Yasuhira Nagakubo

An in situ heating TEM analysis method for an interface reaction.

In order to analyze the thermal property of nano-sized materials, an in situ observation technique that allows highly sensitive energy dispersive x-ray spectroscopic (EDX) analyses and high-resolution in situ heating observation of precision specimens is required. A method for the in situ observation of the interface reaction using an analytical transmission electron microscopy (TEM) and a specimen-heating holder was developed. The specimen holder used in this study was a direct-heating type having a fine tungsten wire heater. For sensitive analyses including an EDX map of composition changes during the interface reaction, a space toward the EDX detector with a take-off angle of 20 degrees was made in the specimen holder. Samples were prepared by attaching a micro-sample directly to the heater using the focused ion beam (FIB) micro-sampling technique. It was confirmed that the sensitive EDX map and electron diffraction analyses were possible during the reaction, and that the resolution of this technique was of the order of 0.223 nm at 550 degrees C.

Design of a 300-kV gas environmental transmission electron microscope equipped with a cold field emission gun

A new in situ environmental transmission electron microscope (ETEM) was developed based on a 300 kV TEM with a cold field emission gun (CFEG). Particular caution was taken in the ETEM design to assure uncompromised imaging and analytical performance of the TEM. Because of the improved pumping system between the gun and column, the vacuum of CFEG was largely improved and the probe current was sufficiently stabilized to operate without tip flashing for 2-3 h or longer. A high brightness of 2.5 × 10(9) A/cm(2) sr was measured at 300 kV, verifying the high quality of the CFEG electron beam. A specially designed gas injection-heating holder was used in the in situ TEM study at elevated temperatures with or without gas around the TEM specimen. Using this holder in a 10 Pa gas atmosphere and specimen temperatures up to 1000°C, high-resolution ETEM performance and analysis were achieved.

The development of electron beam absorbed current imaging system using scanning transmission electron microscope and its application

To realize higher spatial resolution than conventional SEM-based nano-probing system, a novel Electron Beam Absorbed Current imaging system was newly developed using a Hitachi HD-2700 200 kV dedicated STEM. Its specimen holder accommodates a mechanical probe for current detection and TEM grid specimen. This holder also has a micrometer-based coarse positioning and piezoelectric-elements-based fine positioning mechanism respectively for X, Y and Z-axis probe control. The absorbed current from the probe and the specimen are displayed as an image by STEM software via EBAC amplifier. We successfully made a probing onto FIB-prepared lamella specimen of semiconductor device to get an electrical contact. EBAC and EBIC images were clearly visualized in higher spatial resolution.

Development of a cryo-FIB technique for the 3D structural characterization of liquid samples

The observation of three-dimensional distributions in some liquids or colloids is important, for example in cosmetics, functional paints and a catalyst. Furthermore, there is increasing demand to microscopically investigate the structures inside a liquid colloid, such as the interface of a dispersoid and dispersant. In order to meet these requirements, we have developed a cryo-transfer holder which is fully compatible between FIB and TEM/STEM. The cross section of frozen emulsions and a thin film sample were made by FIB-SEM (NB5000). As a result, the dispersion state of a dispersoid was observed by sequential FIB and SEM. Furthermore a 100nm thick sample was made by FIB and observed by 200 kV STEM (HD- 2700). The dispersoid (TiO2 and Fe2O3) morphology and distribution were shown at nanometer level.