Surface
structure
of f
selenium-treated
GaAs
(001)
studied
by yf
field
ionon
Sur
f
aces
t
r
uct
ur
eo
sel
eni
um･
t
r
eat
edG
aAs(
001
)
St
udi
edb
i
el
di
scanning
tunneling
microscopy
Scannmgt
unnel
i
ngmi
cr
oscopy
H.HShigekawa
.Shi
gek
awa
Institute
of
Materials
Science,
University
of･o
Tsukuba,
Tsukuba
Science
City
305,0
Japan
l
n
s
t
i
t
ut
eo
fMat
e
7
･
i
al
sSc
i
e
nc
e
,t
T
ni
v
e
r
s
i
o
fT
s
ukub
a
,Ts
ukub
aSc
i
e
nc
eCE
'
t
y3
5
,Ja
pan
.Hashi
zume
T.T
Hashizume
Institute
for
Materiais
Research,
Tohoku
University,
Katahira,
Aoba-ku,
Sendai
980,
Japan
L
n
s
t
z
.
l
ut
efo
rMat
e
r
E
'
al
sRe
s
e
ar
c
h
,To
ho
kut
T
t
u
'
u
e
7
Ti
t
y
,Kat
ahi
f
l
a
,Ao
b
aku
,Se
nda
i980
,Ja
pan
H.HOigawa
.Oi
gawa
Institute
of
Materials
Science,
University
of fT
Tsukuba,
Tsukuba
Science
City
305,
Japan
L
n
s
t
i
t
ut
eo
fMat
e
r
z
'
al
sSc
L
'
e
nc
e
,t
T
ni
u
e
f
l
S
i
t
yo
s
ukub
a
,Ts
ukub
aS
c
i
e
nc
eCi
O
,
30
5
,J
a
pan
K.KMotai
.Mot
ai
Institute
for
Materials
Research,
Tohoku
University,
Katahira,
Aoba-ku,
Sendai
980,
Japan
L
n
s
t
i
t
ut
ef
o
rMat
e
r
i
al
sRe
s
e
ar
c
h
,To
ho
kut
T
ni
v
e
t
T
i
t
y
,Kat
ahi
r
a
,Ao
baku
,Se
nda
i980
,J
a
pan
Y.YMera
.Mer
a
Department
ofto
Applied
Physics,
The
University
of fT
Tokyo,
Hongo,
Bunkyo-ku,
Tokyo
Japan
De
par
t
me
n
fAppI
L
'
e
dP
h
ys
L
'
cs
,Th
et
r
nE
'
U
e
Y
S
i
t
yo
o
k
yo
,Ho
n
go
,Bunk
yo
ku
,To
k
y113,
oII
3
,Ja
pan
.Nanni
chj
Y.YNannichi
Institute
of
Materials
Science,
University
of fT
Tsukuba,
Tsukuba
Science
City
305,0
Japan
hs
t
i
t
ut
eo
fMat
e
r
i
al
sSc
i
e
nc
e
,Uni
z
J
e
r
s
i
t
yo
s
ukub
a
,Ts
ukub
aSc
i
e
nc
eCi
t
y3
5
,Ja
pan
T.T
Sakurai
.Sakur
ai
Institute
for
Materials
Research,
Tohoku
University,
Aoba-ku,
Sendai
980,
Japan
l
T
n
s
t
L
'
t
ut
efo
rMat
e
7
･
i
al
sRe
s
e
ar
c
h
,To
ho
kuU
ni
u
e
r
s
i
OKatahira,
T
,Kat
ahi
r
a
,Ao
b
aku
,Se
nda
i980
,Ja
pan
(Received
7 June
1991;
accepted
for o
publication
10 0S
September
1991)
(
Re
c
e
i
v
e
d7J
u
ne1
991
;a
c
c
e
pt
e
df
rpubl
i
c
a
t
i
on1
e
pt
e
mbe
r1
9
91
)
For
aras
selenium-treated
GaAsAs
(001)
surface
followed
by yh
heate
treatment
at
-530 3
“C,
have
(
001
)
s
ur
f
a
c
ef
o1
l
owe
db
a
tt
r
e
a
t
me
n
ta
t-5
0c
cwe
,we
ha
ve
Fo
e
l
e
iumm
t
r
e
a
t
e
dGa
observed
using
fielde
ionons
scanning
tunneling
microscopy
ordered
arrays
with
regular
o
bs
e
r
v
e
du
s
i
ng丘
l
di
c
a
ml
ngt
un
ne
l
i
ngmi
c
r
os
c
opyo
r
de
r
e
da
r
r
a
ys
wi
t
hr
e
gul
a
r
intervals
of
4Xperiodicity
in nt
theheL
[ilO]
direction
( 1.6
nm)m)
to t
linei
upupi
in nt
thehel
[l lo]
direction.
i
nt
e
r
v
a
l
so
f4×pe
iodi
r
c
i
t
yi
TI
O
】di
r
e
c
t
i
on
(1
.
6n
ol
ne
11
0
]di
r
e
c
t
i
on.
These
ordered
arrays
are
in
good
agreement
with
the
4X
1
structure
previously
The
s
eor
de
r
e
da
r
r
a
ysa
r
eh gooda
g
r
e
e
me
ntwi
t
t
lt
he4×1s
t
r
uc
t
ur
epr
e
v
i
ous
l
y
observed
by yo
other
methods.
In
a closer
view,
4~structure
was
found
to ob
be e
formed
by y
o
bs
e
r
v
e
db
t
he
r
me
t
hods
.I
nac
l
os
e
r
v
i
e
wthe
,t
he
4×s
t
uc
r
t
ur
e
wa
sf
oundt
f
or
me
db
closely
placed
double
rows.
c
l
os
e
l
ypl
a
c
e
ddoubl
er
ows
.
Formation
of surface/interface
states
within
thehe
band
arer
rather
complex
compared
to ot
thehes
structuresFor
ma
t
i
ono
fs
ur
f
a
c
e
/i
nt
e
r
f
a
c
e
s
t
a
t
e
s
wi
hi
t
nt
ba
nd mentally
me
nt
a
l
l
ya
er
a
t
he
rc
ompl
e
xc
ompa
r
e
dt
t
r
uc
t
ur
e
s
for o
the
theoretical
calculations;
the
interfaces
are
notnot
gaps-of
compound
semiconductors
hasa
been
a persistent
us
e
df
rt
he
t
he
or
e
t
i
c
l
a
c
a
l
c
ul
a
t
i
ons
;t
he
i
nt
e
r
f
a
c
e
sa
r
e
g
a
psof
c
ompounds
e
mi
c
onduc
t
or
sh
sb
e
e
nap
e
r
s
i
s
t
e
nt used
and
important
problem
in i
developing
ana
advanced
technolbut ut
involved
at a
thet
a
br
upt
,b
i
nv
ol
v
e
da afew
f
e
wlayers
l
a
y
e
r
s
t
heinterface
i
nt
e
r
f
a
c
e
a
nd
i
mpor
t
a
n
tpr
obl
e
m
n
de
v
e
l
opi
ng
na
dv
a
nc
e
dt
e
c
hnol
- abrupt,
5-‘
75
ogy
in
semiconductors.
Thus,
passivation
of
compound
In
order
to
pinpoint
the
models
y･
5
,
1
1
71
no
r
de
rt
op
l
nPOi
n
tt
hstructural
es
t
uc
r
t
ur
a
lmode
l
s
bounda
r
og
y帆 s
e
mi
c
onduc
t
o
r
s
.Thus
,pa
s
s
i
v
a
t
i
onorc
ompo
und boundary.5*‘
to ou
understand
thehe
passivation
mechanism,
it i
isti
impor
semiconductor
surfaces
has
been
studied
extensively.“
’y･
Rel
･
2Re
- and
s
e
mi
c
onduc
t
o
rs
ur
f
a
c
e
sha
sbe
e
ns
t
udi
e
de
x
t
e
ns
i
v
e
l
a
ndt
nde
r
s
t
a
ndt
pa
s
s
i
v
a
t
i
onme
c
ha
ni
s
m,
si
mpor
.
.
and
urgently
needed
to oc
characterize
thei
structure
of f
cently,
sulfur
and
selenium
treatments
have
been
attracting
c
e
nt
l
y
,
s
ul
f
u
ra
nds
e
l
e
ni
umt
r
e
a
t
me
nt
sha
v
ebe
e
na
t
t
r
a
c
t
ng tant
i
t
a
nt
a
ndu
r
g
e
nt
l
yn
e
e
de
dt
ha
r
a
c
t
e
r
i
z
et
l
eS
t
r
uc
t
ur
eO
c
ons
i
de
r
a
bl
ea
t
t
e
nt
i
onb
e
ca
us
eo
ft
he
i
rbe
ne
丘c
i
a
le
qe
c
t
son thet
terminal
layers
on
an na
atomic
scale.
considerable
attention
because
of
their
beneficial
effects
on
he
t
e
r
mi
na
ll
a
ye
r
sona
t
omi
c
s
c
a
l
e
.
improving
the
electronic
properties
of
compound
semiconIn
this
letter,
we
report
the
surface
structure
of f
Se-;
i
mpr
ov
mgt
hee
l
e
c
t
r
oni
cpr
ope
r
t
i
e
sorc
ompounds
e
mi
c
onI
nt
hi
sl
e
t
t
e
r
,wer
e
por
tt
hes
ur
f
a
c
es
t
uc
r
t
ur
eo
Se
j
treated
GaAs(
001)
observed
by
a
field
ion
scanning
tunductor
surfaces.3-9
Understanding
the
passivation
mechaduc
t
ors
ur
f
a
c
e
s
･
3
9Unde
r
s
t
a
ndi
ngt
hepa
s
s
i
v
a
t
i
onme
c
ha
- t
r
e
a
t
e
dGa
As
(
001
)ob
s
e
r
ve
dbya丘e
l
di
ons
c
a
nni
ngt
un･
･
microscope
(FI-STM)
.I8.
nism
employed
by yt
those
materials
is
very
important
from
ni
s
m
e
mpl
oy
e
db
hos
e
ma
t
e
ia
r
l
si
sv
e
r
yI
mpor
t
a
n
tf
r
om neling
ne
l
i
ngmi
c
r
os
c
ope(
FI
STM)
l
S
GaAS
(001)
surfaces,
oriented
to ow
within
l/2”
of
thet
both
fundamental
and
practical
points
of
view.
ur
f
a
c
e
s
,or
i
e
nt
e
dt
i
t
hi
n
1
/2
oof
hC
l
GaAS(
001)s
bot
hf
unda
me
nt
a
la
ndp
r
a
c
t
i
c
a
lpoi
nt
so
fv
ie
w.
l]ol
direction
andndS
Si doped
at -t-1
1 X ×1
lOI*01
cm
- s,
were
pre..
The
surface/interface
gap
states
have
been
considered
The
s
ur
f
a
c
e
/i
nt
e
r
f
a
c
e
ga
ps
t
a
t
e
sha
v
e
be
e
nc
ons
i
de
r
e
d [00l
o
]di
r
e
c
t
i
ona
idope
da
8c
m
13
,we
r
epr
e
･
to t
beb
caused
byby
thet
of surface/interface
defects.’
by yt
thermal
cleaning.
Selenium
was
evaporated
ontont
o
ec
a
us
e
d
hformation
ef
or
ma
t
i
ono
fs
ur
f
a
c
e
/i
nt
e
r
f
a
c
ede
f
e
c
t
s
.
I pared
pa
r
e
db
he
r
ma
l
c
l
e
nl
a
ng
.Se
l
e
n
i
um
wa
se
v
a
por
a
t
e
do
o
GaAsA
surface
using
a Knudsen
celle
with
a Se e
However,
recently,
Feenstra
et
al.
showed
byby
scanning
l
y
,Fe
e
ns
t
r
ae
tal
.s
howe
d
s
c
a
nni
ntungt
un- thet
Howe
v
e
r
,
r
e
c
e
nt
heGa
s(001).
(
001
)
S
ur
f
a
c
eu
s
i
ngaKn
uds
e
nc
l
lwi
t
haS
'
of
-f∼1
1 X 汰1
10 -06-Torr.
The
thicknesses
of
the
Se
neling
spectroscopy
on nme
metal/GaAs
that,
for
cerne
l
i
ngs
pe
c
t
r
os
c
opyo
t
a
l
/Ga
ssurfaces
A
s
ur
f
a
c
e
st
ha
t
,f
o
rc
e
r
- backpressure
6To
r
r
･
Th
et
hi
c
kne
s
s
e
so
ft
h
eSc
;
ba
c
kpr
e
s
s
ur
eo
tain
metals
such
as sAu
Au, the
metal-GaAs
bonding
states
thus
deposited
weree
estimated
to ob
be e1
100-300
nm.m.t
a
i
nme
t
a
l
ss
uc
ha
,t
heme
t
a
l
-Ga
Asb
ondi
ngs
t
a
t
e
s films
氏l
ms
t
hu
sde
pos
i
t
e
dw
r
e
e
s
t
i
ma
t
e
dt
00
-3
00n
For
theheo
observation
by yt
thel
STM,
thet
samples
weree
themselves
arer
responsible
for b∫t
theheg
gapa
states
rather
than
t
he
ms
e
l
ve
sa
er
e
s
pons
i
bl
ef
ps
t
a
t
e
sr
a
t
he
rt
ha
n
Fort
bs
e
r
v
a
t
i
onb
l
eS
TM,
hes
a
mpl
esw
r
e
from
preparation
chamber
to o
thet
STM
defects.*@-i2
Therefore,
in n
such
cases,
theheme
metal-GaAs
de
f
e
c
t
s
.
1
0
1
2T
he
r
e
f
or
e
,i
s
uc
h
c
a
s
e
s
,t
t
a
l
｣ユa
s transferred
A
t
r
a
ns
f
e
r
r
e
d
f
r
omthet
hep
r
e
pa
r
a
t
i
on
c
ha
mbe
rt
heS
TM
bonds
at tt
thehei
interfaces
must s
be er
replaced
by ys
some
other
through
air.ir
Heat
treatments
weree
given
in nt
theh:
bo
ndsa
nt
e
r
f
a
c
e
smu
tb
e
pl
a
c
e
db
omeo
t
he
r chamber
c
ha
mbe
rt
hr
oug
ha
･He
a
t
t
r
e
a
t
me
nt
sw
r
eg
l
V
e
ni
t
structures
in n
addition
to t
thehef
formation
of ort
theheo
ordered
s
t
r
uc
t
ur
e
si
a
ddi
t
i
on
ot
わr
ma
t
i
on
r
de
r
e
d STM
chamber,
the
base
pressure
of
which
wasa
-4X
lo- 0-l
‘I l
STM
c
ha
mbe
r
,
t
h
eba
s
epr
e
s
s
ur
eo
rwhi
c
hw
s
-4×1
surface/interface
without
defects.
Since
thet
electronic
Tungsten
tips
were
prepared
byby
electrochemical
etchs
ur
f
a
c
e
/i
nt
e
r
f
a
c
e
wi
t
houtd
e
f
e
c
t
s
.S
nc
i
e
he
e
l
e
c
t
r
oni
c Torr.
Tor
r
.
Tungs
t
e
n
t
i
p
swe
r
epr
e
pa
r
e
d
e
l
e
c
t
r
oc
he
mi
c
a
le
t
c
h･
･
properties
of
the
Au-GaAs
interface
are
improved
by
the
ing,
and
the
surface
condition
of
the
tips
was
characterized
ng
,a
ndt
hes
ur
f
a
c
ec
ondi
t
i
onoft
het
i
pswa
sc
ha
r
a
c
t
e
iz
r
e
d
pr
ope
r
t
i
e
soft
heAu
-Ga
s i
A
nt
e
r
f
a
c
ea
r
ei
mpr
ov
e
dbyt
he l
manipulated
byby
means
of fa
a field
ioni
microscope
S/Se
treatments,4’
7,
thet
structures
of ft
thehet
terminal
layers
s
4
,
7
hes
t
uc
r
t
ur
e
so
e
mi
r
na
l
l
a
ye
r
s and
s/set
r
e
a
t
me
nt
a
nd
ma
nl
Pul
a
t
e
d
me
a
nso
丘e
l
d
on
mi
c
r
os
c
opt
∋
formed
by
S
or
Se
atoms
are
expected
to
satisfy
the
require(FIM)
mounted
in
the
STM
chamber.‘
*,t9
(
FI
M)mou
nt
e
di
nt
heS
TM c
ha
mbe
r
.
1
8
,
1
9
f
or
me
dbySorSea
t
omsa
r
ee
xpe
c
t
e
dt
os
a
t
i
s
f
yt
her
e
qulr
eAccording
to t
thet
diffraction
measurements
on
ments
given
above.
me
nt
sg
l
V
e
na
bove
.
Ac
c
or
di
ng
o
helectron
ee
l
e
c
t
r
ond
i
駄a
c
t
i
onme
a
s
ur
e
me
nt
sOI
T
According
to ot
thehe丘
first-principle
study
of ft
theheGa
GaAsAs thet
GaAsAs
(001)
surface,
a,a
stable
4X
1 structure
hSe-treated
eSe
t
r
e
a
t
e
dGa
(
001
)s
ur
f
a
c
e
s
t
a
bl
e4×1
s
t
r
uc
t
ur
e
Ac
c
or
di
ngt
r
s
t
pr
inc
i
pl
es
t
udyo
(001)-l
X1×1
1 surfaces
adsorbed
withi
a monolayer
of o
sulfur
upon
heate
treatment
at
500-600
(
001
)
s
ur
f
a
c
e
s
a
ds
or
be
dw
t
hamo
nol
a
ye
r
fs
ul
ur appears
f
C･
5
･
8
7
2
0
ap
pe
a
r
suponh
a
tt
r
e
a
t
me
n
ta
t5
00
二6
0oC.5*8,20
0｡
Figure
1 shows
a STM
(404
nmX40
nm)m)o
of f
oror
selenium,
thet
surface
gapa
state
density
is s
markedly
re- e
s
e
l
e
ni
um,
hes
ur
f
a
c
eg
ps
t
a
t
e
de
ns
i
t
yi
ma
r
ke
dl
yr
Fi
g
ur
e1s
howsaS
TMimage
i
ma
g
e(
0n
mx40n
duced
by yt
thehef
formation
of S/Se-Ga
bondings.i3,”
Recent
GaAs
(001)
withi
heate
treatment
at a
-S30 3
“C.
Se
t
r
e
a
t
e
dG
a
As(
001
)w
t
hh
a
t
t
r
e
a
t
me
nt
t-5
0c
c.
duc
e
db
or
ma
t
i
ono
fS
/Se
-Gab
ondi
ngs
･
1
3
,
1
4Re
c
e
nt Se-treated
bias
was
kept
at
- 2.0 .
V throughout
the
experimental
results
support
the
bond
formation
ondf
わr
ma
t
i
on The
Thsample
es
a
mpl
ebi
a
swa
sk
e
p
ta
t-2
0Vt
hr
oughou
tt
hmeaeme
a
･
e
x
pe
r
i
me
nt
a
lr
e
s
ul
t
ss
uppor
tt
hS/Se-Ga
eS/SトGab
at a
the
interfaces;
however,
the
structures
observed
experiand
STM
imaging
was
performed
in nt
thehconstant
tt
he
i
nt
e
r
f
a
c
e
s
;howe
v
e
r
,t
he
s
t
r
uc
t
ur
e
so
bs
e
ve
r
de
xpe
r
i
- surement
S
ur
e
me
n
ta
ndS
TM
i
ma
g
l
ng
Wa
sPe
r
f
om e
di
ec
ons
t
nt
a
2986
Phys.
Lett.
59
(23),
2,
December
1991
19919
American
Institute
of
Physics
6951/
91/
48298603$02.
00 @ @1
9
1Ame
r
i
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i
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u
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eo
fP
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:
S 2986
2
9
8
6
2
9
8
6 Appl.
Ap
p
LP
h
y
s
･
L
e
t
t
･
5
9
(
2
3
)
2De
c
e
mb
e
r1
9
9
1 0003-6951/91/482986-03$02.00
0
0
0
3
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[ii01
[i 101
rwl
<
~1101
05
2
0
-
(
Eu)uO竃 的nLtOU
FIG.
STM
image
of
the
Se-treated
GaAsa
surface
after
heat
FI
G1..I
.S
TM
i
ma
g
eo
ft
h
eS
e
･
t
r
e
a
t
e
dG
s(001)
A
(
0
0
1
)s
u
r
f
a
c
ea
f
t
e
rh
e
a
t
treatment
att
-53O’
C3
( Vs
=5--2
- 2.0 ･
V,
I,=
20 pA,
40
nmx40
nm).
V
OV
,75-2
0p
A
,4
0n
mx4
0n
m)
･
t
r
e
a
t
me
n
a
t∼5
0℃
(
0.05
DID
D2 2
…
DI
A
B
↓
l
門
門
7
1
門
I
p
i㌣
＼
P
i㌣
ヽ
Icurrent
mode
(setting
current:
Is:Z
=s=
2020p
PA).A)
As
in n
c
ur
r
e
n
tmode(
s
e
t
t
i
ngc
ur
r
e
nt
.A
sshown
S
howni
Fig.
the
surface
is s
rather
rough
at an
atomic
level
and
Fi
g1,
.1
,t
hes
u血 c
ei
r
a
t
t
l
e
rr
ougha
ta
na
t
omi
cl
e
ve
la
nd
there
are
many
islands
which
arer
considered
to o
bebSe
overt
he
r
ea
r
ema
ny
i
s
l
a
nd
swhi
c
ha
ec
ons
i
de
r
e
dt
eS
eove
r
layers
remaining
on nt
thehes
surface.
This
roughness
may yb
be e
1
a
ye
r
sr
e
ma
l
nl
ngO
ur
f
a
c
e
･Thi
sr
oug
h ne
s
sma
responsible
for ort
thehed
diffuse
low-energy
electron
diffraction
r
e
s
po
ns
i
bl
ef
i
f
f
us
el
o
we
ne
r
g
ye
l
e
c
t
r
ond
i
qr
a
c
t
i
on
I
patterns
have
been
reported
concerning
this
surface.
pa
t
t
e
nwhich
r
swhi
c
hh
a
v
ebe
e
nr
e
por
t
e
dc
onc
e
r
ni
ng
t
hi
ss
ur
f
a
c
e
･
However,
the
ordered
linear
arrays
are
clearly
seen
lining
Howe
ve
r
,t
heo
r
de
r
e
dl
i
ne
a
ra
r
r
a
y
sa
r
e
c
l
e
a
r
l
ys
e
e
nl
i
ni
r
唱
cc>
upupi
in nt
theh[le【
lo]
direction
in nt
thehflat
area
of
the
The
1l
o
ョdi
r
e
c
t
i
o
ni
ena
ta
r
e
ao
ft
hsurface.
es
ur
f
ac
e
･
The
distance
between
thehrows
1.6
nm
and
is very
close
to
the
di
s
t
a
nc
ebe
t
we
e
nt
er
owis
si
s1
.
6mm
a
ndi
sv
e
r
y
c
l
os
et
ot
i
l
e
4Xperiodicity
of the
GaAsA
in nt
theheL
[ilO]
di(
001surface
)s
ur
f
a
c
ei
TI
O
】di
4×pe
iodi
r
c
i
t
yo
ft
heGa
s(001)
rection.
This
4Xstructure
thus
observed
in nt
thei
STM
r
e
c
t
i
on
.Thi
s
4×S
t
r
uc
t
ur
et
hus
obs
e
r
ve
di
l
eS
TMim-i
mages
is
in
good
agreement
with
theh4eX4×1
1 structure
reported
a
ge
si
si
ng
ooda
g
r
e
e
me
n
twi
t
ht
s
t
r
uc
t
ur
er
e
por
t
e
d
bybyC
Chambers
et
aL5’
*
tal
･
5
･
8
ha
mbe
r
se
Figure
2e(a)
shows
image
of
the
treated
surface
Fi
gur
2(
a
)s
howanother
sa
not
he
ri
ma
g
eo
ft
h
et
r
e
a
t
e
ds
ur
f
a
c
e
(25(
nmX
25 5
nm),
and
a cross
section
is drawn
along
A-B -B
25
nmX2
nm)
,a
nda
c
r
os
ss
e
c
t
i
oni
sdr
a
wna
l
ongA
in i
Fig.i
2(b).
The
ordered
arrays
observed
in nF
Fig.i
1 arer
nF
g
.2(
b)
･Theo
r
de
r
e
da
r
r
a
yso
bs
e
r
v
e
di
g.ia
e
-0.1
resolved
in nt
thishi
figure
to
have
aedouble-row
structure;
each
r
e
s
ol
v
e
di
sf
igur
et
o
ha
v
adoubl
e
r
ows
t
uc
r
t
ur
e
;e
a
c
h
array
which
appears
to
be es
single
in i
Fig.
1･consists
of
two
a
r
r
a
yw
hi
c
ha
ppe
a
r
st
ob
i
ngl
e
n
Fi
g
1c
ons
i
s
t
so
ft
wo FIG.
FI
G
2
,(
a
)S
TMi
ma
g
eo
ft
h
eS
e
t
r
e
a
t
e
dGa
s(001)
A
(
0
0
1
)s
u
r
f
a
c
ea
f
t
e
rh
e
a
t
2..
(a)
STM
image
of
the
Se-treated
GaAs
surface
after
heat
closely
placed
rows
shown
in nF
Fig.i
2.･2
The
c
l
os
e
l
yp
l
a
c
e
dr
o
was
sa
ss
howni
g
･Th4Xperiodicity
e4×pe
r
i
odi
c
i
t
y treatment
0V
0p
A
,2
5血1
×2
5n
m)
･(
b)
t
r
e
a
t
me
n
a
t5
3
0o
C
att
530
“C
( V,(V
=s--2
- 2.0 .
V,
Is,Z=s-2
20 pA,
25
rimx25
nm).
(b)
of of1
1.6.
nm m
is i
formed
by yt
twowok
kinds
alternating
distances
Cr
o
s
ss
e
c
t
i
o
na
lo
n
gABi
n
a
)
,
n
o
r
ma
l
d
i
ne
ra
n
db
u
c
k
l
e
dd
i
ne
rs
t
uc
r
6n
sf
わr
me
db
i
ndof
so
fa
l
t
e
ma
t
i
ngd
i
s
t
a
nc
e
s Cross
section
along
A-B
in
(a),(
normal
dimer
and
buckled
dimer
struc･β
1
t
u
r
e
sa
r
ed
r
a
w
nt
o
g
e
t
h
e
r
.
(
C
)Cr
o
s
ss
e
c
t
i
o
na
l
o
n
gCDi
n(
a
)
are
drawn
together.
(c)
Cross
section
along
C-D
in (a).
D,
=1- -1
1.1 ･
between
thehrows,
i.e.,
Dt
1.11
nm
and
D,D=2-0.5
nm.
be
t
we
e
nt
er
ows
,i
.
e
.
,D=1-- .
1nm
a
nd
-0･
5nm･ tures
,D
.
5n
m.
m
Dz
=2--0.5 0
run.
When
a - 0.25.
monolayer
of
aluminum
is deposited
on n nm,n
Whe
na-0
2
5monol
a
ye
ro
ra
l
umi
numi
sde
pos
i
t
e
do
thet
1)
-2)
X2×4s
4 surface,
a,a
4 X4×i
1 symmetry
appears.21
s(00(
A
0
01
1
ur
f
a
c
e
s
ymme
t
r
ya
p
Re
a
r
S･
21
hGaAs
eGa
Dormer
et
al.
interpreted
theh4Xstructure
in
thehel
[ilO]11
didepend
on nt
thehea
amount
of of
SeSea
atoms
included
in nt
thehe
l
lde
pe
ndo
mount
t
omsi
nc
l
ude
di
Donne
re
tal
.i
nt
e
r
pr
e
t
e
dt
e4xs
t
r
uc
t
ur
ei
nt
0
]di
- willwi
rection
as st
thehep
pairing
of the
As-dimer
rows,
which
they
s
ur
f
a
c
e
di
ne
rl
a
y
e
r
.
dimer
layer.
r
e
c
t
i
ona
a
l
nngO
ft
heA
sdi
ne
rr
ows
,whi
c
ht
he
y surface
considered
to o
occur
through
Al
adsorption
between
thehe
Since
a dip i
structure
around
thehea
adsorption
sites
be- e
Si
nc
ead
ps
t
r
uc
t
ur
ea
r
oundt
ds
or
pt
i
ons
i
t
e
sb
c
ons
i
de
r
e
dt
oc
c
u
rt
hr
oug
hthet
h
eAl
a
ds
or
pt
i
onb
e
t
Oe
e
nt
dimer
rows.
A
similar
model
is
proposed
for
the
GaAs
l
y,s
uc
h
t
we
e
nthet
he
di
ne
r
s
wa
s
o
bs
e
r
ve
dexperimentally,
e
xpe
r
i
me
nt
a
l
dimers
was
observed
such
di
ne
rr
ows
.A s
i
mi
l
a
rmode
li
spr
opos
e
df
b∫t
heGa
As tween
(001)-4X
1 structure
bybyDa
Daweritz.22
In
order
to t
compare
transfer
appearing
in nt
theheGa
GaAsAs(
(011)
surface
or r
c
ha
r
get
r
a
ns
f
e
ra
ppe
a
ingi
r
011
)s
ur
f
a
c
eo
.
2
21
no
r
de
r
oc
ompa
r
e charge
(
001
)
4×1
s
t
r
uc
t
ur
e
we
it
r
z
such
models
withi
ouroure
experimental
results,
thehed
dimer
modi
丘e
da
ds
or
ba
t
ec
on8gur
a
t
i
onmu
tb
nt
r
oduc
e
di
adsorbate
configuration
must s
be ei
introduced
in n
s
uc
h
mode
l
sw
t
h
xpe
ime
r
nt
a
lr
e
s
ul
t
s
,t
i
ne
r modified
structure
is i
drawn
schematically
in nt
thehe
lower
part
of
Fig.
to oi
interpret
theheS
Se-GaAs
(001)
surface
structure
or
de
rt
nt
e
r
pr
e
tt
e
-Ga
As
(
001
)S
ur
f
a
c
es
t
uc
r
t
ur
e
s
t
r
uc
t
ur
e
sdr
a
wns
c
he
ma
t
i
c
a
l
l
yi
l
owe
rpa
r
to
fFi
g･ order
2(b)
consideration
of the
of o
the
section.
this model.
For
example,
the
peaks,
which
arer
wi
t
h血i
smode
l
.Fo
re
x
a
mpl
e
,t
hdouble
edoubl
epe
a
ks
,whi
c
ha
e
2(
bin
)i
nc
ons
i
de
r
a
t
i
ono
ft
hsymmetry
es
y
mme
t
r
y
ft
hcross
ec
r
os
ss
e
c
t
i
on･ with
Adsorption
sites
in
thehe
models
are
indicated
by ya
arrows.
by yt
thehed
dip i
structure
as s
shown
in nt
thehec
cross
secs
e
pa
r
a
t
e
db
ps
t
r
uc
t
ur
ea
s
howni
r
os
ss
e
c
Ads
or
pt
i
ons
i
t
e
si
nt
mode
l
sa
r
e
i
ndi
c
a
t
e
db
r
r
ows
･ separated
Taking
theher
recent
results
intont
considermay
correspond
to ot
thehtwo
adsorbates
on
the,dimers.
t
i
on
,ma
yc
or
r
e
s
pondt
et
woa
ds
or
ba
t
e
sont
he'
di
me
r
s
･
Ta
ki
ngt
e
c
e
nexperimental
te
xpe
r
i
me
nt
a
lr
e
s
ul
t
si
oc
ons
i
de
r
- tion,
ation,
As
atoms
at a
the
Se-treated
surface
may yb
be partially
at the
asymmetric
positions
theheb
bridge
Ads
or
pt
i
ona
tt
he
a
s
ymme
t
r
i
cp
os
i
t
i
onon
sont
r
i
dgsite
es
i
t
e
a
t
i
on
,As
a
t
oms
tt
he
Se
t
r
e
a
t
e
ds
ur
f
a
c
ema
epa
r
t
i
a
l
l
y Adsorption
replaced
by yS
Se e
atoms.
If･
the
states
of
the
1 surface
very
likely
because
of
the
effect.23
The
covcovsve
r
yl
i
ke
l
vb
e
c
a
us
eo
ft
hJahn-Teller
eJ
a
hn-Te
l
l
e
re
fe
c
t
･
2
3The
I
ft
hgap
ega
ps
t
a
t
e
so
ft
h4X
e4×1
s
ur
f
a
c
e is i
r
e
pl
a
c
e
db
a
t
oms
area
removed
by y
thet
bond
formation,
as
is
calculated
becomes
equal
to
or rh
higher
than
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a
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the
effect
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001
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2987
Phys.
Lett.,
Vol.
59,
No.
23,
2,
December
1991
2987 Appl.
Ap
p
l
.
P
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y
s
.
L
e
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t
.
.
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l
.
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9
,
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.
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e
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9
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. 2887
2987
Shigekawa
al.
Downloaded 30 Jan 2008 to 130.158.131.51. Redistribution subject to AIP license or copyright; see http://apl.aip.org/apl/copyright.jsp
Some
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the
authors
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and
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S.
,
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ea
ul
t
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apan.
FIG.
3.･
STM
image
of
the
Se-treated
GaAs
surface
after
complete
FI
G
3
･
S
TMi
ma
g
eo
ft
h
eS
e
t
r
e
a
t
e
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u
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a
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ea
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w･
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l
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e
n
t
a
l
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b
e
r
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･We
b
e
r
,NNewman,
･Ne
wma
n
,TKen..-･Ke
r
L
･
/
removal
ofl
Se
overlayers
(s(
VsV
=s- -2
2.0 .
V,
Is,
=s-2
20 pA,
6.0
nm
X 3.53
nm).
r
0V
I
0p
A
,6
.
0nmx
.
5n
m)
. delewicz, R. Cao, C. McCants, P. Mahowald, K. Miyano, and I. Linr
e
mo
v
a
o
fS
eo
v
e
r
l
a
y
e
d
e
l
e
wi
c
z
,R.Ca
o
,C.Mc
Ca
nt
s
,P.Ma
ho
wa
l
d
,K.Mi
y
a
n
o
,a
n
dI
.Li
n
d
a
u
J
.Va
c
.S
c
i
.
Te
c
hn
o
l
B6
,1
2
4
5
(
1
9
8
8)
.
dau,
J.,
Vat.
Sci.
Technol.
B.
6, 1245
(1988).
L
.Br
il
l
s
o
n
,RE.
.E
･Vi
t
ur
r
o
,C
.Ma
ihi
o
t
,J
.L
.S
h
a
wN.
,NTache,
.Ta
c
h
e
,I
.
“L.2
J.･J
Brillson,
R.
Viturro,
C.
Maihiot,
J.
L.
Shaw,
4,
AsAs
is i
mentioned
above,
according
to ot
theher
recent
s
me
nt
i
one
da
bove
,ac
cor
di
ngt
e
ce
nexperte
xpe
r
G.
J.
M.
Woodall,
P.
D.
G.
Mc
k
i
n
l
e
y
,GMargaritondo,
.Ma
r
g
a
r
i
t
o
n
d
o
,J
.M.
Wo
o
d
a1
l
,P
.DKirchner,
.Ki
r
c
hn
e
r
,GD.
.D.
imental
results,
the
Se/GaAs
(001)-4x
1 surface
hasast
thehe Mckinley,
i
me
nt
l
a
r
es
ul
t
s
,t
heS
e
/GaAs(
001)
4x1s
ur
f
ac
eh
and
S. S
S.
Wright,
J.,
Vat.
Sci.
TechnoL
B B6
6, 1263
(1988).
Pe
t
t
i
t
,a
n
d
.S
.Wr
i
ht
g
I
.Va
c
.S
c
i
.
Te
c
mo
l
L
,1
2
6
3(
1
9
8
8)
. I’
GaAsr
structure
oververaf
a fewewlayers.5’
85
Therefore
thehe Pettit,
e
x
s
t
r
uct
ur
eo
l
aye
r
s
･
･
8
The
r
e
f
or
et
Gas
A -,$e,
1_xS
‘C 3
J. J
Sandroff,
R.R
N.
J.,
C.
BischoK
and
R. Bhat,
Appl.
c
_S
nd
a
r
o
杭
.NNottenburg,
.No
t
t
e
n
b
u
r
g
I
_C
.Bi
s
c
h
o
f
r
.a
n
dR
.Bha
t
,Ap
p
l_
reconstruction
such
dimer
pairing
may yb
be caused
by yt
thehe
r
e
cons
t
r
uc
t
i
ons
udasa
sdi
ne
rpal
r
l
ngma
ecaus
e
db
Phys.
Lett.
51,
33
(1987).
Phy
s
.Le
t
t
.5
1
,3
3日
9
8
7)
.
partial
replacement
As
atoms
bybyS
Se in
thehe
surface
layers
par
t
i
a
lr
e
pl
ac
e
me
nof
to
fAs
at
oms
ei
nt
s
ur
f
ac
e
l
aye
r
s 4H.4
Oigawa,
J.,
F.･
Fan,
Y.
Nannichi,
H.
Sugahara,
and
M.M･
Oshima,
Jpn
托
･
Oi
g
a
wa
J
F
･
Fa
n
,Y
･
Na
n
n
i
c
h
i
,
H
･
S
u
g
a
ha
r
a
,
a
n
d
Os
hi
ma
,
J
p
n
rather
than
the血e
adsorbate-induction
A
r
at
l
l
e
rt
hanbyby
ads
or
bat
e
i
nduct
i
onmechanism.
me
cl
l
ani
s
m.A
J. I
Appl.
Phys.
30,
322
(1991).
.
Ap
p
l
.Ph
y
s
.3
0
,3
2
2日
9
91).
buckling
dimer
may y
produce
thet
4xperiodicity
in i
thet
A.
andn
V. S.
Sundaram,
Phys.
Lett.
57,
2342
buc
kl
i
ng
di
ne
rma
pr
oduc
e
he4
×pe
r
i
odi
c
i
t
y
n
he ‘S.5
S
･AChambers
･Cha
mb
e
r
sa
dV
･S
･S
u
n
d
a
r
a
mAppI.
,Ap
p
LP
h
y
s
･Le
t
t
･5
7
,2
3
4
2
(
1
9
9
0)
.
[TlO]
in ns
such
a case,
as
shown
schematically
in n (1990).
L
TI
Odirection
】di
r
e
ct
i
oni
uc
hac
as
e
,ass
howns
c
he
mat
i
c
al
l
yi
“C.6
J.･
Sandroff,
M.
S. S
Hegde,
L.,LA
A. Farrow,
J.,
P.･
Harbison,
R.,
Bhat,
and
C
J
･
S
a
n
d
r
o
H
,
M･
,
He
g
d
e
･
Fa
r
r
o
w
J
P
･
f
l
a
r
b
i
s
o
n
R
･
Bh
a
t
,
a
n
d
Fig.
2(b)
for or
comparison.24
Fi
g
.2(
b)f
c
ompar
is
on.
2
4
C.
C
Chang,
J.
Appl.
Phys.
67,
586
(1990).
C
･
a
C
h
a
n
g
,
I
.
A
p
p
l
,
P
h
y
s
.
6
7
,
5
8
6
(
1
9
9
0
)
.
Overlayers
withi
certain
orderings
cananb
be es
seen
in mF
Fig.i
0Ve
r
l
ayer
sw
t
hc
e
r
t
ai
no
r
de
r
i
ngsc
e
eni
g.
‘J. 7
R.
Waldrop,
J.,
Vat.
Sci.
Technol.
B
3, 1197
(1985).
J
.R
.Wa
l
dr
o
p
I
.Va
c
.S
c
i
.
Te
c
mo
l
LB3
,1
1
9
7(
1
9
8
5)
,
2 (a).
Domain
labeled
RR
seems
to t
have
a structure
similar
2(
a)
.Domai
nl
abe
l
e
d
s
e
e
ms
oh
aveas
t
r
uct
ur
es
i
mi
l
ar
‘F.8
S.･
Turco,
C,a
J. J
Sandrotf,
M.
S. S
Hegde,
and
C. C
Tamargo,
J.,
Vat.=･
S
nd
a
r
o
l
f
,M･
･He
g
d
e
,a
nM.
dM･
･Ta
ma
r
g
o
J
･Va
c
F
S
･
Tu
r
c
o
to t
theh4ex4×l
layer
below,
rotated
by y9
90”.00
A.A
cross
section
is s Sci.S
ot
aye
rbe
l
owbut
,bu
tr
ot
at
e
db
c
r
os
ss
e
ct
i
oni
c
i
.Te
c
h
n
o
l
.B8
,8
5
6(
1
9
9
0)
.
Technol.
B
8, 856
(1990).
drawn
along
C-D
2(c).
The
corrugations
of ft
thehe ‘J. 9
C-Din i
nFig.
Fi
g
.2(
C)
.Thec
or
ugat
r
i
onso
dr
awna
l
ong
Lee,
L.,L
Wei,
S.
Tanigawa,
H.,
Oigawa,
and
Nannichi,
Appl.
Phys.
･
We
i
,
S
I
Ta
n
i
g
a
wa
H
1
0i
g
a
wa
,
nY.
a
dY
･
Na
n
n
i
c
h
i
,
Ap
p
l
･
Phy
s
･
J
･Le
e
double
rows
botho血
layers
are
-0.05 .
nm.m.
The
of
doubl
er
owin
si
nb
l
aye
r
sar
e-0
05n
Ththickness
et
hi
ckne
s
sof Lett.
Le
t
t
.5
S
,1
1
6
7(
1
9
91).
58,
1167
(1991).
thet
overlayer,
determined
by yt
theheh
heights
of
both
edges
of
Martensson
and
R.
M.
Feenstra,
Phys.
Rev.
B.
39, 9
7744
(1989).
l
o
p
.Ma
r
t
e
n
s
s
o
na
n
dR
.M.
Fe
e
n
s
t
r
a
,Ph
y
s
.Re
v
B3
,7
7
4
4(
1
9
8
9)
.
heo
ve
r
l
aye
r
,det
e
r
mi
ne
db
e
i
ght
so
rbot
he
dge
sor ‘OP.
M.
Feenstra,
Phys.
Rev.
Lett.
63,
1412
(1989).
l
R
.M_
Fe
e
n
s
t
r
a
,Phy
s
.Re
v
.Le
f
t
.
6
3
,1
41
2(
1
9
8
9)
.
thet
cross
section
in nFig.
2(c),
is,i
-0.15 .
nm,m,
which
correC
)
s∼0
1
5n
whi
c
hc
or
r
e
- “R.l
hec
r
os
ss
e
ct
i
oni
Fi
g
.2(
B.･
Mclean,
M.･
Feenstra,
A.,
Talev-Ibragimi,
Ludeke,
Phys.
2
A
B
･
Mc
l
e
nR.,
a
R
M･
Fe
e
n
s
t
r
a
A
I
Ta
l
e
v
I
b
r
a
g
i
mand
i
,
nR.
a
dR
･
Lu
d
e
k
e
,
Ph
y
s
･
sponds
a single
atomic
layer
of
GaAs
(001).
Comparis
pondto
st
oas
i
ngl
ea
t
omi
cl
aye
ro
rGaAs(
001)
.Compad- “A.1
R
e
v
,
B3
9
,
1
2
9
2
5(
1
9
8
9
)
.
Rev.
B
39,
12925
(1989).
son
of those
cross
sections
show
that,
the
layer
consists
ono
ft
hos
ecr
os
ss
e
ct
i
on
ss
howt
hat
,t
h4ex4×l
aye
rcons
i
s
t
13T.
Ohno
and
K.
Shiraishi,
Phys.
Rev.
B.
42, 2
11194
(1990).
1
3
T
_Ohn
oa
n
dK
S
h
i
r
is
a
h
i
,Ph
y
s
.Re
v
B4
,1
1
1
9
4(
1
9
9
0)
.
ingl
of Ord
double
rows
is sp
probably
aa
single
atomic
layer.
ng
oubl
e
r
owsi
r
oba
bl
y
s
i
ngl
e
at
omi
c
l
aye
r
. 14T. Ohno (private communication).
1
4
T.0l
mO(
p
iv
r
a
t
ec
o
mmu
n
i
c
a
t
i
o
n)
.
Therefore,
such
a as
structure
as sab
a buckling
dimer
modeldel “H.Ⅰ
The
r
ef
わr
e
,s
uch
t
r
uct
ur
ea
uckl
i
ng
di
ne
rmo
Sugahara,
M.,
Oshima,
H.,
Oigawa,
H.,
Shigekawa,
and
Y.
Nannichi,
5
H
･
S
u
g
a
h
a
r
a
M･
Os
hi
ma
H
･
Oi
g
a
wa
H
･
S
h
i
g
e
k
a
wa
,
a
n
dY
･
Na
ic
m
h
i
､
without
adsorbates
is
more
probable.
wi
t
l
l
Ou
tads
or
bat
e
si
smor
epr
obabl
e.
J. ∫
Appl.
Phys.
69,
4349
(1991).
.
Ap
p
l
.Ph
y
s
.6
9
,4
3
4
9(
1
9
91
)
.
Figure
3 shows
a STM
of the
treated
surface
Katayama,
Aono,
H.,
Oigawa,
Y.,
Nannichi,
H.
Sugahara,
and
M.
Fi
gur
e3s
howsaS
TMimage
m ageo
l
ft
het
r
e
at
e
d
s
ur
f
ac
e ‘6M.
1
6
M･
Ka
t
a
y
a
mM.
a
,
MI
Ao
n
o
H
･
Oi
g
a
wa
Y
･
Na
n
n
i
c
h
i
,
H
･
Su
g
a
h
a
r
a
,
a
n
dMl
Jpn.
J..
Appl.
Phys.
30,
315
(1991).
after
complete
removal
of
the
(6.06.
nmx3.5
0s
hi
ma
,J
p
n
I
.Ap
p
l
･Ph
y
s
･3
0
,31
5(
1
9
91)･
af
t
e
rc
ompl
e
t
er
e
mova
lo
ft
hSe
eSoverlayers
eover
l
aye
r
s(
0n
mx3.
5 Oshima,
Hirayama,
Matsumoto,
H.,
Oigawa,
and
Y.
Nannichi,
Appl.
Phys.
7
H
･
f
hr
a
y
a
mY.
a
,
Y
･
Ma
t
s
u
mo
t
o
H
･
Oi
g
a
wa
,
a
n
dY
･
Na
n
n
i
c
h
i
,
Ap
p
l
.
Ph
y
s
L
nm,
V,Vis,Z
=s2020p
PA).A)
The
units
consistnmVs
,V=s - 2.02.
0
.Th4x2
e4×2u
ni
t
sc
ons
i
s
t
- “H.1
54,
2565
(1989).
et
L
t
.5
4
,2
5
6
5(
1
9
8
9)
.
ingmgo
of three
Ga
dimers
are
resolved
well.em
The
rt
hr
e
eGad
i
ne
r
sar
er
e
s
ol
ve
dw
ThSTM
eSTMimage
i
mage L&t.
Sakurai,
T.,
Hashizume,
I.,Ⅰ
Kamiya,
Y.,
Hasegawa,
N.
Sano,
H.,
W.
S
T
･S
a
k
u
r
i
a
T
･Ha
s
h
i
z
u
me
･Ka
iy
m
a
Y
･Ha
s
e
g
a
wa
,N
･S
a
n
°
H
.W.
is i
similar
theheAs
As-rich
GaAsAs(
(001)-2x
4 structure
ob- b- “T.l
ss
m
li
l
ato
rt
ot
ichGa
r
001)
2×4s
t
r
uc
t
ur
eo
Pickering,
and
A.
Sakai,
Progr.
Surf.
Sci.
33,
3,
(1990).
Pi
c
k
e
in
r
g
,a
n
dA
.
S
a
k
i
a
,Pr
o
g
r
.S
u
r
f
･S
c
i
.
3
3
3(
1
9
9
0)
,
tained
by yP
Pashley
et e
al.
except
a 90”0rotation
of the
t
ine
a
db
as
hl
e
y
ial
lexce
pfor
tf
ora9
0r
ot
at
i
ono
ft
he 19T. Hashizume, Y. Hasegawa, I. Kamiya, T. Ide, I. Sumita, S. Hyodo, T.
ordering.“
‘g
-”.
Since
the GaAs
(001)
surfaces
wereer
pre-r
a
As(
001)s
u血 c
esw
ep
e
- Sakurai,
or
der
i
n
2
52
7s
i
nc
e血eG
S
a
ku
r
i
a
H
.
To
c
hi
h
a
r
a
,M.
Ku
b
o
t
a
,a
n
dY
.Mu
r
a
t
a
J
.Va
c
.S
c
i
.Te
c
h
H.,
Tochihara,
M.
Kubota,
and
Y.
Murata,
J.,
Vat.
Sci.
Tech..
pared
by
cleaning,
the
surfaces
before
the
treatpar
e
dbthermal
yt
he
r
ma
lc
l
e
ni
a
ng
,t
h
es
ur
f
ac
e
sbe
f
or
et
hSe
eS
et
r
e
at
- nol.n
o
,A8
,2
3
3(
1
9
9
0)
.
Al
8, 233
(1990).
ment
are
thought
to
have
similar
Ga-rich
structures.
zcRecently
structures
such
as
the
2X
and
4X3
reported
for
2
0
Re
c
e
n
t
l
ys
t
uc
r
t
u
r
e
ss
u
c
ha
st
h
e21,2x3,
XI
,
2×3
,
a
n
d4×were
3we
r
er
e
p
o
r
t
e
df
o
l
･
me
n
tar
et
hough
tt
oh
av
es
i
il
m
a
rGaic
r
hs
t
uct
r
ur
e
s
.
h
eS
e
t
r
e
a
t
e
dGa
A(001)
s(
0
01
)s
u
r
f
a
c
e
s
.Ta
k
a
t
a
n
i
,T
.Ki
k
a
w
aa
n
dM_
Se-treated
GaAs
surfaces,
S.,S
Takatani,
T.
Kikawa
and
M.
In I
order
to o
complete
thehes
structural
analysis
andnd
to t
n
or
dert
c
ompl
e
t
et
t
mc
t
ur
a
lanal
ys
i
sa
o thet
Na
k
a
z
a
wa
,Ex
t
e
n
d
e
dAb
s
t
r
a
c
t
ft
h
e2
3
r
dCo
n
f
e
r
e
n
c
eo
nS
o
l
i
dS
t
a
t
e
Extended
Abstracts
ofso
the
23rd
Conference
on
Solid
State-~
understand
thehep
passivation
mechanism,
a aw
well-controlled
unde
r
s
t
a
ndt
aS
S
i
vat
i
onme
cI
l
ani
s
m,
e
l
l
cont
r
ol
l
e
d Nakazawa,
Devices
&s&
Materials,
Yokohama,
1991,
p.
299;
S.;
A..
Chambers
and
V.
Ma
t
e
ia
r
l
s
,Yo
k
o
h
a
ma
,1
9
9
1
,p
.2
9
9
S
A
.
Cha
mb
e
r
sa
n
dV_
De
v
i
c
e
surface
preparation
technique
is necessary,
and
a proces
u血 c
ep
r
epar
at
i
ont
e
chni
quei
sne
ce
s
s
a
r
y
,andap
r
oc
e
.
S
u
n
d
a
r
a
m
J
.Va
c
.
S
c
i
.
Te
c
h
n
o
.
B9
,2
2
5
6(
1
9
91
.げt
es
t
r
u
c
t
u
f
a
iS. S
Sundaram,
J.,
Vat.
Sci.
Technol.
Bl
9,
2256
(1991).
If)
the h
structural
dure
for
isti
currently
being
under
consideration.
Precise
dl
l
r
ef
わitri
scur
r
e
nt
l
yb
e
i
ngu
nde
rcons
i
de
r
at
i
on
Pr
e
c
i
s
e change from 2 X 1 to 4X 1 is caused by the dimer row pairing upon heat
c
h
a
n
g
ef
r
o
m2xIt
o4×Ii
sc
a
u
s
e
db
yt
hedi
ne
rr
o
wp
a
l
nn
gu
p
o
nh
e
a
t
measurements
of
the
of the
treated
surface
meas
ur
e
me
nt
so
ft
hstoichiometry
es
t
oi
c
hi
ome
t
r
yo
ft
het
r
e
at
e
ds
ur
f
ac
e treatments,
surface/interface
electronic
structure
may
be
designable.
,s
u
r
f
ac
e
/
i
nte
r
fa
c
ee
l
e
c
t
r
o
n
i
cs
t
uc
r
t
t
l
r
ema
yb
ede
s
i
g
n
a
b
l
e
.
t
r
e
a
t
me
n
t
s
forf
structures
must
be
performed,
together
with
de-de
- *‘S2
othe
rt
hes
t
uct
r
ur
e
smus
tbep
e
r
f
or
me
d
,t
oge
t
he
rw
it
h
s
Do
n
n
e
r
,R
.Bl
u
me
J
l
t
h
l
a
J
L
He
r
ma
n
.Tr
e
h
a
n
.Fu
r
ma
.
.l
.K
K.
Donner,
R.
Blumenthal,
J.,
L..
Herman,
R.,R
Trehan,
E.,E
Furman.
-n
t
ai
l
e
dc
al
cul
at
i
ons
.
tailed
calculations.
anda
N.
Winograd,
Appl.
Phys.
Lett.
55,
1753
(1989).
n
dN
.Wi
n
o
g
r
a
d
,Ap
p
LPh
y
s
.Let
t
.5
5
,1
7
5
3(
1
9
8
9)
.
2
L
Da
we
it
r
z
,Sur
f
.S
c
i
.1
1
8
,5
8
5(
1
9
8
2)
.
Daweritz,
Surf.
Sci.
118,
585
(1982).
In I
conclusion,
for
the
GaAs
(001)
surface
a
As(
001
)S
ur
f
ace “L. 2
nc
oncl
us
i
on
,f
o
rt
hSe-treated
eSe
t
r
e
at
e
dG
Uchida
and
M.
(private
communication).
.Ok
a
z
a
k
i(
p
iv
r
a
t
ec
o
mmun
i
c
a
t
i
o
n)
.
2
3
H
.Uc
h
i
d
aa
n
dMOkazaki
with
heat
treatment
at
-530
OC!,
arrays
with
wi
血
he
a
tt
r
e
at
me
n
ta
t-53
0℃the
,t
hordered
eor
de
r
e
da
r
r
ay
swi
t
h 23H.
“‘E.2
Kaxiras,
Phys.
Rev.
B,
43,
6824
(1991).
4
E
.
K
a
x
i
r
a
s
,
P
h
y
s
.
R
e
v
B4
3
,
6
8
2
4(
1
9
9
1
)
.
regular
intervals
of
4Xperiodicity
in
the
[TlO]
direction
r
e
gul
ari
nt
e
r
val
sof4×pe
iodi
r
c
i
t
yi
nt
heL
TI
O】di
r
e
ct
i
on
25M.
D. D
Pashley,
K.,K
W.
Haberem,
anda
J.dJ
M.
Gaines,
Appl.
Phys.
Lett.
7t
2
5
M･
TPa
s
h
l
e
y
IW･
Ha
b
e
r
e
m,
n
･M･
Ga
i
n
e
s
,Ap
p
l
･Ph
y
s
･L
et
･
_
7
( 1.6
nm)
were
observed
by
to t
line
up
the
[1
lo]
(1.
6mm)
we
r
eobs
e
Ⅳe
dbFI-STM
yFI
STM
ol
i
n
euin
pi
nt
h
e【
11
01
6(
1
9
91)
.
58, 406 0
(1991).
direction,
which
is
insi
good
with
the
4x
1 strucdi
r
e
c
t
i
on
,whi
c
l
li
ngooagreement
dagr
e
e
me
n
twi
t
ht
h
e4×1
s
t
rc 26D K. Biegelsen,
L.
E. E
Swartz,
and
R.
D.･
Bringans,
Vat.
Sci.
Technoi.
;m
i
e
g
e
l
s
e
n,
L
･
S
wa
r
t
z
,
a
n
dR
D
･
Br
in
g
nJ.S
a
,
J
･
Va
c
I
Sc
i
･
Te
c
hno
l
･_
ture
observed
by
the
previous
methods.
In.I
anac
close-up
view,
t
ur
eobs
er
ve
db
yt
h
epr
e
vi
ou
sme
t
hods
l
os
e
u
pvi
e
w, A’8,A8
,
2
8
0(
1
9
9
0)
し
280
(1990),
a 4Xstructure
was
found
to be
formed
by the
ada4×S
t
r
uct
ur
ewa
sf
oundt
ob
ef
or
me
db
yt
hclosely
ecl
os
e
l
yad- “M.ヱ
D. D
Pashley,
K.,K
W.I
Haberern,
W.
Friday,
J.
M.
Woodall,
and
P.
D..D.
7
M･
,Pa
s
h
l
e
y
W.
Ha
b
e
r
e
r
n
,
W.
Fr
id
a
y
,
J
.M.
Wooda
l
l
,a
n
dP
jacent
double
rows.
Kirchner,
Phys.
Rev.
Lett.
60,
2176
(1988).
Ki
r
c
h
n
e
r
,Ph
y
s
.Re
v
.Le
t
t
.6
0
,21
7
6(
1
9
8
8)
.
j
ace
n
tdoubl
er
ows
.
-
･= -
--
5
u
2 6
2988
Phys.
Let,
Vol.
59,
No.
23,2
December
1991
29
88 Appl.
Ap
p
LPh
y
s
.L
e
t
t
.
,
Vo
l
.5
9
,No
.2
3,
2Dec
embe
r1
991
8
,
4
-
D
･
K
･
B
Shigekawa et al.
2988
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