Hfse vs. MoSe

8/17/2019 Hfse vs. MoSe

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Epitaxial growth and study of 2DSe-based ultrathin films: Bi2Se3,

MoSe2, fSe2 , !rSe2

"retouli E# $leopatra

2%&2&'( NCSR DEMOKRITOS, Athens, Greece


2/14

Outline

• )opologi*al insulators: Bi2Se3MBE growth and stru*tural *hara*teri+ation• Semi*ondu*ting )ransition metal di*hal*ogenides

)MDsMoSe2fSe2

!rSe2• .on*lusions& /uture wor0


3/14

3D Topological InsulatorsBi2Se3 , Bi2Te3, Bi1-xSbx

Y. Xia et al., Nat. Phys. 5 , 3! "#$$%

Topologically protected

Spin locked to orbital momentum

Backscattering is suppressed o!el s"itc#ing mec#anisms$%unctionalities

k -k k

-k

spin

e-Non-magneticimpurity

“insulating” bulk

&apless metallic sur%ace states

-k

relati!istic mo!ement o% e- ' light-like particles

Spin polari(ed )#elical* Dirac cones


4/14

+ltra #ig# !acuum c#ampers %or gro"t# and structuralc#aracteri(ation

ST

./0S

B0

/S.00D


5/14

.T0 and /S

1 4 5 1 nm

T#ick 5 26 uintuple 4ayers )4*

1 QL

High epitaxial quality and “clean” crystalline interfaces

711-268

Bi2Se3$l

o reaction 9s#arpcrystalline inter%aces

31 epitaxial Bi2Se3

* P. Tsi&as et al., ACS Nan', ! "(%, ))*+ "#$*+%

Substrates ' 266 nm l)6661* $266 mm Si )111*


6/14

k//,y (Å-1) k //,y (Å

-1) k //,y (Å-1) k //,y (Å

-1)

Γ ΜΜ

0.4 e!

"n# #eri$ati$e "n# #eri$ati$eΓ ΜΜ

%&

!&

Gaplesssurfacestates

3 4 Bi2Se3$l)6661* : 4 Bi2Se3$l)6661*

'(

E B

( e V )

E B

( e V )

'(

&apless sur%ace states in ultrat#in Bi2Se3

3QL: Thinnest Bi !e3 "ith gapless surface states #$irac c%ne& e'er rep%rted

experi(entally )

*educe surface t% '%lu(e rati% - applicati%ns in nan%electr%nics

Insit- "4ES

Gaplesssurfacestates

ltrathin /il0s1 2yri4i5ati'n6a& '&enin6 Thic7 /il0s "8)9: e;&.%1 N'ninteractin6


7/14


8/14

Semiconducting 2D Transition etals Dic#alcogenides )TDs*

anisotropic mec#anical optical and electrical propertiesSi(able band gap in t#e !isible and I. region o% t#e solar spectrum

x y

+).+

x

y

+

o

Se

4ayered TDs crystals o% t#e composition 2 '

' transition metal )IB' o, C and IB' r,% *' ;#alcogen species )S, Se, Te*

+pplicati%ns in ,pt%electr%nic de'ices#energy c%n'ersi%n syste(s&

and ield .ffect Transist%rs/ l%" p%"er l%gic de'ices

2 structure 1T structure

Indirect to direct band gapcrosso!er "#en t#ickness reduces to

a single layer

Indirect band gap!ery close to Si

H%neyc%(0 like structures superi%r pr%perties t% th%se %f graphene 111

M'Se# 1 E. Xen'6iann'&'-l'- et al. s-0itte4 #$*+ 2/Se# 1 K.E. Aret'-li et al. s-0itte4 #$*<

Se

%


9/14

#

b

,

MoSe2

350°C

MoSe2

690°C

AlN

Bi2Se3

300°C

MoSe2

300°C

.00D, T0, ST o% 34 oSe2$l)6661*

ST image' #oneycomb structure

#

e

l

oSe2

3:6E;

oSe2

F@6E;

estimated distance o% 3>3 ? bet"een Se-Se atoms 5 aoSe22@@ ?

!dC gap

"

1

Line 1

.+

eeSe

o"+

Line "

e/o

T"o step gro"t# processl

oSe2

3:6E;

oSe2

F@6E;

oSe2

3:6E;


10/14

e 9

e 99

1st Brillouin(one

oSe2

K

A

ΓL

M

H

alence Band Imaging

.T measurements

S#i%t o% B at G-point

to #ig#er binding energy

Indirect to direct bandgap transition in t#e14 limit

GH oSe2 2= ?-1

'(

k //,y +-1

E. Xen'6iann'&'-l'- et al. s-0itte4 #$*+

-4

-"

0

"

4

ΓMKΓ

& i n # i n g ' n e r g y 0 e ! 1

14 oSe2 3 4

'(

F4Γ 2 Γ3 235 Γ3 235

(a) (b) (c)

6e 7

00k // 8y+-1

6e 77

(d) (e) (f)

k //,y +-1


11/14

.aman and /4 c#aracteri(ation o% oSe2 %ilms at

4-limit on l)6661*

"00 400 )00 900 1000 1"00

/oe"

i peak

i *"1cm-1

:1g

"40.9 cm-1

7 n t e n s i t y 0 a . u . 1

;aman

A L 7 n t e n s i t y

0 a . u

1

'nergy e!

)he dire*t band gap in single layers results inintense room temperature photolumines*en*e 4

pplications %rom optoelectronics to energycon!ersion

cti!e modes o% oSe2'

1g at 2=6>J cm-1

02g at 2JJ>: cm-1

Bg at 35 c(-2 in fe" layer

(aterial

1"# meV

Γ $%

& B

"00 "0 00 0 400

LoB!2"

#!2"

l o g 0 7 n t e n s i t y 1 0 a

. u .

1

;aman s


12/14

" l 5

' M f S e 2

: M f S e 2

3 M M o S e

2

6''-2%7 a+imuth

K G L

0%

2

-'

'

%

-2

-3

-;

-(

E n e r g y , e

< -

$&=&>&? >M

B i n d

i n g E n e r g y E B , e


13/14

;onclusions• )hinnest Bi2Se3 31 with gapless surfa*e states

Dira* *one e@er reported experimentally• igh stru*tural Auality MoSe2 and fSe2 on "l5&Si

substrates• MoSe2&Bi2Se3 and MoSe2&fSe2 multilayers *an be

produ*edMuture "ork • Exploring the semi*ondu*tors fSe2, !rSe2

• Ele*tri*al *hara*teri+ation of Bi2Se3, MoSe2 fSe2 ,!rSe2 and their heterostru*tures

• Magnetoresistan*e measurements& all effe*t

measurements


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Documents

Hfse vs. MoSe