FePc/Au(111) and H2O/FePc/Au(111)

XPS and XAS Study

Cristina IsvoranuLund University, Dep. of Synchrotron Radiation Research

Berlin, October 1st 2007

• Summary

- FePc monolayers on Au(111)(XPS, XAS study)

- Interaction of water with FePc monolayers on Au(111)

• The molecular structure of FePc

• XPS principle

hν

Core level

Unoccupiedvalence

OccupiedValence

EV

hν=Eb+EK+Φ

•FePc monolayers - Characteristic XPS peaks

Inte

nsity

/

arb

. uni

ts

290 288 286 284 282Binding Energy / eV

Monolayer FePcC1s XPS

C=C

C=N

satelite C=N

satelite C=C

Inte

nsity

/

arb

. uni

ts

290 288 286 284 282Binding Energy / eV

experimental fit

C=C

C=Nsatelite C=C

satelite C=N

Inte

nsity

/

arb

. uni

ts

401 400 399 398 397 396 395Binding Energy / eV

Monolayer FePc N1s XPS

Core level

Unoccupiedvalence

OccupiedValence

HOMO-2

HOMOHOMO-1

LUMO

LUMO+2LUMO+1

hν

What happens?Result

Inte

nsity

/

arb

. uni

ts

406404402400398 Photon Energy / eV

XAS spectrumLUMO

LUMO+1 LUMO+2

•XAS (NEXAFS)

Principle:-maps the unnocupied states- by variation of the photon energy the absorption into the different unoccupied levels is probed

•XAS – Proof of Molecular Orientation Dipole selection rule Δl = ±1 must befulfilled. For excitations from the 1s orbital,only states that have a component withp-character at the excitation site are mapped.

The scalar product of E (electrical field of the light) and p (linear momentum operator) gives rise to an angular dependence of the cross section that can be used to determine the molecular geometry.

E vector

Max. cross section

Min. cross section

•Molecular orientation of FePc Monolayers on Au(111)In

tens

ity

/ a

rb. u

nits

410408406404402400398Photon Energy / eV

N1s NEXAFS

NE NI

π*

σ*

Molecular plane parallel to surface

NE - E vector normal to the surface

hν

E

NI - E vector parallel to the surface

E

hν

•Interaction of water with FePc Monolayers on Au(111)

290 288 286 284 282 280Binding Energy / eV

multilayer FePc monolayer FePc

C1s XPS

Monolayer FePc/H2O/Au(111)

Multilayer FePc/Au(111)

Monolayer FePc/Au(111)

Annealing

Dose water

Different amounts of water

Temperature influence

Monolayer FePc/H2O/Au(111)

•Water dosing on FePc monolayers on Au(111)

402 400 398 396 Binding Energy

without water 2L H2O 2L H2O

Monolayer FePcN1s XPS

402 400 398 396 Binding Energy / eV

Monolayer + 2L waterN1s XPS -195C

-170C 290 288 286 284 282 280Binding Energy

C-N

without water 2L H2O fepcau0183_s

Monolayer FePcC1s XPS

•Water desorption

402 400 398 396 BInding Energy / eV

Monolayer FePc + 2L H2O N1s XPS -195C

-188C -168C -150C -138C -134C

540 538 536 534 532 530

Binding Energy / eV

-195C -188C -168C -150C -138C -134C

Monolayer FePc+2L H2O O1s XPS

410408406404402400398 Photon Energy / eV

N1s XASNormal Incidence

without water with water with water, heat-178C

296294292290288286284282 Photon Energy / eV

C1s XASNormal Incidence

without water 2L water -195C heat to -178C

•XAS measurements on water/FePc/Au(111) System

• Future plans

- continue experiments on H2O/FePc/Au(111)(XPS and STM)

- try H2O/FePc/HOPG

- finalisation of some XPS, XAS, RPES measurements on FePc/HOPG

- interaction of H2Pc monolayers with water

Thank You!