Alkanethiol self-assembled monolayers (SAMs) of various methylene group chain lengths [HS(CH2)nCH3](n=9,11,13,15,17) were fabricated on the GaAs(001) surface followed by characterization using Fourier transform infrared spectroscopy. Modal analysis of the CH2 stretching mode region (28003000cm1) showed that linear scaling of the n-dependent factors accurately reproduced the spectral data, supporting a chain-length consistent physical model upon which a measurement of the absorption coefficient was based. Evaluated from the linearity of the absorbance data, a peak coefficient of 3.5×104cm1 was obtained and a domain for ordered self-assembly was assigned for values n>9. Compared with measurements of the absorption coefficient made in the liquid phase, the SAM phase coefficient was determined to be about six times greater. This enhancement effect is discussed in terms of contributions relating to the locally ordered environment and is largely attributed to the chemical properties of the interface. We believe this to be the first demonstration of IR spectral enhancement of a molecular species chemisorbed on the semiconductor surface.

1.
O. S.
Nakagawa
,
S.
Ashok
,
C. W.
Sheen
,
J.
Märtensson
, and
D. L.
Allara
,
Jpn. J. Appl. Phys., Part 1
30
,
3759
(
1991
).
2.
C. W.
Sheen
,
J. X.
Shi
,
J.
Märtensson
,
A. N.
Parikh
, and
D. L.
Allara
,
J. Am. Chem. Soc.
114
,
1514
(
1992
).
3.
K.
Adlkofer
and
M.
Tanaka
,
Langmuir
17
,
4267
(
2001
).
4.
Y.
Jun
,
X. Y.
Zhu
, and
J. W. P.
Hsu
,
Langmuir
22
,
3627
(
2006
).
5.
S.
Ye
,
G.
Li
,
H.
Noda
,
K.
Uosaki
, and
M.
Osawa
,
Surf. Sci.
529
,
163
(
2003
).
6.
Q.
Zhang
,
H.
Huang
,
H.
He
,
H.
Chen
,
H.
Shao
, and
Z.
Liu
,
Surf. Sci.
440
,
142
(
1999
).
7.
C. L.
McGuiness
,
A.
Shaporenko
,
C. K.
Mars
,
S.
Uppili
,
M.
Zharnikov
, and
D. L.
Allara
,
J. Am. Chem. Soc.
128
,
5231
(
2006
).
8.
C. L.
McGuiness
,
A.
Shaporenko
,
M.
Zharnikov
,
A. V.
Walker
, and
D. L.
Allara
,
J. Phys. Chem. C
111
,
4226
(
2007
).
9.
C. L.
McGuiness
,
D.
Blasini
,
J. P.
Masejewski
,
S.
Uppili
,
O. M.
Cabarcos
,
D.
Smilgies
, and
D. L.
Allara
,
ACS Nano
1
,
30
(
2007
).
10.
O.
Voznyy
and
J. J.
Dubowski
,
J. Phys. Chem. C
112
,
3726
(
2008
).
11.
D. M.
Wieliczka
,
X.
Ding
, and
J. J.
Dubowski
,
J. Vac. Sci. Technol. A
24
,
1756
(
2006
).
12.
S.
Lodha
and
D. B.
Janes
,
J. Appl. Phys.
100
,
024503
(
2006
).
13.
G.
Nesher
,
A.
Vilan
,
H.
Cohen
,
D.
Cahen
,
F.
Amy
,
C.
Chan
,
J.
Hwang
, and
A.
Kahn
,
J. Phys. Chem. B
110
,
14363
(
2006
).
14.
L.
Mohaddes-Ardabili
,
L. J.
Martínez-Miranda
,
J.
Silverman
,
A.
Christou
,
L. G.
Salamanca-Riba
, and
M.
Al-Sheikhly
,
Appl. Phys. Lett.
83
,
192
(
2003
).
15.
X.
Ding
,
K. H.
Moumanis
,
J. J.
Dubowski
,
E. H.
Frost
, and
E.
Escher
,
Appl. Phys. A: Mater. Sci. Process.
83
,
357
(
2006
).
16.
X.
Ding
,
K.
Moumanis
,
J. J.
Dubowski
,
L.
Tay
, and
N. L.
Rowell
,
J. Appl. Phys.
99
,
054701
(
2006
).
17.
L. H.
Dubois
and
R. G.
Nuzzo
,
Annu. Rev. Phys. Chem.
43
,
437
(
1992
).
18.
R. G.
Nuzzo
,
L. H.
Dubois
, and
D. L.
Allara
,
J. Am. Chem. Soc.
112
,
558
(
1990
).
19.
D.
Li
,
B. I.
Swanson
,
J. M.
Robinson
, and
M. A.
Hoffbauer
,
J. Am. Chem. Soc.
115
,
6975
(
1993
).
20.
I.
Zawisza
,
A.
Lachenwitzer
,
V.
Zamlynny
,
S. L.
Horswell
,
J. D.
Goddard
, and
J.
Lipkowski
,
Biophys. J.
85
,
4055
(
2003
).
21.
A. N.
Parikh
and
D. L.
Allara
,
J. Chem. Phys.
96
,
927
(
1992
).
22.
D. L.
Allara
and
R. G.
Nuzzo
,
Langmuir
1
,
52
(
1985
).
23.
S.
Flink
,
F. C. J. M.
van Veggel
, and
D. N.
Reinhoudt
,
Adv. Mater. (Weinheim, Ger.)
12
,
1315
(
2000
).
24.
M. V.
Lebedev
,
D.
Ensling
,
R.
Hunger
,
T.
Mayer
, and
W.
Jaegermann
,
Appl. Surf. Sci.
229
,
226
(
2004
).
25.
C.
Bryce
and
D.
Berk
,
Ind. Eng. Chem. Res.
35
,
4464
(
1996
).
26.
Sample preparation carried out in a nitrogen purged glovebox mitigated the negative effects of humidity and oxidation as described in Ref. 7. This was particularly relevant in order to achieve good results for SAMs n<15.
27.
Alkanethiols n15 (solid/liquid) and n17 (solid) cannot be measured in the liquid phase at room temperature.
28.
K. D.
Truong
and
P. A.
Roundtree
,
J. Phys. Chem.
100
,
19917
(
1996
).
29.
J.
Hautman
and
M. L.
Klein
,
J. Chem. Phys.
93
,
7483
(
1990
).
30.
H. L.
Casal
,
D. G.
Cameron
, and
H. H.
Mantsch
,
Can. J. Chem.
61
,
1736
(
1983
).
31.
D. L.
Allara
, personal communication (14 May
2008
).
32.
M.
Osawa
, in
Near-Field Optics and Surface Plasmon Polaritons
,
Topics in Applied Physics
Vol.
81
, edited by
S.
Kawata
(
Springer-Verlag
,
Berlin
,
2001
), p.
163
.
33.
J.
Hautman
and
M. L.
Klein
,
J. Chem. Phys.
91
,
4994
(
1989
).
34.
A.
Ulman
,
J. E.
Eilers
, and
N.
Tillman
,
Langmuir
5
,
1147
(
1989
).
35.
H.
Torii
,
J. Comput. Chem.
23
,
997
(
2002
).
36.
S.
Howell
,
D.
Kuila
,
B.
Kasibhatla
,
C. P.
Kubiak
,
D.
Janes
, and
R.
Reifenberger
,
Langmuir
18
,
5120
(
2002
).
37.
B. N. J.
Persson
and
A.
Liebsch
,
Surf. Sci.
110
,
356
(
1981
).
38.
P.
Dumas
,
R. G.
Tobin
, and
P. L.
Richards
,
Surf. Sci.
171
,
555
(
1986
).
39.
D.
Enders
and
A.
Pucci
,
Appl. Phys. Lett.
88
,
184104
(
2006
).
40.
M.
Osawa
and
M.
Ikeda
,
J. Phys. Chem.
95
,
9914
(
1991
).
41.
B. N. J.
Persson
and
R.
Ryberg
,
Phys. Rev. B
24
,
6954
(
1981
).
You do not currently have access to this content.