Toru Fujii

Effect of poling on piezoelectric properties of lead zirconate titanate thin films formed by sputtering

Lead zirconate titanate (PZT) thin film was formed on Pt/Ta/Si3N4/Si(100) substrate at 400 °C by sputtering and then annealed at 650 °C in air. The PZT film was 1 μm thick and had dielectric permittivity of 980, loss tangent of 0.05, remanent polarization of 31 μC/cm2, and coercive field of 110 kV/cm. Piezoelectric property of the film formed on silicon cantilever was estimated from the converse effect. Poling at 5 kV/mm increased the property by a factor of 1.2 to 3.4, resulting in converse piezoelectric constant (d31) varying from −84 to −102 pC/N.

Application of lead zirconate titanate thin film displacement sensors for the atomic force microscope

Elimination of optical and tunneling displacement sensors from the atomic force microscope (AFM) is an important breakthrough for improved performance of the AFM. The interaction of an oscillating tip and a surface has become a popular tool for obtaining information which could not be obtained by the conventional repulsive force AFM mode. In this application, lead zirconate titanate (PZT) is one of the most promising materials with large piezoelectric constants which can be used not only for detecting distortions such as the displacement detection of an AFM cantilever, but also oscillations of the cantilever. However, incorporating PZT into the microfabrication process to make the AFM cantilever has not been easily accomplished because PZT has a delicate chemical nature. We have successfully developed an AFM with a microfabricated cantilever which had a PZT thin film applied for displacement sensing. The linearity of the output signal was sufficient for displacement sensing. Images of a compact disk were ...

Micro‐fabricated piezoelectric cantilever for atomic force microscopy

We successfully developed an atomic force microscope (AFM) with a batch‐fabricated silicon cantilever with a pyramidal stylus. The high quality lead zirconate titanate (PZT) piezoelectric thin film allows simultaneously displacement sensing and actuating. The PZT thin film with a dielectric constant of 1000, a remanent polarization of 30 μC/cm2, and a piezoelectric constant of −100 pC/N, which are as high as those of bulk ceramics PZT, has been formed by sputtering at 400 °C and subsequent annealing at 650 °C. A Si(111) mono‐atomic step whose height is 4 A has been observed clearly in an AFM cyclic contact mode by a PZT‐AFM lever as a displacement sensor. A PZT‐AFM lever has been used as an actuator for z feedback positioning for AFM imaging of a compact disk pit.

Feedback positioning cantilever using lead zirconate titanate thin film for force microscopy observation of micropattern

An atomic force microscope cantilever with PZT thin film with pyramidal stylus was used for actuation of feedback motion. The maximum stroke of the cantilever was more than 1 μm within a frequency range from direct current up to natural resonant frequency, e.g., 28.48 kHz. An image of a pit of a compact disk with a depth of 100 nm was successfully obtained using only cantilever actuation in a vertical direction.

Non-contact atomic force microscope with a PZT cantilever used for deflection sensing, direct oscillation and feedback actuation

A non-contact atomic force microscope (NC-AFM) based on a microfabricated piezoelectric cantilever is presented. A single piezoelectric lead zirconate titanate thin film layer on the cantilever serves as deflection sensing, cantilever oscillation and feedback actuation. Since such an AFM requires neither external oscillator nor external deflection sensor, considerably simple instrumentation becomes possible even for extreme environments such as low temperature or ultra-high vacuum. Also feedback control by the integrated actuator in the cantilever makes faster scanning possible. Images of atomic steps on annealed sapphire (0001) surfaces have been observed in air atmosphere in frequency modulation mode.

Micropattern measurement with an atomic force microscope

The atomic force microscope (AFM) can profile both the surfaces of conductors and insulators with nanometer resolution. One of the most promising applications of the AFM is micropattern measurement of semiconductor devices such as linewidth. An AFM with high precision positioning stages using monolithic, parallel spring mechanisms with flexture hinges has been applied to the measurement of nonconducting surfaces. The X‐Y scanner is equipped with the two‐dimensional optical interferometer to measure displacements of the scanner. The sensing lever is a microfabricated V‐shaped Si3N4 cantilever with a tip made using electron beam deposition. Distortion‐free images of a polycarbonate compact disk nonconducting surfaces with details around the pits have been successfully obtained.

High Density Optical Recording on Dye Material Discs: An Approach for Achieving 4.7 GB Density

High density optical media is proposed together with a recording method for achieving a density of 4.7 GB per single 12 cm diameter disc at a recording speed of 3.5 m/s.

Nanoscale investigation of optical and electrical properties by dynamic-mode atomic force microscopy using a piezoelectric cantilever

We demonstrated a novel application of a microfabricated force-sensing cantilever with a lead zirconate titanate (PZT) thin film as an integrated deflection sensor for a dynamic-mode atomic force microscope (AFM) combined with a scanning near-field optical microscope (SNOM). This experimental setup was also applied to a Kelvin-probe force microscope (KFM) for the investigation of local electrical properties. A frequency modulation (FM) detection method was used for enhancing the detection sensitivity of electrostatic forces between a probe tip and a sample. Local optical properties of a PbTiO3 single crystal were investigated using the conductive PZT cantilever as an AFM/SNOM probe. Furthermore, studies on local optical and electrical properties of ferroelectric copolymer films were also presented.

Multi-Probe Atomic Force Microscopy Using Piezoelectric Cantilevers

We developed a multi-probe atomic force microscopy (AFM) system using piezoelectric thin film (PZT) cantilevers. The use of self-sensing cantilevers with integrated deflection sensors as probes markedly reduced complexity in the ordinary AFM setup. Address-patterned samples having microfabricated x–y coordinate patterns, fabricated by electron beam lithography, were developed as well. These samples allow us to evaluate the relative distance between the probes by the comparison of the images obtained. Although the minimum distance between these probes was 126 µm using the original cantilevers, it was reduced to 9.2 µm by using the PZT cantilevers modified by a focused ion beam. Furthermore, we found that the interaction forces between the cantilevers were detected by determining the change in the amplitude of each cantilever.

Linewidth Measurement by a New Scanning Tunneling Microscope

We have developed a new STM using monolithic parallel spring mechanisms with fiexture hinges. The STM is equipped with a two-dimensional optical interferometer to calibrate the motion of the scanner with subnanometer accuracy in real time. Distortion-free images of a grating pattern have successfully been observed.