WHAT DIFFERENCE EXISTS IN THE STRUCTURE OF SiO2 AND GeO2 BETWEEN MELT-QUENCHED BULK GLASS AND SPUTTER-DEPOSITED AMORPHOUS FILM

(1)

HAL Id: jpa-00225252

https://hal.archives-ouvertes.fr/jpa-00225252

Submitted on 1 Jan 1985

HAL is a multi-disciplinary open access

archive for the deposit and dissemination of

sci-entific research documents, whether they are

pub-lished or not. The documents may come from

teaching and research institutions in France or

abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est

destinée au dépôt et à la diffusion de documents

scientifiques de niveau recherche, publiés ou non,

émanant des établissements d’enseignement et de

recherche français ou étrangers, des laboratoires

publics ou privés.

WHAT DIFFERENCE EXISTS IN THE STRUCTURE

OF SiO2 AND GeO2 BETWEEN MELT-QUENCHED

BULK GLASS AND SPUTTER-DEPOSITED

AMORPHOUS FILM

K. Suzuki, M. Misawa, Y. Kobayashi

To cite this version:

(2)

JOURNAL DE PHYSIQUE

Colloque C8, supplement au n°12, Tome 46, decembre 1985 page C8-617

WHAT DIFFERENCE EXISTS IN THE STRUCTURE OF S i 02 AND G e 02 BETWEEN

MELT-QUENCHED BULK GLASS AND SPUTTER-DEPOSITED AMORPHOUS FILM

K. Suzuki, M. Misawa* and Y. Kobayashi**

The Research Institute for Iron, Steel and Other Metals, Tohoku University, Katahira 2-1-1, Sendai 980, Japan

Abstract The [ S i 0 4 ] t e t r a h e d r a l s t r u c t u r e u n i t i s s t i l l preserved i n s p u t -t e r - d e p o s i -t e d SiC&g-t;2 amorphous film as w e l l as i n mel-t-quenched Si02 g l a s s . The angle d i s t r i b u t i o n for mutual connection between [ S i 0 4 ] - t e t r a h e d r a has a more extended f l u c t u a t i o n i n s p u t t e r - d e p o s i t e d SiC>2 amorphous film, which i n c l u d e s voids w i t h t h e average s i z e of about 10 A i n diameter. S i m i l a r behaviors have been a l s o observed for Ge02 amorphous s o l i d s .

I - INTRODUCTION

Significant attention has been paid to characterizing and controlling the structure defects included inherently in Si02 and Ge02 films prepared by gas deposition tech-niques, particularly from the point of elctronic and optical device applications. For example, there are two kinds of structure defects in RF sputter-deposited Si02 amor-phous films. One is the atomic scale defect such as oxygen deficiency, Si-Si direct bond, bond strain and so on, which are responsible for electron spin resonance signal and/or infrared absorption band shift/1-5/. The other is the macroscopic defect such as local density fluctuation over a range of 10 to 1000 A in the network structure/6/. These structure defects are expected to be introduced through the geometrical distor-tion and the way of mutual connecdistor-tion of [SiO^-tetrahedral structure units during the sputter-deposition process.

This study is aimed at examining how the atomic scale structure of Si02 and GeC>2 amorphous solids is modified depending on the different preparation methods of melt-quenching and sputter-deposition by means of pulsed neutron total scattering. II - EXPERIMENTAL METHODS

Si02 and Ge02 amorphous films of about 0.3 mm in thickness were deposited on water-cooled copper substrate from corresponding oxide glass targets in RF argon-qas plasma using an ULVAC high rate sputtering apparatus(Model:ME 55-0070). Details of sample preparation have been described in a previous paper/7/. Melt-quenched SiC>2 and GeC>2 glasses available commercially were used in this study.

The total structure factors S(Q) for all the samples were measured by the T-O-F total scattering spectrometer HIT using a spallation pulsed neutron source installed at 500 MsV proton booster synchrotron, National Laboratory for High Energy Physics, Tsukuba. The detailed procedures of data processing and analysis have been fully described in previous reports/8,9/.

Conventional measurements of X-ray diffraction, infrared absorption band, average density and scantling electron microscopy were also carried out for the both of Si02

Present address : *National Laboratory for High Energy Physics, Tsukuba, Japan **Hippon Mining Co., Ltd., Hitachi, Japan.

Résumé : La structure en unités tétraèdriques [siO. ] est préservée dans les films de SiO, obtenus par pulvérisation et dans les verres obtenus par trempe du liquide. La distribution angulaire des connexions entre trétraè-dres est plus large dans les matériaux pulvérisés où il existe des pores dont le diamètre moyen est de 10 A. Des résultats analogues sont aussi ob-tenus avec Ge^O amorphe.

(3)

C8-6 18 JOURNAL DE PHYSIQUE

and Ge02 amorphous solids samples.

I11

-

RESULTS AND DISCUSSION

?he R? sputter-deposited S i Q amorphous film(hereafter called a-Si02)

was

found to have a ~ l l o x y g e n deficiency of the chemical conpsition corresponding to Si01.97. 'Ihe average density of a-Si02 i s 2.1650.09 g/c.c, which i s about 2 % l e s s than a standard density of 2.20k0.09 g/c.c for mlt-q~lenched Si02 glass(hereafter called g-SiO2). 'Ihe a-Si@ film sample prepared in this study is colorless and transparent, but e x t m l y hygroscopic. 'Ihe columnar structure of'about 10 pm i n dimter, which is often observed i n the film sputter-deposited a t low w r a t u r e , is reaxpized in a-SiO2 a s well/lO/. Since the sputter-deposited Ge02 mrphous film has a

at

a m u n t o f oxygen deficiency corresponding to Ge0lag7, the color of the film is brown but s t i l l transparent.

Figure l ( a ) shows the neutron total structure' factors S (Q) of a-SiO2 and g-Si02 ma- sured a t m m w r a t u r e . Significant amount of small angle scattering intensity and drastic decrease i n the f i r s t and second peak heiaht are found i n the S (Q) of a-SiQ. By annealing a-Si02 in air a t 1200 OC, these peak heights are almost recovered to approach the peak heights in the S ( Q ) observed f o r g-SiQ but the small angle scattering intensity is s t i l l preserved

,

a s shown i n Figure l ( a ) . Similar behavior of S (Q) is observed for a-GeQ and g-Ge02 amorphous solids a s sham i n Fiqure 1 (b)

.

The analysis of the small arigle scattering intensity in the S(Q) for a-SiO2 suggests the existence of void of about 10 A in dimter with a v o l m fraction of about 4 %.

F i g . 1

-

( a ) N e u t r o n

t o t a l s t r u c t u r e

Sputter-deposited

Si02

f a c t o r s S ( Q ) o f

s p u t t e r - d e p o s i t e d

Annealed

at

1200

'CC)

S i 0 2 amorphous f i l m and SiO2 g l a s s , and

(4)

Fig. 3

-

Radial distribution functions

(RDF) of sputter- deposited Si02 amorphous film and Si02 glass.

The characteristic density correlation

function y (r) defined a s the Fourier 1.50 transform of the small angle scattering

in the S (Q) i s Shawn

i n

Figure 2. Figure 3 shows the radial distribution functions(RDF) for a-Si% and g-SiO;!

. . .

, . . . , . . . , ~ ' ' , " '

defined as the Fourier transform of the I .DO

S (Q) truncated a t

&

= 40 A - ~ . The A structural paramters obtained from the

&

neutron RDF i n combination with X-ray

L

RDF are swnrarized i n Table 1.

-kable conclusions deduced from the 0.50 -

RDF are as follows:

[ l ] Compared with the mlt-quenched glasses, the both of Si-0 and Ge-0 bond

are

slightly expanded

i n

the sputter-deposited amr-

phous films, i n which therefore the 0-0 0. " " " " " " " ~ " " " " ' . " ' ~ ' - ' '

atomc distances are also stretched. 0 2 4 6 8 10 12 14 0

-[21 [Si041-.tetrahedral s u v c t u r e units

r

( A )

are

s t i l l preserved in a-SiO2 a s

w e l l

a s Fig. 2

-

Characteristic density corre- i n g-Si02. Hawever the fluctuation of lation fmction y (r) for sputter- Si-0 bondlength and 0-0 atomic distance deposited Si@ arrorphous film.

are sligbtly larger in a-Si02 than i n g-SiO2.

[31 In spite of the f a c t that the average m r d i n a t i o n n&r of 0 atoms bound t o

a Ce atom is apparently l e s s than four due t o the large oxygen deficiency i n a-Ge02, the polyhedral structure unit existing in a-Ge02 i s mainly a .[GeOql-tetrahedron, because

the

Ge-0 bondlength and the bondangle <cXe-0 are rather close

to

the values

found i n the regular tetrahedron. However we can e x p c t t h a t [GeOgI-octahedral structure units are partially contained in the network structure of a-Ge02, since -11 h q appears on the high r side of the f i r s t peak and the second

peak

corresponding t o the 0-0 correlation is extended toward

lawer r

region i n the RDF. The positions of the h q

(nl.

9 A) and the extension (02.6-2.9 A) are close to the Ge-0

bondlength and the 0-0 interatomic distance i n [Ge06]-octahedron existing i n Ge02- based glasses respectively/ll/.

(5)

(3-620

JOURNAL

DE

PHYSIQUE

Table 1

-

Bondlengths and coordination n-rs

i n

s p u t t e r - d e p s i t e d S i 0 2 ( W 2 ) m r p h o u s f i l m and mlt-qwnched Si02 ( W 2 ) g l a s s .

a-Si02 g-Si02

stretching s t r e t c h q bending a-W2

g-Geo2

Fig. 4

-

I n f r a r e d absorption spectra o f s p u t t e r - d e p s i t e d SiO2(-) m r p h o u s f i l m and mlt-quenched Si02 ((3202) g l a s s .

In Figure 4(a)

the

i n f r a r e d absorption spctra o f a.-Si02 and g-SiO2 are compared t o g e t h e r ith that of a-Si02 a f t e r annealed a t 1200 OC. The Si-0 s t r e t c h i n g band

(1080 at-') and hending band (460 an-') observed in g-SiO2 s h i f t toward lmer vibra- t i o n a l e n e r g i e s in those of a-SiO2, while the Si-Si s t r e t c h i n g band(800 an-l) does n o t show any changes. These band s h i f t s are recovered by annealing a-SiO2 a t 1200

OC i n air. Figure 4 ( b ) i n d i c a t e s that similar v a r i a t i o n is observed i n the i n f r a r e d absorption spectra of a-W2 and g-&O2.

(6)

fig. 5

-

The mfkl S(Q) defined as the Fourier 4 transform of Eq. (1) a s a function of RF, value and the e x p r k t a l S (Q)

of sputter-deposited n

sio2

aroorphous film.

C

v,

2

-

deposited

SiO2

1

In order to examine h m the p a i r distribution function g ( r ) of a-Si02 is obtained by disordering the standard go

(r)

for g-Si02, we introduce a broadening function a ( r ) as follows:

where

3 a ( r ) = 1

-

(3/2) (r/2Rs)

+ (1/2) (r/2Rs)

and 2Rs mans the characteristic len* where the atomic m r r e l a t i o n is l o s t . ?he model S (Q) calculated as the Fourier transform of g (r) -1 defined by Eq. (1)

are

sham a s a function of the

Rs

value i n Figure 5. The model S (Q) calculated f o r - 7 A

can reproduce the e x p 5 m m t a l S(Q) very w e l l . Therefore it is canoluded

k

b

;

the

atomic correlation in sputter-deposited Si02 arooqhous film disappears beyond the m r r e l a t i o n length of about 21t,=14 A, while the significant correlation p e r s i s t s i n the structure of rrelt-quenched Si02 glass up to the 2%;=30 A o r mre.

l?J?x'Emm

/1/ ~ i h t t , T. W. and Baglin, J. E., J. Appl. Phys. 50 (1979) 317. /2/ Pliskin, W. A. and Lehman, H. S., J. Electrochem. g c .

112

(1965) 1013.

/3/ H i h t t , T. W., -1. Phys. Lett. 15 (1969) 232.

/4/ Kubota, T. and Kamshida, M., ~ a p a n T ~ . Appl. Phys. 11 (1972) 15.

/5/ Pliskin, W. A., Davidse, P. D., Lehman, H. S. and ~ ? s e l , K. I., IBM Journal 11 (1967) 461.

F/

Hauser, J. J., Pasteur, G. A., Staudinger, A. and Hutton, R. S., J. Non-Cryst. Solids 46 (1981) 59.

/7/ ~ o b F a s h i , Y.

,

Master Thesis (Tohoku University, 1983)

.

/8/ Suzuki, K., Misawa, M., K a i , K. and Watanabe, N . , Nucl. Instrum. ~ t h c d s

147

(1977) 519.

/9/ Watanabe, N., E'ukunaga, T., Skinohe, T., Yamada, K., and Mizapchi, T., ?he High Intensity Total Scattering Spectromter HIT, in: Proc. 4th E e t i n g of Inter- national Collaboration on Advanced Neutron Sources( edited by Ishikawa, Y. e t a 1

,

National Laboratory f o r High Energy Physics, Tsukuba, Japan, 1981)p.539.

/lo/

Misawa, M., Kobayaski, Y., and Suzuki, K., Proc. International Ion Engieering Coqress-ISIAT183 & I~Al"83-(edited by Takagi, T., I n s t i t u t e of Electrical Engineers of Japan, Tokyo, 1983)p.957.