Physical aspects in glass surface analysis

Journal of Non-Crystalline Solids 95 & 96 (1987) North+loUand, Amsterdam

PHYSICAL

Paolo *

ASPECTS

MAZZOLDI’

Unite 35131

and

SURFACE ANALYSIS

Antonio

MIOTELLO+ Fisica dell’Universit8, Nazionali INFN,

Studi de1 Consiglio Nazionale Scientificm e Tecnologica,

Surface

analysis

techniques,

problems when by electrons,

applied

which insulating

to

protons models.

theoretical

and

heavy

Via Legnaro,

delle Ricerche Pow (Trento),

use charged materials.

ions

and Italy

particles Surface

irradiations

Marzolo Italy

Istituto

8,

per

as probe, modifications

are

la

present induced

discussed,

including

INTRODUCTION The

surface

termination ion,

analysis of

surface

sis

one

interaction the the

cause

electrical

physical the

paint

of In

view

this

(Auger

Electron

phasizing, A brief they

for

review

NRA (Nuclear

we

the

deducing want

not

to

are

applicability

discuss

the to

SIMS

nuclear the

techniques

0022-3093/87/$03.50 @ Elsevier Science F’ublishers (North-Holland Physics Publishing Division)

scientists’

B.V

use

induce

ions).

determiparticles

radiation

mobile

governing

may

ions,

of

interaction both

such

in

from

techniques,

Ion

such

89 AES

Spectrometry),

Mass

Spectrometry)

by

the

incident

(RBS

and

NRA)

Community.

bea basic

techniques.

Backscattering

induced

glass

which

important,

analysis

(Secondary

modifications

analyzed emitted

that

limits

some

be

analyor

region.

very

RBS (Rutherford

the of

effects analyzed

materials

the

de-

atoms.

techniques

mechanisms

glass

and

of

the

corros-

electrons to

energy

in

leaching,

modern

material

matrix

other the

the the

Analysis)

common

the

interaction

and

particular,

description we

leave

Spectroscopy), Reaction

in

of

particles

and

and

to

the

of

In

as

(photons,

and

analytical

formation

aspects

charged

with kind

important

such

mechanisms.

identification

elements,

extremely

glass,

radiation

beam

the

is

upon

of

Both

insulators

field

alkali

The

incident

or to

a source

radiation.

signature

particular

tween

the

of

applied

glasses acting

ion-exchange

with

of

emission

When

insulating

processes

concerned

The

allow

of

various

contamination,

is

nes

since

161

CISM-GNSM, Oipertimento di Padova, Italy; and Laboratori

+ Centro Ricerca

1.

IN GLASS

161 - I72

em-

beam. will

be

given,

2. rwcr,E~R

TECHNIQUES

Beckscattering get to

constituents a few

energy’

and

. A beam

get

surface

to

of

target

tering

and

the

particle

scattering atom

will

during

below those

its

the

ratio

without

spectrum get.

Five

ments

1.8

depth

steps

ced

low

reaction

analyzed

with

section

of

the

of

incoming

the

total

the

cross-section

If the

the

products

the

also

at-a

usually

the

of

the

of

nuclear is

particles

is

nuclear

greater

target nuclei

penetrate

elastic

into

backscat-

due

to

anelastic

is

from

lower

an

than

that

permits

de-

the

corresponding oxygen

reaction

useful

for of

the

the

be most

resonance energy

are

at

The

detected

for

energy

determine

structure

depth

upon

a depth

the to

resonance

and cross-

of

appropriate

energy

eleindu-

differential

as a function

useful

of

reactions

which

quite

ele-

information.

When the

However,

tar-

target

analysis

nuclear

particles RBS.

energy

be seen.

isotope-sensitive

is

nuclei.

to

can

analysis

constant

this

concentration

glass

for

can

their

and

1 shows

nearly

the

tar-

the

a thick

charged

reach

target

from

provide

than will

of

the

Fig.

specially

reactions

and

backscattered

on the

investigated

angle

the

ion

but

of

as reference.

and

used

reaction

particles,

beam energy

material,

These

large of

spectrum

elements

energy,

sodium

same apparatus

nuclear

amount

sample

based

fraction

to

backscattering

compound

technique,

beam

undergo

which

A”

a Van de Graaf

backscattered

an energy

100

surface.

elastically

is

energy,

elastically

tar-

analysing

element

atoms,

a lower

at

of

incident

After

energy

of

order

number,

the

the

magnesium,

particles.

observed

of

to

surface

ions

the in

by an

enough

the from

A small

excitation. with

on the

to

nuclei

close

of

ranging

sample.

the

with

Thus

atoms

ions

nuclear

of

mass

produced

scattered

come

be detected

in decreasing

atomic

by charged

path.

the

target

mass do not

a standard

silicon,

A complementary of

the

profiles

MeV aHe+

calcium,

ments

the ions

be detected

will

requiring

of

to the

analysis

the

of

of

by similar

So an appropriate of

4He’

by electronic

return

surface

scattered

termination

according

usually

surface

the

depths

ions,

interaction

energy

over

surface,

ions

through loose

about

distribution

close

of

incident

be backscattered

the

of

a function the

information

target

the

The energy

is

Most

onto

sufficiently

scattering.

atom.

the

monoenergetic

directed

beam comes

elastic

in-depth

from

of

is

provides

their

micrometers,

accelerator, the

(RBS AND NRA)

spectrometry

slowing

below

in

profiling.

the

down surface

in

P. Mo;:oldi.

and

the

reaction

depth.

yield

By varying

invesligated )ZONe

le.

Fig. the

will

the

for

2 shows

the

surface

ions

as

a

glass

is

basically

Two

Sodium

of

of

FIGURE

one

useful and

(upper

can

By

depth

to

the

obtain

the

reactions

it

and

that Na+

from

Many

mobile

ions,

phenomena 3.1 a)

dielectric

part

occur

when

an

electric

preferential

Low-mess

While small

of

determine

Electric

ion field

much

profiles concentrat-

hydratation

process

in

profiles

leached

of

( -)

an

unleached

glass.

INTERACTION

phenomena formation

part)

relative

are profi-

Ht.

H depth

( A ) and

tor:

field

Hydrogen

a glass

Na and

RADIATION-GLASS

the

1

1.8 MeV RBS spectrum target

3.

the

with

that

of

glass

the

the

at

profile

(lower

of

appears of

for

hydrogen

comparison

replacement

depth the

)“C

163

concentration

in

*H(15N,ay

part)

glassz.

the

~~prspec~s irr ,qlu.~s srrrfurce LIIIU!I.SIS

proportional

very

the to

be energy

sodium

due

Pl~prol

detection

hydrated

function

/

thus

incident

element.

z3No(p,a

near

A. M~o~llo

work

concerns

an

ionizing

sputtering

a modification or

electron

beam

field,

of

strikes

radiation

the

damage,

and

cooperative

near

surface

surface

of

enhanced

transport glass

an

insula-

diffusion

of

effects3.

Such

composition.

irradiation

formation has

been

done

the

basic

phenomena

solids.Electrostatic

on

potentials

radiation of

effects

in

radiation-induced are

induced

insulators, electric

at

the

surfaces

only fields of

a in

insu-

lating se

materials

sible

in

dielectric

and

of

trons

to

charges.

prevented

insulators.

In

the

dielectric

conditions

ce

electric

field

occurs)

is

down,

however,

is

mobile

condary

primary

electron

typically

much deposition

continuity

where

is

temperature. well B(x,t)

for

the

es by the

E(x,t)

in

the

is

surface

may be calculated

by

been

other

that

end

charge integrating

in

in

a

silicate

experimenta surfacertainly

breakdown

Dielectric In

surface

Since

the

break-

order

to

is

charge,

in

the

reasonable

due

to

seis

problem

density

at

field due

time

the

diffusion

of

form:

(1)

t

e the

and electron

induced

by

to

secondary

Poisson’s

the

(i.e.

consider

8 (s(x,t)q(x,t))+s(x,t) 8x

constant,

be-

beam size

to

field-assisted

a one-dimensional

explain

process

electron

involved

electric

choice

temperature.

and

typical

sec.

that field

verified

B recombination

positive

it

show

electric

recombination,

experiments.

lengths

-pe

electric

field

dielectric

depth)

in

beam

electric

lo-”

elec-

appropriate

electron

the

positive

experimentally by an

about

over

supply

authors the

beam

es probe

film

introduced

of

analysis

point of

involved

present

ions,

incident

layers

the

undergoing

immobile

charge

the

an

be operating.

Boltzmann

positive

the

proposed

8zqkt) ~ 8X”

the

has

reported

ordinary

electron

the

Auger

which

concentration

ks

for

dynamics

of

time

the

the

of

not

and migration

= (wkksT/e)

mobility,

(at

and

than range

electron

q(x,t)

electron

are

must

larger

6q(x, t) .st

during

electrons

equation

primary

ions

Miotelloq

emission,

the it

angle

electrons

observed

metallic

by

in

growth

an interval

finding

electron

the

not

the

may be prevented

the

107 V/cm in

that

analysis

incidence

of

attained

experimental

tween

Auger

primary

metallic

role

phenomena

alkali-metal . If

nre

a thin

pos-

mobile

the

charges

The-

beam,

the

of

positive

performed

quantitatively

containing

al

this

of

beam energy,

us describe

glass

case

of

Deflection

compensating

utilized.

incident

depositing

clear thus

a major

breakdown

electron

is

are the

electromigration

when

calculations play

of

particles.

by

glasses

mobility

formation.

Let

It

irradiated

Preliminary

electronic

that

phenomena,

particles

deflection

sample,

emitted

frequently

the

the

the

the

charged

induce

breakdown are

surface

in

of

energy

involving may

breakdown

the

particles,

techniques

potentials

dielectric

a shift

of

when

electrostatic

the

equation:

depth

x,

charge primary electron

PC is end

the T the

electrons emission.

as

165

GE(x,t) -=-

n(x,

6x 6

is

cal

the

vacuum

glass).

dary

S(x,t) for in

electric the

ref.

field

a time

ration

of

by

yield

MC is

different

analysis.

alkali

much

fig.

an Auger

cess ( since cally

In

(10-q

ions

does

the

number

smaller

3

It

is

small

with

role

in

number

of

the in

charge

the

electron

are

attained

to

a typical

du-

the

mobility

of

recombination

electron

primary

surface choosing

for

that

is

and

conditions

proved

involved

the

1,2

respect

Boun-

electrons of

eqs. values

state

a typi-

electrons.

evolution

different

for

primary

of

be easily

ions

global

primary

time

steady

very

a relevant

positive the

four

zero,

may also

play

of

the

(+=5

of

integration

at

which

of

process

we report

from

constant

function

numerical y’=l)

set)

not

than

dielectric

recombination

obtained

interval

the

6

depth-deposition

surface

electron When

63 Er

and

the the

4.

(as

secondary

mobility.

the

is

condition

discussed

in

permittivity

t)

migration

prois

typi-

electrons.

ELECTRICFIELDAT x IO (“km, FIGURE 3 evolution of surface in AES experiments.

Time field

Reducrd depth IyRgl

electric Primary

In

fig.

line)

4

calculated

shed-line)

both

according

calculated

this

section

addit

ion

(i.e.

we report

pal).

we want of

the

total

Moreover

the to

the

primary usually

by numerical to

note

that

positive the

drift

of

primary

distribution

quoted

by requiring and negative

electron

electron

integration

FIGURE 4 distribution

models of that

charge electrons,

eqs.

functions.

function

as well 1,2.

as the Before

IX<107 V/cm turns

out towards

(solid

the to

one

algebraical

be about the

(da-

concluding

surface

zero of

P. Mor:oldi

166

the

analyzed

glass,

secondary

to

electron

layer

where

these

figures

positive and of

/ Pl!,~~nl

compensate

emission,

the

contribution

A. Mioreh

image

;,I ,~luss surfore

positive reduces

are

located.

charge

charged the

we we

effects

mo!rs;.,

holes

thickness

in

by the

the

on the

justified

the

left

of

As B conclusion,

l ,=5-10,

typically

the

the

drastically charges

since

for

mperrs

in

calculation

surface basis

of

neglecting of

the

the

electric

field. b)

Alkali

In

fig.

da-lime

transport 5 we

glass.

FJ surface

the

towards

the

proton the

surface the

surface

(proton

target

has

temperature

evolution

of

Moreover, elapsed and

alkali

(incubation of

FIGURE of alkali

proton

lime

(fig.

occurs

exe

present alkali

by a

irradiation) migration

time). or electron

a so-

depletion.

Such

a depth

roughly

the

interior

in

the

case

Ce surface accompanied

after

interval

current

from

migration

is starts

This

at

of

6).

glasses:

accompanied

(electron

surface

migration effects

soda

analysis

accumulation

range

Other

during

an alkali

alkali

is

depletion

Irradiation

Time

7,8).

irradiation) Na

accumulation. interval

electron

bombardment

(Figs.

recorded

by an alkali

primary

irradiation

surface

signal produces

accompanied

proton

surface

or electron

while

time

of

glasses

Na Auger

irradiation is

to maximum case

analyzed

the

Electron

depletion

corresponding In

in

report

is

depletion, by a Ca

a characteristic a function

of

density.

time (sect 5 Auger

signal Normalized les after

of

towards

FIGURE 6 Na and Ca depth profielectron irradiation.

the

167

Time 600

FIGURE 7 surface alkali bombarded glasses.

evolution keV

of

proton

signal

in

i

oMPTH

FIGURE 8 Na and Ca depth profiles keV proton irradiation.

Normalized after 600 The

alkali

flux

due

one-dimensional

to

the

form)

ordinary

and

electric

(nm)

field

assisted

diffusion

(in

is: 8c(x,t) J = -D ~

+C(x.t)@(x)

(3)

8x

where

D and

w are

Nernst-Einstein

the

alkali

relation

gligible,

and C(x,t)

continuity

equation

diffusion

if is

alkali

0 to

time

be

@C(x,t) = D ___

boundary

(see

should

calculated those

profiles.

Numerical starting

species

x and time

is

t.

ne-

By the

The

full fields

for

the

the

the

lines

in

fig.

for

positive irradiated

of

initial

including quantitative

electron

(C(x,t)E(x))

(4)

8x

integration

from

conditions, yield

electric evaluated

mobile

depth

by the

8 - p -

8x2

constant.

appropriate

alkali

at

connected

we obtain

interval,

ref.3)

between

concentration

8t

assuming

constants,

correlation-phenomena

the

8C(x,t) ~

diation

mobility

and

the

ionic

description 5,7,8 ion

eq.

4 during

alkali

are irradiation glasses.

desorption of

the

the

irra-

concentration

the

final

theoretical are

opposite

and with cross-section experimental profiles. in

The sign

to

3.2

Enhanced

The

diffusion

in

coefficient

literature

particle literature

In

Fig.

rent

of

the

dependence the

bond

the

DX of

process

magnitude

that

to

the

irradiated

the

DL~,

of

cur-

temperature

literature.

than

break

quoted

irradiation

from

higher

ones

proton

when

taken are

we ascribe

the

the

we report

coefficient,Dth,

reported by charged

measurements.

600 keV

figure

coefficients

of

than

temperature

same

data

self-diffusion for

target the

the induced

greater

alkali

coefficient

the In

diffusion

irradiation

STIMULATED

of

Na self-diffusion

diffusion

during

by anelyzing modifications,

standard

15 ~.~A/cmz.

calculated

en enhanced

orders

calculated

of

obtained profile

through

es e function order

of

T<500'K

cal

the

glasses

D*,

alkali

some

obtained

9 we show

is

the ere

end

soda-lime

values

concerning

irradiation,

in

4.

diffusion

the

For

indicating

alkali

chemi-

energy)

stri-

glasses.

DBSORPTION

When ions

(or

ke .s surface

primary

of

electrons

en insulator,

and also emission

photons

of

ions

of

sufficient

end neutrals

is

frequently

ob-

serveds. Two different of

processes

electrons

and

excitations ing

be long There

enough are

in

possible:

cm)*

I to

moval

of

state

ABZ+.

sible

in

insulators,

how this

from

the

to

three

electronic

deexcitations

glasses,

we

electron

irradiation

in of

to

many the

ground

ionized

excited

final

If

processes state states

Electronic of

to

states atomic

AB to

an excited

es example dissociation, neutral

characterized or

A++B,

to

state

by the

e

A++B*

may

motion.

we consider molecule

electron

insulat-

electronic

for

(An+)*

products

ionization

sputtering

be transferred

or bonding

various

glasses:

scattering.

the

be accomplished.

antibonding

Dissociation last

ten

AB+ or excited

e nonbonding,

the

energy

in

by elastic role

lifetimes

At-excitation,

transitions ionized

effects

atoms

a dominant

excitation

ways

molecule

desorption of

probably,

allow

numerous

are

As to

to

induce

displacement

most Indeed

e diatomic

Auger

direct

play,

materials.

q ey

doubly or

re-

ionized

A++B+

is

pos-

situations. excitation

play

q ey quote

the of

mechanisms

e central

role.

results

experimental

soda-silica

notice

glass.

that

As en indicative of

The alkali

inter-

end

example,

intra-atomic pertinent

Na+ desorption desorption

induced is

initially

to by

P. Marzoldi,

I. A

A. Miorello

promoted

by the

core

holes

the

levels

(see

fig.

Si-2p

I

/ Plry.vicul avpec~~ in glrrrs surface ondysis

created

either

in

the

04s

169

electronic

levels

or

in

10j6.

l

1%

FIGURE Calculated enhanced ficient for proton

5.

COOPERATIVE Many

the

and

same

tential

diffusion irradiation.

are

rank

are

R,

an electric

where

9

mical

potential,

is

the

charges

ion

induced

allow Here

the

in

the

field,

migrate.

in

simply the

K-Ce

of

A thorough

of report

its

two

pri-

ions,

induced

charged

transport

carrier

independent

of

the

in

structure

an indicative

and Na-Ca

include

each

is

migration

charged

a non-uniform have

the

by

defects,

processes

affected

temperature

defined

by the

has

of po-

?I

with

of

a silicate

the

p is

potential

connection

the in

with

some suggestions

presented

in

ref.

cooperative glass

a de-

expression:

p + 4,

q

and

T distribution,

electric 5 in

along been

example in

eq.

i,j

general

as:

@ the of

glasses

species

following

carrier,

discussion

phenomena

processes

principle,

of

potential

charge

transport

Curie

flux

fluxes

electrochemical q the

of

fluxes3.

presence the

a simplification we

the

transport

These

the

independent with

the

glasses. to

i.e.

all

a system

species

and of

FIGURE 10 yield as a function beam energy .

Na sputtering mary electron

in

of

According

coupled, of

Energylrvl

PROCESSES

irradiation

we consider

pendent

coef-

generally’involved

photons.

gradient

If

curring

9

particle

phonons

HI

Electron

TRANSPORT

carriers

charged

Cl ml 4006W 8001

during

chewhich

radiatwhich

3. effects AIL?.

oc-

An interesting the

one reported

coefficients bly

result

are

due

tice

to

in

fig.11

not

accompanied

is

electrodynamical

deformations,

transport

emerging

from

connected by

to

high

screening

when

a theoretical

charges

the ionic

effects,

of

analysis

effects

possibility

that

high

mobilities.

This

is

possibly

different

of

kinds

diffusion most

connected

to

local

involved

in

the

are

like

probaletglobal

processes3.

20Na,OlOCa0 70 SiO

Experimental and calculated electron bombardment time. 6.

the

ion

irradiation

of

near-surface

preferential From

general

points:

(1)

the

thickness

ion

dose,

reaching

The

alkali

profile,

cident

the

ion

(3)

The depleted

(4)

The

alkali

of

The

in

alkali

for

layer

with

heights

agreement

as function

of

produces

be explained

in

in

diffusion

literature

we can

layer

is

alkali of

terms

in

the

an

alkali

implanted

underline

a function

depletion

the

of

the

re-

following

implantat-

value.

a fixed

irradiation

dose,

is

independent

of

the

in-

density. thickness

increases

mechanisms of

with

glasses

enhanced

depleted

the

electronic the

seem

alkali

cross-section the

may

a steady-state

depletion

sputtering

pendence

which

reported

the

current

silicate

and radiation

results

rc~om temperature) (6)

alkali

region3*7,

sputtering

gion7-8.

(2)

peak

HGAVY ION IRRADIATION Heavy

in

FIGURE 11 and Ca Auger

alkali

physical

with to

element of

the

implantation

independent

present

alkali

stopping

be

in

elements power

mechanisms

for

energy. (at

the

least

en almost

a variety

of

in

near-

glass.

shows

discussed

for

section

linear

incident 4.

deions,

P. Mn::uldi. (6)

The

modified

A. Mmello

layer

pnrticutar

for

is

high

/ PI!,:kwl

thicker

energy

171

rrspem in ~C$US.Y srrr/crre oru~!,~is

than

the

culculated

doposiI.ion,

incident

indiwl.ing

H

ion

migrcllion

rouge,

in

of’ produced

defects. More

recent.

radiation, an elwtrir dent

Fig.

is

to

of

at

about

Ar

evaluated

the

alkali

where

the

B 5 8

indicating movement of DEPTH 500 500 400 300 I 4 I I 300 lb”

ot

of from that

the Rb ion (run) zoo 100 0 1 I I A,*

FIGURB 12 RBS spectrum from Rb in Ar glasses at 300 keV.

data radiation occurs

it-radiated

of evi

also

of

the

Fig.

2)

3000

Lhe

pro

a maximom

at

a

A, corresponding

an Hb segregation

calculation are

one eV for 13.

effects without

of

reported of

beam

irradiation

doses

Lemperatures, is

For

keV Art

oc-

range.

concerning

hundredlhs

the the

are

Rb atoms,

a 300

peak,

a depth

implantation

Dth, some

effec1.s

with

low dose

Ar projected

target

coefficient

ir--

process

from

LOO’C

1) a surf;icc

(f or details different

energy

may be evaluated

energy,

at

Such

scattering of

For

depletion

At higher

DX values

the

features:

the

after

diffusion

ion.

ions/cm”.

to

profiles,

the

r.hurgc.

concorning

a large

range.

element

activation

process ksT

three

corresponding

nlknli to

a temperature

10.5~10’6

by

Rb self-diffusion

fective

run at

A, 3)

in Ibe

deposilrd

incident

RBS specl

projected

ion

of

and

1000

u depth

fcoturrs as a contribution

incident.

irradiated

4.5x1O’e

The

The

to

characterized

of

the

the

glass, of

pcculi~r

velocity

12 shows

al. doses

curs

duo

a higher

a RbzO-SiO2

file

showed

may be explained

field

with

depth

work

which

This create

see

reported

for

in

comparison. the

value

alkali is

a defect

ref.

An eftransport

comparable distribuLion

jump.

Calculated cient of ed-glasses.

3)

Fig.13.

FIGURB 13 enhanced diffusion alkali in heavy ion

coeffiirradiet-

to

7.

INCUBATION Many

last

TIME

attempts

decade,

problem

to

but

explain

the

seers

at

the

question

incubation is

present

still

an

phenomenon open.

have

been

Some connection

interesting

stwting

made

during

the

wilh

a percolation

for

R theoretical

point

*“S”et-.

8.

CONCl,USIONS A review

charged field and

of

transport

particle formation,

preferential

processes

induced

irradiation

has

correlation

transport

sputtering,

have

been

in

alkali

given.

Many

effects,

been

containing processes,

enhanced

glass such

by fesl as electric

diffusion

processes

emphasized.

REFERENCES 1)

P.

Mezzoldi

2)

G. Della mentale

3)

P.

and

G.

Mea, M. de1 Vetro

Mazzoldi

and

Della

Guglielmi 6 (1985) A.

Verres

Mea,

Refract.

and R. 139.

Dal

Rad.

Eff.

Miotello:

35

Maschio,

98

(1981)

Rivista

(1986)

205,

31. della

and

Stezione

reported

Speri-

referen-

ces . 4)

A.

Miotello,

5)

D.

Menzel,

6)

Y.X.

7)

P.

Wang, Mazzoldi,

Phys. Nucl. F.

L&t. Instr.

Ohuchi Nucl.

and Instr.

103A

(1984)

Meth.

B13

P.

Holloway,

M&h.

279. (1986)

209

J. (1983)

507. Vat.

Science

1089.

Tech.

A2 (1984)

732.