Laurent Sagalowicz

Texture control of PbTiO3 and Pb(Zr,Ti)O3 thin films with TiO2 seeding

The nature and the role of 1 to 5 nm thick TiO2 seed layers for the growth of textured PbTiO3 and Pb(Zr, Ti)O-3 thin films on textured Pt(111) thin film substrates have been studied. Under otherwise identical in situ sputter deposition process conditions, the PbTiO3 texture could be turned from (100) to (111) orientation by adding the seed layer. This is demonstrated by patterning the TiO2 film. Auger electron spectroscopy and x-ray photoemission spectroscopy showed that the seed layer was a continuous TiO2 film. X-ray photoelectron diffraction measurements revealed epitaxial ordering in the seed layer. As there is no azimutal order among the Pt grains, the reduced information of azimutally averaged polar cuts is obtained. These give strong evidence for a strained rutile (110) structure. Various deposition experiments indicated that the TiO2 is effective only when it is ordered before the PbTiO3 nucleation starts. The epitaxial relationship between PbTiO3(111) and Pt(111) is thus mediated by the intermediate, epitaxial TiO2 film, which is dissolved of transformed to PbTiO3 afterwards. The observed growth behavior is discussed in terms of surface and interface energies

Stabilized platinum electrodes for ferroelectric film deposition using Ti, Ta and Zr adhesion layers

Pt-based metallizations using different adhesion layers (Ti. Zr and Ta) were studied for use as electrodes for Ferroelectric thin films on oxidized silicon substrates. Different ways of oxidizing the adhesion layers prior to ferroelectric film growth are compared. with regard to obtaining stable. adherent Pt films of well-defined (111) orientation, while avoiding lead diffusion through the electrode. Upon in-situ deposition of PbTiO3 nt high excess lead flux. lead diffusion through the Pt film was found to depend strongly on the adhesion layer and the stabilization treatment. Pre-oxidation reduces leed diffusion during the later processing Ti diffuses through the electrode upon oxidation. whereas Ta and Zr stay in piece, in analogy to the diffusivities in the corresponding oxides. A novel oxidation treatment was developed to produce stable. adherent metallizations with controlled orientation and good barrier properties against lead diffusion.

PLANAR DEFECTS IN ZNO THIN FILMS DEPOSITED ON OPTICAL FIBERS AND FLAT SUBSTRATES

The microstructure and the defects of ZnO coatings deposited at room temperature by sputtering onto fibers and flat substrates were characterized using transmission electron microscopy (TEM), scanning electron microscopy, and x-ray diffraction (XRD). XRD shows that the films have a [0001] preferred orientation and a large angular width of the 0002 reflection. According to TEM observations, the film microstructure consists of columnar grains which contain large concentrations of basal planar defects and dislocations. High-resolution transmission electron microscopy analysis and the associated image simulation are in full agreement with the presence of single (type I) and double (type II) stacking faults. The relation between the observed defects and the 0002 peak broadening is discussed.

Relaxor behavior and electromechanical properties of Pb(Mg1/3Nb2/3)O3 thin films

Pb(Mg1/3Nb2/3)O-3 (PMN) alkoxide precursor solutions were synthesized and used to prepare thin films by spin coating on TiO2/Pt/TiO2/SiO2/Si substrates. Many parameters like the use of homogeneous and stable precursor solutions and appropriate processing were used to greatly reduce the presence of the nonferroelectric pyrochlore phase. Transmission electron microscopy investigations, dielectric, electrostrictive, and direct current field induced piezoelectric measurements were carried out and have shown that PMN thin films exhibit a relaxor-like behavior

Pb(Zr,Ti)O3 thin films on zirconium membranes for micromechanical applications

An efficient, electrically conductive, chemical barrier for the integration of piezoelectric Pb(Zr,Ti)O3 (PZT) films on reactive metal substrates has been developed, opening new possibilities for PZT integration on micromechanical and semiconductor devices. Very reactive zirconium films have been taken in order to test the quality of the specially designed RuO2/Cr buffer under the condition of in situ sputter deposition of PZT at 600 °C. The PZT/RuO2 interface was found to be free of intermediate phases. A PZT activated metallic micromechanical element was demonstrated with a thin film Zr membrane.

Microstructure, structural defects, and piezoelectric response of Bi4Ti3O12 modified by Bi3TiNbO9

Microstructure, structural defects, and piezoelectric response of bismuth titanate (Bi4Ti3O12)1−x and bismuth titanium niobate (Bi3TiNbO9)x solid solution with x=0.05 and 0.2 were investigated. Depending on x and on the sintering temperature different microstructures and piezoelectric responses were observed. For a low content in Bi3TiNbO9 (x=0.05) and a high sintering temperature (1130 °C), a coarse grain size is present, the number of structural defects within the grain is small, and there is a strong dependence of d33 on the ac pressure. For higher Bi3TiNbO9 (x=0.2) content or for lower sintering temperature (1080 °C) and x=0.05, the grain size is finer and a large number of structural defects is present within the grains. In particular, for x=0.2, high resolution transmission electron microscopy shows a high concentration of intergrowth defects which consist of Bi3TiNbO9 layers inserted in the Bi4Ti3O12 matrix in a more or less random way. In these samples, there is a very small dependence of d33 on t...

Wafer fused p-InP/p-GaAs heterojunctions

This article reports on the fabrication and characterization of wafer fused heterojunctions between p-InP and p-GaAs. Secondary ion mass spectroscopy was used to characterize doping profiles across the interface as well as the interface contamination with oxygen or carbon. The crystalline quality of the fused material was characterized using cross section and plan-view transmission electron microscopy. The electrical properties of the fused interface were studied as a function of various doping elements such as Be and Zn in InP or Zn and C in GaAs as well as for different acceptor concentrations in GaAs. Finally, the electrical characteristics were analyzed using a numerical model that includes thermionic emission and tunneling across the heterobarrier.

ALUMINUM NITRIDE THIN FILMS FOR HIGH FREQUENCY APPLICATIONS

Abstract A piezoelectric thin film sandwiched between two conductors is the basic structure for high frequency bulk acoustic wave devices. For that purpose, AIN thin films deposited by DC reactive sputtering on various electrode materials were investigated. Highly c-axis oriented thin films as thick as 2.5 μm were grown on various substrates and analyzed. Intrinsic stress values ranging from strong compression to high tension were observed and piezoelectric d33, f coefficients up to 3.9 pm/V were measured. The first fabricated acoustic resonators showed a pronounced resonance peak centered at 2 GHz with a very high Q factor.

Excess lead in the perovskite lattice of PZT thin films made by in-situ reactive sputtering

Abstract The incorporation of up to 40 % lead excess into the perovskite lattice of Pb(Zr,Ti)O3 (PZT) has been investigated. Three independent chemical composition analysis methods confirmed the correct determination of the lead excess, present as Pb2O3. High resolution TEM excludes any second phases and restricts the occurrence of lead excess to the perovskite lattice, suggesting a lead oxide perovskite of the form Pb2+Pb4+O3 with a 4-valent ion on the B-site. PZT containing such lead excess is thus a solid solution of PbZrO3, PbTiO3 and PbPbO3. The measured volume increase of the lattice due to a larger average B-ion matches very well with the calculated behavior based on standard ion radii and the B-ion radius dependence of the unit cell dimensions of PZT crystals. Structure factors as determined from Synchrotron X-ray diffraction are much better compatible with the B-site lead model than with the standard PZT ion lattice.

Growth of (111)-oriented PZT on RuO2(100)/Pt(111) electrodes by in-situ sputtering

Growth of (111)-oriented Pb(Zr,Ti)O-3 has been achieved on a RuO2 film which was (100) textured. This texture could be obtained by using a (111)-textured Pt film as a template. The whole layer stack was grown on an amorphous SiO2 layer, that is a thermal oxide of a silicon wafer. A good (111)-orientation of the Pt template layer is thus the starting point of oriented growth. XRD and TEM studies have been carried out to find the orientation relationship between Pt(111), RuO2(100) and PZT(111)