No data available.
Please log in to see this content.
You have no subscription access to this content.
No metrics data to plot.
The attempt to load metrics for this article has failed.
The attempt to plot a graph for these metrics has failed.
Quantitative determination of molecular structure in multilayered thin films of biaxial and lower symmetry from photon spectroscopies. I. Reflection infrared vibrational spectroscopy
1.J. D. Swalen, D. L. Allara, J. D. Andrade, E. A. Chandross, S. Garoff, J. Israelachvilli, T. J. McCarthy, R. F. Pease, J. F. Rabolt, K. J. Wynne, and H. Yu, Langmuir 3, 932 (1987), and selected references cited therein.
2.V. Narayanamurty, Science 235, 1023 (1987);
2.M. B. Panish, Science 208, 916 (1980)., Science
3.Organic Materials for Non-linear Optics, edited by R. A. Hann and D. Bloor (CRC, Florida, 1989);
3.Non-linear Optical Effects in Organic Polymers, edited by J. Messier, F. Kajzar, P. Prasad, and D. Ulrich (NATO Adv. Sci. Ins. Series, 1989);
3.W. L. Barnes and J. R. Sambles, Surf. Sci. 177, 399 (1986);
3.A. S. Dewa, C. D. Fung, E. P. Dipoto, and S. E. Rickert, Thin Solid Films 132, 27 (1985);
3.A. Al-Mohamad, C. W. Smith, I. S. Al-Saffar, and M. A. Slifkin, Thin Solid Films 189, 175 (1990), and references cited therein.
4.J. D. Swalen, J. Mol. Electron. 2, 155 (1986).
5.G. G. Roberts, Adv. Phys. 34, 475 (1985).
6.A. T. Hubbard, Langmuir 6, 97 (1990), and references cited therein;
6.L. R. Faulkner, Chem. Eng. News 28 (1984);
6.R. W. Murray, in Electroanalytical Chemisty, 13, edited by A. J. Bard (Marcel Dekker, New York, 1984);
6.R. W. Murray, Annu. Rev. Mater. Sci. 14, 145 (1984);
6.C. E. D. Chidsey and R. W. Murray, Science 231, 25 (1986);
6.M. S. Wrighton, Science 231, 32 (1986)., Science
7.B. D. Ratner, in Biomaterials: Interfacial Phenomena and Applications, edited by S. L. Cooper and N. A. Peppas, Advances in Chemistry (ACS, Washington, D. C., 1982), Vol. 199, Chap. 2;
7.Surfaces and Interfacial Aspects of Biopolymers, edited by J. D. Andrade (Plenum, New York, 1985);
7.A. A. Durrani and D. Chapman, in Polymer Surfaces and Interfaces, edited by W. J. Feast and H. S. Munro (Wiley, Chichester, 1987), Chap. 11;
7.T. H. Watts, A. A. Brian, J. W. Kappler, P. Marrack, and H. M. McConnell, Proc. Natl. Acad. Sci. 81, 6159 (1984), and references cited therein.
8.G. L. Gaines, Insoluble Monolayers (Interscience, New York, 1966);
8.Langmuir Blodgett Films, edited by G. G. Roberts (Plenum, New York, 1990).
9.P. S. Pershan, Proc. Natl. Acad. Sci. U.S.A. 84, 4692 (1987).
10.S. R. Wasserman, G. M. Whitesides, I. M. Tidswell, B. M. Ocko, P. S. Pershan, and J. D. Axe, J. Am. Chem. Soc. 111, 5852 (1989).
11.S. B. Dierker, C. A. Murray, J. D. Lagrange, and N. E. Schlotter, Chem. Phys. Lett. 137, 453 (1987).
12.S. S. Perry and A. Campion, Surf. Sci. Lett. 234, 1275 (1990).
13.S. H. Chen and C. W. Frank, Langmuir 5, 978 (1989).
14.T. Murakata, T. Miyashita, and M. Matsuda, Langmuir 2, 786 (1986).
15.H. Arwin and D. E. Aspnes, Thin Solid Films 138, 195 (1986).
16.Y.-T. Kim, D. L. Allara, R. W. Collins, and K. Vedam, Thin Solid Films 193, 350 (1990).
17.D. L. Allara and R. G. Nuzzo, Langmuir 1, 52 (1985).
18.R. G. Nuzzo, L. H. Dubois, and D. L. Allara, J. Am. Chem. Soc. 112, 558 (1990).
19.M. D. Porter, Anal. Chem. 60, A1143 (1988).
20.R. G. Greenler, J. Chem. Phys. 44, 310 (1965).
21.J. D. E. McIntyre, in Advances in Electrochemistry and Electrochemical Engineering, edited by P. Delahay and C. W. Tobias (Wiley, New York, 1976), Vol. 9, p. 61.
22.W. N. Hansen, in Advances in Electrochemistry and Eletrochemical Engineering, edited by P. Delahay and C. W. Tobias (Wiley, New York, 1976), Vol. 9, p. 1.
23.R. A. Dluhy, J. Phys. Chem. 90, 1373 (1985).
24.M. L. Mitchell and R. A. Dluhy, J. Am. Chem. Soc. 110, 712 (1988).
25.A. Udagawa, T. Matsui, and S. Tanaka, Appl. Spectrosc. 40, 794 (1986).
26.Y. S. Yen and J. S. Wong, J. Phys. Chem. 93, 7208 (1989).
27.M. D. Porter, T. B. Bright, D. L. Allara, and T. Kuwana, Anal. Chem. 58, 2461 (1986).
28.D. W. Berreman, Phys. Rev. 130, 2193 (1963).
29.In fact, based on the initial work by Berreman, the physical basis of Yen and Wong’s calculation is identical to an earlier treatment of very similar film spectra which gave quantitative understanding of the spectra (see Ref. 31). It thus seems likely that their calculations of LO modes from dielectric function inversion suffered from numerical errors. In fact, in this regard one unphysical consequence of their approximations is the appearance of LO modes outside the bandwidth of optical constants as an independent absorption peak. This must be erroneous since the LO and TO modes represent the minimum and maximum limiting absolute values of the complex dielectric function and must be confined within the bandwidth of the optical resonance.
30.P. A. Chollet, J. Messier, and C. Rosilio, J. Chem. Phys. 64, 1042 (1976).
31.D. L. Allara, A. Baca, and C. A. Pryde, Macromolecules 11, 1215 (1978).
32.Y. Ishino and H. Ishida, Langmuir 4, 1341 (1988).
33.The equations presented in by Ishino and Ishida (Ref. 32) do not lead to correct simulations of spectra. Derivation of these equations from their original sources do lead to correct relationships. Since there appear to be significant errors, the reader should refer to the original sources.
34.F. Abeles, H. A. Washburn, and H. H. Soonpaa, J. Opt. Soc. Am. 63, 104 (1973).
35.D. E. Aspnes, J. Opt. Soc. Am. 70, 1275 (1980), and references cited therein.
36.D. E. Aspnes, in Optical Properties of Solid: New Developments, edited by B. O. Seraphin, (North-Holland, Amsterdam, 1976), p. 799;
36.D. E. Aspnes, Thin Solid Films 89, 249 (1982).
37.J. C. Charmet and P. G. De Gennes, J. Opt. Soc. Am. 73, 1777 (1983).
38.B. B. Sauer, H. Yu, and M. W. Kim, Langmuir 5, 278 (1989).
39.G. T. Ayoub and N. M. Bashara, J. Opt. Soc. Am. 68, 978 (1978).
40.D. J. De Smet, J. Opt. Soc. Am. 64, 631 (1974);
40.I. J. Hodgkinson, F. Horowitz, H. A. Macleod, M. Sikkens, and J. J. Wharton, J. Opt. Soc. Am. A 2, 1693 (1985).
41.A. N. Parikh and D. L. Allara (manuscript in preparation).
42.D. A. Holmes and D. L. Feucht, J. Opt. Soc. Am. 56, 1763 (1966).
43.S. Teitler and B. W. Hanvis, J. Opt. Soc. Am. 60, 830 (1970).
44.P. Yeh, J. Opt. Soc. Am. 69, 742 (1979).
45.P. Yeh, Surf. Sci. 80, 41 (1979).
46.P. Yeh, Optical Waves in Layered Media (Wiley-Interscience, New York, 1988).
47.D. W. Berreman, J. Opt. Soc. Am. 62, 502 (1972).
48.P. J. Lin-Chung and S. Teitler, J. Opt. Soc. Am. A 1, 703 (1984).
49.R. S. Weis and T. K. Gaylord, J. Opt. Soc. Am. A 4, 1720 (1987).
50.D. Y. K. Ko and J. R. Sambles, J. Opt. Soc. Am. A 5, 1863 (1988). The scattering matrix approaches are based on relating the outgoing waves from a layered media to the incoming waves by a scattering matrix, each outgoing and incoming wave expressed in terms of forward and backward propagating modes. The treatment effectively separates exponentially growing modes from decaying modes and thus adds stability in computations for angles of incidence beyond the critical angle for which evanescent waves are generated. The formalism is mathematically and computationally more complicated, and the increased overhead is justified only for cases involving angles higher than the critical angle.
51.M. Born and E. Wolf, Principles of Optics, 5th ed. (Pergamon, New York, 1965).
52.D. Bohm, Quantum Theory (Prentice-Hall, Englewood Cliffs, 1951).
53.For example, see F. Stern, in Solid State Physics, Advances in Research and Applications, edited by F. Seitz and D. Turnbull (Academic, New York, 1963), Vol. 15, p. 299.
54.There are two important points to mention about Eq. (3.3). First, to avoid the singularity at the pole some approximation must be used in numerical evaluation and the symbol P (principal part) implies that the integration goes around (avoids) the singularity. The range to generally contains the spectral absorption of interest, viz., is zero outside this range. However, since a variety of transitions occur from the x-ray regions through the rf region, in fact can never precisely be zero over large frequency ranges. Thus to avoid integrating from to the approximation term is added. The quantity represents the values of n outside the range and and is evaluated independently. In general, is actually a slowly varying function of ν (a dispersion tail) and the validity of a constant must be shown for each particular case. Errors in do not affect the functional form of but rather only introduce bias, usually an error of small significance. A comparison of the efficiencies of specific types of computational procedures for these transforms have been published (Ref. 55).
55.K. Ohta and H. Ishida, Appl. Spectrosc. 6, 952 (1988), and references cited therein.
56.R. G. Snyder, S. L. Hsu, and S. Krimm, Spectrochima Acta A 34, 395 (1978).
57.R. G. Snyder and J. H. Schachtschneider, Spectrochim. Acta 19, 85 (1963).
58.J. H. Schachtschneider and R. G. Snyder, Spectrochim. Acta 19, 117 (1963).
59.R. G. Snyder, J. Mol. Spectrosc. 4, 411 (1960).
60.G. Zerbi, in Advances in Applied Fourier Transform Infrared Spectroscopy, edited by M. W. MacKenzie (Wiley, New York, 1988).
61.M. Maroncelli, H. L. Strauss, and R. G. Snyder, J. Chem. Phys. 82, 2811 (1982).
62.In the limit of an optically excited electric dipole transition, the absorption spectrum of an isolated excited mode (a resonance) can be described by a classical damped oscillating dipole (Ref. 63). It can be specifically shown that the absorption coefficient, k, associated with an ensemble of independent oscillators in a material exhibits a Lorentzian line shape (Ref. 64), where is the maximum value of k and occurs at frequency As the complexity of the system increases from an ensemble of identical oscillators to an ensemble of slightly different noninteracting oscillators, inhomogeneous broadening (Ref. 64) of the line shape occurs due to the same nominal transition occuring at slightly different frequencies for different molecular oscillators in the ensemble. Typically, a Gaussian distributiòn of the density of oscillator states will occur in condensed phases of low degree of ordering. Thus, in general, each resonance line can be considered to have a distribution function which is a convolution of Lorentzian and Gaussian functions for condensed phase systems.
63.See, for example, A. C. G. Mitchell and M. W. Zemansky, in Resonance Radiation and Excited Atoms (Cambridge University, New York, 1961).
64.G. M. Barrow, Introduction to Molecular Spectroscopy (McGraw-Hill, New York, 1962).
65.The dipole moment transition matrix element is defined as where the and refer to the upper and the lower state wave functions and μ is the electric dipole operator (Ref. 52). In classical terms, p is the change in the dipole moment during an oscillation and for the case of vibrations of nuclei in the molecules, where q represents the normal coordinate direction of the vibrational mode and μ is the dipole moment of the associated group of vibrating nuclei. The quantity is often refered to as the dynamic dipole derivative.
66.E. B. Wilson, J. C. Decius, and P. C. Cross, Molecular Vibrations (McGraw-Hill, New York, 1950), p. 285.
67.For certain calculations, particularly polarization scrambling, it is necessary to define the simplest diagonalized optical tensor in terms of the direction (optic axis) of the transition moment at a given frequency, e.g., where the transition moment direction has been aligned along the z axis (x or y also would do). This tensor, defined for the principal optical axis is then rotated to any desired molecular configuration (or any desired external coordinate system) by a rotation transform as usual.
68.R. G. Greenler, J. Vac. Sci. Technol. 12, 1410 (1975).
69.A. N. Parikh and D. L. Allara (manuscript in preparation).
70.Analytical expressions, in general, are very difficult to derive for biaxial films and when derived are very complex and cumbersome. Some simplification results by considering films of lower than biaxial symmetry and, of course, for the well-studied case of isotropic films, the closed form analytical expressions for reflectivities and transmissivities can be easily obtained for the cases of two- and three-phase systems. For biaxial films, the best simplification to be made is a three phase isotropic/biaxial/isotropic system. For this system the matrix operations inherent in the method leads to a few dozen complex terms in the reflectivity expressions. Physical interpretation of these terms is unrewardingly complicated. One useful simplification arises when the incident beam is contained in the XZ plane (see Fig. 2, ) rendering β, the y component of propagation vector zero. If, further, the optical tensor is described in a diagonal form, then the analytical solution of the quartic polynomial in Eq. (A3) of the Appendix is easily afforded. The s- and p-mode propagation vectros are uncoupled and the z component γ of these propagation vectors is evaluated rather easily. For the s-mode propagation vector, and the polarization unit vector can be determined from the co-factors of the second row elements of the matrix equation (A3) of the Appendix. The polarization unit vector is For the p mode, However, the polarization unit vector for the p mode, in contrast to the s mode, does not provide a simple expression, but rather is complicated in its dependence on incidence angle and the tensor elements. The expressions beyond this point in the method become tedius and numerical computations provide a better alternative.
71.D. L. Allara and J. D. Swalen, J. Phys. Chem. 86, 2700 (1982).
72.J. F. Rabolt, F. C. Burns, N. E. Schlotter, and J. D. Swalen, J. Chem. Phys. 78, 946 (1983).
73.M. K. Debe, Appl. Surf. Sci. 14, 17 (1983).
74.M. K. Debe, J. Appl. Phys. 55, 3354 (1984).
75.P. A. Chollet, Thin Solid Films 52, 343 (1978).
76.X. Yang, M. Kardan, S. L. Hsu, D. Collard, R. B. Heath, and C. P. Lillya, J. Phys. Chem. 92, 196 (1988).
77.Specifically, in terms of Fig. 1, medium 1 is considered as the high refractive index propagating medium of the in/out beams, viz., the internal reflection element. Correspondingly, the medium 2 is the film and finally, after other intervening film media if required, the last medium is air. For purposes of the calculation the dense medium 1 can be correctly considered to contain the spectrometer and the detector since no power is lost during propagation through the medium itself, but only on reflection at the 1,2 interface. For n multiple internal reflections the final reflectivity change is where R is the fraction of input intensity exiting after one reflection. If the blank internal reflection element is used as a reference experimentally with reflectivity then the simulation should be done accordingly to give where refers to one bounce off a sample surface with the absorbing film removed.
78.G. M. Whitesides and P. E. Laibinis, Langmuir 6, 87 (1990), and references cited therein.
79.C. D. Bain, E. B. Troughton, Y.-T. Tao, J. Evall, G. M. Whitesides, and R. G. Nuzzo, J. Am. Chem. Soc. 111, 321 (1989).
80.M. D. Porter, T. B. Bright, D. L. Allara, C. E. D. Chidsey, J. Am. Chem. Soc. 109, 3559 (1987).
81.C. D. Bain and G. M. Whitesides, J. Phys. Chem. 93, 1670 (1989).
82.L. S. Strong and G. M. Whitesides, Langmuir 4, 546 (1988).
83.C. E. D. Chidsey, G.-Y. Liu, P. Rowntree, G. Scoles, J. Chem. Phys. 91, 4421 (1989).
84.A. Ulman, J. E. Eilers, and N. Tillman, Langmuir 5, 1147 (1989).
85.J. Hautman and M. L. Klein, J. Chem. Phys. 91, 4994 (1989).
86.R. G. Nuzzo, E. M. Korenic, and L. H. Dubois, J. Chem. Phys. 93, 767 (1990).
87.P. E. Laibinis, G. M. Whitesides, D. L. Allara, Y.-T. Tao, A. N. Parikh, and R. G. Nuzzo, J. Am. Chem. Soc. 113, 7152 (1991). Tables of optical function data are available upon request from the authors (D.L.A.).
88.W. L. Wolfe, in Handbook of Optics, edited by W. G. Driscoll and W. Vaughan (McGraw-Hill, New York, 1978), pp. 7–150.
89.If at a given frequency, the average orientation of a group of transition dipole moments for a given oscillator ensemble is at an oblique angle to the direction of polarization, then the resultant reflected beam can exhibit polarization scrambling, viz., some s component is created out of p or vice versa. Consequently four reflection spectra can be determined in principle for a given spectral condition. In general, the phenomenon depends upon the size of mismatch of optical functions at the film interface. For organic materials in the infrared region, oscillator strengths are not sufficient to induce measurable effects ( absorbance units scrambling from our calculations) However, for electronic transitions which can exhibit orders of magnitude larger oscillator strengths, such scrambling effects can be measurable and are accurately calculated from our calculations. In order to calculate these effects correctly it is necessary to choose the principal optic axis directly along the transition moment direction (Ref. 67). Arbitrary tensor construction will not keep track of the polarization correctly across an optical interface.
90.S. Garoff, H. W. Deckman, J. H. Dunsmuir, M. S. Alvarez, and J. M. BlochJ. Phys. (Paris) 47, 701 (1986).
91.T. Ohnisi, A. Ishitani, H. Ishida, Y. Yamamoto, and H. Tsubomura, J. Phys. Chem. 82, 1989 (1978).
92.The details will be published elsewhere. Briefly, the glassy carbon substrates were prepared by polishing and cleaning as reported previously (Ref. 27). The glass surface was cleaned using (5:1 v/v) solution at followed by extensive rinses with organic-free purified water (Millipore system). The LB films were deposited from a subphase buffered to
93.W. L. Wolfe, in Handbook of Optics, edited by W. G. Driscoll and W. Vaughan (McGraw-Hill, New York, 1978), pp. 7–17.
94.H. R. Philipp, in Handbook of Optical Constants of Solids, edited by E. D. Palik (Academic, New York, 1985), pp. 760–763.
95.For a special case of propagation of an incident beam contained in the XZ plane through a material whose optical tensor can be represented by a diagonal tensor, co-factors of only one of the rows yield a correct polarization vector and cofactors of other rows do not give any information about the polarization vector. This follows from the analytical solution of the partial waves or γ values.
96.Inverses of the dynamic matrices were calculated by solving a general system of equations for matrix X using standard Gaussian elimination with the partial pivoting method [G. E. Forsythe and C. B. Moler, Computer Solutions of Linear Algebraic Systems (Prentice-Hall, Englewood Cliffs, 1967)]. When I is chosen as the identity matrix of the same order as D, then the solution X is The procedure used to solve the matrix equation consists of an LU decomposition algorithm that decomposes the D matrix into lower and upper triangular matrices [G. W. Stewart, Introduction to Matrix Computations (Academic, New York, 1973)]. These matrices are then solved to obtain the forward and back solution phases of the general system of the matrix equation (a). The programs should be written in double precision digits to work smoothly.
Article metrics loading...
Full text loading...
Most read this month
Most cited this month