Photolytic Carbon Deposition by IR-Multiphoton Dissociation of Molecules

Specm~chmrco Actu. Vol. GA. Printed m &cat Britam

Photolytic

U.

Central

,

One pulses.

by

the

lie

have

we have dical

of

by

power

equilibrium. not

the

carbon with

carbon

the

GOR,

way

usual

one

to

of

a IlaCl

try re-

intense

the

IR-multipho-

Assuming

order

can

materials

produced

in

to

thermal

by by

may

rise

solid-state

molecules

of

pulses

this

molecules.

conditions

laser give

deposition

concentration

experimental

of

which

by of

of

hydrogen

the

Sciences

In

available

deposition

the

different

high

reactants

decomposition

investigated

the

the

are

is

Academy

that

carbon

the

radicals,

achieve

a high

ra-

concentration.

our

experiments

TEA-CO2 length

laser of

C3h4) cus. The ments

9 cm.

the

The

were

cell

cence

signal,

length

516

after

which

can

Ue report

the

optimum

molecules

and

show,

tion

is

are

of

the

lecule can

for

C2H4 an be

achieved

by

an

so-called

sticking-effect. laser

strate room

focus

solid

photolytic

effect

carbon carbon

temperature.

of

be

in the

films The

the

are

distance

near

for

tuo

an

and

for

225

centre

at

the

of

the

radical

and

the

wave-

on

to

the

For to

different the

the

g. laser

0.9 the

J mo-

a factor

5

fre-

basis

of

of

investigated e.

of

upto

C3H4.

surface

IJe have

precursor concentra-

up with

substrates, the

of

energies

fields

it.

fo-

measure-

fluores-

each

C2H5C1

parallel on

or

laser

spontaneous

concentration

laser

C2H5Cl the

concentration

optimum laser

of

focus

band).

qualitatively

different between

the

C2 radicals

applied

case

deposited on

of

for

C2 radical by

relative

Swan

The the

C2H4,

the

absorption

CO2 laser

understood

directed

deposition

g., the

multimode with

in

infrared

means

pressure

yield

excitation can

is

of

gas

2 . . . 3 kPa.

enlargement

This

the

of

the

a high

quencies.

e. of

wavelengths

order

sufficient

by

by

observed,

lens

molecules

The

monitored

a line-tunable

dissociation

estimated

transition

that

precursor

irradiation.

be

of

means

IR-multiphoton

was

was

(0,O)

radiation by

the

by

laser

radicals

nm (the

the cell

contains

yield

and

carbon

focused

reaction

decomposed

dissociation

before

produced

b,e have into

which

If

thermal

Molecules

Freudenberg

species

which

example

increases

optimized

the

phases

of

6

of

unimolecular

of rate

T.

Chaussee

molecular

from

product

dissociation

deposition

of

Dissociation

Spectroscopy,

distributions

interes,ting

substrates

ton

and

and

Rudower

far

novel

IR-Multiphoton

Albrecht

Optics

state

reactions

ubtain

laser

H.

excitation

nonthermal

actions.

In

of

by

Berlin-Adlershof,

chemical

on

t-I. Hohmann,

selective

create

0SRC853Y~87 $3.00+0.00 ~ergamon Journals Ltd

lY87

Deposition

Institute

LIDR-1199

to

2. pp 225-226.

Carbon

Radloff

The

No

the

a subthe

NaCl

or

focus

Si, and

at the

226

etal.

W.RADLOFF

surface

of

the substrate

homogeneous

carbon

was about

films

0.8

mm. We obtained

in a reproducible

way.

relatively

The elemental

shown only spurious impurities. By the method of electron fuse diffraction fringes were obtained with lattice plane are

typical

for

The deposition meter.

rate

identical

experimental

0.6

of

about

modification

was derived

We have compared

of

larger

the carbon

the

conditions.

J at the optimum wavelength 0.1

A per pulse.

whereas

for

sures

the deposition

leads

to a rapid

rate

was less increases

deposition

measurements

the different

At a pressure we obtained

The deposition

CJH4 it

carbon

for

diffraction distances

and has

difwhich

hard-amorphous.

from thickness

rates

clean analysis

rate

of for

for

in comparison but the strong on the cell

precursor 0.8

with

a profilo-

molecules

at

kPa and an energy

C2H4 a deposition

rate

C2H5C1 was 2 . . . 3 times to C2H4. At higher homogeneous

windows.

pres-

nucleation