In situ SR-XPS observation of Ni-assisted low-temperature formation of epitaxial graphene on 3C-SiC/Si

Hasegawa, Mika*; Sugawara, Kenta*; Suto, Ryota*; Sambonsuge, Shota*; Teraoka, Yuden; Yoshigoe, Akitaka; Filimonov, S.*; Fukidome, Hirokazu*; Suemitsu, Maki*

Nanoscale Research Letters, 10, p.421_1 - 421_6, 2015/10

https://doi.org/10.1186/s11671-015-1131-9

Graphene has attracted much attention as a promising material in electronics and photonics. The graphitization temperature of 1473 K or higher of graphene-on-silicon(GOS), however, is still too high to be fully compatible with the Si technology. Here, the first application of Ni-assisted formation of graphene to the GOS method was reported. We demonstrate that the graphene formation temperature can be reduced by more than 200 K by this method. Moreover, solid-phase reactions during heating/annealing/cooling procedures have been investigated in detail by using synchrotron-radiation X-ray photoelectron spectroscopy. As a result, we clarify the role of Ni/SiC reactions, in which not only Ni silicidation and but also Ni carbonization is suggested as a key process in the formation of graphene.

Direct measurement of surface stress during Bi-mediated Ge growth on Si

Asaoka, Hidehito; Yamazaki, Tatsuya*; Yamaguchi, Kenji; Shamoto, Shinichi; Filimonov, S.*; Suemitsu, Maki*

Surface Science, 609, p.157 - 160, 2013/03

https://doi.org/10.1016/j.susc.2012.12.002

We have focused on stress measurements during Bi termination of Si(111) and Ge growth on this Bi-mediated Si(111). In order to obtain information on both the surface stress and the surface structure simultaneously, we have combined the surface-curvature and the reflection-high-electron-energy-diffraction instrumentations in an identical ultrahigh vacuum system. We find the Bi-terminated Si(111) - surface releases 1.8 N/m (=J/m), or (1.4 eV/(11 unit cell)), of the surface energy from the strong tensile Si(111) 77 reconstruction. Subsequent Ge deposition on the Bi-terminated Si surface develops a compressive stress, which oscillates with a period corresponding to the growth of a single bilayer. The real-time stress measurement provides a direct evidence for this oscillatory stress relaxation in the layer-by-layer growth.

Controls over structural and electronic properties of epitaxial graphene on silicon using surface termination of 3C-SiC(111)/Si

Fukidome, Hirokazu*; Abe, Shunsuke*; Takahashi, Ryota*; Imaizumi, Kei*; Inomata, Shuya*; Handa, Hiroyuki*; Saito, Eiji*; Enta, Yoshiharu*; Yoshigoe, Akitaka; Teraoka, Yuden; et al.

Applied Physics Express, 4(11), p.115104_1 - 115104_3, 2011/11

https://doi.org/10.1143/APEX.4.115104

Low-energy-electron-diffraction and X-ray-phototelectron-spectroscopy studies of graphitization of 3C-SiC(111) thin film on Si(111) substrate

Takahashi, Ryota*; Handa, Hiroyuki*; Abe, Shunsuke*; Imaizumi, Kei*; Fukidome, Hirokazu*; Yoshigoe, Akitaka; Teraoka, Yuden; Suemitsu, Maki*

Japanese Journal of Applied Physics, 50(7), p.070103_1 - 070103_6, 2011/07

https://doi.org/10.1143/JJAP.50.070103

Initial oxidation of Si(110) as studied by real-time synchrotron-radiation X-ray photomission spectroscopy

Suemitsu, Maki*; Yamamoto, Yoshihisa*; Togashi, Hideaki*; Enta, Yoshiharu*; Yoshigoe, Akitaka; Teraoka, Yuden

Journal of Vacuum Science and Technology B, 27(1), p.547 - 550, 2009/02

https://doi.org/10.1116/1.3021032

Initial oxidation processes of the Si(110) surface and the chemical bonding states of silicon atoms in the initial oxides have been investigated by using real-time synchrotron-radiation photoemission spectroscopy. Time evolutions of the Si (=1-4) components in the Si 2 spectrum indicates that the Si component always overwhelms the Si component during the oxidation up to one monolayer. This is in sharp contrast to the Si(001) surface where Si is always larger than Si. The dominance of the Si component is related to presence of two types of bonds on the Si(110) surface and to their possible different reactivity against insertion of oxygen atoms.

SR-PES and STM observation of metastable chemisorption state of oxygen on Si(110)-162 surface

Yamamoto, Yoshihisa*; Togashi, Hideaki*; Kato, Atsushi*; Takahashi, Yuya*; Konno, Atsushi*; Teraoka, Yuden; Yoshigoe, Akitaka; Asaoka, Hidehito; Suemitsu, Maki*

Applied Surface Science, 254(19), p.6232 - 6234, 2008/07

https://doi.org/10.1016/j.apsusc.2008.02.148

The room temperature adsorbed state of oxygen molecules on Si(110)-162 surface and the structural change after a mild annealing has been investigated by synchrotron radiation photoemission spectroscopy. As a result, despite the very small dosage of oxygen, Si and Si components already appear in addition to Si. This is likely to be caused by a selective adsorption of O molecules into the vicinity of already oxidized sites. After annealing, we found that binding energy of Si and Si increase and approach to their corresponding peak positions of a thermally-grown oxide, and this increase indicates relaxation of the Si-O bond length and Si-O-Si bond angle of metastable oxygen atoms.

Bonding structure of ultrathin oxides on Si(110) surface

Yamamoto, Yoshihisa*; Togashi, Hideaki*; Kato, Atsushi*; Suemitsu, Maki*; Narita, Yuzuru*; Teraoka, Yuden; Yoshigoe, Akitaka

Materials Research Society Symposium Proceedings, Vol.1074, p.36 - 40, 2008/00

In this study, we have investigated the bonding structure of ultrathin oxide films on Si(110) surface by real-time SR-PES experiments. Experiments were conducted at surface chemistry end-station settled at BL23SU in SPring-8. The oxidation temperature was 813 K and the O pressure was 1.110 Pa. As a result, we found that one of the surface core-level shifts in Si 2p spectrum, related to the 1st and the 2nd layer Si atoms, decreases rapidly, coincident with the rapid initial development of the O1s spectrum. This indicates high reactivity of the Si(110)-162 reconstructed surface with oxygen molecules.

Observation of initial oxidation on Si(110)-162 surface by scanning tunneling microscopy

Togashi, Hideaki*; Takahashi, Yuya*; Kato, Atsushi*; Konno, Atsushi*; Asaoka, Hidehito; Suemitsu, Maki*

Japanese Journal of Applied Physics, Part 1, 46(5B), p.3239 - 3243, 2007/05

https://doi.org/10.1143/JJAP.46.3239

On Si(110) surface, the hole mobility is enhanced as compared with that on Si(001) surface. This surface is also to be used in the next-generation three-dimensional devices. We conducted scanning-tunneling-microscopy (STM) observation on the initial oxidation of Si(110)-162 surface. The present result suggests less occurrence of etching under the oxidation condition. There is a possibility to form an abrupt oxide/Si interface on the Si(110) surface.

XPS and STM studies on initial oxidation of Si(110)-162

Suemitsu, Maki*; Togashi, Hideaki*; Kato, Atsushi*; Takahashi, Yuya*; Konno, Atsushi*; Yamamoto, Yoshihisa*; Teraoka, Yuden; Yoshigoe, Akitaka; Asaoka, Hidehito

Materials Research Society Symposium Proceedings, Vol.996, p.19 - 25, 2007/00

https://doi.org/10.1557/PROC-0996-H01-04

From its high hole mobility, as well as its inevitable usage as an active layer in multi-gated FETs, Si(110) surface is expected to play a crucial role in the next generation CMOS devices. We have investigated the initial oxidation of Si(110) surface by using SR-XPS and STM. Reflecting its atomistic structure of the 162 reconstruction, initial oxidation of Si(110) surface shows a unique behavior which is not observed on other surfaces like (111) and (001).

Real-time observation of initial thermal oxidation on Si(110)-162 surface by photoemission spectroscopy

Suemitsu, Maki*; Kato, Atsushi*; Togashi, Hideaki*; Konno, Atsushi*; Yamamoto, Yoshihisa*; Teraoka, Yuden; Yoshigoe, Akitaka; Enta, Yoshiharu*; Narita, Yuzuru*

ECS Transactions, 3(2), p.311 - 316, 2006/00

https://doi.org/10.1149/1.2356291

Initial thermal oxidation of Si(110) surface has been investigated by using real-time X-ray photoemission spectroscopy with synchrotron radiation. The Si(110) initial oxidation is characterized by presence of a rapid oxidation just after the introduction of gaseous oxygen molecules. Peak separation of the O1s photoemission spectra suggests the presence of at least two distinct oxidation sites on the surface, which may reflect the complicated surface structure of the Si(110)-162 reconstruction.