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1

NIST Database for the Simulation of Electron Spectra

For Surface Analysis (SESSA)*

Cedric Powell National Institute of Standards and Technology, Gaithersburg

1. What is it?

2. What can it do?

3. Summary

*https://www.nist.gov/srd/nist-standard-reference-database-100.

222

1. What is SESSA*?

SESSA can be used to simulate AES and XPS spectra of multilayer films and of

nanostructures such as islands, lines, spheres, and layered spheres on

surfaces. Users can specify the compositions and dimensions of each material

in the sample structure and the measurement configuration.

SESSA contains needed physical data: differential inverse inelastic mean free

paths, total inelastic mean free paths, differential elastic-scattering cross

sections, total elastic-scattering cross sections, transport cross sections,

photoionization cross sections, photoionization asymmetry parameters,

electron-impact ionization cross sections, photoelectron lineshapes, Auger-

electron lineshapes, fluorescence yields, and Auger-electron backscattering

factors.

SESSA can be operated through a graphical user interface (GUI) or through a

command line interface (CLI). The GUI enables a user to enter needed

information in an intuitive way (sample morphology, composition, dimensions,

instrument configuration, excitation source, spectrometer energy range) while

the CLI facilitates simulations for similar conditions (i.e., batch runs).

*https://www.nist.gov/srd/nist-standard-reference-database-100

3

GUI for a Planar Sample (C/SiO2/Si)

44

GUI for a Planar Sample (C/SiO2/Si)

55

GUI for Periodic Array of Cu Islands or Lines on a Si Substrate

666

GUI for Periodic Array of Au-core/C-shell Nanoparticles on a

Si Substrate

77

GUI for a Planar Sample (C/SiO2/Si): Peak Tab

8

GUI to Specify Excitation Source

GUI for Spectrometer: Specify Energy Range

999

GUI for Instrument Settings

10

GUI for Simulation [Example: Planar Sample (C/SiO2/Si)]

O 1s

C 1s Si 2s Si 2p

11

2. Examples of SESSA Applications

(a) Absolute Quantification of Surface Impurities on Layered Samples

Schematic of Multilayer Mirrors Used for Extreme Ultraviolet Lithography

XPS has been used to assess detect and quantify trace levels of surface

impurities on mirrors arising from outgassing of resists

We developed a procedure to quantify amounts of surface impurities rather than

assuming sample to be homogeneous and using instrumental software

N. S. Faradzhev, S. B. Hill, and C. J. Powell, Surf. Interface Anal. (in press);

DOI: 10.1002/sia.6289

(e.g., N, S, P, F, Cl, Br)

12

Comparison of Measured XPS Spectrum for a Multilayer Mirror Sample

(solid blue circles) and a Simulated Spectrum (solid red triangles) for

0.25 nm SiO2/0.25 nm CCl0.01/0.25 nm C/0.25 nm RuO2/3 nm Ru/4.3 nm Si/

3 nm Mo/Si


DOI: 10.1002/sia.6289

0

1

2

3

4

5

6

7

0100200300400500600700800

BB

Inte

nsity (

co

unts

x 1

0-5

)

Simulated Spectrum

Measured SpectrumRu

3d

Ru

3p

Ru

3s

O

1s

C

1s

13

Comparison of Measured XPS Spectrum for a Multilayer Mirror Sample

(solid blue circles) and a Simulated Spectrum (solid red triangles) for

0.25 nm SiO2/0.25 nm CCl0.01/0.25 nm C/0.25 nm RuO2/3 nm Ru/4.3 nm Si/

3 nm Mo/Si

Comparison of

measured and

simulated Cl 2p

intensities gives

a surface Cl

coverage of

0.20 ML (± 21 %)


DOI: 10.1002/sia.6289

0.0

0.2

0.4

0.6

0.8

050100150200250

BB

Inte

nsity (

counts

x 1

0-5

)

Binding Energy (eV)

Simulated Spectrum

Measured Spectrum

Ru

4sMo

3dCl

2p

Ru

4p

Si

2s

Si

2p

(b) Comparison of Simulated Cu 2p Spectra from Cu/Au Nanoparticles

We used SESSA to determine the Au-shell thicknesses that gave a selected

Cu 2p peak intensity for different Cu-core diameters

C. J. Powell, M. Chudzicki, W. S. M. Werner, and W. Smekal, J. Vac. Sci. Technol. A

33, 05E113 (2015).14

0.0

0.5

1.0

1.5

2.0

2.5

450 500 550

Spectrum 58Spectrum 56Spectrum 54Spectrum 52ASpectrum 60

Rela

tive I

nte

nsity

Electron Energy (eV)

Elastic scattering on

0.775 nm Au/10 nm Cu0.70 nm Au/5 nm Cu

0.475 nm Au/2 nm Cu0.255 nm Au/1 nm Cu0.085 nm Au/0.5 nm Cu

CuAu

15

We used SESSA to determine the Cu-shell thicknesses that gave a selected

Cu 2p peak intensity for different Au-core diameters


33, 05E113 (2015).15

0.0

0.5

1.0

1.5

2.0

2.5

450 500 550


Rela

tive I

nte

nsity



0.073 nm Cu/10 nm Au0.068 nm Cu/5 nm Au

0.060 nm Cu/2 nm Au0.050 nm Cu/1 nm Au0.050 nm Cu/0.5 nm Au

AuCu

16

We used SESSA to determine the Au-shell thicknesses that gave a selected

Cu 2p peak intensity from Au-core/1 nm Cu-shell/Au-shell nanoparticles for

different Au-core diameters


33, 05E113 (2015).

0.0

0.5

1.0

1.5

2.0

2.5

450 500 550


Rela

tive I

nte

nsity



0.51 nm Au/1 nm Cu/10 nm Au




0.34 nm Au/1 nm Cu/0.5 nm Au

AuAu

Cu

17

We used SESSA to determine the Au content of CuAux nanoparticles that gave

A selected Cu 2p intensity for different nanoparticle diameters


33, 05E113 (2015).

0.0

0.5

1.0

1.5

2.0

2.5

450 500 550


Rela

tive I

nte

nsity



d = 10 nm, x = 2.70

d = 5 nm, x = 2.60

d = 2 nm, x = 2.10

d = 1 nm, x = 1.32

d = 0.5 nm, x = 0.55

CuAux

18

(c) Validation of the Shard Formula for Determining Shell Thicknesses of

Core-Shell Nanoparticles.

We determined shell thicknesses, TNP, from the Shard formula using peak

intensities from SESSA simulations for (a) Au-core/C-shell, (b) C-core/Au-shell,

(c) Al-core/Cu-shell, and (d) Cu-core/Al-shell NPs and compared these values

with the corresponding true values, T, used in the simulations for different

Au-core diameters, D.

C. J. Powell, W. S. M. Werner, H. Kalbe, A. G. Shard, and D. G. Castner (to be published).

0.8

0.9

1.0

1.1

1.2

0 1 2 3

1 nm2 nm5 nm10 nm

TN

P/T

C-shell Thickness T (nm)

Au-core/C-shell NPs

D (nm)

19







0.8

0.9

1.0

1.1

1.2

0 1 2 3

1 nm2 nm5 nm10 nm

TN

P/T

Au-shell Thickness T (nm)

C-core/Au-shell NPs D (nm)

20







0.8

0.9

1.0

1.1

1.2

0 1 2 3

1 nm2 nm5 nm10 nm

TN

P/T

Cu-shell Thickness T (nm)

Al-core/Cu-shell NPs D (nm)

21







0.8

0.9

1.0

1.1

1.2

0 1 2 3

1 nm2 nm5 nm10 nm

TN

P/T

Al-shell Thickness T (nm)

Cu-core/Al-shell NPs D (nm)

22

3. Summary

SESSA* is a NIST database that contains extensive data for

quantitative AES and XPS

SESSA can be used to simulate AES and XPS spectra for

multilayer thin films and of nanostructures such as islands, lines,

spheres, and layered spheres on surfaces.

Users can specify the compositions and dimensions of each

material in the sample and the measurement configuration.

*https://www.nist.gov/srd/nist-standard-reference-database-100

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