in an oxygen ambient at a substrate temperature of 200 °C. A subsequent postdeposition RTA at 600 °C for 5 s crystallizes the films into a perovskite‐type structure through various intermediate phases. Due to the short postdeposition processing times inherent in the RTA method, the initial nature of the as‐grown films has a critical influence on the crystallization kinetics. The reaction sequence in the formation of perovskite PZT from the films deposited at low substrate temperatures by the sputtering technique has been evaluated, and various key factors influencing the crystallization of PZT have been identified. As‐grown films are constituted of polycrystalline orthorhombic lead oxide in an amorphous matrix of titania and zirconia. During annealing lead oxide transforms into a cubic ph...

Lead zirconate titanate films by rapid thermal processing

Lead zirconate titanate films have been fabricated by a dc sputtering technique with a post deposition rapid thermal annealing treatment at 650 °C for 10 s. The films exhibited good structural, dielectric, and ferroelectric properties compared to conventional furnace‐annealed films. The measured dielectric constant and loss tangent at 1 kHz were 900 and 0.04 and the remanent polarization and coercive field values were 10 μC/cm2 and 23 kV/cm, respectively. No significant fatigue in polarization was observed in the films up to 1010 cycles of bipolar stress. The films were optically transparent and showed a linear electro‐optic (EO) effect after poling with an EO coefficient of 1.5×10 −11 m/V.

Interdiffusion and strain relaxation in (SimGen)p superlattices

We report an x‐ray diffraction study of interdiffusion and strain relaxation in (SimGen)p short‐period superlattices. An interdiffusion coefficient Dλ was determined by monitoring, as a function of time, the decay upon annealing of the first order 000 satellite peak arising from the compositional modulation of the superlattice. Strain relaxation was obtained from the shift of the 400 superlattice peak on annealing. In the early stage of annealing the low angle satellite exhibited a rapid nonexponential decay after which a slower exponential decay was observed indicating a larger initial interdiffusion coefficient. This enhancement was correlated with the presence of strain and it disappeared upon relaxation. Diffusion was faster in structures alternating thin Si and thick Ge layers suggesting that migration of Si into Ge is the dominant diffusion process.

Rapid thermal processing of zirconia thin films produced by the sol-gel method

The kinetics of the amorphous‐to‐tetragonal transformation has been studied in sol‐gel‐derived thin films of zirconia deposited on alumina substrates. A rapid‐thermal‐annealing system was used which allowed good control of processing parameters such as temperature and heating rates. The effect of these two parameters on the transformation kinetics was studied and the experimental results were analyzed in terms of conventional nucleation and growth models. The use of two‐step thermal processing cycles shows potential for the modification of the microstructural features of crystallized films and for a reduction in processing times.

Simulation of the crystallization of thin films by rapid thermal processing

A computer simulation has been performed of phase transformations taking place in thin films under various time–temperature regimes. The conditions used resemble those encountered in the rapid thermal processing of thin films. The effect of heating rate and final temperature have been studied in detail. It is observed that the two parameters can strongly influence the grain size and the grain size distribution within the films. The feasibility of using multiple step rapid thermal processing to optimize thin film microstructure is demonstrated.

Ferroelectric lead niobate films by pulsed thermal processing

Ferroelectric lead niobate (PbNb2O6) exists in an orthorhombic phase at room temperature. The fabrication of lead niobate in this ferroelectric form has often been reported to be difficult due to the stabilization of nonferroelectric phases during processing. In this letter, the stabilization of the orthorhombic phase in magnetron sputtered lead niobate films using ‘‘pulsed thermal processing’’ is reported, and various processing factors which influence the destabilization of this phase are discussed. The room‐temperature dielectric constant and loss tangent of the resulting films at 1 kHz were 320 and 0.4, respectively. Polarization versus electric‐field hysteresis loops showed no saturation, with a remanent polarization of 15 μC/cm2 and a coercive field of 500 kV/cm. The films were highly resistive with a dc conductivity of 1−10 Ω−1 cm−1 at 300 K.

Cosio 2 Formation on Strained Ge x Si 1−x Layers BY Co/Ge x Si 1−x Thermal Reaction

The formation of CoSi 2 on Ge .17 Si .83 layers by Co/Ge .17 Si .83 thermal reaction nas been studied with a variety of analytical techniques. Co films deposited on strained Ge .17 Si .83 layers were annealed at 600°C for 0–240 min. Following 240 rain annealing, the reacted surface layer was composed of CoSi, CoSi 2 and Ge x Si 1-x precipitates (the latter probably rich in Ge) as identified with transmission electron microscopy, x-ray diffraction and/or Raman spectroscopy. Lateral phase non-uniformity was evident with both transmission and scanning electron microscopy. For samples annealed with and without an evaporated Co film, enhanced relaxation of the underlying Ge .17 Si .83 layer was apparent in the former.

Fabrication of modified lead iron niobate films

The fabrication of new ferroelectric modified lead iron niobate films having an approximate composition Pb[(Fe0.7Cr0.2Ni0.1)0.5Nb0.5]O3 is reported. A magnetron sputtering technique was used for the deposition of the films and a post‐deposition annealing at 800 °C for 5 s in a rapid thermal processing furnace crystallizes the films principally into a perovskite‐type structure. Ferroelectricity in these films was confirmed by the presence of hysteresis loops, with a remanent polarization of 15 μC/cm2, and coercive field of 100 kV/cm. The room‐temperature dielectric constant measured at 1 kHz was 640 and the dissipation factor was 0.1.