FIELD EMISSION FLICKER NOISE FROM SMALL REGIONS OF GERMANIUM EMITTERS WITH ATOMICALLY CLEAN SURFACE

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FIELD EMISSION FLICKER NOISE FROM SMALL REGIONS OF GERMANIUM EMITTERS WITH

ATOMICALLY CLEAN SURFACE

R. Bakhtizin

To cite this version:

R. Bakhtizin. FIELD EMISSION FLICKER NOISE FROM SMALL REGIONS OF GERMANIUM EMITTERS WITH ATOMICALLY CLEAN SURFACE. Journal de Physique Colloques, 1986, 47 (C7), pp.C7-161-C7-163. �10.1051/jphyscol:1986729�. �jpa-00225922�

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JOURNAL DE PHYSIQUE

Colloque C7, suppl6ment au n o 11, Tome 47, Novembre 1986

FIELD EMISSION FLICKER NOISE FROM SMALL REGIONS OF GERMANIUM EMITTERS WITH ATOMICALLY CLEAN SURFACE

R.Z. BAKHTIZIN

Department of Experimental Physics, Bashkir State University, Vfa, U.S.S.R.

Abstract - An attempt was made t o study e l e c t r o n s t a t e s on evapora€ed and annealed c l e a n (011) plane of Germanium by the f i e l d - e m i s s i o n current-fluctuation method.

I - INTRODUCTION

S p e c t r a l c h a r a c t e r i s t i c s of low-frequency f i e l d emission c u r r e n t f l u c t u a t i o n s from semiconductors contain an information about tem- p o r a l and s t a t i s t i c parameters of e l e c t r o n and adsorption-rnigration processes on surface /I/. Moreover f o r r e c e i v i n g r e l i a b l e quantita-

t i v e r e l a t i o n s h i p s i t i s necessary t o c a r r y out researches on sur- f a c e s w i t h d e f i n i t e s t r u c t u r e and e l e c t r o n c h a r a c t e r i s t i c s .

I n the present paper t h e r e a r e given the r e s e a r c h r e s u l t s of low- frequency f i e l d emission c u r r e n t noises from c l o s e l y packed ( O n ) Ge plane with atomically c l e a n surface. The choice of (011) plane i s a l s o connected w i t h the knowledge of i t s parameters by o t h e r methods / 2 / . L!oreover it was important t o t r y determining minimal dimensions of the region where I/f noise i s s t i l l observed /3/.

I1 - EXPl%RnmmQL

The experiments were c a r r i e d out i n the probe-hole a l l g l a s s f i e l d emission microsco e with a screening suppressor Paraday c o l l e c t o r i n vacuum 3 . ^'⁰¹ Pa. The probe-hole i s 2 mm i n diameter and l e t s t o probe e m i t t e r surface a r e a not more than 200 a. The e m i t t e r s were prepared from Ga-doped p-type Ge s i n g l e c r y s t a l s with r e s i s t i - v i t y 3 Ohm

.

cm and viere cleaned by dc f i e l d desorption t i l l get- t i n g a symmetrical f i e l d emission p a t t e r n .

A block diagram of the measurement i s shown i n Fig.1. Measurements were c a r r i e d out by a d i r e c t s t a r t i n g i n d i g i t a l code and the f o l - lowing a n a l y s i s of d i s c r e t e samplings of the i n i t i a l s t o c h a s t i c process with the help of micro-computer. Noise s i g n a l a n a l y s i s was c a r r i e d out i n the r e a l time s c a l e with the use of multi-processing system excluding s i d e d i g i t a l f i l t e r i n g d i s p l a y s . The used algorithu of the f a s t Fourier transformation l e t t o do without multiplying the taken sampling by a d i s t i n g u i s h i n g (prominent) function.

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1986729

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JOURNAL DE PHYSlQUE

111.- RESUllPS AND SHORT DISCUSSION

Fig.2 shows t h e s p e c t r a of f l u c t u a t i o n s taken a t emission c u r r e n t I = 10'"~ from t h e plane c e n t r e (011) of atomicallg c l e a n annealed (curve I ) and evaporated (curve 2) Ge surfaces. It i s seen from the f i g u r e t h a t the main component of f i e l d emission c u r r e n t f l u c t u a - t i o n a t frequency band lower than I 0 Hz i s f l i c k e r n o i s e , moreover t h e e m i t t e r surface s t a t e doesn't influence on t h e f l u c t u a t i o n spe- c t r a form w i t h i n the q u a s i s t a t i o n a r i t y . Besides f o r t h e s p e c t r a l d e n s i t y f u n c t i o n S the empirical Hooge r e l a t i o n i s c o r r e c t /4/:

where:d= 2

.

^{103, f} ^-i s frequency, N - ^thenumber of e l e c t r o n s t a t e s . The received d a t a a r e well c o r r e l a t i n g with t h e r e s u l t s r e - ceived by L B D method (about t h e existence of two types of surface s t r u c t u r e s on (011) Ge plane a t d i f f e r e n t temperatures / 5 / ) .

I/f noise appeared t o be more s t a t i o n a r y ( i n l e v e l ) on a thermo -

dynamically s t a b l e annealed surface. I n these conditions e l e c t r o n s t a t e d e n s i t y n c a l c u l a t e d according t h e s t a t i s t i c s u r f a c e model /I/, (connecting e l e c t r o n s u r f f c e c h a r a c t e r i s t i c s and c u r r e n t f l u c t u a t i o n parameters, = I /2N, where D - i s d i s p e r s i o n of c u r r e n t

G e plane appeared t o be equal:

n = ( 8

'

^I)

.

^10'3 ^cm'2.

On the metastable evaporated surface t h e number N i s r a t h e r c r i t i c a l t o i t s s t a t e and a t s a f e emission p a t t e r n and unchanged current-vol- tage c h a r a c t e r i s t i c s n f o r (011) Ge plane i s changing w i t h i n

( 0 , 0 - ^10,O)

.

^1oX4^cm-2*

It 1s observed t h a t e l e c t r o n s t a t e d e n s i t y changes from the plane c e n t r e t o i t s outlying a r e a s .

/I/ R.Z.B&tizin, S.S.Gots, R.G.Ilyasov, Poverkhnost, 4 /I98LC/ 54.

/2/ S.Roy Morrison. The Chemical Physics of Surf aces, Plenum P r e s s . New York and London, 1977.

/3/ K.S.Ralls, Vl.J.Skocpo1, L.D.Jacke1, R.E.Howard, L.A.Fetter, R.W. Epworth, D .Id.'Pennant, Phys .Rev .Lett., /I964/ 228.

/4/ F .N .Hooge , Physica, 8 B /I976/ 14.

/5/ B.Z.Olshanetsky, A . k h l y a e v , Surface S c i . , a /T977/ 581;

Surface Sci., 82 /I979/ 445.

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Dl SPLA

El

Pig. I. Block-diagram of measurene nt

.

^AS: anode -screen;

PC: Baraday c o l l e c t o r ,

S: suppressor, PA: p r e a m p l i f i e r ,

LA: l i n e a r a m p l i f i e r , LfP: low frequency f i l t e r , W: sampling-memory scheme, BDG: analog-digital converter, G : master pulse generator, G:: time marker generator.

P i g .2. P m e r s p e c t r a l d e n s i t y f u n c t i o n s of f i e l d emission c u r r e n t f l u c t u a t i o n s from annealed (curve I) and evapo- r a t e d ( c a v e 2) ,Ge (011) clean c r y s t a l plane.

FREQUENCY, f