Akira Akiba

Effect of Crystal Orientation on Dielectric Properties of Lead Zirconium Titanate Thin Films Prepared by Reactive RF-Sputtering

Theoretical calculations based on phenomenology of ferroelectrics have been previously reported for lead zirconium titanate (PZT) system. This paper offers an experimental comparison of the crystal orientation dependence of dielectric properties for PZT thin films grown using reactive RF-sputtering. Highly oriented PZT thin films with a rhombohedral composition have been grown in different orientations using selective rapid thermal annealing cycles. The PZT(100) oriented films showed larger dielectric constant and loss compared to PZT(111) films. The PZT(100) films possessed sharp square-like hysteresis loops indicating a instantaneous switching of domains at the coercive field whereas the PZT(111) films showed smooth hysteresis loops as expected from our phenomenological calculations.

Highly (111) oriented lead zirconate titanate thin films deposited using a non-polymeric route

Abstract This paper presents a simple non-polymeric solution route and its process conditions for depositing reproducible very highly (111) oriented lead zirconate titanate Pb(Zr 0.53 , Ti 0.47 )O 3 (abbreviated PZT) thin films, with an excellent combination of electrical properties, on Pt(111)/Ti/SiO 2 /Si wafers. Unlike sol–gel derived routes, non-polymeric methods do not rely on polymerisation in solution of metal precursors, so that the viscosity of the starting sol remains constant, which is important for good reproducibility in the commercialisation of ‘micro electro mechanical systems’ (MEMS). The route presented uses Pb 2-ethylhexanoate, Ti (diisopropoxide) bis (2,4-pentanedionate), and Zr n -butoxide, mixed in the solvent xylene. Sol preparation is performed in an open atmosphere, without the need for refluxing. Crystallisation was carried out both by conventional furnace annealing and rapid thermal annealing (RTA). With furnace annealing, precursor solutions with 30% excess Pb produced films with satisfactory ferroelectric properties; whilst by reaching the onset of perovskite crystallisation rapidly with RTA, starting solutions with only 10% Pb excess produced perovskite PZT films with excellent electrical properties (relative permittivity e r ∼1700, remnant polarisation P r ∼20 μC/cm 2 and coercive field E c ∼55 kV/cm), with a high degree of (111) orientation. Both (111)/(100) and (111)/(110) X-ray diffraction peak intensity ratios were above 100. The films were 1 μm thick.

PZT thin-film actuator driven micro optical scanning sensor by 3D integration of optical and mechanical devices

In this paper, a novel functional element integration method is proposed and demonstrated by highly miniaturized micro optical scanning sensor with dimensions of W2.0/spl times/L4.0/spl times/H2.8 mm/sup 3/. In the sensor as small as a wheat grain, the functional elements such as a laser diode (LD), photo detectors (PDs), a beam splitter, a ball lens, and a PZT thin-film actuator integrated optical scanner are integrated on separate substrates each consisting a functional module and the substrates are stacked. And the sensor is capable of multi-optical sensing: the 2D object shape recognition (+/- 10 degs scanning area for two direction) and the range measurement (50 mm +/- 10 mm with 0.5 mm resolution).

Optical characteristics of PZT thin film actuator-driven micro-optical scanning sensor with multilayer stacked device structure

We developed a micro optical scanning sensor with the dimension of 2.0 mm X 4.0 mm X 3.0 mm for a micro inspection robot. In this sensor, the functional elements such as a laser diode (light source), photo diodes, pin-holes, a beam splitter, a ball lens, and a PZT thin film actuator driven micro optical scanner are integrated on separate substrates each consisting a functional modules and the substrates are stacked. Performance of the optical sensor depends on its optical characteristics. This sensor has spot size of output beam is 256 micrometer X 580 micrometer at 60 mm from the sensor, output power is 0.5 mW, optical scanning angles are plus or minus 10 deg. two-dimensionally, and detecting sensitivity of photo diodes are 0.3 A/W. The sensor is capable of distance measurement between the sensor and an object at 50 mm plus or minus 10 mm and the object shape recognition two-dimensionally based on the optical scanning method. By using these functions, the sensor can measure dimensions of the object and measuring resolution is less than 0.5 mm.