Work function lowering of LaB by monolayer hexagonal boron nitride coating for improved photo- and thermionic-cathodes

Yamaguchi, Hisato*; Yusa, Ryunosuke*; Wang, G.*; Pettes, M. T.*; Liu, F.*; Tsuda, Yasutaka; Yoshigoe, Akitaka; Abukawa, Tadashi*; Moody, N. A.*; Ogawa, Shuichi*

Applied Physics Letters, 122(14), p.141901_1 - 141901_7, 2023/04

https://doi.org/10.1063/5.0142591

A lowering of work function for LaB by monolayer hexagonal BN coating is reported. Photoemission electron microcopy (PEEM) and thermionic emission electron microscopy (TEEM) both revealed that the hBN coated region of a LaB(100) single crystal has lower work function compared to the bare (i.e., non-coated) and graphene coated regions. A larger decrease of work function for the hBN coated LaB(100) compared to graphene coated LaB(100) was qualitatively supported by our density functional theory (DFT) calculations. Adding an oxide layer in the calculations improved consistency between the calculation and experimental results. We followed up our calculations with synchrotron-radiation X-ray photoelectron spectroscopy (SR-XPS) and confirmed the presence of an oxide layer on our LaB.

Study on the sputter-cleaning processes of Ni by means of Kelvin probe

Luo, G.-N.*; Yamaguchi, Kenji; Terai, Takayuki*; Yamawaki, Michio*

Surface Science, 505, p.14 - 24, 2002/05

https://doi.org/10.1016/S0039-6028(02)01394-8

no abstracts in English

Impact of interfaces on nuclear materials

Yamawaki, Michio*; Yamaguchi, Kenji; Suzuki, Atsushi*

Ionics, 7(4-6), p.339 - 345, 2001/07

https://doi.org/10.1007/BF02373568

no abstracts in English

PEEM observation of work function changes on LaB coated by 2D materials

Ogawa, Shuichi*; Yusa, Ryunosuke*; Wang, G.*; Pettes, M. T.*; Liu, F.*; Tsuda, Yasutaka; Yoshigoe, Akitaka; Abukawa, Tadashi*; Moody, N. A.*; Yamaguchi, Hisato*

no journal, , 

Lanthanum hexaboride (LaB) has a low work-function and is widely used as a thermionic cathode. For practical application, further reduction of its work-function and high durability have been required. In this study, the effect of 2D material coating materials (graphene and hexagonal boron nitride (hBN)) prepared by a wet-transfer method on the work-function of LaB(100) was studied by using photoelectron emission microscopy (PEEM), synchrotron radiation photoemission spectroscopy, Raman spectroscopy, atomic force microscopy and DFT calculations. PEEM images for samples after 905C heating clearly showed strong photoemission in the hBN coating region. DFT calculations indicated that the work-function increases in graphene due to the inward dipole formation, while the work function decreases in hBN due to the outward dipole forming at the interface.

負イオン源及び負イオン生成方法

松原 章浩; 國分 陽子

not registered

JP, 2022-021830  Patent licensing information

【課題】高い負イオン生成効率を達成可能な負イオン源及び負イオン生成方法を提供する。 【解決手段】試料が導入される導入口106と、導入口106と連通し、放電によりプラズマが生成されるプラズマ生成領域113と、生成されたプラズマと試料との反応により解離または励起した粒子が負イオン化される負イオン生成領域114と、負イオン生成領域114と連通し、生成された負イオンが外部に引き出される引出口107と、を備える筐体108を有し、負イオン生成領域114には、高周波加熱により熱電子を生成する熱電子放出物質116が充填されている。