Hiroyuki Odagawa

Theoretical and Experimental Study on Nanoscale Ferroelectric Domain Measurement Using Scanning Nonlinear Dielectric Microscopy

We describe theoretical and experimental studies for nano-scale ferroelectric domain measurements using scanning nonlinear dielectric microscopy (SNDM). We calculate one-dimensional images of a 180° c-c domain boundary and show that SNDM has an atomic-scale resolution theoretically. Experimental results show that we measure the c-c domain on the lead zirconate titanate (PZT) thin film with the width of 1.5 nm and that the resolution of the microscope is less than 0.5 nm.

Simultaneous observation of nano-sized ferroelectric domains and surface morphology using scanning nonlinear dielectric microscopy

Abstract A new type of scanning nonlinear dielectric microscope (SNDM), with an additional function of simultaneous observation of surface morphology, has been developed. This was achieved by using an electrically conducting atomic force microscopy cantilever as a probe needle. Using this new SNDM, simultaneous measurements of several ferroelectric materials, such as LiNbO3 single crystal and lead zirconate titanate (PZT) thin films on SrTiO3 substrates, were performed. Topographic and domain images, which were simultaneously taken from the same location on the materials, were successfully obtained. The result shows that nano-sized ferroelectric 180° c–c domains of PZT thin film having a good correlation with a topographic image were observed.

Measurement of the Ferroelectric Domain Distributions Using Nonlinear Dielectric Response and Piezoelectric Response

Scanning nonlinear dielectric microscopy (SNDM) is the first successful purely electrical method for observing the ferroelectric domain distributions. At present its resolution is of the sub-nanometer order. As another method for measuring the ferroelectric domains, the piezoelectric response imaging method is often used. In this study, we compare the resolution of SNDM with that of piezoelectric response imaging and confirm that SNDM gives a much higher resolution than that obtained by piezoelectric imaging. A fundamental study to apply the SNDM system to the ferroelectric reading and writing system is also performed.

Quantitative Measurement of Linear and Nonlinear Dielectric Characteristics Using Scanning Nonlinear Dielectric Microscopy

The theory for quantitative measurement of linear and nonlinear dielectric constants using scanning nonlinear dielectric microscopy is explained in this paper. Using this theory, quantitative measurements for linear and nonlinear dielectric constants of dielectric materials were performed successfully.

Development of scanning microwave microscope with a lumped-constant resonator probe for high-throughput characterization of combinatorial dielectric materials

A scanning microwave microscope (SμM) for combinatorial characterization of dielectric materials has been developed using a lumped-constant resonator probe. The probe consists of a commercially available microwave oscillator module equipped with a thin conducting needle and an outer conductor ring. The capacitance between needle and ring changes with the dielectric constant of the sample just beneath the needle, which can be detected as a frequency shift of the resonator with high accuracy. The frequency shift values measured for various standard samples lay on a master curve theoretically predicted, which guarantees the quantitative evaluation of the dielectric constant. Applicability of the present system to the characterization of combinatorial samples is demonstrated.

Determination of the polarities of ZnO thin films on polar and nonpolar substrates using scanning nonlinear dielectric microscopy

Using scanning nonlinear dielectric microscopy (SNDM) which we developed, we determined the polarities of ZnO thin films on various substrates including polar materials. SNDM is a useful tool for investigating the anisotropy of polar materials by measuring the nonlinear dielectric constant, whose sign changes in accordance with the polarity of the specimen. In conventional methods based on detecting the piezoelectric and pyroelectric responses, it is very difficult to determine the polarities of thin films, particularly in the case of laying these films on the polar substrates, because the detected signals from thin films are very small and those from the substrates are large. Our SNDM method, however, enables us to determine the polarities of thin films on polar substrates easily. Using SNDM, the polarities of ZnO thin films on several kinds of polar and nonpolar substrates were determined. We also determined experimentally that ZnO thin films grew with a sign opposite to the substrate polarity and it was suggested that pyroelectric effects mainly governed the polarity of ZnO films.

Simultaneous Observation of Ferroelectric Domain Patterns by Scanning Nonlinear Dielectric Microscope and Surface Morphology by Atomic Force Microscope

A new type of scanning nonlinear dielectric microscope (SNDM), with an additional function of simultaneous observations of surface morphology, has been developed. This was achieved by employing an electrically conducting atomic force microscopy cantilever as a probe needle. Using this new SNDM, simultaneous measurements of several ferroelectric materials, such as lead zirconate titanate (PZT) thin films on both SrTiO3 and MgO substrates, were performed. Topographic and domain images were simultaneously obtained from the same location on the materials. Finally, the resolution of the SNDM was theoretically calculated and it was revealed that atomic scale resolution is possible using the SNDM technique.

Single crystal growth of KNbO3 and application to surface acoustic wave devices

Potassium niobate (KNbO 3 ) has large piezoelectric constants. The surface acoustic wave (SAW) substrates with high couplings are very important for wide-band SAW filters and SAW devices. Therefore, the large size KNbO 3 single crystals are required for SAW device applications. In this paper, the techniques of a large size of KNbO 3 using the top seeded solution growth techniques (TSSG) with large size of crucible of 60 mmo platinum are described. The results show that 50x50x 15 mm 3 single crystals are obtained. Also, the poling techniques of KNbO 3 crystal are investigated by using the nonlinear scanning dielectric microscope. The propagation characteristics of SAW and piezoelectric leaky surface waves in KNbO 3 single crystal were investigated theoretically. The results show that the electro-mechanical coupling coefficient of the surface wave propagating along the X-axis of the rotated Y-cut plane is extremely large: K 2 = 0.53, compared to K 2 of 0.055 for LiNbO 3 . The experimental results of the above KNbO 3 substrates agree with the theoretical ones. Also the KNbO 3 substrates showed experimentally the zero temperature coefficients of frequency (TCF) around 20 C.

Measuring ferroelectric polarization component parallel to the surface by scanning nonlinear dielectric microscopy

A scanning nonlinear dielectric microscope (SNDM) probe, called the e311-type probe, and a system to measure the ferroelectric polarization component parallel to the surface have been developed. This is achieved by measuring the ferroelectric material nonlinear dielectric constant e311 instead of e333, which is measured in conventional SNDM. Experimental results show that the probe can satisfactorily detect the direction of the polarization parallel to the surface. Moreover, we propose an advanced measurement technique using a rotating electric field, which can be applied to measure three-dimensional polarization vectors.

GHz-range low-loss wide band filter using new floating electrode type unidirectional transducers

K. Yamanouchi et al. (1991) reported a very low loss surface acoustic wave (SAW) filter with minimum insertion loss of 1.9 dB at 1.0 GHz using a floating electrode type unidirectional transducer (FEUDT). The dependence of directivity on the electrode thickness for the lambda /10 type FEUDT is investigated here. Experimental results show minimum insertion loss of 6.2 dB at 4.1 GHz and 2.5 dB at 2.0 GHz. The dependence of directivity on the electrode thickness at 4 GHz differs from that at 2 GHz. The resistivities of various Al films were measured, and their surfaces are observed by scanning tunneling microscopy. An increase of the resistance due to pinholes which appear after heating is noted.<<ETX>>