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 discusse

Microstructural evolution of dense and porous pyroelectric Pb1−xCaxTiO3 thin films

Pb1−xCaxTiO3 thin films with x = 0−0.3 for pyroelectric applications were deposited on platinized silicon wafers by chemical solution processing. Ca-substitution for Pb in PbTiO3 results in a reduced c/a ratio of the unit cell, which, in turn, leads to better pyroelectric properties. Control of nucleation and growth during rapid thermal annealing to 650 °C allowed the formation of either highly porous or dense (111) oriented films. The inclusion of pores creates a matrix-void composite with the low permittivity desired for pyroelectric applications, resulting in a high figure of merit. The growth mechanisms for the microstructural evolution of both dense and porous films were analyzed by x-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Rutherford backscattering spectrometry and allowed establishment of microstructure/property relationship

Buffer electrodes for deposition of lead zirconium titanate films on metallic substrates

Piezoelectric thin films of PbZrxTi1-xO3 (PZT) on membranes are the subject of keen interest for the fabrication of micro-sensors and actuators. Piezoelectric activity of the PZT on Si-based membranes has been shown, and a micromotor has been demonstrated. Standard substrates are based on Si due to the good barrier properties of SiO2 and Si3N4 layers, which protect the Si against further oxidation. For some applications, however, such structures are not appropriate. For instance, thin metallic sheets, which are more robust and do not need micromachining, should be better substrates for actuator and motor applications. Direct deposition of PZT on common metals or Si is not possible. Metals degrade readily during the high temperatures and oxidising conditions needed to deposit PZT. Additionally, they can interdiffuse with the PZT and alter its properties. Hence, suitable barriers are needed, which can also work as bottom electrodes for the PZT. In this work, we have characerised a functioning metal-barrier-PZT structure by transmission electron microscopy. The extent of metal, oxygen and lead diffusion was assessed by nanoprobe measurments. A slight, acceptable metal diffusion into the PZT layer has been found, as well as some oxidation at the metal-barrier interfac

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). (C) 1999 Elsevier Science S.A. All rights reserved

In-situ sputter deposition of PT and PZT films on platinum and RuO2 electrodes

The in-situ growth of PbZrxTi1-xO3 (PZT) and PbTiO3 (PT) thin films by reactive sputter deposition has been investigated for applications with silicon substrates. In-situ deposition from three simultaneously operating magnetron sources was applied. At the selected growth temperature range (550-600 degrees C), self-stabilisation of lead composition by a lar ge desorption rate of Pb on stoichiometric PZT surfaces has been observed. Interlayer mixing was found to be limited to a few monolayers. Both Pt and RuO2 on Si-SiO2 wafers were used as top and bottom electrodes. The type of bottom electrode, together with the lead flux and the presence of a bottom PT layer to help nucleate the growth of PZT, was found to have a marked influence on the crystallisation behaviour of the PZT films. Dielectric characterisation has been performed on the films, and the dependence on the deposition parameters is discussed

Chemical analysis of lead zirconium titanium oxide films

Lead zirconium titanium oxide (PZT) thin films are used for their ferroelectric and piezoelectric properties. The composition of the PZT is very important for these properties, and may also be influenced by inter- diffusion with the bottom electrode, on which the PZT film has been grown at rather elevated temperature (550°C-600°C). The bottom electrode is essentially made of RuO2 deposited on a chromium adhesion layer which also helps to block oxygen diffusion. A part of the multi-layer device is shown in Figure 1. Since now no comprehensive study concerning rnicroanalysis of the device have been made, the composition of the films as well as the other layers are not precisely known. It is therefore not possible to relate the composition to the functional properties of the device and to optimize the parameters of deposition. It was the aim of this work to study the composition of the Pb(Zr,Ti)O3 layer, and the bottom electrode by mean of energy dispersive X-ray analysis (EDX) and energy electron loss spectroscopy (EELS). The experiments were performed with the Hitachi HF 2000 equipped with a field emission gun located at the EPFL

Conducting barriers for direct contact of PZT thin films on reactive substrates

Several bottom electrode systems for ferroelectric thin film deposition onto reactive substrates or reactive metal films have been investigated with respect to chemical barrier properties and contact resistivity. Such electrode systems should not deteriorate by oxidation, and should prevent oxygen diffusion into the underlying base metal. First, the protective performance of Pt, Ru, RuO2/Ru, and Cr has been evaluated on reactive substances such as W, Zr, Mo, and TiN; On most materials, a reactive and passivating metal such as Cr offers protection up to a higher temperature than noble metals. This is explained by preferential oxidation. On Cr, a RuO2 electrode allowed oxidation resistance to more than 800 degrees C without any Cr diffusion: the RuO2 serves both as an electrode and as a barrier to Cr. In order to reduce the contact resistance due to the formation of a Cr2O3 film at the RuO2/Cr interface, a Ru interlayer was inserted, giving an RuO2/Ru/Cr. This combination allowed maintaining a low contact resistance up to 700 degrees C. (C) 1999 The Electrochemical Society. S0013-4651(98)12-012-8. All rights reserved

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

The incorporation of up to 40 % lead excess into the perovskite lattice of Pb(Zr,Ti)O-3 (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

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 zir conium 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 degrees 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. (C) 1996 American Institute of Physics