EDS

2.1 Introduction

EDS spectrometer is an instrument for analyzing the elements of a matter, usually used in conjunction with a scanning electron microscope or a transmission electron microscope. It bombards the surface of the sample with an electron beam under a vacuum chamber to stimulate the substance to emit characteristic X-rays, and carries out qualitative and semi-quantitative analysis of B-U elements in the periodic table according to the wavelength of the characteristic X-rays^[3^]. The spectrometer can be used for qualitative or semi-quantitative analysis of the composition and elements in micro-regions of the sample surface, as well as point and line scanning and cartographic analysis of specific regions^[4^]

2.2 The working principles

When X-ray photons enter the detector, they excite a certain number of electron hole pairs in the Si(Li) crystal. The lowest average energy ε generated by a pair of holes is fixed, while the hole pair consists of an X-ray photon N =△E /ε, so the higher the energy of the incident X-ray photon, the more N. The deviation applied to both ends of the crystal is used to collect electron hole pairs, converted by a preamplifier into a current pulse whose height depends on the magnitude of N^[5^]. The current pulse is converted into voltage pulse by the main amplifier, and then the height of the pulse is counted by the multi-channel pulse height analyzer, so as to generate the X-ray energy profile.

2.3 Characterization

Before the characterization, the sample surface was cleaned to avoid the impurity forming undesired peaks and influencing the element analysis result.

Fig 2 and Fig 3 shows the result of the EDS element anlysis of the sample surface. Through the image, the element content of every position on the scanned surface can be clearly shown.

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Fig 2. The overall element distrIbution on the sample surface by EDS

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^{Fig 3. The element distribution of each element on sample surface by EDS}

^{The spectrum of the scanned surface is shown in Fig 4 while the direct element content of the surface was calculated by the computer and the result is shown in Table 1.}

^{Fig 4. The spectrum of the scanned surface}

	Si	B	C	N	Ni	Fe	Cr	Nb	Al
at%	0.2070	16.172	6.4182	1.1502	38.900	15.297	18.449	2.6685	0.7821

^{Table 1. The element content of the scanned surface}

Characterization ( EXP2-5 )

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