MPI-MF

AbteilungDosch

M. Delheusy

SXRD IN-SITU INVESTIGATION OF THE O/Nb(110) INTERFACE

M. Delheusy (MPI Stuttgart, DAPNIA/CEA Saclay)A. Stierle (MPI Stuttgart)C. Antoine (DAPNIA/CEA Saclay)N. Kasper (MPI Stuttgart)I. Costina (MPI Stuttgart)H. Dosch (MPI Stuttgart)

Département d‘Astrophysique, de physique des Particules, de physique Nucléaireet de l‘Instrumentation Associée - Saclay

MAX-PLANCK-INSTITUT FÜR METALLFORSCHUNGAbteilung Dosch

MPI-MF

AbteilungDosch

M. Delheusy

3 complementary Surface X-ray techniques

Nb

InterfaceInterstitial oxygen

Oxide layers

Truncated Crystal

Substrate

Overlayerθ θ

Depth-resolved diffuse scattering induced by interstitial oxygen

Crystal Truncation Rods (CTR)X-ray Reflectivity

L

Z

Evolution of the oxide layers Depth-distribution evolution

of the interstitial oxygen

RODSRODS

Bulk

K

0321

L 1

2

H

αi → 0 αi → αcrit (~mrad)

~2 nm

MPI-MF

AbteilungDosch

M. Delheusy

X-Ray Reflectivity

1Formalisme de L.G. Parrat, Phys. Rev. 95, 359 (1954)

-15 -10 -5 0 5 10 15 20 25 30 35 400.0

5.0x10-6

1.0x10-5

1.5x10-5

2.0x10-5

2.5x10-5

3.0x10-5

NbO

Nb bulk

NbO2

Room Temperature 120°C 200°C 300°C

Ele

ctro

n de

nsity

(arb

. uni

ts)

z (Ang.)

Nb2O5

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0

1E-7

1E-6

1E-5

1E-4

1E-3

0.01

0.1

1

10

100

1000

10000

Ref

lect

ed In

tens

ity (a

rb. u

nits

)

θ (deg.)

DataFits

300°C200°C160°C120°C

RT

Optical properties of the materialParrat1 formalism layers model :

Electron density profilesThicknessRoughness

α αα

Nb(100) oxidized 14 days in air

MPI-MF

AbteilungDosch

M. Delheusy

Near Surface region :Reciprocal map for αi : 0.6°, αf : 0.5° (Λ~150nm) Nb(110) oxidize in air (atm. conditions)

DIFFUSE SCATTERING IN THE NEAR SURFACE REGION

0 1 2 3 4 50.0

0.5

1.0

1.5

2.00 1 2 3 4 5

(40) Bragg peak

(21)

(42) Bragg peak

(20) Bragg peak

(22) Bragg peak

Hsurf (r.l.u.)

K sur

f(r. l

. u.)

2.0002.4733.0593.7834.6785.7857.1548.84710.9413.5316.7320.6925.5931.6539.1448.4059.8674.0291.54113.2140.0

Intensity(02) Bragg peak [21]

1H. Dosch et al., Phys. Rev. B, vol. 34 n°3, 19862J.M. Rowe and A. Magerl, Phys. Rev. B 21(4) (1980), 1706

1st shell(1.65A)

NbO

f1

f3

f2

2nd shell(2.33A)

3rd shell

Interstitial O atom on octahedral site

Previous study on Nb bulk

1 2 3 4

0

100

200

300

400

500

378 nm Scattering depth 337 nm 249 nm 174 nm 101 nm 10 nm 4.5 nm

Inte

nsity

(a.u

.)

Hsurf (r.l.u.)

(22)[21]

qi

qf

MPI-MF

AbteilungDosch

M. Delheusy

DEPTH-SENSITIVE SURFACE STUDY

H. Dosch, Springer Tracts in Mod. Phys. 1992, Springer Berlin, pg. 126

0.0 0.5 1.0 1.5 2.01

10

100

1000 αi = 2° αi = 1° αi = 0.32° αi = 0.3° αi = 0.2°

Λ [n

m]

αf [deg]

αi=αc

αi αf

Grazing Incidence X-ray diffraction geometry

0.0 0.5 1.0 1.5 2.0 2.5 3.0

10

100

1000

αi=2 αi=1

Λ [n

m]

αf [deg]

Nb oxide

Nb

Interface Nb oxide

10nm

400nm

~ 5nm

50-100nm200nm

Scattering depth Λ = f(αf,αi)

nm resolution

MPI-MF

AbteilungDosch

M. Delheusy

0.0 0.5 1.0 1.5 2.0

101

102

103

0.5 1.0 1.5101

102

103

⎜Fhk

l⎜ (ar

b.un

its)

L (r.l.u.)0.0 0.5 1.0 1.5 2.0

101

102

103

L (r.l.u.)

(02)

L (r.l.u.)

In-situ results

0.0 0.5 1.0 1.5 2.0 2.5 3.01E-6

1E-5

1E-4

1E-3

0.01

0.1

1

Ref

lect

ed In

tens

ity (a

rb. u

n.)

Theta (deg.)

As prepared

700°C (5 min.)

Oxidation P = 5.10-6mbar 300°C (1h)

300°C (30min.)

1000°C (5min.)

120°C (2h)

a)

300°C 120°C, P=5.10-6mbar

300°C

120°C

1.5 2.0 2.5 3.0 3.5 4.00

20406080

100120140160180200220240260

Inte

nsity

(arb

. un.

)

H (r.l.u.)

Depth ~ 70nm Room temperature

700°C

b) As prepared120°C, 2h (UHV)300°C, 30min.Oxidation120°C, P=5.10-6mbar300°C, 1h700°C, 5min.1000°C, 5min.

Figures : a) X-ray Reflectivity, b) grazing incidence diffuse scattering and c) CTR

c)

MPI-MF

AbteilungDosch

M. Delheusy

10 100

100

1000

Cor

rect

ed In

tens

ity (a

rb. u

nits

)

Depth (nm)

Room Temperature 180°C 40°C 300°C

Oxidation 200°C After Oxidation 300°C After Oxidation

First estimation of the evolution of the oxygen concentration as a function of depth and temperature for the Nb(110) oxidized 6h in air.