Excitation Source: Tunable SR (UV –X rays)

Photon-out phenomena:

- Scattering (elastic, inelastic, resonant)

- Fluorescence (core-hole decay)

X-ray fluorescence (hard x-rays)

X-ray emission (soft x-rays)

Luminescence (UV-visible)

Auger (pseudo-photon)

De-excitation spectroscopy II:

Photon-in Photon-out spectroscopy

X-ray fluorescence (XRF)

X-ray emission (XES)

X-ray excited optical luminescence (XEOL)

Photon-in Photon-out Spectroscopy

hvex

XA

NE

S

Abs.

E

core

Edge

hvf

E

core

EF

Fluorescence Energy (eV)

XRF

X-ray fluorescence (XRF)

X-ray fluorescence: shallower core electron

(e.g. L shell) to deeper core hole (K) transition

XA

NE

S

Abs.

E

core

Edge

hvf

E

core

(Auger) Secondary

processes

EF hvop

Optical XAFS

Mono

XEOL

200 850

Wavelength (nm)

PLY

Mono

Ef

X-ray Energy (eV)

XES

X-ray emission (XES) and X-ray excited optical

luminescence (XEOL)

hvex

NBG defect

XES: valence electron to shallow core

XEOL: CB to VB & defects

Core level directly

below valence band

X-ray Fluorescence measurements

• Scintillation counter

• Ion chamber (Lytle detector) (with filters)

Nondispersive (no energy resolution)

Moderate energy resolution

High energy resolution

Solid state detectors (Ge, Si), order of 10 to102 eV

WDX detector (crystal monochromator) E/E ~ 800

Very high energy resolution

MiniXS (Jerry Seidler, U. of Washington)

E/E ~ 4000 5

X-ray Fluorescence properties of elements

Auger yield = 1 – FLY

FLY for low z elements

(C, N, O etc.) is << 1 %

Normal Fluorescence: Core-Core

XES: L or M = valence band

Resonant: Core-CB excitation

Ca:

Z= 20

X-ray Fluorescence:

X-ray photons in, x-ray photons out.

Results from the decay of a deep core

hole (e.g. K, or L)

Monitor the absorption spectrum using

fluorescence yield (FLY) → element

specificity

Detection Schemes

• High sensitivity, non-dispersive

Channel plate, Ion chamber

(solar slits, filters, e.g. Lytle)

• High sensitivity, moderate energy resolution

Solid state detector (e.g. Canberra 13 element

at PNC-CAT, Si drift detector at CLS)

Gas proportional counters (e.g. Fisher/Ohta)

• High sensitivity, more moderate resolution

Multi-layer Array Analyzer Detector (MAAD)

Log spiral detector (asymmetric Laue bent)

13 element detector

transmitted beam

specimen

KB mirror

PNC-XSD Microprobe

hvf

Photon Energy (eV)

2000 4000 6000 8000 10000 12000

Inte

ns

ity (

co

un

ts)

10

100

1000

10000

Ca Fe Cu

Zn

Ni

elastic

peak

Metals in mouse kidney tissue (hard X-ray)

XRF

Photon Energy (eV)

9000 9200 9400 9600 9800

FL

Y (

arb

. u

nit

s)

0

1

2

3

Photon Energy (eV)

8950 9000 9050

FL

Y (

arb

. u

nit

s)

0

1

2

3

Cu K-edge, mouse kidney (10 micron pixel)

quartz slide

Incident X-ray

hv =10 keV

Lu, soft x-ray [Phys. Rev. B, 58 (1998)]

20 element Multi-Array Analyzer Detector (MAAD)

[Ke Zhang et al. HD Technologies Inc. ]

Energy scan: elastic,

Ca K and K

E = 150 eV at Ca K

Ca

K, K

Schematic of an asymmetric cut

Si (100) wafer where in polar

Coordinate: r() = ae b,

b = tan [Khelashvili et al.

Rev. Sci. Instru. 73, 1534 (2002)]

Variable width

thickness

• Low sensitivity, good resolution WDX

(Rowland circle crystal optics)

LiF crystals (electron microprobes): 2-5 keV

[e.g. PNC-CAT]

Ge (3,3,3), Si (4,4,0): Fluorescence > 5 keV

• Low sensitivity, good resolution (< 2 keV)

Grating monochromator [e.g. BL 8.0.1, ALS]

Detection Schemes (continues..)

WDX from an electron microprobe

Wavelebgth

2.1 2.2 2.3 2.4 2.5 2.6

Inte

nsity

0.000

0.002

0.004

0.006

Photon Energy (eV)

5710 5720 5730 5740 5750 5760 5770

FLY

0.000

0.002

0.004

0.006

0.008

0.010

0.012

Ce L3-edge

Fluorescence

X-rays

Ce L

Ce L

Green Titanite

Brown Titanite

Ce L3 edge of Ce in Titanite: WDX detection

Ti K 1 4932 eV Ce L2 4823.0 eV

Ce L1 4840.8 eV Ce L1 5262.2 eV

0.06%

0.1%

Neither SS nor WDX detector will resolve Ce L from Ti K

But WDX can resolve Ce L nicely

Ce in Titanite: Microprobe using WDX

17

Titanite (CaTiSiO5,

sphene) is a common

mineral in mafic-felsic

igneous and meta-

morphic rocks, and it

is widely used for

geochronologic and

petrogenetic studies

American Mineralogist, Volume 98, 110–119, (2013)

K Fluorescence of MnO using Ge(333) and Si(440)

crystals (Rowland circle optics, S. Cramer X-25

NSLS, 2002)

2p

2s

3p

3s

3d

K (core-

valence)

emission

19

Dickinson et al. Rev. Sci. Instrum. 79, 123112 (2008)

Pilatus 100K PAD

High resolution fluorescence using Minixs

CePd3 RXES data collection (~3 hours)

Ce L Ge(440)

Sample

holder

2D-PAD

Rowland Circle

5710

5723

Absorption & de-excitation @

resonance:

Photon channel:

X-ray fluorescence

Electron channel:

Auger electron

Resonant

X-ray emission

Unoccupied bound state

Resonant

Augerspectator

Inelastic X-ray scattering

(core level excitation)

hv1

hv2

E = hv1 - hv2

Cross-section is very small except at resonance

When hv1 = hv (threshold resonance)

Same shallow hole left behind when the e

drops down to fill a deeper core hole emitting a

fluorescence X-ray photon

RIXS @ Ce L3-edge

hv1

hv2

i

n

f

M4,5

L3

4d

N4,5

3d

2p3/2

dispersion when

hv1 < threshold,

constant when

hv1 > threshold

- Information: dispersion

(constant energy transfer);

core-hole lifetime

suppression

RIXS measurements (electron and photon)

- Experiment requires

high flux, high photon

energy resolution

(incident and emission)

and high electron

energy resolution

WDX

E ~ 6 eV

MiniXS

E <1 eV

5722 eV

5705 eV

E =1 eV

Resonant Inelastic X-ray Scattering (RIXS)

XES : X-ray Emission Spectroscopy

X -ray photons in, x-ray photons out

For shallow core excitations, XES measures

the projected densities of states of the element

in the valence band element and

chemical specificity

.

h

h'

UnoccupiedMOs

OccupiedMOs

O 1s

Inte

nsi

ty (

a.u

)

540535530525520515

Energy (eV)

XASXES

4a1

2b2

3a1

1b2

1b1

O K-edge XAS and XES of H2O

Guo et al., PRL 89,

137402 (2002)

HOMO-LUMO

gap

Resolution of Grating Spectrometer

1200 lines/mm, 5 m, resolution:

670 meV (at 1000 eV)

370 meV (O K-edge at 525 eV)

400 lines/mm, 5 m, resolution:

300 meV (C K-edge at 275 eV)

100 meV (S L-edge at 150 eV)

300 lines/mm, 3 m, resolution:

80 meV (Cu M-edge at 72 eV)

1st order

275275.1

1st order 2nd order

Slit size 10um, Detector resolution 50um

9090.05

3rd order2nd order10001000.31800 lines/mm, 5 m, resolution:

300 meV (at 1000 eV)

150 meV (O K-edge at 525 eV)

1200 lines/mm, 5 m, resolution:

100 meV (C K-edge at 275 eV)

600 lines/mm, 3 m, resolution:

50 meV at 90 eV

Very High Resolution Spectrometer

Cu 3p;

75eV+/- 10meV

RP~7,500

870mm

150mm

Ruling (center) = 2000 lines/mm

14o 0th order

130 mm X 25 mm

R = 4060 mm

Magnification 1.3

MERLIN at ALS:

Acceptance: ~33mrad (V) by 12mrad (H)

6mm by 15mm source

Uppsala University:

Source size: 6 mm x 60 mm

Grating: 1800 l/mm

Angle of incidence: 85 deg., inside order

Acceptance angle: 20 mrad x 50 mrad

h [eV]

75.25 10 meV

75.00

Source size: 6 mm x 60 mm

Grating: 1200 l/mm

Angle of incidence: 78 deg., outside order

Acceptance angle: 100 mrad x 50 mrad

10 meV

Courtesy of J.H. Guo

lsv

l

Source Grating

F

' = 10 mm / 20 mm = 0.5 mrad

= 2.5 cm / 5 m = 5 mrad

'XSource

Slit

Beam size (1994):➢ 1 mm at BW3 (HASYLAB) & X1B (NSLS)

➢ 100 mm at BL7.0.1 (ALS)

The beam size can be seen at 20 mm distance:

5 mrad x 20 mm = 100 mm

2 cm

100 mm

Intensity of X-ray emission Spectra

❖ Fluorescence Yield

➢ Photon hungry experiment

➢ Resonance enhancement

❖ Excitation➢ Synchrotron radiation

➢ Undulator (Linear, EPU)

➢ Monochromator

❖ Detection

✓ Diffraction efficiency of grating

▪ Blaze

▪ Grove density

▪ Surface quality

✓ Quantum efficiency of detector

▪ MCP (Photon cathode coating)

▪ CCD

✓ Beam spot size

✓ Solid angles to collected (slit size)

YBa2Cu3O6 YBa2Cu3O7-Guo et al., Phys. Rev. B 61, 9140 (2000)

XES + XAS : Bandgap determination

Guo, Int. J. Nanotech. 1-2, 193 (2004)

Band

gap

No

band

gap

85 90 95 100

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

5500

6000

clean Si (100)

clean PS

dirty nanowires

dirty PS

clean nanowires

Files: .r01; Plot: Ian.opj

XES spectra of Si samples

Co

un

ts

Emission Energy [eV]

Si L XES: Si → Valence Band

SiNW

(as prepared)

XPS: Valence Band

SiNW

(HF)

L3,2-edge

as-prepared PS

clean Si(100)

as-prepared SiNW

clean PS

clean SiNW

SiNW (HF)

XES of Alq3

XES:PDOS (occupied) XANES:PDOS (unoccupied)

XES

XES

P.-S.G. Kim et. al. J. Elect. Spectros. , 901, 141(2005)

N

NO

OAl

N

O

- +

Glass

Indium Tin Oxide (ITO)

Hole transport layer

Electron transport layer

Emission layer

Ag/Mg

LightEmission

OLED (Organice Light Emitting Device)

XES of Alq3

XES:PDOS (occupied)

XES

P.-S.G. Kim et. al. J. Elect. Spectros. , 901, 141(2005)

XESXES

XPS: Caruso et al. Chem. Phys. Lett. 413 (2005)

HOMO, HOMO-1:

Mainly C character

XEOL: X-ray Excited Optical Luminescence

X-ray photons in, optical photons (UV, visible,

near IR) out.

Luminescence can be element and excitation

channel specific.

Monitor the absorption spectrum using the photo-

luminescence yield (PLY) element and

chemical specificity

XEOL - Conversion of X-ray energy into

optical emission

Core level

Recombination

via exciton

Recombination via bound exciton,

impurity and defect statesoo

UV

vis.

X-ray phosphorThermalization: electrons in

the CB, holes in VB

hv ~ Eo

hv >Eo

Elliot & Gibson

Solid State

Physics Haper

& Row, 1974

36

hvop

hvexPLY (l selected) XANES

Mono

XEOL

XA

NE

S

Abs.

E

200 850

Wavelength (nm)

CB

VB

EF

XAS and XEOL (Optical XAFS)

Edge

NBG defect

1050104010301020

Energy (eV)

520 nm

OL

ZB XAS

PLY

TEY

ZnS Zn L-edge

De-excitation, Energy transfer in nanostructures

Core leveloo

hv ~ Eo

hv ~>Eo

• Decay channels

• Attenuation of e and fluorescence x-

rays (thermalization) in the solid

yields secondary electrons (holes)

hvf

VB

core

Auger,

LVV

• Thermalization track is confined

(truncated) in nanostructures

Photon-in: Synchrotron Light

• Tunability → Element, edge,

excitation channel specificity

• High brightness

• Polarization

• Time structure

XEOL Techniques

Energy DomainXEOL: Luminescence induced by selected excitation photon energy (usually across an absorption edge)

Optical XAFS: Monitored with the optical signal

Time DomainLifetime: Synchrotron pulse Time-resolved (gated) XEOL: Luminescence within a selected time window between pulsesTime-gated Optical XAFS: Time window

40

Alternative: fiber optics,

spectrograph with CCD

detectors (e.g. Ocean

Optics QE65000)

XEOL: Experimental Layout

41

• Case studies

Si nanostructure

ZnS nanoribbons (crystal structure

engineering)

Soft matter

Alq3 (OLED materials)

2D – XEOL TiO2 nanowire

XEOL - Energy Domain

Photon Energy (eV)

1800 1900 2000 2100 2200 2300

TE

Y

0

1

2 Porous Si

Si nanowire

Si (100)

Si K-edge XAFS

42

Si L-edge XEOL (porous silicon)

Photon Energy (eV)

85 90 95 100 105 110 115 120

To

tal

Ele

ctr

on

Yie

ld (

ab

r.

un

its)

10

20

Porous Silicon

Si(100)

20 mA

5 mA

200 mA

500 mA

50 mA

Si L3,2

-edge

current (cm-2

)

Photon Energy (eV)1 2 3 4

Ph

oto

lum

ines

cen

ce (

arb

. u

nit

s)

0

200

400

600

a

b

a. ambient (H25)

b. HF refreshed

Porous Silicon

Excitation Energy: 100 eV

Wavelength (nm)

200 300 400 500 600 700 800 900

Ph

oto

lum

ines

cen

ce (

arb

. u

nit

s)

0

100

200

300

400

Excitation Energy

b

a. 100 eV

b. 110 eV

Porous Silicon

(ambient) a

Fig.1

Wavelength (nm)

200 300 400 500 600 700 800

Inte

nsity

(arb

. uni

ts)

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

460 nm 630 nm

530 nm

hvex

(eV)

1890

1867

1851

1847.5

1845

1842

1840

1838.5

1830

Wavelength (nm)

300 400 500 600 700

Inte

nsity

0

1000

2000

3000

40001847.5 eV

1842 eV

difference

curve

Photon Energy1840 1850 1860 1870

TEY

0

1

2

3Si K-edge

SiO2

Si

(a) (b)

Si K-edge XEOL of silicon nanowires

Phys. Rev. B 70, 045313 (2004) 43

Si nanowire

Photon Energy (eV)

1830 1840 1850 1860 1870 1880

Inte

nsi

ty (

arb

. un

its)

0

10

20

30

40

PLY zero order

TEY

FLY

630 nm

460 nm

530 nm

SiSiO

2

Si K-edge: PLY

Wavelength (nm)

200 300 400 500 600 700 800

Inte

nsit

y (a

rb. u

nits

)

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

460 nm 630 nm

530 nm

hvex

(eV)

1890

1867

1851

1847.5

1845

1842

1840

1838.5

1830

Wavelength (nm)

300 400 500 600 700

Inte

nsi

ty

0

1000

2000

3000

40001847.5 eV

1842 eV

difference

curve

Photon Energy1840 1850 1860 1870

TE

Y

0

1

2

3Si K-edge

SiO2

Si

(a) (b)

460nm

530nm

630nm

530nm

630nm

460nm

44

shell

core

interface

45

Inte

ns

ity

(a

rb.

un

its

)

0

5000

10000

15000

20000

25000

30000

1897.5

1852.5

1847.5

1845.5

1841.5

1831.5

Wavelength (nm)

200 300 400 500 600 700 800

Inte

ns

ity

(a

rb.

un

its

)

0

2000

4000

6000

8000

10000

12000

1831.5

1841.5

1845.5

1847.5

1897.5

1852.5

(a) before HF

(a) after HF

SiNW

hvex

(eV)

hvex

(eV)

450 nm

Photon Energy (eV)1840 1850 1860

TE

Y

0

1

2

3

XEOL and chemistry of SiNW

46

1050104010301020

Energy (eV)

332 nm

OL

W XAS

1050104010301020

Energy (eV)

520 nm

OL

ZB XAS

ZnS hetero-crystalline nano-ribbon

ZnS nw

(wurtzite)

ZnS nw

(zinc blend)

700600500400300

Wavelength (nm)

280 K

10 K Total

800700600500400300

Wavelength (nm)

Total

0-14 ns

520 nm

332 nm

X.-T. Zhou et al., J. Appl. Phys. 98,

024312(2005)

R.A. Rosenberg et al., Appl. Phys. Lett. 87,

253105(2005)

47

XEOL from soft matters

200 300 400 500 600 700 800

0

5

10

15

20

25

30

35

40

Rabbit IGG-FITC Conjugated XEOL

Co

un

ts

Wavelength (nm)

285 eV

400 eV

533 eV

Fluorescein isothiocyanate (FITC) label

FITC conjugated concanavalin A (Con A)

lectin (Con A-FITC) and goat anti-rabbit

immunoglobulin G (IgG) (IgG-FITC)

200 300 400 500 600 700 800

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

FITC label XEOL

285 eV (FITC02)

410 eV (FITC03)

552 eV (FITC01)

Co

un

ts

Wavelength (nm)200 300 400 500 600 700 800

0

5

10

15

20

25

30

35

40

Con A-FITC conjugated XEOL

Co

un

ts

Wavelength (nm)

B

C

D

E

F

G

FITC

Con A

FITC

IGA-

FITC

P.-S. G. Kim et al. Chem. Phys. Lett. 39, 44(2004)

radiation

damage

48

PLY from labeled proteins

280 285 290 295 300 305 280 285 290 295 300 305

280 285 290 295 300 305

280 285 290 295 300 305

IgG

Con A

FITC

No

rma

lize

d Y

ield

s (

a.u

.)

280 285 290 295 300 305

280 285 290 295 300 305

PLYFLYTEY

280 285 290 295 300 305

Photon Energy (eV)

280 285 290 295 300 305

Photon Energy (eV)

280 285 290 295 300 305

Photon Energy (eV)

385 390 395 400 405 410 415 420 425 430 435 385 390 395 400 405 410 415 420 425 430 435

390 395 400 405 410 415 420

385 390 395 400 405 410 415 420 425 430 435

IgG

Con A

FITC

No

rma

lize

d Y

ield

s (

a.u

.)

385 390 395 400 405 410 415 420 425 430 435

385 390 395 400 405 410 415 420 425 430 435

PLYFLYTEY

385 390 395 400 405 410 415 420 425 430 435

Photon Energy (eV)

385 390 395 400 405 410 415 420 425 430 435

Photon Energy (eV)

385 390 395 400 405 410 415 420 425 430 435

Photon Energy (eV)

515 520 525 530 535 540 545 550 555 560 515 520 525 530 535 540 545 550 555 560

515 520 525 530 535 540 545 550 555 560

515 520 525 530 535 540 545 550 555

IgG

Con A

FITC

Norm

aliz

ed

Yie

lds (

a.u

.)

515 520 525 530 535 540 545 550 555

515 520 525 530 535 540 545 550 555 560

(c) PLY(b) FLY(a) TEY

515 520 525 530 535 540 545 550 555 560

Photon Energy (eV)

515 520 525 530 535 540 545 550 555 560

Photon Energy (eV)

515 520 525 530 535 540 545 550 555 560

Photon Energy (eV)

N K-edge O K-edge

C K-edgeO

N

COOH

OHO

C

S

Wavelength (nm)

100 200 300 400 500 600 700 800 900

Inte

nsit

y (

arb

. u

nit

s)

0

10

20

30

40

50

402.7

560

540.9

532

520

395

285.2

400.4

275

Alq3 XEOLhv (eV)

TEY

FLY

PLY

Photon Energy (eV)

530 540 550

2

4 O K-edge

400 410 420

1

2

3

4

N K-edge

PLY

280 290 300

Yie

ld (

arb

. u

nit

s)

0.5

1.0

1.5

C K-edge

PLY

TEY

PLY

TEY

TEY

TEY

Alq3 XEOL

XAFS (near-edge)

Naftel et al. Appl. Phys. Lett. 78, 1847(2001).

Energy (eV)

1.5 2.0 2.5 3.0 3.5

No

rma

lize

d in

ten

sit

y (

arb

. u

nit

s)

0

10

20

30

40

50

60

70

Al K-edge

1565 eV

C K-edge

285.2 eV

N K-edge

402.7 eV

O K-edge

540.9 eV

XEOL

Alq3 Excitation Energy

2.28 eV

2.56 eV

2.81 eV

542.4 nm

XEOL from Alq3

Luminescence Energy (eV)

2.0 2.5 3.0

Inte

ns

ity (

arb

. u

nit

s)

0

5

10

15

20

Al K-edge

(1565 eV)

Below C K-edge

(275 eV)

Excitation Channel Dependent XEOL

450 455 460 465 470 475 480

0

10

20

30

NW-ap

c2c1

b2

a1

b1

NW-1000

NW-900

NW-800

NW-750

NW-700

NW-650

NW-500

NW-400

NW-300

NW-200

Inte

nsity (

a.u

.)

Energy (eV)

NW-120

Photon in photon out (UV-visible)2-D XAS-XEOL TiO2 Nanowire (1000 ℃)

O K edge

Ti L3,2 edge

anatase

A. Zhao et al. unpublished

rutile Ti L3,2-edge

TiO

51

TRXEOL-Time-resolved XEOL

Optical XAFS

time &

wavelength

selectedPhoton Energy (eV)

imaging

XEOL - Time Domain

T.K. Sham and R.A. Gordon SRI 2009

TRXEOL from SRC, APS and CLS

APS top up: 24 bunches

15010050

Time (ns)

153 ns

0 200 400 600 800 10000

50

100

150

200

547 nm 5D4 to

7F1382 nm

5D3

to 7F4

Time (ns)

Inte

nsi

ty (

arb

. u

.)

Channels

0 500 1000 1500 2000

0

5000

10000

15000

320 ns

SRC single bunch

CLS single bunch

TbCl3

570 ns

F. Heigl, et.al. SRI2006, AIP CP879, 1202 (2007)

R.A. Rosenberg et. al., J. Phys. Chem., 112, 13943 (2008)

F. Heigl, et al. JACS, 128, 3906 (2006)

Si nowire

Ir(PPY)3

53

De-excitation and energy transfer in

nanostructures

Core leveloo

hv ~ Eo

hv ~>Eo

• Attenuation of e (thermalization)

yields secondary electrons (holes)

hvf

VB

core

Auger,

LVV

Thermalization track is confined (truncated) in

nanostructures ! The smaller the size, the shorter

the track, the faster the decay 54

55

• ZnO: nanoneedle vs nanowire

(crystallinity)

• ZnO: nano vs micro (size)

• Ru(phen)32+: (metal vs ligand)

TRXEOL – Case studies

56

0-20 nsungated 20-150 ns

nanoneedle

nanowire

TRXEOL from ZnO nanostructure

Wavelength (nm)Wavelength (nm) Wavelength (nm)

R.A. Rosenberg et. al. Appl. Phys. Lett. 89, 093118(3) (2006)

NBG

NBG

defect

Time gated-optical XAFS

9600 9800 10000 10200 10400 10600

3.0

3.5

4.0

4.5

5.0 ZnO(0001) single crystal

0 -20 ns

20 -150 ns

Inte

nsity (

arb

. units)

Photon Energy (eV)

9600 9700 9800 9900

0.0

0.5

1.0

1.5

ZnO nanowire

(486 nm)PLY

(arb

. units

)

Photon Energy (eV)

ZnO nanoneedle

(383 nm)

9600 9700 9800 9900-5.0

-4.5

-4.0

-3.5

-3.0

0 -20 ns

20 -150 ns

ZnO(0001) Time-gated

PL

Y (

arb

. u

nits)

Photon Energy (eV)

F. Heigl et al. XAFS 13 AIP Proc., (2007)

200 300 400 500 600 700 800 9000

5000

10000

15000

20000

25000

486 nm

383 mn

un-gated

slow (10 ns - 130 ns) x 10

fast (0 -10 ns)

Inte

nsity (

arb

. u

nits)

Wavelength (nm)

Morphology and size dependent dynamics

L. Armelao et. al. ChemPhysChem

2010, 11, 3625

nano

micro

micro

TRXEOL from Ru(phen)3 2+

200 300 400 500 600 700 800 900

- slow

- fast

- total

Inte

nsity (

arb

. u

nits)

Photon Energy (eV)

hvex

= 22140 eV

22000 22200 22400 22600 22800

0

2

4

6

8

10

(b)

Ru K-edge: Ru(phen)3

2+

PL

Y (

arb

. u

nits)

Photon Enery (eV)

0 200 400 600

0.000

0.001

0.002

0.003

0.004

0.005

Decay

324nm

613nm

Intensity (arb. u.)

Time (ns)

200 300 400 500 600 700 800 900

(a)

- slow

- fast

- total

Inte

nsity (

arb

. units)

Photon Energy (eV)

S. Lam, et al. AIP Proc., XAFS13, CP882, 687 (2007)

Prospect: TRXEOL with an optical streak camera

T. Regier et al. CLS Activity Report, 2009

Optical

photon

Hamamatsu C4780

ZnO nanoneedle excitonic emission

lmax~ 380 nm (hvex = 530 eV)

Tim

e

Energy

Energy

What determines the decay

lifetime of XEOL ?

In general,

•The larger the energy separation

the faster the decay

•The faster the thermalization, k1,

the faster the decay

(nanostructures)

•The faster the energy transfer

process, k2, the faster the decay

•NBG emission is always faster

than defect emission