Lin-Tao Zhang

Silicon-Based PbTiO3/Pb(Zr, Ti)O3/PbTiO3 Sandwich Structure

A silicon-based PbTiO3/Pb(Zr0.53Ti0.47)O3/PbTiO3 (PT/PZT/PT) sandwich structure prepared by sol–gel method is proposed. The two PT layers in the structure are used as seeding layers to improve the crystallization of the PZT ferroelectric thin films. X-ray diffraction analysis (XRD) and Energy-dispersive X-ray spectroscopy (EDX) results show that the sandwiched PZT films are well crystallized at lower temperature. Compared with the ferroelectric structure with only one PT seeding layer, the electrical and ferroelectric properties of the PZT films in the sandwich structure are further improved. The maximum dielectric constant of about 900 is obtained at the coercive field 20 kV/cm, and the remnant polarization is 19 µC/cm2. The leakage current density is less than 5×10-9 A/cm2 as the applied voltage is below 200 kV/cm. The retained polarization does not reduce clearly after 8×109 read/write cycles.

A novel ferroelectric based microphone

A novel ferroelectric based microphone with lead zirconate titanate [Pb(Zr, Ti)O3, PZT] coated silicon cantilever has been proposed in this paper. The cantilever structure is composed of a Pt/PZT/Pt/Ti/SiO2/ Si3N4/SiO2/Si multilayer and is designed using a multimorph model. Optimum fabrication process of the PZT thin films and the cantilever has been developed. The acoustic outputs of the fabricated microphones have been measured with a standard microphone and a high sensitivity of 40 mV/Pa can be obtained. The frequency response of the microphone is very flat in the audio frequency range.

High Quality Ferroelectric Capacitor for FeRAM Applications

Lead zirconate titanate (PZT) based ferroelectric capacitor using lead titanate (PT) as seeding layers has been prepared on silicon wafer by an improved sol-gel method. The novel ferroelectric capacitor has high dielectric constant of about 1200, ultralow leakage current density of 0.1nA/cm 2 , high remanent polarization of 20 w C/cm 2 at coercive field of about 30kV/cm, and almost fatigue free properties. The capacitor structure can be valuable for FeRAM applications.

Fabrication of a Cantilever Structure for Piezoelectric Microphone

In this paper, a novel piezoelectric microphone based on a lead zirconate titanate [Pb(Zr, Ti)O3, PZT]-coated silicon cantilever is presented. The main structure of the cantilever is composed of the Pt/PZT/Pt/Ti/SiO2/Si3N4/SiO2/Si multilayer structure. An optimum fabrication process of the PZT thin films and the cantilever has been developed. The acoustic outputs of the fabricated microphones have been measured with a standard microphone and a high sensitivity of 40 mV/Pa can be obtained. The frequency response of the microphone is very flat in the audio frequency range.

Interface and Surface Characterization of Lead Zirconate Titanate Thin Films Grown by Sol–Gel Method

The ferroelectric Pb(Zr, Ti)O3 (PZT) thin films have been directly synthesized on silicon substrates by sol–gel method. X-ray diffraction (XRD) analysis reveals that besides the rhombohedral structure, the random oriented tetragonal perovskite PZT is formed with the lattice parameters of a=3.97 A and c=4.10 A. Energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) results indicate that the chemical composition of the PZT thin film is stoichiometric just as designed. High resolution electron microscopy (HREM) results show that amorphous SiOx (x=1–2) layer and nanometer lead grains are formed at the interface between the silicon substrate and PZT thin film.

Design of a new PZT based microphone and microspeaker

Abstract A new Pb(Zr0.53Ti0.47)O3 (PZT) based cantilever structure composed of Pt/Ti/PZT/Pt/Ti/SiO2/Si3N4 multilayer is designed for integrated microphone and mirospeaker. The cantilever structure is theoretically studied and designed using a multimorph model. The properties of the PZT-based and ZnO-based cantilevers are compared.

Miniature Microphone with Silicon-Based Ferroelectric Thin Films

A miniature microphone with silicon-based lead zirconate titanate (PZT) thin films has been fabricated and tested. The main structure of the device is composed of Al/Pt/PZT/Pt/Ti/SiO2/Si3N4/SiO2/Si multi-layer diaphragm. The PZT thin films have been prepared using an improved sol-gel method. Optimized fabrication process of the device has been developed, especially, RIE (reactive ion etching) and IBE (ion beam etching) processes have been used to etch the PZT thin film and electrode metal successfully. The sensitivity of microphone is 16 mV/Pa at 1 KHz and 158 mV/Pa at the resonant frequency of 17.3 KHz. The electrical and thermal reliability of the microphone is satisfactory. This miniature microphone can be widely used in hearing aids, mobile phones, and many other applications.

Studies of a PT/PZT/PT sandwich structure for feram applications using sol-gel processing

Abstract A silicon-based PbTiO3/Pb(Zr,Ti)O3/PbTiO3 (PT/PZT/PT) sandwich structure with Pt electrodes are prepared by a sol-gel method. Effects of the PT buffer layers to the phase formation of the PZT films are studies. Dielectric and ferroelectric properties of the sandwich structure are measured. Maximum dielectric constant of about 900 is obtained at the coercive field 20 kV/cm. The leakage current density is less than 5 × 10−9 A/cm2 below 200 kV/cm, which is much lower than that of PZT/PT structure. And there is almost no fatigue even after 5 × 109 read/write cycles for the PT/PZT/PT sandwich structure.

Preparation and Etching of Silicon-Based Piezoelectric Thin Films for Integrated Devices

Lead-zirconate-titanate (PZT) and ZnO thin films on silicon substrates were prepared by a sol-gel method. Phase characterization and crystal orientation of the films were investigated by X-ray diffraction analysis (XRD). It was shown that the PZT thin films had a perfect perovskite structure after annealed at a low temperature of 600 , and the ZnO thin films were well crystallized with (002) preferred orientation at a low annealing temperature of 400 . PZT thin films were chemically etched using HCl/HF solution through typical semiconductor lithographic process, and ZnO thin films were wet etched using acidic and alkaline etchants. The etching conditions were optimized. The etching precision can be higher than 1 w m.

Design of a PZT based cantilever structure

A PZT-based cantilever structure for microphone and microspeaker applications is designed using a multimorph model. The use of zirconate titanate (PZT) greatly improves the characteristics of the microphone and microspeaker. The sensitivity and the sound pressure level (SPL) of the integrated microphone and microspeaker are calculated. It is found that the sensitivity of the microphone and the SPL of the microspeaker are higher than those using normal piezoelectric materials.