Download ppt - SEWG Meeting Mixed Materials 2007 First results from beryllium on carbon Florian Kost Christian Linsmeier

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: 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 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





1070 K 1170 K





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.