SEWG Meeting Mixed Materials 2007 First results from beryllium on carbon Florian Kost Christian...

SEWG Meeting Mixed Materials 2007

First results fromberyllium on carbon

Florian KostChristian Linsmeier


The binary system C/Be

First results on Be/C

Future plans

Introduction • XPS system• preparation• analysis

Overview

• coverage variation experiments• annealing experiments• results

• annealing experiments• results


The binary system

Aim: Understandig of the interaction beryllium – carbon – tungsten (ITER)

Understanding of binary systems

Understanding ofternary systems

Approach: „bottom-up“


CBe

The binary system

+

C substrate Be substrate

not yet investigated


XPS apparatus


substrate

evaporation

Preparation

crucible

C

Be


Ccarbide formationduring evaporation

Be

Preparation


CBe

970 K

Preparation


hkinE

ABkin EhE

E1s

EVak

EF

Ekin

h

S

XPS principle

1486 eV


Be1s

Analysing XPS spectra


alloyBe1s



alloy

metal

Be1s



alloy

metaloxide

Be1s



XPS information

• quantities of components surface composition

• chemical states (elements, oxides, carbides, alloys)

• sputter depth profiles

XPS depth of information: ML…nm

XPS measurements


The binary system C – Be

C/Be(P. Goldstraß)


Be

C

Be

C

…

XPS

C/Be: coverage variation experiments


C/Au


C/Be: coverage variation experiments


C/Be: binding energy shift


Be

C …XPS

C/Be: annealing experiments


C/Be: sample composition


Two possible reactions:

Transition disordered graphite

Transition disordered carbide



-215cm104~ -216cm105~ C amount:



C/Be: SummaryInterface• thin Be2C ( ) layer at RT, island structure?• RT: Be2C limited to interface, additional C elementary

Reaction • first additional Be2C after 473K, lower than literature

• full Be2C formation: (673-) 773K, coverage dependent• indications against layer growth (Be visible!)• graphitic/disordered carbon:

disordered Be2C or disordered graphitic Be2C

ML6cmC106 215


The binary system C – Be

Be/C


Be 1smetallic

-216cm105~ C amount:



Be 1smetallic



Be 1smetalliccarbidic



Be 1s C 1smetallic graphitic

carbidic

carbidicdisordered



Be 1s C 1smetallic graphitic

carbidic

carbidicdisordered

Increasing intensity Cgraph

► Substrate visible► Hint to island growth



C 1s binding energies C 1s elemental composition

Be/C: Results

770 K


-216cm105~ C amount:

200 400 600 800 1000 1200 14000

10

20

30

40

50

60

70

80

90

100

C 1

s co

mp

osi

tio

n [

%]

temperature [K]

Be2C

Cgraph

Cdiss

ratio

Cgraph / Cdis

const.

Be/C: Results


Possible reasons for BE-Shift:

• Growth/Shrinking of islands

970 K CC

Be/C: binding energy shift



• Island charge effects

isolatingBe2C islands

++

C




• Influence of oxygen: Be – O – C compound

970 K

+ O



1070 K


• Two different peaks

1170 K




• Two different peaks

1070 K 1170 K



Be/C C/Be• thin Be2C layer at RT, island structure?

• RT: Be2C limited to interface

• first additional Be2C after 773 K

• full Be2C formation: 773 K

• indications for island growth: graphitic C peak increasing carbide peak shifting

• graphitic/disordered carbon:

disordered Be2C and

graphitic Be2C

• first additional Be2C after 473 K, lower than literature

• full Be2C formation: (673-) 773 K, coverage dependent

• indications for island growth (Be visible!)• graphitic/disordered carbon:

disordered Be2C or

disordered graphitic Be2C

Summary


Future plans


Future plans

• AFM measurements• coverage variation experiments

(different thicknesses at RT)• Modifying substrate• Measurements at BESSY

Open questions:

Be/C• Reactions and compounds in Be/C (Diffusion, Desorption, Size

Effects ….)

• Influence of Be layer thickness

• Actual reason for shifting binding energy

• Influence of substrate (pyrolytic/amorphous carbon)

• Surface morphology


Thank you.

SEWG Meeting Mixed Materials 2007 First results from beryllium on carbon Florian Kost Christian...

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