The interaction of water with freshly cleaved surfaces has been studied using scanning force microscopy operated in different modes at room temperature and under controlled humidity. The Kelvin probe microscopy (KPM) mode has been used to study the evolution of the surface potential differences (SPDs). In the 20%–50% relative humidity (RH) range, adsorbed water forms two-dimensional solidlike bilayers (islands). The SPD between water islands and the bare substrate surface exhibits a sign crossover from negative at low RHs to positive at higher RHs, evidencing a cooperative and irreversible flipping of the preferential orientation of water dipoles, from pointing toward the surface evolving into the opposite direction. The KPM results suggest that the classical hexagonal bilayer configuration is not the most favorable structure.
REFERENCES
1.
C. Y.
Lee
, J. A.
McCammon
, and P. J.
Rossky
, J. Chem. Phys.
80
, 4448
(1984
).2.
M. A.
Henderson
, Surf. Sci. Rep.
46
, 1
(2002
).3.
G. A.
Kimmel
, N. G.
Petrik
, Z.
Dohnálek
, and B. D.
Kay
, Phys. Rev. Lett.
95
, 166102
(2005
).4.
R.
Zangi
and J. B. F. N.
Engberts
, J. Am. Chem. Soc.
127
, 2272
(2005
).5.
A.
Verdaguer
, G. M.
Sacha
, H.
Bluhm
, and M.
Salmeron
, Chem. Rev.
106
, 1478
(2006
).6.
K. B.
Jinesh
and J. W. M.
Frenken
, Phys. Rev. Lett.
96
, 166103
(2006
).7.
S.
Yamamoto
, K.
Andersson
, H.
Bluhm
, G.
Ketteler
, D. E.
Starr
, T.
Schiros
, H.
Ogasawara
, L. G. M.
Pettersson
, M.
Salmeron
, and A.
Nilsson
, J. Phys. Chem. C
111
, 7848
(2007
).8.
J.
Vogt
, J. Chem. Phys.
126
, 244710
(2007
).9.
B.
Vonnegut
, J. Appl. Phys.
18
, 593
(1947
).10.
J. P.
Devlin
and V.
Buch
, J. Phys. Chem.
99
, 16534
(1995
).11.
G. E.
Ewing
, Chem. Rev. (Washington, D.C.)
106
, 1511
(2006
), and references therein.12.
J. E.
Zink
, J.
Reif
, and E.
Matthias
, Phys. Rev. Lett.
68
, 3595
(1992
).13.
V.
Sadtchenko
, P.
Conrad
, and G. E.
Ewing
, J. Phys. Chem.
116
, 4293
(2002
).14.
B.
Wassermann
, J.
Reif
, and E.
Matthias
, Phys. Rev. B
50
, 2593
(1994
).15.
K.
Miura
, Phys. Rev. B
52
, 7872
(1995
).16.
V.
Sadtchenko
, G. E.
Ewing
, D. R.
Nutt
, and A. J.
Stone
, Langmuir
18
, 4632
(2002
).17.
D. R.
Nutt
and A. J.
Stone
, J. Chem. Phys.
117
, 800
(2002
).18.
D.
Takaiwa
, I.
Hatano
, K.
Koga
, and H.
Tanaka
, Proc. Natl. Acad. Sci. U.S.A.
105
, 39
(2008
).19.
J.
Hu
, X. -D.
Xiao
, and M.
Salmeron
, Appl. Phys. Lett.
67
, 476
(1995
).20.
H.
Fukazawa
, S.
Ikeda
, and S.
Mae
, Chem. Phys. Lett.
282
, 215
(1998
).21.
S.
Gómez-Moñivas
, J. J.
Sáenz
, R.
Carminati
, and J. J.
Greffet
, Appl. Phys. Lett.
76
, 2955
(2000
).22.
N.
Nonnenmacher
, M. P.
O’ Boyle
, and H. K.
Wickramasinghe
, Appl. Phys. Lett.
58
, 2921
(1991
).23.
A.
Verdaguer
, G. M.
Sacha
, M.
Luna
, K. D.
Ogletree
, and M.
Salmeron
, J. Chem. Phys.
123
, 124703
(2005
).24.
A.
Verdaguer
, C.
Weis
, G.
Oncins
, G.
Ketteler
, H.
Bluhm
, and M.
Salmeron
, Langmuir
23
, 9699
(2007
).25.
M.
Luna
, J.
Colchero
, and A. M.
Baró
, J. Phys. Chem. B
103
, 9576
(1999
).26.
J.
Fraxedas
, A.
Verdaguer
, F.
Sanz
, S.
Baudron
, and P.
Batail
, Surf. Sci.
588
, 41
(2005
).27.
G. M.
Sacha
, A.
Verdaguer
, and M.
Salmeron
, J. Phys. Chem. B
110
, 14870
(2006
).28.
We cannot exclude the contribution of contaminants as the source of the dispersion on SPD values since experiments were performed in ambient conditions.
29.
Y.
Wu
, J. T.
Mayer
, E.
Garfunkel
, and T. E.
Madey
, Langmuir
10
, 1482
(1994
).30.
S.
Gómez-Moñivas
, L. S.
Froufe
, R.
Carminati
, J. J.
Greffet
, and J. J.
Sáenz
, Nanotechnology
12
, 496
(2001
).31.
K.
Miura
, T.
Yamada
, M.
Ishikawa
, and S.
Okita
, Appl. Surf. Sci.
140
, 415
(1999
).32.
Y.
Wu
, K.
Hayashi
, N.
Saito
, H.
Sugimura
, and O.
Takai
, Surf. Interface Anal.
35
, 94
(2003
).33.
In our experimental setup, , , and , so that the applied voltage is always positive [see Eq. (1)]. Such polarity should induce a negative charge in a polarizable sample. Since the observed dipolar distribution at higher RHs is positive we can safely exclude any instrumental contribution, although a minor contribution for negative SPD values cannot be excluded.
34.
For a discussion on the stabilization of metastable films, see, i.e.,
A.
Glebov
, A. P.
Graham
, A.
Menzel
, and J. P.
Toennies
, J. Chem. Phys.
106
, 9382
(1997
);Fig. 9 from Ref. 5;
J.
Fraxedas
, J.
Caro
, J.
Santiso
, A.
Figueras
, P.
Gorostiza
, and F.
Sanz
, Europhys. Lett.
48
, 461
(1999
).© 2008 American Institute of Physics.
2008
American Institute of Physics
You do not currently have access to this content.
