In-situ analysis of morphology induced surface scattering phenomena via resistance measurements.

Goal

Lateral roughness

[1] G. Jnawali, H. Hattab, B. Krenzer, and M. Horn-von Hoegen, Phys. Rev. B 74,195340 (2006).

[2] G. Jnawali, H. Hattab, F.-J. Meyer zu Heringdorf, B. Krenzer, and M. Horn-von Hoegen, Phys. Rev. B 76, 035337 (2007).

[3] H. Hattab, E. Zubkov, A. Bernhart, G. Jnawali, C. Bobisch, B. Krenzer, M. Acet, R. Möller, M. Horn-von Hoegen, Thin Solid Films, (2008) in Press.

[4] H. Kiessig, Ann. Phys. 10, 769 (1931).

[5] H. Sondheimer, Adv. Phys. 1 (1952) 1elaar, Phys. Rev.B , 1609 (1996).

[6] B.N.J. Persson et al., Chem. Phys. Lett. , 204 (1991).

[7] M. Horn-von Hoegen, Z. Kristallogr. , 591-629 and 684-721 (1999).

[8] G. Jnawali, H. Hattab, C. A. Bobisch, A. Bernhart, E. Zubkov, R. Möller, and M. Horn-von Hoegen, Phys. Rev. B 78, 035321 (2008).

[9] R. Smoluchowski, Phys. Rev. 60, 661 (1941).

[10] P. Hahn, J. Clabes, and M. Henzler, J. Appl. Phys. , 2079 (1980).

[11] G. Meyer, J. Wollschläger, and M. Henzler, Surf. Sci. 231, 64 (1990).

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51

References

B5SFB 616 C2

Growth, Morphology, and Resistivity:

Bi/Si(001) and Bi/Bi(111)

SFB 616H. Hattab, G. Jnawali, A. Bernhart, E. Zubkov, C. Bobisch, B. Krenzer, R. Möller,

and M. Horn von Hoegen

University Duisburg-Essen, Campus Duisburg

�

�

�

(00)-spot intensity oscillation at 80 K.

Layer by layer growth.

Decay of the oscillation.

Kinetic roughening.

Step flow growth > 300K.

Bi/Bi(111)

Vertical roughness

Surface diffusion barrier

Growth at 150 K

�

�

�

In-situ measurements of the resistance andLEED (00)- spot intensity during deposition ofBi on Si(001) at 150 K.

Quasi-bilaye growth > 5.6 BL [1].

slope of the resistance curve changes withchanging the crystal phase.

At 5.6 BL coverage, quasi-12-fold symmetryLEED pattern and a ring of intensitysurrounding it.

ordered (111) & rotationally (110)

Ring disappears at higher coverage.

disorderedcrystallites.

Bi/Si(001)

500 nm

30 nm Bi film/Si(001) 8 nm

Twins

rotated

grain boundary

104

105

106

107

(00)-

spot

Inte

nsi

ty(c

ps)

151050Coverage (nm)

403020100Coverage (BL�

Bi/Bi(111) @ 80 K

Shutter open

6

789

105

2

3

4

5

6

789

106

2

3

4

5

Inte

nsi

ty (

a.u

.)

151050

Coverage (BL)

300 K

250 K

180 K

1.0

0.5

0.0

G(S

)

86420Energy

1/2(eV)

1.0

0.5

0.0

G(S

)

10 20 300 40 50 60 70 80

S=3 S=4 S=5

0.5 BL Bi/Bi(111) @ 80 K

0.5 BL Bi/Bi(111) @ 180 K

S=3 S=4 S=5

Energy (eV)

40

30

20

10

Isla

nd

sep

ara

tion

,<

L>

(n

m)

Inv. Temperature, 1/ T (×10-3

K-1)

Islan

d d

en

sity,(cm

-2)

141210864

100125150175200 75

= 135 meV10

11

1012

LEEDSTMPower spectrum (STM)Fit

1013

120nm

0.5 Bi on Bi(111) @ 130 KT = 130 KD

k (% BZ)ll

E = 71 eVe0.5 BL Bi on Bi(111) @ 80K

T = 80 KD

(00) (01)

(01)*

In-situ (00)-spot profile analysis:

�

�

Profile changes periodically from sharp (in-phase)to shoulder (out-of-phase).

Perfect 2D growth in the first layer.10

1

102

103

104

105

Inte

nsi

ty (

Counts

/s)

-40 -20 0 20 40kll (%BZ)

1.0

0.8

0.6

0.4

0.2

0.0

Coverage (BL)

(00)-spot profiles:

Ee = 179 eVS = 3.5

= 24°

Surface

e

�

(00)-spot

6exp d

b

EL

k T

� �� � � �

� �

101

102

103

104

105

106

107

108

Inte

nsi

ty (

cou

nts

/s)

9080706050403020

Scattering angle 2 θ (deg)

Bi(111)Bi(222)

Bi(333)

Si(002)

Si(004)

Bi(111) Peak

24°22°

25 nm Bi/Si(001)6nm Bi: T = 150 K

T = 450 K+19nm Bi: T = 450 K

D

A

D

�

�

�

Henzler ring at 0.5 BL coverage.

Well-defined terrace size distribution [10].

Ring diameter decreases with increasing thedeposition temperature.

Island separation increases.

Quasidendritic island shape (kinetic limitation ofedge diffusion).

�Arrhenius plot of the average island separation< > and the island density (< > ~ ) [11]:L n L n

x x

1/2

�The slope of the fit gives an intraterrace diffusionenergy of = 135 meV [8].Ed

�

�

�

�

Normalized central spike intensity G(S) of the LEED(00)-spot profile as a function of scattering phase S.

The curves fit well with 2D model, i.e., cosine behavior[7].

Island height: d =0.389 nm at 80 K and d =0.395 nmat 180 K [8].

Observation of the electron density smoothening effectfor small islands (Smoluchowski effect) [9].

80 K 180 K

�

�

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�

Periodic change of central spike from one in-phase condition to the next one.

Spike vanishes at out-of-phase, showing onlyshoulders.

Total intensity is conserved.

2D island distribution.

-20 0 20

0.5 BL Bi on Bi(111) film @ 80 K

k (%BZ)ll

-10 0 10 -10 0 10-10 0 10

103

104

105

106

Inte

nsi

ty (

Co

un

ts/s

)

-40 -20 0 20 40 -20 0 20 -20 0 20-20 0 20

< > = 4.6 nmL < > = 11 nmL < > = 18 nmL < > = 14 nm

@ 130 K

E =50 eV, S = 4.5

(00)-spote

@ 150 K @ 200 K

k (%BZ)ll

k (%BZ)ll

k (%BZ)ll k (%BZ)ll

k (%BZ)llk (%BZ)ll

k (%BZ)ll

104

105

106

Inte

nsi

ty (

cps)

-50 0 50

k [% BZ]

60

50

40

Energy (eV)

4244

4648

5254

5658

0.5 BL Bi on Bi(111) @ 80 K(00)-spot profiles

k||(%BZ)

S = 4

S = 5

S = 4.5

Annealing behavior (80 K- 450 K)

�

�

�

(00)-spot profile variation during the annealing.

Central spike increases in the expense ofshoulder.

The shoulder diameter decreases after 220 K.

Rapid increase of island separation at 220 K.

35

30

25

20

15

10

5

0

Isla

nd S

epera

tion (

nm

)

400300200100

Temperature (K)

< > = 4.94 nmL

0.5 BL Bi/Bi(111) film

TD= 80 K

0.5 Bi on Bi(111) @ 130 KT = 130 KD

T = 300 KA

200 nm

�Coalescence of islands can be observed in STMtopography.

2 BL

3.5 BL

5.6 BL

(1)

(2)

(3) (4) (5)

-100 0 100

5.6 BL Bi/Si(001) @ 150 KT = 150 KD

E = 60 eVe

k (%BZ)ll

(00) (01)

(01)*

-100 0 100

E = 95 eVe

5.6 BL Bi/Si(001) @ 300 KT = 150 KD

T = 450 KA

k (%BZ)ll

(00) (01)

(01)*

-100 0 100

17 BL Bi/Si(001) @ 150 KT = 150 KD

k (%BZ)ll

(00) (01)

(01)*E = 60 eVe

-200 -100 0 100 200

25 nm Bi on Si(001)6 nm Bi: T = 150 K

T = 450 K

+19 nm Bi: T = 450 K

D

A

D

k (%BZ)ll

E = 293 eVe

(01)

(01)*

(00)

104

105

106

107

108

109

1010

1011

Inte

nsity (c

ps)

543210

Coverage (BL)

15

10

5

0

-5

Re

l. Re

sist

anc

e (

DR/R

in %

)

10

5

0

FW

HM

(%BZ)

Bi/Bi(111) @ 80 K

(00)-spot intensityrel. resistance (8nm film)FWHM of (00)-spot (shoulder)

�

�

�

Drastic change in resistance at submonolayercoverage (Scattering at surface adatoms) [5,6].

Resistance oscillation almost matches with theoscillation of lateral surface roughness.

Bulk contribution dominates at higher coverages.

Morphology

Ex-situ film characterization

AFM

XRD

- 3 fold symmetry Bi islands.

- Twins & rotated islands.

- Low density of screw dislocations.

- Film relaxed to bulk (d = 0.394 nm).

-

Homogenious thickness & high crystallanity

Bi(111)

Kiessig fringes [4]:

.

Annealing to 450 K

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�

Ring disappears during (at T = 230 K).Annealing

Spot splitting in LEED & height contrast in STM.

Periodic surface height undulation via interfacialmisfit dislocation network [2].

Average dislocation distance = 1.9% BZ (~20nm).

Additional Bi deposition at 450 K

�

�

�

Caping of height undulation.

Average terrace size > 400 nm.

No defects and surface contamination [3].

Inte

nsi

ty (

arb

. u

nits

.)

-40 0 40kll (%BZ)

80 K

240 K

400 K

280 K

360 K

320 K

200 K

160 K

120 K

0.5 BL Bi on well-annealed 25 nm Bi(111)/Si(001):Spot profiles during annealing right after growth @ 80 K

Ee = 49.3 eV

k (%BZ)ll

-200 -100 100 200

17 BL Bi/Si(001) @ 300 KT = 150 KD

T = 450 KA

E = 60 eVe

(00) (01)

(01)*

-200 -100 0 100 200100

-4 0 4

k�� (% BZ)

(10)*-Spot

59 eV

-4-4 00 44

k�� (% BZ)

10096 104

(10)-Spot

59 eV

-4 0 4

k�� (% BZ)

(00)-Spot

59 eV

100 nm

2.2 nm

25 nm Bi/Si(001):

6 nm : T = 150 K

T = 450 K

19 nm:

D

A

DT = 450 K

He

igh

t (Å

)

Lateral distance, (nm)x

-0.5

0.0

0.5

100806040200

Measured

Fitted by:

||,edge| |= 0.377 nm

= (6.6 ± 0.3) nm

b

t

< >adis

� �

2||,edge

2 2( )

nn

b th x

x x t�� �

� �� �� ��

100 nm

1n

m

grain boundary

Bi steps

Si steps

20 nm20 nm

6 nm Bi/Si(001):T = 150 K

T = 450 KD

A

eBi(111) film

< >L < >

island