Semiconducting form of nitrogen discovered at 1.4m atmospheres

Equipment & Materials Processing

Semiconducting form of nitrogen discovered at 1.4m atmospheres T h e new, d e n s e form o f nitrogen stores a large a m o u n t o f e n e r g y

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a n d c o u l d potentially s e r v e as a

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n e w s e m i c o n d u c t i n g material. For years, t h e o r i s t s h a v e pred i c t e d that m o l e c u l a r n i t r o g e n

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(N2) w o u l d b e c o m e e i t h e r a s e m i c o n d u c t o r o r a m e t a l at p r e s s u r e s o f a b o u t 100 GPa.

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A similar t h e o r y h o l d s for gaseous hydrogen, which u n d e r similarly h i g h p r e s s u r e s is e x p e c t e d to t u r n into solid metallic h y d r o g e n (yet to b e

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p r o d u c e d in t h e lab). However, r

previous experiments have b e e n limited in p r e s s u r e a n d in

240

the number of measurements

Pressure, GPa

performed under pressure.

Graph showing the sharp reduction in resistance of nitrogen at pressures from 140 GlgaPascals (1.4 million atmospheres) up to at least 240 GPa.

Newly developed techniques allowed m e a s u r e m e n t o f electrical c o n d u c t i v i t y at v e r y h i g h

With s u p p o r from t h e National

semiconducting from pressures

Science Foundation's Division

of 140 GigaPaseals (1.4m atmos-

s e m i c o n d u c t i n g form of nitrogen

o f Materials Research, Russell

p h e r e s ) u p to at least 240 GPa.

w a s stable over a w i d e p r e s s u r e

Hemley a n d colleagues Mikhail

T h e effect o f t h e p r e s s u r e is to

range, a n d s o m e s a m p l e s - w h e n

Eremets, Ho-kwang Mao a n d

t r a n s f o r m t h e nitrigen f r o m a

h e l d b e l o w 100K - retained this

Eugene Gregoryanz at t h e C a r n e g i e I n s t i t u t i o n of

transparent, insulating molecu-

state w h e n d e c o m p r e s s e d to

lar gas into an o p a q u e , semicon-

a t m o s p h e r i c pressure.

W a s h i n g t o n ' s Geophysical

d u c t i n g solid ( w i t h a b a n d g a p

Laboratory (a core institution o f

of just 0.4 eV) w h i c h is stable at

Last year t h e r e s e a r c h e r s report-

t h e NSF's Science a n d

a m b i e n t p r e s s u r e (Nature 411,

ed signs o f t h e material's trans-

T e c h n o l o g y C e n t e r for High-

10 May, p l 7 0 - 4 ) . T h i s is t h e also

f o r m a t i o n at r o o m t e m p e r a t u r e ,

Pressure Research) have created

first time that electrical meas-

u s i n g optical t e c h n i q u e s alone.

a new form of non-molecular

u r e m e n t s have b e e n m a d e o n a

nitrogen w h i c h , at 30OK, is

c o n d e n s e d gas over 200 GPa.

Eomai1: Hollis Wickman, NSF hwickmanc~nsf.gov

pressures.The non-molecular

Agilent accepts GEN200; first order for dual-reactor GEN2000 T h e first GEN200 multi-wafer

delivery a n d w a s p r o d u c t i o n -

7x6" GEN2000 MBE s y s t e m ,

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qualified w i t h i n eight w e e k s "

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Applied Epi I n c

said Applied Epi's p r e s i d e n t a n d

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(St Paul, MN, USA) h a s received

CEO David R e a m e r . " T h e clus-

t h a n a n y o t h e r multi-6" system.

final a c c e p t a n c e at Agilent

ter-tool d e s i g n o f t h e s y s t e m

T e c h n o l o g i e s Inc's lab in Santa

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system from

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The design can accommodate u p to t h r e e g r o w t h reactors, or

* Applied Epi h a s also received

any o t h e r c o m b i n a t i o n o f six

"The s y s t e m w a s g r o w i n g mate-

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III-Vs REVIEW THE ADVANCED SEMICONDUCTOR MAGAZINE VOL : 4 - NO S - June/July ;toot

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