X-ray analysis and mapping by wavelength dispersive X-ray spectroscopy in an electron microscope Miyoko Tanaka à , Masaki Takeguchi, Kazuo Furuya National Institute for Materials Science, 3-13 Sakura, Tsukuba, Ibaraki 305-0003, Japan article info Keywords: WDS SEM STEM MCX Boron compounds W Si Elemental mapping abstract A compact and easy-to-use wavelength dispersive X-ray spectrometer using a multi-capillary X-ray lens attached to a scanning (transmission) electron microscope has been tested for thin-film analysis. B–K spectra from thin-film boron compounds (B 4 C, h-BN, and B 2 O 3 ) samples showed prominent peak shifts and detailed structural differences. Mapping images of a thin W/Si double-layer sample resolved each element clearly. Additionally, a thin SiO 2 film grown on a Si substrate was imaged with O–K X-rays. Energy and spatial resolution of the system is also discussed. & 2008 Elsevier B.V. All rights reserved. 1. Introduction X-ray spectroscopy performed with electron microscopes is becoming more and more important as a tool to provide complete micron- or nano-scale quantitative chemical information. The most widely adopted X-ray spectroscopy method is energy dispersive X-ray spectroscopy (EDS) using semiconductor detec- tors, due to its compactness, high detection efficiency, and ease of operation [1,2]. Meanwhile, wavelength dispersive X-ray spectro- scopy (WDS) surpasses EDS at high-energy resolution, for its detection limits and its ability to detect light elements [3,4]. WDS is usually installed in electron probe micro analyzers (EPMAs), not in scanning electron microscopes (SEMs) or in transmission electron microscopes (TEMs). In this type of spectrometer, the curved analyzing crystal and detector are required to move along the Rowland circle; thus there are many movable parts that generate vibration and noise. Additionally, the vacuum deteriora- tion needs to be also considered. Also, sample alignment requires micrometer-order height adjustments, which makes this type of spectrometer difficult to use as a microscope accessory. Other types of X-ray spectroscopy are being investigated to achieve better performance. EDS by microcalorimetry using transition edge sensors is one solution. It provides about 10 times better energy resolution than traditional EDS while covering a relatively wide energy range at one time, typically around 2 keV when in a wide photon energy range configuration [5,6]. Other manufacturers aim for higher-energy resolution (0.2 eV) and light element detection down to Li or B using varied-line-spacing gratings and back-illumination CCD detectors for EPMA [7] and TEM [8]. These methods are, however, rather for special laboratory use than for ordinary use since the instruments are very complicated and either too large or too expensive, or both. Recent development in parallel beam X-ray spectrometers using multi-capillary X-ray (MCX) optics to collimate divergent X-rays has made it possible to perform WDS readily and easily in electron microscopes [9]. Since parallel beam spectrometers use flat crystals and simple y–2y scanning systems instead of curved crystals and Rowland circle mountings, they are compact and generate less vibration and noise. These characteristics make parallel beam spectrometers suitable for use in SEMs or in TEMs for materials analysis, which has been difficult to perform with EDS. Using a MCX–WDS system (SHIMADZU) attached to a SEM (JEM-7000F, JEOL), we achieved light element analysis down to B for both bulk and TEM thin-film samples with high-energy resolution [10]. In the present study, we modified this SEM–WDS system to a scanning transmission electron microscopy (STEM) compatible system and carried out light element analysis such as B, C, N, and O as well as elemental mapping. Thin-film TEM specimens were analyzed, as well as bulk specimens. A set of boron compounds (h-BN, B 2 O 3 , and B 4 C), a-Al 2 O 3 , W/Si double layer specimen, and a SiO 2 film grown on a Si substrate were analyzed. 2. Instrumentation The MCX–WDS system is attached to the column of the JEM- 7000F SEM. The microscope chamber is specially modified with ARTICLE IN PRESS Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/ultramic Ultramicroscopy 0304-3991/$ - see front matter & 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.ultramic.2008.05.011 à Corresponding author. E-mail address: TANAKA.Miyoko@nims.go.jp (M. Tanaka). Ultramicroscopy 108 (2008) 1427–1431