Rep ese tatio al
AI
photo
Resea che s
f om
Taiwa ‘s
Natio al
Ya g
Mi g
Chiao
Tu g
U ive sity
(NYCU)
a d
TSMC
Co po ate
Resea ch
have
developed
a
ew
way
to
imp ove
t a sisto s
made
f om
atomically
thi
mate ials.
They
focuses
o
the
ti y
bou da y
whe e
two
mate ials
meet,
which
allowed
them
to
build
t a sisto s
with
a
ext emely
thi
i sulati g
laye
while
mai tai i g
st o g
elect ical
pe fo ma ce.Acco di g
to
Scie ce
Daily,
atomically
thi
semico ducto s
have
bee
studied
fo
mo e
tha
a
decade
because
some
ca
be
just
o e
atom
thick
while
still
showi g
useful
elect ical
p ope ties.
Such
mate ials
could
allow
t a sisto s
to
become
smalle ,
faste
a d
mo e
e e gy
efficie t
tha
co ve tio al
silico -based
devices.Howeve ,
maki g
these
ve y
thi
t a sisto s
wo k
well
has
bee
difficult.
O e
majo
p oblem
i volves
the
gate
dielect ic,
a
ext emely
thi
i sulati g
laye
that
helps
co t ol
the
moveme t
of
elect o s.
Maki g
it
thi e
ca
imp ove
t a sisto
co t ol,
but
whe
it
is
placed
o
a
atomically
thi
semico ducto ,
p oblems
ca
develop
at
the
bou da y
betwee
the
two
mate ials.
These
ca
i te fe e
with
elect o
moveme t
a d
educe
pe fo ma ce.
The
ew
study,
published
i
Natu e
Elect o ics,
add esses
this
p oblem
by
e gi ee i g
the
atomic
i te face
betwee
the
semico ducto
a d
the
i sulati g
laye .
Focus
o
Atomic
Bou da y
The
NYCU
team
wo ked
with
TSMC
Co po ate
Resea ch
to
e gi ee
the
a ow
egio
whe e
the
two
mate ials
meet.
I stead
of
focusi g
o ly
o
fi di g
a
ew
semico ducto ,
the
esea che s
cha ged
the
i te face
itself.The
team
used
mo olaye
molybde um
disulfide,
o
MoS2,
as
the
semico ducto .
A
mo olaye
is
a
mate ial
that
is
o ly
o e
laye
of
atoms
thick.
The
esea che s
fi st
placed
a
ult athi
epitaxial
alumi ium
laye
di ectly
o
the
MoS2.They
the
oxidised
the
alumi ium
to
c eate
a
alumi ium
oxide
laye
about
0.42
a omet es
thick.
Afte
this,
they
added
a
high-κ
haf ium
oxide
gate
dielect ic,
a
i sulati g
mate ial
that
ca
p ovide
st o g
elect ical
co t ol
while
emai i g
ve y
thi .The
0.42- a omet e
alumi ium
oxide
laye
acted
as
a
buffe
betwee
the
MoS2
a d
haf ium
oxide.
It
c eated
a
smoothe
su face,
helpi g
the
haf ium
oxide
g ow
mo e
u ifo mly,
while
also
educi g
u wa ted
elect ical
i te actio s
betwee
the
two
mate ials.”Fo
ma y
yea s,
effo ts
to
imp ove
atomically
thi
t a sisto s
have
la gely
focused
o
discove i g
bette
semico ducto
mate ials,”
said
P ofesso
We -Hao
Cha g,
the
study’s
co espo di g
autho
f om
NYCU.
“Ou
esea ch
shows
that
the
atomic
i te face
betwee
mate ials
ca
be
just
as
impo ta t.
By
e gi ee i g
that
bou da y,
we
we e
able
to
educe
o e
of
the
fu dame tal
t ade-offs
that
has
limited
two-dime sio al
t a sisto s
fo
ma y
yea s,”
he
added.
Why
i te face
matte s
Atomically
thi
semico ducto s
c eate
a
pa ticula
challe ge
because
thei
su faces
do
ot
have
da gli g
bo ds.
This
makes
it
difficult
to
g ow
a
ext emely
thi
dielect ic
laye
eve ly
ac oss
the
su face.Sta da d
depositio
methods
ca
leave
gaps
a d
defects
at
the
i te face.
These
ca
c eate
elect ical
diso de
a d
educe
ca ie
mobility,
which
efe s
to
how
easily
elect o s
move
th ough
a
mate ial.
Scie ce
Daily
photo
Resea che s
have
explo ed
diffe e t
dielect ic
mate ials,
molecula
seed
laye s
a d
othe
oxide
depositio
methods.
Howeve ,
achievi g
a
ve y
thi
equivale t
oxide
thick ess,
st o g
elect ostatic
co t ol
a d
high
ca ie
mobility
at
the
same
time
emai s
difficult.The
challe ge
is
especially
impo ta t
fo
wafe -scale
CVD-g ow
mo olaye
MoS2.
CVD,
o
chemical
vapou
depositio ,
is
a
method
used
to
p oduce
thi
mate ial
laye s
ove
a
la ge
a ea.
0.42- a omet e
buffe
laye
The
esea che s’
app oach
was
to
edesig
the
i te face
athe
tha
eplace
the
semico ducto
o
gate
dielect ic.
They
placed
the
ult athi
epitaxial
alumi ium
laye
o
mo olaye
MoS2
a d
oxidised
it
to
p oduce
the
0.42- a omet e
alumi ium
oxide
laye .
The
high-κ
haf ium
oxide
was
the
added
o
top.The
team
built
sho t-cha el
top-gate
t a sisto s
usi g
CVD-g ow
mo olaye
MoS2.
The
devices
had
a
equivale t
oxide
thick ess
of
about
o e
a omet e.Tests
showed
low
leakage
cu e t
a d
mi imal
hyste esis.
Hyste esis
efe s
to
u wa ted
diffe e ces
i
a
t a sisto ‘s
elect ical
espo se
depe di g
o
its
p evious
ope ati g
co ditio .The
t a sisto s
eached
a
maximum
t a sco ducta ce
of
0.45
mS
μm-1,
with
cha el
le gths
of
about
100
a omet es.
T a sco ducta ce
measu es
how
st o gly
a
t a sisto ‘s
cu e t
espo ds
whe
the
gate
voltage
cha ges.The
devices
combi ed
a
ve y
thi
dielect ic
with
st o g
elect ical
co t ol
a d
co ti ued
ca ie
t a spo t,
a
combi atio
that
has
bee
difficult
to
achieve
i
atomically
thi
t a sisto s.
Releva ce
fo
futu e
chips
The
fi di gs
highlight
the
g owi g
impo ta ce
of
i te faces
as
t a sisto
compo e ts
become
smalle .
Whe
mate ials
a e
o ly
a
few
atomic
laye s
thick,
the
egio
whe e
two
mate ials
meet
ca
st o gly
affect
how
the
device
pe fo ms.”Whe
t a sisto
compo e ts
become
o ly
a
few
atomic
laye s
thick,
the
i te face
is
o
lo ge
simply
the
bou da y
betwee
mate ials,
it
becomes
a
active
pa t
of
the
device,”
said
P ofesso
Tsu g-E
Lee,
the
study’s
co espo di g
autho .
“Lea i g
to
e gi ee
these
i te faces
with
atomic
p ecisio
ope s
ew
oppo tu ities
fo
desig i g
futu e
semico ducto
devices
that
would
be
difficult
to
achieve
by
cha gi g
i dividual
mate ials
alo e,”
p ofesso
Lee
added.The
esea che s
believe
the
app oach
could
co t ibute
to
futu e
two-dime sio al
elect o ics.
Usi g
CVD-g ow
mo olaye
MoS2
also
b i gs
the
wo k
close
to
mate ials
a d
p ocesses
that
could
eve tually
be
co side ed
fo
wafe -scale
ma ufactu i g.
