Photoluminescence of Mesoporous Silica Film Impregnated with an Erbium ComplexOun-Ho Park†, Jae Young Bae, Ji-in Jung, and Byeong-Soo Bae

Laboratory of Optical Materials and Coating (LOMC), Department of Materials Science and Engineering, KAIST, Daejeon 305-701, Republic of Korea

E-mail: oh-park@kaist.ac.kr http://www.sol-gel.net/lomc

Research direction

The 5th International Meeting of Pacific Rim Ceramic Societies

September 29 – October 2 2003, Nagoya Congress Center, Nagoya, Japan

Sample preparation of the mesoporous silica film impregnated with ErQ

Conclusions

References

FT-IR Spectra

Since planar optical amplifiers have a smaller interaction length with respect to erbium-

doped fiber amplifiers, higher erbium concentration is required to obtain a sufficient

optical gain.

high doping levels of erbium quench the fluorescence emission and reduce the

performance of the amplifier.

Theoretically, the most effective method for uniform dispersion is the periodic

arrangement of erbium ions in a matrix when high doping levels of Er3+ ions are required.

In this study, we impregnate Er complex into mesoporous silica film, and then measure

the photoluminescence for 1.5 m amplification.

Oun-Ho Park, Se-Young Seo, Ji-In Jung, Jae Young Bae, and Byeong-Soo Bae, J. Mater.

Res. 18[5], 1039 (2003)

Jae Young Bae, Ji-in Jung, Oun-Ho Park, Byeong-Soo Bae, Koodali T. Ranjit, L. Kevan, S

tudies in Surface Science and Catalyst 146, 65 (2003)

Jae Young Bae, Oun-Ho Park, Ji-in Jung, Koodali T. Ranjit, Byeong-Soo Bae, Micropor.

Mesopor. Mat., in press

Preparation of mesoporous silica films

- Precursor : Tetramethylorthosilicate

(TMOS)

- Solvent : Methanol (CH3OH)

- Surfactant : n-Cetyltrimethylammonium

Chloride [CH3(CH2)15N(CH3)3]Cl (CTACl)

Transparent mesoporous silica films are successfully fabricated using a sol-gel spin coating

method.

The obtained mesoporous silica films have hexagonal structure with 2 nm pore size.

Er complex is homogeneously impregnated into the mesoporous silica films by an immersing

technique, and its concentration can be easily controlled by changing the concentration of Er

complex solution.

Schematic Structure

PL intensity increases as the concentration of ErQ solution

increases due to the impregnation of ErQ into the pore.

Thermogravimetric Analysis

Abrupt weight losses take place at 280 & 310 oC due to the desorption

and the decomposition of CTACl, respectively.

Temperature profile is determined to calcine the residual

organic surfactants effectively.

XRD Result

Photoluminescence

Pore size : 2 nm Expected molecular size of ErQ : >1 nm It is expected that the impregnated ErQ

molecules are homogeneously distributed

due to the periodic pore arrangement.

FT-IR spectra of (a) as-synthesized and (b) calcined mesoporous

silica films Residual OH and organic templates are almost removed.

Synthesis of Mesoporous Silica Film

XRD patterns of (a) as-synthesized and (b)

calcined hexagonal mesoporous silica films

Characterization of Mesoporous Silica Film

Optical Properties of Mesoporous Silica Film Impregnated with ErQ

Temperature Profile for Calcination

N2 Adsorption Er distribution & Concentration Concentration Effect

Microstructure High Resolution TEM images

Obtained mesoporous silica films are optically

transparent in the range of visible wavelength. TEM cross-sectional images of perpendicular (a, b) and through (c) the pores of hexagonal

mesoporous silica thin films Pore size : ~ 2 nm

Transmittance

Erbium 8-hydroxyquinoline (ErQ) was incorporated

into the mesoporous silica films by impregnation. The

silica films were placed into 10 ml of 1.5 10-3–1.5

10-2 M erbium 8-hydroxyquinoline in ethanol. Ethanol

was removed by flowing nitrogen gas over the sample.

TMOS + HCl

Stirring for 1hr

Add methanol and

stirring for 1 hr

Add CTACl and stir for 24 hrs

Filtering and spin coating

Drying at 60, 130, & 200oC

Calcination at 550oC

for 12 hrs in air

NO

Er

N

ON

O

ErQ

Dissolve ErQ in EtOH

Immersion of mesoporous silica film

Ultrasonic treatment

Surface Cleaning

EtOH

Mesoporous silica film

0 100 200 300 400 500 600 70060

70

80

90

100

Der

iv. W

eig

ht

(%/o C

)

Temperature (oC)

Wei

gh

t (%

)

0.0

0.1

0.2

0.3

0.4

Water

Decomposition

of CTACl

Desorption of CTACl

0 4 8 12 16 20 24 280

100

200

300

400

500

600

700

Furnace cooled

Decomposition of CATCl

Desorption of CATCl

Tem

per

atu

re (

o C)

Time (hr)4000 3000 2000 1000

0.0

0.1

0.2

0.3

0.4Si-O-Si

Si-OCH3Organic templates

OH

(b)

(a)

Abs

orba

nce

(a.u

.)

Wavenumber (cm-1)

2 4 6 8 10

X 10

X 10

(a)

(b)

Inte

nsi

ty (

a.u

.)

2 / o

433 ± 2 nm

(a)

(b)

Average Roughness : 2 nm

50nm 20nm 20nm

(c)(b)(a)

Substrate

(a) SEM & (b) ARM Images

200 300 400 500 600 700 80040

50

60

70

80

90

100

Fused silica Coated film

Tra

nsm

itta

nce

(%

)

Wavelength (nm)

Silica wall

ErQ

Pore

Si wafer

ErQ impregnatedmesoporous silica film

1400 1450 1500 1550 1600 1650

0.0

0.2

0.4

0.6

0.8

1.0

Nor

mal

ized

PL

inte

nsit

y

Wavelength (nm)

1.5*10-2 N

0.7*10-2 N

1.5*10-3 N 0 N

0.0 0.2 0.4 0.6 0.8 1.0

100

200

300

400

500

600

700

800

adsorption desortion

ErQ Doped

ErQ undoped

Vol

ume

Ads

orbe

d cm

3 /g S

TP

Relative Pressure (P/P0)

  Surface area (m2/g)

Pore size(nm)

ErQ undoped 920 2.1

ErQ doped 725 2.0

ErQ is impregnated into the pore!

500 1000 1500 20000

500

1000

1500

O

Si

Er

Yie

ld (

a.u.

)

Energy (keV)

Measured Silmulated

Depth profile and composition was

obtained by RBS measurements. Er is impregnated up to ~1021 ions/cm3.

0.0 0.4 0.8 1.2 1.6 2.0

0.0

0.2

0.4

0.6

0.8

1.0

Max

imum

PL

inte

nsit

y

Er atomic density ( 1021 ions/cm3)

PL is linearly proportional to erbium

atomic density., which implies No concentration quenching was

found up to ~1021 ions/cm3 of erbium

concentration.

ErQ impregnated mesoporous silica film shows a clear 1.5 m photoluminescence.

Impregnation of ErQ into the pore is confirmed by N2 adsorption.

Homogeneous distribution of ErQ in depth is confirmed by RBS measurement.

High concentration of erbium is impregnated without concentration quenching

PL is linearly proportional to the erbium concentration.

ErQ concentrationin ethanol solution

Er/Si ratio

Er atomic density (cm-

3)

1.5 10-3 N 0.012 1.8 1020

0.7 10-2 N 0.052 0.8 1021

1.5 10-.2 N 0.12 1.8 1021