本文／２　研究紹介（鷺坂・他）３０６－３１４Ｃ

Vol. 26, No. 6, pp. 306 314, 2005 Si 100 305 0047 1 2 1 2005 2 24 Phase Manipulation on Si(100) Surfaces and their Ground State Structure Keisuke SAGISAKA and Daisuke FUJITA Nanomaterials Laboratory, NationalInstitute for Materials Science 1 2 1 Sengen, Tsukuba, Ibaraki 305 0047 (Received February 24, 2005) Scanning tunneling microscopy (STM) and spectroscopy (STS) were used to study the surface phase manipulation between c(4 2) and p(2 2) on the Si(100) surfaces at 6 K. We found that there is a correlation between the sample voltage range that induced p(2 2) (c(4 2)) and the energy position of the π (π )state with respect to the Fermi level. This suggests that electron injection into the π state caused the emergence of p(2 2), while the hole injection into π state retrieved the c(4 2) surfaces. Moreover, field emission from the STM tip and the subsequent STM observation confirmed that electron beam irradiation onto the Si(100) surfaces caused flip-flop motion of dimers. Such findings resolved recent controversy in the observations of the Si(100) surfaces at low temperatures using STM and low energy electron diffraction. We concluded that the c(4 2) structure is the most stable and the p(2 2) phase is a meta-stable structure. 1 STM STM STM Si 100 STM Si 100 2 1 Si 1 2 Fig. 1 b Fig. 1 c E-mail: SAGISAKA.Keisuke@nims.go.jp 2 1 2 200 K 3 2 STM Fig. 1 f c 4 2 Fig. 1 d p 2 2 Fig. 1 e c 4 2 p 2 2 Fig. 1 f p 2 2 c 4 2 200 K STM c 4 2 2

307 Fig. 1. (a) (e) Schematic models for Si(100) reconstruction. (a) Ideal surface, (b) 2 1 symmetric dimer, (c) 2 1 asymmetric dimer, (d) c(4 2), (e) p(2 2), (f) STM image of Si(100) surface. 4 6 c 4 2 c 4 2 p 2 2 mev 7 STM c 4 2 p 2 2 Yokoyama Takayanagi 5 K 8 Shigekawa 9K n p 2 2 40 K c 4 2 p 2 2 9 c 4 2 STM 10 STM Matsumoto LEED 40 K 4 2 11 Si 100 Si 100 STM c 4 2 p 2 2 12 Fig. 2. A series of empty state images of Si(100) observed with an increasing sample voltage at 6 K. Sample voltage: (a) 0.75 V, (b) 0.9 V, (c) 1.0 V, (d) 1.1 V, (e) 1.2 V, and (f) 1.6 V, Tunneling current: 5.0 na, Sample: 0.01 Ω cm (P-doped). p 2 2 STM 13 670 mk c 4 2 14 Si 100 STM 2 p 2 2 Fig. 2 a 6 K V 0.75 V I 5.0 na n Si 100 0.01 Ω cm STM c 4 2 p 2 2 0.05 V 3

308 26 6 2005 c 4 2 p 2 2 Fig. 2 b V 0.9 V p 2 2 Fig. 2 c d p 2 2 V 1.2 V Fig. 2 e V 1.6 V Fig. 2 f STM 2 STM Si 100 1 STM Qin 15 Hata 5 Fig. 2 STM 1 2 4 nm 10 20 V STM 1 STM 30 30 nm c 4 2 p 2 2 Fig. 3 2 3 Fig. 3 a 0.01 Ω cm Fig. 2 I 0.05 na V 0.43 V c 4 2 90 p 2 2 10 V 0.6 V p 2 2 V 0.9 V p 2 2 V 1.0 V Fig. 2 f Fig. 3. Domain populations of c(4 2), p(2 2), and flip-flop dimers as a function of the sample voltage. Sample: (a) 0.01 Ω cm (P-doped), (b) 0.001 Ω cm (Asdoped). 4

309 I 0.5 na 5.0 na STM I 5 pa 100 na Fig. 3 b 0.001 Ω cm 0.01 Ω cm STM Ge 100 16 17 Takagi 17 Fig. 3 I 0.05 na 5.0 na 0.23 nm Fig. 3 a Fig. 3 b Fig. 3 Fig. 2 Fig. 3 a 0.01 Ω cm Si 100 STM STS Fig. 4 6 K 0.01 Ω cm 0.001 Ω cm STS Si 100 2 1 25 3 π π 1 π 2 18 19 20 22 π 2 Fujimoto π2 STM 22 Fig. 4. STS spectra from the Si(100) surface at 6 K as a function of the set point current. Sample: (a) 0.01 Ω cm (P-doped), (b) 0.001 Ω cm (As-doped). 0.01 Ω cm Fig. 3 a I 0.05 na 5.0 na π π 2 0.3 ev 5

310 26 6 2005 0.6 ev 23 n Si 100 π1 π1 1eV π 2 21 22 π 1 0.001 Ω cm 24 Fig. 3 Fig. 4 π 1 π 2 p 2 2 p 2 2 π2 p 2 2 π 1 π 2 Fig. 2 STM Fig. 5 a 0.001 Ω cm V 0.9 V 1 0.1 V V 0.3 V STM 4 p 2 2 V 0.9 V 1 V 0.3 V Fig. 5 b Fig. 5 a p 2 2 Fig. 5. Empty state images of the Si(100) surface at 6 K recorded with V= 0.3 V. (a) After the sample voltage was decremented from V= 0.9 V to 0.3 V by 0.1 V every one frame, (b) Immediately after the surface was scanned with V= 0.9 V, (c) Immediately after the surface of (b) was scanned with V= 1.2 V. Sample: 0.001 Wcm (As-doped), Tunneling current: 5.0 na. 0.1 0.2 ev 25 26 π p 2 2 p 2 2 6

311 Fig. 5 b p 2 2 c 4 2 p 2 2 c 4 2 Fig. 5 a c 4 2 p 2 2 12 27 STM π 2 STM Fig. 2 f Fig. 5 b Fig. 5 c Fig. 5 b V 1.2 V 1 V 0.3 V STM c 4 2 V 0.3 V π 2 STM p 2 2 3 STM Fig. 6 a 6K 0.01 Ω cm p 2 2 STM V 0.8 Fig. 6. (a) (b) Empty state images of the Si(100) surface at 6 K (a) before and (b) after a pulse voltage of 0.8 V (5-ms duration) was applied. Sample: 0.01 Ω cm (P-doped), Sample voltage: 0.55 V, Tunneling current: 0.5 na. (c) The size of the affected area by a pulse voltage as a function of the applied pulse voltage. The inset shows monitored tunneling current when a pulse voltage of 1.0 Vwasapplied. 7

312 26 6 2005 V 5 ms STM Fig. 6 b Fig. 6 a c 4 2 Fig. 6 c c 4 2 p 2 2 1 Fig. 4 a STS π π Fig. 6 c V 1.0 V 1.0 na 0.1 na 0.5 na 0.06 na π c 4 2 4 Si 100 π 1 π 2 π p 2 2 π c 4 2 π c 4 2 p 2 2 c 4 2 1 c 4 2 p 2 2 mev dimer 7 4 6 Nara 28 Seino 29 c 4 2 p 2 2 Nara c 4 2 28 p 2 2 c 4 2 Fig. 2 Fig. 5 p 2 2 p 2 2 STM Fig. 6 c 4 2 30 19 7 21 22 π π 1eV π π 31 π 1 32 33 π 2 π p 2 2 π c 4 2 Fig. 5 π c 4 2 π p 2 2 8

313 5 Si 100 LEED 40 K 11 STM Si 100 LEED Yoshida Fig. 2 p 2 2 10 p 2 2 c 4 2 STM Fig. 7 a p 2 2 5 STM Fig. 7 b 50 nm LEED V 60 V I 0.1 µa 5 STM Fig. 7 c p 2 2 c 4 2 Fig. 7 3 STM Fig. 7 c 4 2 c 4 2 Fig. 7 c c 4 2 p 2 2 c 4 2 p 2 2 p 2 2 LEED c 4 2 Fig. 7. Empty state images of the Si(100) surface at 6 K. (a) the initial surface of p(2 2), (b) 5 min after the tip was kept away from the tunneling region, (c) after 5- min electron beam irradiation by field emission from the STM tip (V= 60 V, I=0.1 µa, tip-surface distance: approximately 50 nm). Sample: 0.01 Ω cm (Pdoped), Sample voltage: 0.6 V, Tunneling current: 1.0 na. 11 c 4 2 c 4 2 9

314 26 6 2005 Fig. 7 c c 4 2 LEED Mizuno 34 6 STM Si 100 Si 100 c 4 2 p 2 2 Ge 100 40 K 35 Ge 100 80 K 16 17 Si π1 π 1 π 1 p 2 2 33 1) R.M. Tromp, R.J. Hamers and J.E. Demuth: Phys. Rev. Lett. 55, 1303 (1985). 2) R.J. Hamers, R.M. Tromp and J.E. Demuth: Phys. Rev. B 34, 5343 (1986). 3) R.A. Wolkow: Phys. Rev. Lett. 68, 2636 (1992). 4) H. Tochihara, T. Amakusa and M. Iwatsuki: Phys. Rev. B 50, R12262 (1994). 5) K. Hata, S. Yasuda and H. Shigekawa: Phys. Rev. B 60, 8164 (1999). 6) D. Badt, H. Wengelnik and H. Neddermeyer: J. Vac. Sci. Technol. B 12, 2015 (1994). 7) A. Ramstad, G. Brocks and P.J. Kelly: Phys. Rev. B 51, 14504 (1995). 8) T. Yokoyama and K. Takayanagi: Phys. Rev. B 61, R 5078 (2000). 9) K. Hata, S. Yoshida and H. Shigekawa: Phys. Rev. Lett. 89, 286104 (2002). 10) S. Yoshida, T. Kimura, O. Takeuchi, K. Hata, H. Oigawa, T. Nagamura, H. Sakama and H. Shigekawa: Phys. Rev. B 70, 235411 (2004). 11) M. Matsumoto, K. Fukutani and T. Okano: Phys. Rev. Lett. 90, 106103 (2003). 12) K. Sagisaka, M. Kitahara and D. Fujita: Jpn. J. Appl. Phys. 42, L126 (2003). 13) K. Sagisaka, D. Fujita and G. Kido: Phys. Rev. Lett. 91, 146103 (2003). 14) K. Sagisaka, M. Kitahara, D. Fujita, G. Kido and N. Koguchi: Nanotechnology 15, S375 (2004). 15) X.R. Qin and M.G. Lagally: Phys. Rev. B 59, 7293 (1999). 16) Y. Takagi, Y. Yoshimoto, K. Nakatsuji and F. Komori: J. Phys. Soc. Jpn. 72, 2425 (2003). 17) Y. Takagi, Y. Yoshimoto, K. Nakatsuji and F. Komori: Surf. Sci. 559, 1(2004). 18) K. Hata, Y. Shibata and H. Shigekawa: Phys. Rev. B 64, 235310 (2001). 19) L.S.O. Johansson and B. Reihl: Surf. Sci. 269 270, 810 (1992). 20) H. Kageshima and M. Tsukada: Phys. Rev. B 46, 6928 (1992). 21) J.E. Northrup: Phys. Rev. B 47, R10032 (1993). 22) Y. Fujimoto, H. Okada, K. Endo, T. Ono, S. Tsukamoto and K. Hirose: Mater. Trans. 42, 2247 (2001). 23) M. McEllistrem, G. Haase, D. Chen and R.J. Hamers: Phys. Rev. Lett. 70, 2471 (1993). 24) S.M. Sze: Semiconductor Devices, Physics and Technology 2 nd Ed. (Wiley, 2001). 25) G.S. Hwang: Surf. Sci. 465, L789 (2000). 26) K. Hata, Y. Sainoo and H. Shigekawa: Phys. Rev. Lett. 86, 3084 (2001). 27) H. Shigekawa, K. Miyake, M. Ishida, K. Hata, H. Oigawa, Y. Nannichi, R. Yoshizaki, A. Kawazu, T. Abe, T. Ozawa and T. Nagamura: Jpn. J. Appl. Phys. 35, L1081 (1996). 28) J. Nara, H. Momida and T. Ohno: manuscript in preparation. 29) K. Seino, W.G. Schmidt and F. Bechstedt: Phys. Rev. Lett. 93, 036101 (2004). 30) L.S.O. Johansson, R.I.G. Uhrberg, P. Martensson and G. V. Hansson: Phys. Rev. B 42, 1305 (1990). 31) F.J. Himpsel and Th. Fauster: J. Vac. Sci. Technol. A 2, 815 (1984). 32) T. Yokoyama, M. Okamoto and K. Takayanagi: Phys. Rev. Lett. 81, 3423 (1998). 33) K. Sagisaka and D. Fujita: in press. 34) S. Mizuno, T. Shirasawa, Y. Shiraishi and H. Tochihara: Phys. Rev. B 69, 241306 (R) (2004). 35) K. Sagisaka, D. Fujita, G. Kido and N. Koguchi: Surf. Sci. 566 568, 767 (2004). 10