加速器
Online ISSN : 2436-1488
Print ISSN : 1349-3833
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選択された号の論文の8件中1~8を表示しています
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  • 田中 保宣
    2021 年 18 巻 3 号 p. 128-133
    発行日: 2021/10/31
    公開日: 2021/11/10
    ジャーナル フリー

    Silicon carbide (SiC) is very attractive semiconductor material especially for power device use because of its excellent physical properties like as high critical electric field, high thermal conductivity, and so on. In this paper, the theoretical consideration about the advantages of SiC power devices compared with that of Si and the current status of the social implementation of SiC power devices are introduced.

  • 郭 磊, 山口 尚登, 山本 将博, 松井 文彦, Gaoxue Wang, Fangze Liu, Ping Yang, Enrique ...
    2021 年 18 巻 3 号 p. 134-142
    発行日: 2021/10/31
    公開日: 2021/11/10
    ジャーナル フリー

    Photocathodes that are capable of generating high-performance electron beams are one of the most important devices in an advanced accelerator and electron microscopes. In particular, bialkali photocathodes, such as cesium potassium antimonide (CsK2Sb) is of interest because it can generate a high-brightness electron beam using a high-power green laser. It is known that the quantum efficiency (QE) of these photocathodes is affected severely by their substrates; however, reusability of the substrates is not well known. In this study, we use graphene, silicon (Si), and molybdenum (Mo) substrates to evaluate the effects of substrates on the QE of redeposited CsK2Sb photocathodes after thermal cleanings. We found the QE of CsK2Sb photocathodes redeposited on a graphene substrate after a thermal cleaning at 500°C remained largely unchanged. On the other hand, the QE of redeposited photocathodes on Si and Mo substrates after thermal cleaning at the same temperature decreased drastically. We used X-ray photoelectron spectroscopy (XPS) to quantitatively evaluate the residues of photocathodes after thermal cleaning at 400°C and 500°C. We found that the Sb, K, and Cs are removed by thermal cleaning at 500°C for the graphene substrate, but all or the majority of these elements remained on the Si and Mo substrates. The results were consistent with our density functional theory (DFT) calculations for the case of Si, which we investigated. Furthermore, our angle-resolved photoemission spectroscopy (ARPES) on graphene indicated that its intrinsic electronic structure is preserved after photocathode deposition and thermal cleaning at 500°C. Hence, we attributed the difference in amount of photocathode residue to the unique dangling-bond-free surface of inert graphene. Our results provide a foundation for graphene-based reusable substrates for high-QE semiconductor photocathodes.

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