The effect of gaseous environment on electronic properties of inorganic linear-chain compound

Synthetic Metals, 41-43 (1991) 39994004

THE EFFECT OF

OF GASEOUS

INORGANIC

V.B.

Moscow

ENVIRONMENT

LINEAR-CHAIN

PREOBRAZHENSKY

Kurchatov

and

Institute

123182,

3999

ON ELECTRONIC

PROPERTIES

COMPOUND

M.V.

KOLKUNOV

of A t o m i c

EnerEy

USSR

ABSTRACT The on

preliminary

electronic

results

properties

upon of

the

action

CDW-bearing

of g a s e o u s

system

are

environment

presented

and

discussed. The

room

change

remarkably

90 % NH3), drop

temperature

at

seems

conduction

under

growing

at

influence

to

be

fully

of

low ammonia

NH 3 concentration

of

have

30

under

been

ammonia-argon

concentration

exceeding

reversible

NbS 3

%.

present

mixtures

with

The

found

to (1 ÷

a subsequent

resistance

changes

experimental

condi-

tions. On

the

time

scale

served

: a rapid

a slow

one,

tion

two

distinctly

process

which

may

different

associated

be

with

tentatively

processes

a surface

interpreted

are

ob-

adsorption

and

as

an

intercala-

of N H 3 into N b S 3 lattice.

An

unusual

implies

that

behavior

of

a CDW system

NbS 3 conduction is l i k e l y

in

involved

ammonia

into

environment

a process.

INTRODUCTION The widely

effect studied

of years. pounds Ees

are

of for

adsorbed

Essentially

with

new

semiconductin~

of v o l u m e

Eases

different

nature

on

feature

demonstrate

properties, due

surface

semiconductors

conduction during

has

several

low-dimensional

where

the

to a c a p a b i l i t y

of

resistivity such

been tenth comchan-

compounds

to

Elsevier Sequoia/Printed in The Netherlands

4000 intercalation, 'gap'

e.g.

between

Intercalation t ran s f e r host

for

conduction

Drastic

pounds

during

semiconductor

nearly

zone.

effect

of

electronic including

in to

filling during

CDW

which

with

a

lead

period

well

established

intercalated of

some

and

cases

at

systems

layered a

variation

a

com-

metal

in

to

a degree

intercalation.

linear c h a i n c o m p o u n d s

quarter-filled,

charge

molecules

properties

attributed

zone

by a s t r o n g

is

studied

Vanderwaals

[ I].

acceptor

intercalation,

inorganic

commensurate

This

or

transition, are

of a c o n d u c t i o n In most

donor

into

sample

to be a c c o m p a n i e d

comprehensively

changes

molecules

in a m a s s i v e

intercalated

several

[2,3].

of guest

layers

is b e l i e v e d

between

lattice

least

insertion

adjacent

to

the c o n d u c t i o n

a development

quite

equal

to

of

four

a

zone

is

nearly-

lattice

con-

stants. It has deformed

been

shown

o-TaS3[4],

recently

tem are very s e n s i t i v e buted

to small

to a small d e v i a t i o n

Our p r e s e n t

properties

external

action.

zone

filling

was u n d e r t a k e n

by

transfer

( and hence

from

adsorbed

with

uniaxially

of q u a s i - I D These

were attri-

as an a t t e m p t

s y s t e m while

or

intercalated

to moni-

a degree

incommensurability) (

sys-

from a c o m m e n s u r a b i l i t y .

of n e a r l y - c o m m e n s u r a t e

conduction charEe

experiments

of CDW period

investigation

tor the p r o p e r t i e s

in the

that the n o n l i n e a r

of

is changed ) EaS

mole-

cules.

SAMPLES & INSTRUMENTATION A m o n g a f a m i l y of i n o r E a n i c sulfide

has a h i g h e s t

its type-II especially gaseous

phase

Peierls

[4]

suitable

a room

for

environment

linear-chain transition

on

compounds

temperature

temperature. For

studyinE electronic

In

that

the

s1~u

properties

niobium

reason

effect of

tri-

exceedinE

of

for

NbS 3 is active

CDW-bearinE

sys-

tems. NbS 3 was o b t a i n e d

in a form of thin w h i s k e r s

inE of n i o b i u m p o w d e r conducting a broad

behavior

Peierls

and continued

in s u l f u r

at r o o m

transition,

temperature startinE

well

and

phases.

were

dispose

heat-

a semi-

characterized

by

above a r o o m t e m p e r a t u r e

d o w n to 200K, s h o w i n E a m a te r i a l

ture of d i f f e r e n t

by p r o l o n E e d

vapor. The samples

A n active dc bridEe

to c o n s i s t

of a mix-

with a controlled

4001 i

w

i

i

i

i

l

i

i

i

l

l

l

0o0 o ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ° ~ ° 6

0.04

{J:tcz0,02~ 1 ~

i

o

l

°

llllllllllllllll

o,m

==

E~.xxxxxxx ~

o

~,,,~¢~.

+ + + + + +..

^x x

~'++++ @ ~ ^ ~.^ x x ~ til t "x ~"-,:,+ &, ~ o,

"-==%~J

L -0.0IF

++4++++ ++

o ~ ~ ~ .. " . ---.-..:.Z ~ S S,o ~,"xo ~ ioo "~S

I -o.o2 -

"~' [

I

0

FiE.

c =

1.

The

41.2~,

¢-

curves

have

excitation indium No before

pads

its

i

NbS 3

I

i

conduction

0

$ -

57.5~,

-............... 7 1 . 1 ~ ,

was as

surface

zero

used

in a is

of flow

in

reached.

c

•-

~-

)

though

a dry

pure

been

(at

25.9~,

the

a

conduc-

beEinning

+-

83.6~.

34. I~,

X-

(Note,

all

Pressed

measurements. found

to diminish was

after to

measurements.

2-electrode have

measurements of

variations

resistivity

treatment

measurements,

series

ordinate.

for

contacts

16.6~,

1600

Normalized

concentration -

i

1400

concentration.

Ammonia

at

"

1200

II.4~,

served

value

I

•-

voltage

each

m

~mmonia

oriEin

deEasing

I

600 BOO 1000 T II4 E ( s e c )

argon.

47.4~,

I

dependent

resistivity

resistance

I

of

5.97~,

special

tamination sample

time

pure o-

I

400

chanEe

in 0):

t

200

step-like tion

I

preceded

arEon

until

to

be

necessary

a surface by

con-

a prolonEed

a steady

state

4002

RESULTS & DISCUSSION A typical centration

conduction

of

conduction

inherently different

diverse time

present

are

fitting

sample

#(t)

giving

seems

sec

be

for

rather

obtained duction state"

origins

hence

any

(Each

one.)

processes by

processes

physically time

of

essentially

this

at

meaningful

dependence

change

is

A time depen-

two

of

the

curve

of

a

of c o n c e n t r a t i o n

min. on

a

While

further

rl

semiconductor for

meanings

surface,

intercalation

of

are

the

r2

light

gas

process.

state

hour

the

value

of

of c o n d u c t i o n

exposure

in

considerations

50 min of exposure,

a

the

conduction

when systematic

by thermal

drift,

have not been

predefined

were

ammonia meanings

changes

in con-

taken as

"steady

values. 2 shows

tion of a m m o n i a

the

a sample

was

was

result

a behavior

conductor surface adsorbed

for

steady

state

in a w o r k i n g within

sufficiently

values

chamber.

as

a

func-

The concentra-

a few percents, prolonged

time

provided to a pure

the experiment.

nonmonotonic

surprising

defined

reproducible

subjected

flow before

The

above

concentration

tional d e p e n d e n c e

such

an

are a l r e a d y m a s k e d

Fig.

a rgon

the

characteristic

In

after

I.

con-

concentration

shows

to a s t e p - l i k e

adsorption

after

concentration.

to a next

clearly

impossible),

then for any surface

even

fig.

ammonia

occur, c h a r a c t e r i z e d

f2~15

In fact a proper s t e a d y reached

in

of a m m o n i a

Ai{ l-exp(-t/x i )),

and

are

molecules,

to

change

by two exponentials:

usual

values

value

(and

to

s h o wn

after

Since

response

= #0+i~1,2

r I ~5

shown

known

was a p p r o x i m a t e d

is

variations nature

resistivity

quite

chamber

constants. not

to a s t e p - l i k e

variationes

from a p r e v i o u s

dence

curve

response

in a w o r k i n g

represent changed

sample

concentrational

of a p r e s e n t

is hard

behavior.

adsorption molecules

to e x p l a i n

According model

a

dependence

investigation.

to

within a

a zone

perhaps

frame

behavior

curvature

a

most

mention, of.usual

conventional

nonmonotonic

first change

a

is Worth

that semi-

semiconductor is

expected,

at surface

if

until

4003 1.16

,

I

h14

'

I

,

'

•

!

,-, 1.12 uJ N

-J =:

1.I

O

z

v 1.08 z 0

•

1.06 z

•

•

31'°41" 1.02

8

0

20

Fig.

2.

ammonia

an

NbS 3

intrinsic

duction

A

steady

concentration

carriers

rise.

40 60 CONCENTRATION ( % )

of

first

in a s u r f a c e

sign

drop

are

to

non-trivial implies

into

account

behavior

a more the

dependence

layer

produced.

the

is j u s t c o n t r a r y

ment

conduction

'1 (see

text ]

on

in a g a s m i x t u r e .

conduction opposite

will

This

state

80

intrinsic

is r e a c h e d , a n d

In t h i s value

case and

t h e n the

surface

then

con-

began

to

to o u r o b s e r v a t i o n s . of

NbS 3 conduction

sophisticated

interaction

of

model

in

is n e e d e d

adsorbed

ammonia

environ-

taking

possibly

molecules

with

a

ODW

system.

ACKNO%VLEDGEMENT The

authors

on early

stage

are

indebted

to A.N. T a l d e n k o v

of m e a s u r e m e n t s .

for

his

participance

4004 REFERENCES I F.R. Gamble, T.H. 2

E.

4

Osiecky,

Eurenfreund,

(1972) 3

J.H.

Geballe, Science,

A. B e a l ,

H.

Caiz,

174 (19711

A.C. Gossard,

R.

Pisharody,

F.

DiSalvo,

493. F.R. Gamble t

Phys. Rev.

B,

1708. W. L i a n g ,

V.B.Preobrazhensky,

J.

P h y s . C, 6 A.N.

(1973)

Taldenkov,.

L482.

Synth.

Het.,

29' (1989)

F313. 5

P.

Honceau,

Z.Z. WanE,

H.

Renard,

CDW in Solids,

SprinEer-VerlaE

(1985)

J.

Richard,

Lecture

279.

Notes

H.C.

Saint-LaEer

in Phzsics t 217,

and

5