Scanning Electron-Beam Dielectric Microscopy for the Temperature Coefficient Distribution of Dielectric Materials
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Scanning Electron-Beam Dielectric Microscopy for the Temperature Coefficient Distribution of Dielectric Materials Yasuo Cho Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira Aoba-ku Sendai 980-8577, Japan ABSTRACT Studies on scanning electron-beam dielectric microscopy (SEDM) are reported. This microscopy technique is used for determining the temperature coefficient distribution of dielectric materials using an electron-beam as a heat source instead of a light beam as in photothermal dielectric microscopy. This microscopy technique, which has the ability to simultaneously observe SEM images and the material composition by EPMA, has a resolution better than that of photothermal dielectric microscopy. To demonstrate the usefulness of this technique, the two-dimensional image of a two-phase composite ceramic composed of TiO2 and Bi2Ti4O11 is measured. To shorten a measurement time, a new type of SEDM for measuring the real time transient response caused by a single pulsed electron-beam is also successfully developed. Finally, a quantitative measurement method of temperature coefficient is also developed.
INTRODUCTION A new photothermal technique to evaluate the thermal properties of dielectric materials and to measure the microscopic distribution of the temperature coefficient of the dielectric constant has recently been developed using the photothermal dielectric (PTD) effect[1-4]. This method is based on the temperature characteristic of the dielectric constant of a light-irradiated material. Microscopic measurements of the distribution of the temperature coefficients of the dielectric constant provide more precise information for designing the material than that obtained from a macroscopic measurement[5]. In particular, for the evaluation of combinatorial materials composed of raw materials with different dielectric temperature coefficients, (for example, a positive and a negative coefficient), a microscopic technique to assess the distribution of the temperature coefficient of the dielectric constant is very effective for the precise characterization of the material. This method of using a light beam as a heat source has the advantages of being relatively simple and inexpensive. However its resolution is limited by the light wavelength and it is difficult to perform an in situ measurement identifying each grain of a ceramic and its composition. To give an answer to the above-mentioned problem, a new microscopy for determining the temperature coefficient distribution of dielectric constants was developed using an electron beam as a heat source instead of a light beam. In this paper, the results of the studies on scanning electron-beam dielectric microscopy is described, which has a resolution better than that of photothermal dielectric microscopy and with the ability of in situ observation of SEM images and of material compositions by electron probe micro analyzer (EPMA). To demonstrate the usefulness of this technique, we measured the two-dimensional image of a two-phase composite c
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