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Chemical-state-selective mapping at nanometer scale using synchrotron radiation and photoelectron emission microscopy

放射光軟X線と光電子顕微鏡を組合せたナノメートルスケールの化学結合状態マッピング

平尾 法恵; 馬場 祐治; 関口 哲弘; 下山 巖; 本田 充紀

Hirao, Norie; Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Honda, Mitsunori

放射光軟X線と光電子顕微鏡(PEEM)を組合せ、固体表面の化合物分布をナノメートルオーダーで観察する手法を提案した。本手法の原理は、化合物の内殻吸収端のエネルギーが同一元素であっても原子価状態によって異なることを利用し、エネルギー可変の放射光照射により表面から放出される光電子をPEEMにより拡大し画像化するものである。試料はSiとSiO$$_{2}$$が12.5ミクロン周期で並んだマイクロパターンを用いた。PEEM像の輝度の放射光エネルギー依存性から、ナノメートルオーダーの化学結合状態マッピング観察が可能であることを実証した。また、試料加熱に伴うPEEM像変化をリアルタイムで観測し、表面拡散中におけるSi-SiO$$_{2}$$界面の化学結合状態の変化の過程を明らかにした。

For surface analyses of semiconductor devices and various functional materials, it has become indispensable to analyze valence states at nanometer scale due to the rapid developments of nanotechnology. Since a method for microscopic mapping dependent on the chemical bond states has not been established so far, we have developed a photoelectron emission microscopy (PEEM) system combined with synchrotron soft X-ray excitation. The samples investigated were Si/SiO$$_{x}$$ micro-patterns prepared by O$$_{2}$$$$^{+}$$ ion implantation in Si(001) wafer using a mask. PEEM images excited by various photon energies around the Si ${it K}$-edge were observed. The lateral spacial resolution of the system was about 41nm. The brightness of each spot in PEEM images changed depending on the photon energy, due to the X-ray absorption intensity of the respective chemical state. Since the surface of this sample was topographically flat, it has been demonstrated that the present method can be applied to observations of the microscopic pattern, depending not on the morphology, but only on the valence states of silicon. We have also ${it in-situ}$ measured the changes of the PEEM images upon annealing, and elucidated the mechanism of the lateral diffusion of oxygen and valence states of silicon at the nanometer scale.

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パーセンタイル:90.82

分野:Chemistry, Analytical

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