Scattering properties of ordered mesoporous silica films

Optics Communications 252 (2005) 344–354

www.elsevier.com/locate/optcom

Scattering properties of ordered mesoporous silica films

P. Cheyssac a,*, M. Klotz b, E. Søndergard b, V.A. Sterligov c

a Laboratoire de Physique de la Matiere Condensee, Universite de Nice, 06108 Nice Cedex 2, Franceb Unite Mixte de Recherche CNRS/Saint-Gobain, Surface du Verre et Interfaces, Saint-Gobain, 39 Quai Lucien Lefranc, BP

135, 93303 Aubervilliers Cedex, Francec Institute of Semiconductor Physics, Prosp. Nauki 45, 03028 Kiev-28, Ukraine

Received 22 December 2004; received in revised form 25 March 2005; accepted 12 April 2005

Abstract

Light scattering created by ordered mesoporous and non-porous silica films has been studied. The angular distribu-

tion of the intensity scattered by mesoporous films differs from that of non-porous films. It shows a minimum, which

has been interpreted as an interference pattern produced by the beams scattered by the mesopores distributed into the

volume.

� 2005 Elsevier B.V. All rights reserved.

Keywords: Scattering; Rayleigh; Thin flims; Optical properties; Materials and process characterization

1. Introduction

Ordered mesoporous materials differ from bulk

matter, exhibiting a highly ordered, monodi-

spersed porosity in the range 2–50 nm, giving rise

to a new class of materials. Due to their unique

properties, they have received increasing interestfrom the scientific community since the pioneering

work of Beck et al. [1] in 1992. Initially obtained as

powders, the synthesis of thin mesoporous films is

now achieved [2–4]. These ordered films can be

0030-4018/$ - see front matter � 2005 Elsevier B.V. All rights reserv

doi:10.1016/j.optcom.2005.04.032

* Corresponding author.

E-mail address: [email protected] (P. Cheyssac).

represented as a periodic lattice of holes in an

amorphous dielectric matrix, creating an artificial

material. The porous films show an effective dielec-

tric constant [5,6] that may be tuned through the

amount of pores and their content [7]. In particu-

lar, if holes are filled with air or vacuum, this effec-

tive dielectric constant will be lower than that ofthe same non-porous films. They also strongly

scatter light. Their high specific area opens the

door to catalytic or filtering processes in industrial

world or environment problems [8–14]. Further-

more, such films are of interest for many optical

applications, including the creation of devices

[15] ranging from optical sensors [16] to laser

ed.

mailto:[email protected]

P. Cheyssac et al. / Optics Communications 252 (2005) 344–354 345

sources with promising characteristics [17,18]. Re-

cently, mesoporous films were suggested for three

dimensional optical recording using visible light

[19]. To develop such applications, visible light

properties need be investigated. The mechanismsbehind the formation of mesostructured materials

are still not completely understood. Therefore,

the development of such materials for applications

implies the iteration of cycles formulation–

optimization–material characterization. Unfortu-

nately, the process is often slowed down by the

use of very heavy characterization techniques like

grazing incidence X-ray scattering and electronmicroscopy. A good insight into the potential abil-

ities of these new materials to the suggested appli-

cations is gained when characterizing their

structure at various scales, from grazing X-rays

to visible wavelengths. Visible light properties,

for which possible applications are expected, are

usually described by a set of refractive indices

and absorption obtained through reflectance mea-surements or spectroscopic ellipsometry, this last

procedure being time consuming and expensive.

In the case of a composite medium such as a mes-

oporous film, an effective dielectric constant has

been used for pore size characterization by adsorp-

tion of organic vapor and application of the

Bruggeman Effective Medium Approximation

[20]. Reflectance as given by Fresnel relations doesnot take scattering into account and so does no

longer give all optical properties of the sample.

Then, measurements of scattering from mesopor-

ous films add a new insight into the optical proper-

ties of new materials built from mesoporous layers.

In this paper, we deal with some of the optical

characterization of mesoporous materials in order

to characterize their light scattering properties,their refractive index if it carries a physical mean-

ing, but also to determine to what extent optical

techniques can bring insight into the materials

structure. We present the reflectivity spectra and

the angular distribution of the intensity scattered

by non-porous and ordered mesoporous silica

films. Reflectivity has been applied to the determi-

nation of indices of a given sample as long as it hasa physical meaning. To our knowledge, light scat-

tering of a mesoporous film and new features,

especially an interference pattern in the angular

distribution of scattered light, have not yet been

reported. Scattering occurs whatever the wave-

length to pore�s size ratio is. The coherent scatter-

ing created by the mesoporous film has been linked

to the structure of the film and interpreted as tak-ing place inside the mesoporous layer.

2. Preparation and structure of the samples

Each sample consists of a silicon wafer with a

thermally oxidized layer, covered by either a

non-porous or mesoporous film. Three differentsamples were realized: the first one is Si + thermal

SiO2 (labeled later as Th), the second is Si +

SiO2 + a non-porous layer (NPor) and the third

one is Si + SiO2 + a mesoporous layer (Por).

The thickness of the different samples was char-

acterized by SEM, as shown in Fig. 1. They are

d = 525 ± 10 nm for the thermal SiO2 film,

d = 240 ± 10 nm for the non-porous part of theNPor film and d = 495 ± 10 nm for its porous part.

The mesoporous films were obtained by hydro-

lysis and condensation of silica alcoxydes in the

presence of a templating mesophase. An extended

description of the synthesis and ordered structure

of these films have been reported earlier [21,22].

The films studied in this work are prepared by

adjunction of an ethanolic solution of a cationicsurfactant (CTAB: CH3(CH2)15N

+(CH3)3Br�) to

an acidic silica sol. This silica sol was prepared

by mixing TEOS (Si(OC2H5)4), acidic water (pH

1.25 adjusted by HCl) and ethanol in the molar ra-

tio 1:5:3.8 and refluxing this sol for 1 h at 60 �C.The final composition of the solution was

TEOS:Ethanol:water:CTAB in the ratio 1:3.9:5:

0.1. Thin films were deposited by spin-coating at4000 rpm on silicon wafers covered by a thermal

SiO2 oxide layer (Th film). The as-prepared films

were thermally treated at 450 �C to remove the or-

ganic template. In contrast, an amorphous silica

film was obtained by spinning the silica sol without

adjunction of the template. The obtained film is

denominated non-porous because it does not pres-

ent mesoporosity. It should be noticed that sol–gelfilms contain strong internal constraints due to the

evaporation and drying process [23]. Furthermore,

due to the sol–gel synthesis and low thermal

Fig. 1. Structure of the various samples shown by SEM. (a) Si

covered by a thermal SiO2 layer: Th sample. (b) Th sample

covered by a non-porous silica film. (c) Th sample covered by a

mesoporous silica film.

346 P. Cheyssac et al. / Optics Communications 252 (2005) 344–354

treatment, this film is not as dense as a thermally

created SiO2.

The ordered structure of the mesoporous film

has been characterized by grazing incidence smallangle X-ray diffraction. The analysis was per-

formed with a home built diffractometer [4] and

recorded on image plates. A rotating copper anode

was used and the distance between the thin film

and the image plate was 290 mm, acquisition time

15 min.

The diffraction pattern of the mesoporous thinfilm presented in Fig. 2(a) is characteristic of a

P63/mmc structure; Fig. 2(b) shows such structure

with its c-axis perpendicular to the substrate and

its a-axis randomly oriented in the substrate plane

[22]. The cell parameters are: a = 5.8 nm and

c = 6.9 nm. The ratio c/a = 1.2 differs from the the-

oretical value of 1.63 obtained for a close packed

hexagonal structure. This is consistent with a27% unidirectional shrinkage of the film perpen-

dicular to the substrate [4,22].

The thin film can best be imagined as composed

of grains approximately 0.5 lm. Inside each grain,

the mesopores form a unidirectional compressed

close packed hexagonal structure. They all have

their c-axis perpendicular to the substrate; how-

ever, they are randomly oriented in the substrateplane. No possible birefringence was detected.

The size of the mesopores was estimated to be

3.6 nm [24,25]. Through AFM shown in Fig. 3, a

typical 3.8 nm r.m.s. roughness has been obtained

for a mesoporous surface.

3. Reflection spectra

Specular reflection spectra Rexp(k) have been

measured from k = 400 up to 800 nm, close to nor-

mal incidence with a dedicated apparatus [26]. The

spectral width of the beam is 1 nm and its angular

divergence is ± 3.9�. These spectra are given in

Fig. 4; all show characteristic interference fringes.

Actually, interpretation of experimental reflec-tance in terms of optical indices and thicknesses

through Fresnel relations means that the film un-

der study satisfies related assumptions: mainly,

reflectance should measure the whole energy re-

flected by an abrupt interface. The NPor and Por

samples scatter; then, analysing their reflectance

by means of Fresnel relations that do not take

the scattered energy into account would be uselessand not physically meaningful. For these last sam-

ples, such a resolution is out of the scope of the

present paper and will not be presented here,

Fig. 2. (a) Grazing incidence small angle X-ray diffraction pattern of the mesoporous film. The film is ordered in a P63/mmc structure

with the c-axis perpendicular to the substrate. (b) Schematic presentation of the porous film structure. Spheres represent mesopores in

SiO2 matrix.

Fig. 3. AFM view of the surface.


although a paragraph in the discussion will give

more details about this point.

On the contrary, the indices nTh = mTh + ijThof the SiO2 layer created by thermal oxydization

onto Si have been determined using two indepen-

dent procedures.

On one hand, a commercial software dedicated

to ellipsometry [27] has been used to extract nTh.The input are the indices of Si taken from tabu-

lated values [28] and a physically meaning model

of nTh is the output. On the other hand, the reflec-

tion coefficients of each interface air–SiO2 and

SiO2–Si have been combined in order to give the

reflection of the Th sample. In this case, a Cau-

chy�s-type relation [29] is used for nTh. Both pro-

cedures use the thickness d = 525 ± 10 nm of

SiO2 given by scanning electron microscopy and

both get nTh through a minimization of the differ-

ence between experiment and theory.

The same values and behaviour of the refractive

index mTh of SiO2 are obtained: a monotonousdecrease when the wavelength k increases as it is

expected for a transparent medium.

Because a non-negligible although small part of

energy is scattered, a perfect agreement between

calculated and published refractive indices mTh of

SiO2 cannot be realized. The best agreement with

[29], better than 2%, is obtained when the thick-

ness of the sample is taken as d0 = 521 nm andwhen one introduces a faint absorption jTh (lower

than 2%) that accounts for the scattered energy

which is lost for the reflectance measurements.

The calculated mTh and jTh that insure the best

fit with published values of nTh [29] are given in

Fig. 5, together with nTh [29].

For the Npor sample, we encountered difficul-

ties when modeling the system. Effective mediumtheories would lead to a decrease of the effective

index when the density of pores increases,

although it should remain higher than 1. This film

does not present a significant amount of scattering,

but the discrepancy may stem from its large inter-

nal constraints and its low density.

For the porous sample, scattering takes so an

important part of energy that trying to solve

Fig. 4. Reflection spectra Rexp(k) of: (a) Th sample: continuous line; (b) Npor sample: dots; (c) Por sample: triangles.

Fig. 5. Calculated index nTh = mTh + ijTh of SiO2.


Fresnel relations loose any physical meaning. Por

films have less internal constraints than Npor sam-

ple due to the templating. Using an effective med-

ium dielectric constant, one finds numericalsolutions for the real and imaginary parts of index

and localized absorption bands. They prove to be

not Kramers–Kronig related as they should be.

Therefore, we consider the main mechanism is that

strong scattering, as recalled earlier, renders the

previous procedures inappropriate.

Numerical computations of indices and thick-

nesses from reflection spectra have been and still

are the subject of many publications [30–33]. Solu-

tions are not unique, an intrinsic difficulty of thiskind of calculation; although knowing the thick-

ness removes one unknown of the problem, the

calculated solutions must present a physical mean-

ing. The real part of the index should decrease

when k increases, a behaviour compatible with

that of a transparent medium; if a small absorp-


tion is present, the index takes complex values and

its imaginary part should be related to its real part

through a Kramers–Kronig relation.

With both our procedures, none trial to fit

Rcalc(k) and Rexp(k) succeeded; of course numer-ical values were obtained but none retained physi-

cal meaning in the previous sense.

4. Scattering properties

An original patented installation [34] has been

used for the measurements of light scattered bynon-porous and mesoporous films deposited onto

Si. It allows also obtaining an optical image of

the scattering area under study (Fig. 6), a valuable

possibility to estimate the presence of defects of all

kind on the surface and simplify the interpretation

of scattering data. The light source is a He–Ne la-

ser switchable at k = 594 and 632.8 nm, with an

optical power of �3 mW. The laser beam impingesat normal incidence onto the sample and is focused

down to �100 lm diameter while remaining quasi-

parallel. Focalization determines the angular reso-

lution, the order of 1� in our case, and enables

choosing the area that exhibits the lowest possible

contamination.

Geometrical images of NPor and Por scattering

areas, Fig. 6(a) and (b), shows the origin of back-ground scattering. For non-porous film, scatter is

produced by a weak background and is present

at grazing incidence; few point-like contaminated

centers located on the surface are then iluminated

and scatter light efficiently. The high sensitivity of

Fig. 6. Image of scattering area. (a) NPor sample,

the camera allows them to be recorded although

the spot size is the order of 100 lm. The well visi-

ble speckle structure Fig. 6(b) is created by inter-

ferences originating from these centers.

For mesoporous film, with an homogeneousand very dense space distribution of mesopores,

the level of background scattering that comes from

clear places is increased.

The bidirectional scatter distribution function

BSDF, function of the polar and azimuthal angles

h and u, is defined as the scattered intensity dI nor-

malized to the incident intensity I0, the solid angle

of the receptor dX and cos h: BSDF = 1/(I0 cos h)dI/dX. This BSDF is represented in a 2D diagram

as a function of the sample�s spatial frequencies fx,fy; at normal incidence, f = sin h/k for any scatter-

ing plane. Due to the range of scattered intensities,

Fig. 7 shows log BSDF(fx, fy), scaled with grey lev-

els on a disc: its center gives the intensity scattered

normally to the sample�s surface, its borderline thegrazing scattering. Average scattered intensitiesmay be obtained in two ways: through the total

integrated scatter TIS or an azimuthal averaging

of BSDF, Fig. 8, performed for a u-range in which

scattering data represents all samples. The TIS due

to the three kinds of sample are given as ratios

using the data shown in Fig. 7: TISNPor/TISTh =

0.39 ± 0.29, while TISPor/TISTh = 21 ± 8 and TIS-

Por/TISNPor = 54 ± 20. Both TIS or azimuthalaveraging of BSDF show that scattering increases

from Npor to Por samples.

The angular distribution of the intensity scat-

tered by a Por sample exhibits well-pronounced

minima given by sin hmin(632.8 nm) = 0.582 ± 0.02

(b) Por sample. Image size is 700 · 500 lm2.

Fig. 7. log BSDF(fx, fy) as a function of the spatial frequencies: (a) Th film; (b) NPor film; (c) Por film: k = 638.8 nm, (d) k = 594 nm.


and sin hmin(594 nm) = 0.721 ± 0.02. A modula-tion of the azimuthal dependence of scattered light

also exists for the Npor sample, due to an increase

Fig. 8. Azimuthally averaged cross-section of BSDF(fx, fy) as a functi

NPor films at 632.8 nm. Simulated minima (Sim) are also drawn.

in the speckle structure. Of course, the angularminimum is still present in the azimuthal averaging

of BSDF.

on of sin h, for a Por film at 594 and 632.8 nm, and for Th and


Fig. 7(c) and (d) also shows that the spatial fre-

quency modulus associated with BSDF�s minimum

is significantly shifted when k varies from 632.8 to

594 nm.

The differences in the levels of scattering fromone kind of layer to the other have to be explained.

We have to question the physical process able to

create and shift significantly this angular minimum

for so small a change of k. Interference is a good

candidate for such a process and its origin may

lay in surface relief and scattering centers. The

pores are homogeneously distributed inside the

film and exhibit order. They can act as coherentscatterers, giving rise to interference.

5. Interpretation and discussion

The determination of film thickness is crucial

when optimizing the synthesis and deposition of

mesoporous films. In general, this quantity isdetermined by SEM, a heavy technique compared

to reflectance, and it drastically limits the number

of characterized samples. Therefore, it would be

interesting if a fairly simple and inexpensive tech-

nique, contrary to SEM, would lead to similar re-

sult, opening a way for a simple table top

apparatus for direct use in the laboratory. In what

preceeds, the limits of such procedures appearsclearly for our samples.

For the thermal layer of SiO2 onto Si, its optical

indices have been determined and turned out to be

very close to that already published. The thickness

d0 of SiO2 controls the position of the interference

peaks and the best agreement between Rcalc(k)and Rexp(k) has been obtained with d0 =

521 nm, a value very close to d = 525 ± 10 nmmeasured by SEM.

The analytical model [29] of SiO2 index we used

has been established from double side polished and

oxidized wafers, and there are no reflective or

absorptive phenomena associated with surface

roughness, damage, or anomalies. Then, it corre-

sponds closely to our experimental situation. How-

ever, due to fabrication process, our Si wafer andits associated thermal SiO2 layer are not perfect:

chemical and thermal treatments open the way to

some remaining impurities of the template. As

well, surface roughness is present, see AFM imag-

ing in Fig. 3 and scattering results in Fig. 7(a).

Hence, a small imaginary part jTh, has been

added to the index of SiO2, usually a pure real

number at least in our visible range under study.jTh increases monotonically with k but remains

lower than 0.02. No absorption band appears so

the impurity level is very small and jTh simulates

the energy scattered by the roughness of the outer

interface of the sample.

For NPor and Por films, the analytic treatment

of reflectance data does not lead to any physically

meaningful values of the real and imaginary partsof the indices that describe their optical properties.

Even with the known thicknesses of the layers as

input, it turns out that the set of values that may

realize a fit between Rcalc(k) and Rexp(k) cannotbe represented by a series development of a Cau-

chy�s-type model of dielectric. On one hand, one

would expect that the output of calculations could

be interpreted as an effective dielectric functionadequate as a description of the optical properties

of the samples. On the other hand, it comes out

that this absorption, imaginary part j of the

layer�s index, is not Kramers–Kronig related to

the real part m of the index as it should be. The

samples scatter so strongly in all directions, as

shown in Figs. 7 and 8, that absorption previously

introduced in order to represent the scattered lightis useless and so no physical meaning can be

attached to its numerical value and wavelength

behaviour.

A part of the problem with the interpretation of

the data can come from the variation in the density

of the materials. Thermal SiO2, Npor and Por lay-

ers are realized from the same material, only their

density differs and a common behaviour as a func-tion of wavelength may be expected. For different

mesoporous samples, ellipsometric data [35–37]

show that the pores are empty and filled by air

immediately after preparation: a characteristic vol-

ume ratio �0.43 between air and matrix had been

determined previously [38]; then the density of Por

samples is much lower than that of Th ones. If

materials would remain perfect dielectrics, theirrefractive index would decrease with the same

ratio as density, the same if one applies an

effective medium theory: this should lead to

Fig. 9. A Si substrate of index n2 supports a SiO2 film of index

nS. The Por film of index n1 is deposited on top. Light is

scattered by homogeneously distributed centers inside the top

film. Beams involved in the interference pattern are drawn.


mPor < mNPor < mTh. Assuming that absorption

also decreases with density, one should expect

jPor < jNPor < jTh, but thermal and chemical

treatment would lead to jPor > jNPor > jTh.More specifically, the composition of Npor filmsis not so well determined. Although they scatter

less than Th films, a Cauchy�s model is unable to

represent their optical properties because we used

as input in Fresnel formulas values intended for

stoechiometric SiO2 and not values describing cor-

rectly their structure.

Then reflectance analysis, as interpreted in

terms of Fresnel relations, that is interfaces sepa-rating homogeneous and non scattering media,

cannot give reliable results as far as strong scatter-

ing remains involved.

Causes of scattering are numerous but may be

summarized as defects or local differences in com-

position, structure or topology of interfaces and

layers where light penetrates; in other words: scat-

tering must be due to rapid changes in the dielec-tric constant caused by the ordered cloud of

pores. Moreover, scattering will occur with an

intensity decreasing with size when compared to k.TIS has been given with wide error margins,

they quantify the surface homogeneity but not

the measurements� errors by themselves. At high

scattering angles, Fig. 7, the azimuthal structure

of the maximum reflects probably some azimuthalanisotropy of the mesoporous structure. Surface

relief and total scattering do not depend on k once

they are presented in their Fourier decomposition.

The scattered intensity decreases from a Th to a

NPor film whereas a Por ones scatters more than

both. Generally, an interface experiences a de-

crease of its roughness when covered by another

layer. In our case, the coverage of the Th layerby a non-porous or porous layer of silica leads also

to a decrease in the index contrast on both sides of

the interface. For light scattered by interfaces, the

so-called anti-scattering effect [39–41] has the same

physical background than an antireflection

coating.

Both reasons should lead to the decrease of the

intensity scattered by the interface itself. This is thecase from Th to Npor layers but, as previously

said, the Por layer scatters much more than others

so additional causes should intervene. The chemi-

cal composition of the samples being almost the

same, their high degree of porosity makes the dif-

ference, giving rise to a significant change of the in-

dex contrast and to the amount of scattered

energy.Figs. 7 and 8 show, to our knowledge, the first

report of light scattered by a mesoporous film: the

intensity of a plane wave incident normally to the

surface is scattered and exhibits a deep minimum,

very sensitive to k, in the direction hmin. This direc-

tion is not represented by the same point in the

spatial frequencies space, then the position of hmin

cannot originate in a Fourier decomposition of thesurface relief and should be related to interference.

In our case, the simplest model of interferences

would be from coherent interaction between light

reflected by the various interfaces. Then, a simula-

tion using the experimental values of thickness and

hmin has led to an effective index of the Por layer so

close to 1 that the material would be almost made

of air. Moreover, hmin decreases with k, contrary tothe experiment. This model and related ones do

not represent the behaviour of our experimental

results. We assume currently that pores are homo-

geneously distributed inside the Por layer and act

as point sources that scatter isotropically and

coherently. Taking into account paths differences

according to the geometrical layout in Fig. 9,

reflection and transmission coefficients by the var-ious interfaces, the analytical expression of the


amplitude of all beams scattered in the direction hhas been calculated as a function of h, indices andthicknesses of the layers. This amplitude is inte-

grated along the mesoporous film thickness. The

scattered intensity I(k sinh) is deduced and goesthrough a minimum hmin, its analytic complexity

does not enable expressing hmin in terms of optical

parameters of the layer. The simulated positions

hmin, relative values of I(k sinh) and behaviour

with k, presented in Fig. 8, are close to the exper-

imental ones, although a perfect agreement is not

obtained.

As surprising as it may appear, we did not findany other explanation of such minimum of the

scattered intensity in a given direction so sensitive

to the wavelength. We are led to conclude that the

mesoporous structure gives rise to an inside coher-

ent scattering detected outside by a minimum of

intensity in a direction hmin very sensitive to k.

6. Conclusion

In this paper, we have studied the reflection and

light scattering properties of a Si substrate covered

by different layers of silica with a non-porous or

mesoporous structure. We have showed that Th

layers created by thermal oxydization of Si pres-

ent, from an optical point of view, very similarproperties to bulk SiO2. We have also shown that

porous layers present specific optical properties

such that interpretation of reflectance using Fres-

nel relations is not straightforward. Therefore,

the Bruggeman effective medium approximation

is generally not directly applicable. As far as scat-

tering and reflectance occur from all positions in-

side a porous layer, a devoted theory taking intoaccount reflectance and scattering should be used

but this was not the purpose of this paper. If such

a theory was to be used, one would expect possible

to estimate a very important parameter for meso-

porous systems namely the filling factor. Then,

simple optical equipment has shown limits during

the optimization of mesoporous film. Complicated

tools like SEM, TEM, GISAXS remain, in thepresent state of the art, necessary for a non-ambig-

uous characterization of thickness and structure of

mesoporous films.

The intensity scattered by mesoporous film

proved to be one order of magnitude higher than

homogeneous films. Most surprisingly, its angular

distribution exhibits a well-marked minimum

characteristic of interferences. These interferenceshave been related with the film structure and ex-

plained by coherent scattering taking place in the

thickness of the film. Future work may settle if

the mesopores or the texture of the films is the ori-

gin of the phenomenon. In all cases, these studies

will enhance the insight in the structure and forma-

tion of mesoporous films.

Acknowledgements

The authors thank Pierre-Antoine Albouy

(Laboratoire des Solides, Universite de Paris

Sud, France) for the acquisition of the diffraction

pattern.

References

[1] J.S. Beck, J.C. Vartuli, W.J. Roth, M.E. Leonowicz, C.T.

Kresge, K.D. Schmitt, C.T.W. Chu, D.H. Olson, E.W.

Sheppard, S.B. McGullen, J.B. Higgins, J.L. Schlenk, J.

Am. Chem. Soc. 114 (1992) 10834.

[2] Y. Lu, R. Ganguli, C.A. Drewien, M.T. Anderson, C.J.

Brinker, W. Gong, Y. Guo, H. Soyez, B. Dunn, M.H.

Huang, J.I. Zink, Nature 389 (1997) 364.

[3] M. Klotz, A. Ayral, C. Guizard, L. Cot, J. Mater. Chem.

10 (2000) 663.

[4] M. Klotz, P.-A. Albouy, A. Ayral, C. Menager, D. Grosso,

A. Van der Lee, V. Cabuil, F. Babonneau, C. Guizard,

Chem. Mater. 12 (2000) 1721.

[5] H. Fan, H.R. Bentley, K.R. Kathan, P. Clem, Y. Lu, C.J.

Brinker, J. Non-Cryst. Solids 285 (2001) 79.

[6] C.-M. Yang, A.-T. Cho, F.-M. Pan, T.-G. Tsai, K.-J.

Chao, Adv. Mater. 13 (2001) 1099.

[7] F.K. de Theije, A.R. Balkenende, M.A. Verheijen, M.R.

Baklanov, K.P. Mogilnikov, Y. Furukawa, J. Phys. Chem.

B 107 (2003) 4280.

[8] V. Dufaud, Mark E. Davis, J. Am. Chem. Soc. 125 (31)

(2003) 9403.

[9] E. Rodriguez-Castellon, A. Jimenez-Lopez, P. Maireles-

Torres, D.J. Jones, J. Roziere, M. Trombetta, G. Busca,

M. Lenarda, L. Storaro, J. Solid State Chem. 175 (2)

(2003) 159.

[10] D. Trong On, D. Desplantier-Giscard, C. Danumah, S.

Kaliaguine, Appl. Catal. A 222 (2001) 299.

[11] D. Brunel, A.C. Blanc, A. Galarneau, F. Fajula, Catal.

Today 73 (2002) 139.


[12] L. Mercier, T.J. Pinnavaia, Adv. Mater. 9 (6) (1997) 500.

[13] Y.-H. Chu, H.-J. Kim, K.-Y. Song, Y.-G. Shul, K.-T.

Jung, K. Lee, M.-H. Han, Catal. Today 74 (2002) 249.

[14] B.L. Newalkar, N.V. Choudary, U.T. Turaga, R.P. Vija-

yalakshimi, P. Kumar, S. Komarneni, T.S.G. Bhat, Chem.

Mater. 15 (2003) 1474.

[15] R.C. Hayward, P. Alberius-Henning, B.F. Chmelka, G.D.

Stucky, Micropor. Mesopor. Mat. 44–45 (2001) 619.

[16] G. Wirnsberger, B.J. Scott, G.D. Stucky, Chem. Commun.

(2001) 119.

[17] G. Wirnsberger, P. Yang, B.J. Scott, B.F. Chmelka, G.D.

Stucky, Spectrochim. Acta A 57 (2001) 2049.

[18] B.J. Scott, G. Wirnsberger, G.D. Stucky, Chem. Mater. 13

(10) (2001) 3140.

[19] J. Wang, G.D. Stucky, Advanced Functional Materials. 14

(5) (2004).

[20] A. Bourgeois, A. Brunet Bruneau, S. Fisson, B. Demarets,

D. Grosso, F. Cagnol, C. Sanchez, J. Rivory, Thin Solid

Films 447–448 (2004) 46.

[21] S. Besson, T. Gacoin, C. Jacquiod, C. Ricolleau, D.

Babonneau, J.-P. Boilot, J. Mater. Chem. 10 (2000)

1331.

[22] S. Besson, C. Ricolleau, T. Gacoin, C. Jacquiod, J.-P.

Boilot, J. Phys. Chem. B 104 (2000) 12095.

[23] C.J. Brinker, G.W. Scherer, Sol–gel Science, Academic

Press, San Diego, 1990.

[24] M. Klotz, S. Besson, C. Ricolleau, F. Bosc, A. Ayral,

Mat. Res. Soc. Symp. Proc. 752 (2003) AA8.6.1.

[25] S. Besson, T. Gacoin, C. Ricolleau, C. Jacquiod, J.-P.

Boilot, Nanoletters 2 (2002) 409.

[26] R. Kofman, P. Cheyssac, J. Richard, Phys. Rev. B 16

(1977) 5216.

[27] Wvase 32, from J.A. Woollam Co., Inc., 645 M. Street,

Suite 102 Lincoln, NE 68508, USA. Available from:

<www.jawoollam.com>.

[28] Virginia Semiconductor, Inc. 1501 Powhatan Street, Fred-

ericksburg, Va 22401, Optical Properties of Silicon. Avail-

able from: <www.vriginiasemi.com>.

[29] C.M. Herzinger, B. Johs, W.A. McGahan, J.A. Woollam,

W. Paulson, J. Appl. Phys. 83 (615) (1998) 3323.

[30] D.A. Minkov, J. Phys. D 22 (1989) 1157.

[31] D.A. Minkov, J. Phys. D 22 (1989) 199.

[32] R. Rusli, G.A.J. Amaratunga, Appl. Opt. 34 (1995) 7914.

[33] J.M. Gonzalez-Leal, E. Marquez, A.M. Bernal-Oliva, J.J.

Ruiz-Perez, R. Jimenez-Garay, Thin Solid Films 317 (1998)

223.

[34] V.A. Sterligov, P. Cheyssac, Appareil et procede de

caracterisation optique d�un objet, CNRS Patent Nos.

0115232, 23.11.2001.

[35] D. Grosso, A.R. Balkenende, P.A. Albouy, M. Lavergne,

L. Mazerolles, F. Babonneau, J. Mater. Chem. 10 (9)

(2000) 2085.

[36] S. Besson, Organized mesoporous silica films: synthesis,

characterization of the structure and application to the

growth of nanoparticles, PhD thesis, Ecole Polytechnique,

Paris, 2002 (in French).

[37] A. Brunet-Bruneau, S. Besson, T. Gacoin, J.P. Boilot, J.

Rivory, Thin Solid Films 447–448 (2004) 51.

[38] A. Brunet-Bruneau, S. Fisson, B. Gallas, G. Vuye, J.

Rivory, Thin Solid Films 377–378 (2000) 57.

[39] P. Roche, E. Pelletier, G. Albrand, J. Opt. Soc. Am. A 1

(1984) 1032.

[40] C. Amra, G. Albrand, P. Roche, Appl. Opt. 16 (1986) 2695.

[41] H. Giovannini, C. Amra, Appl. Opt. 36 (1997) 5574.

http://www.jawoollam.com

http://www.vriginiasemi.com

Scattering properties of ordered mesoporous silica films

Documents

Transcript of Scattering properties of ordered mesoporous silica films