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Atomic hydrogen adsorption behavior of boron nitride nanomaterial
Outline
1. Introduction
2. Sample preparation & Deuteration.
3. TOF
4. NEXAFS- Experiment & Calculation.
5. XPS-Experiment & Calculation.
6. PSID.
7. Why H/D prefers to adsorb on B site ?
Kaveenga Rasika Koswattage (PhD) Senior Lecture
Faculty of Applied Science,
Sabaragamuwa University
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Transportation Fuel cell power technology Renewable
Sustainable
Light-duty vehicles
Light storage system
Introduction
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CNT BNNT
US DOE on board hydrogen system has proposed to achieve 5 wt % hydrogen storage by
Introduction
C-H
Hydrogenation degree
= 0.370.05
A. Nikitin et al., Surf. Sci. 602,
2575 (2008).
C 1s XPS
Bending of C–H
bonds
H adsorbed on
neighbor carbon
Hydrogen adsorption on BN is site selective
H
B N
Wu et al., J. Chem. Phys.
121, 8481 (2003).
V.A Margulis et al.,
springer , 275 (2007).
Graphite
Hydrogenation on BNNT > CNT Ex: R. Ma et al., J. Am. Chem.
Soc. 124 , 7672 (2002).
H atom prefers
to adsorb on the
top site of the B
H atom prefers
to adsorb on the
top site of the N
Two hydrogen atoms adsorbed on-top sites
of adjacent B and N atoms Z. Zhou et al., J. Phys. Chem. B
110, 13363 (2002).
Hydrogenation was examined using thin film of h-BN 3
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Ni(111)
substrate
·lattice constant
·atomic distance
lattice
matching
h-BN 2.51 Å
Ni(111) 2.49Å -0.4 %
Pd(111) 2.76Å 10 %
Pt(111) 2.89Å 15.2 %
Borazine
(B3N3H6)
N N B
B B
H
H H
H
H
H N
Ni(111) ~800 ℃
Precursor gas Nagashima et al., Phys.
Rev. B 51, 4606 (1995).
BN film on Ni(111) substrate
Chemical Vapor Deposition
Thin film of h-BN on a Ni(111) substrate was selected for the investigation
W. Auwarter et al., Surf. Sci.,
429, 229 (1999). h-BN on a Ni(111)
Well ordered Highly commensurate Perfect lattice match
C 1s VB
0 100 200 300 400 500
0
500
1000
1500
2000
Inte
nsi
ty /
cps
Binding Energy / eV
Ni 3s
Ni 3p
B 1s
N KLL Auger
N 1s
B KLL Auger
hν = 695 eV
Fig. XPS after formation of BN film on Ni(111)
Thickness of the BN film was estimated to be 6.6 Å 4
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5
Photon Factory- High Energy Accelerator Research Organization (KEK), Japan
Experiment using Synchrotron Radiation
Beam line 11-A
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F
BK EhE
X-ray Photoelectron spectroscopy (XPS)
(a). XPS spectra of clean HOPG
(b). H treated HOPG with H saturated coverage
A. Nikitin et al., Surf. Sci. 602, 2575 (2008).
(a)clean HOPG
(b).H treated
HOPG
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180 188 196 204 212 220 228
Vacuum
*
Core level
σ*
Unoccupied
levels
Excitation
Energy
Photon Energy / eV
Ab
sorp
tion I
nte
nsi
ty
Synchrotron
Radiation
*
σ*
Photon Energy (eV)
Ab
sorp
tion
in
ten
sity
(ar
b. un
its.
)
NEXAFS
σ*
*
(a) (b)
Continuum States
Eπ*
Eσ*
IP
IP
FL
ValenceBand σ*
(b). A typical B – Kedge NEXAFS spectrum of
bulk h-BN which shows two features, π* and σ*.
(a). Schematic representation of the processes involved in NEXAFS for unsaturated
compounds with double or triple bonds.
Near-edge X-ray absorption fine structure (NEXAFS)
I. Shimoyama et al., J. Elec. Spec. Relat. Phenom.
137, 573 (2004).
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Grazing incidence : Enhancement of 1s *
Normal incidence : Enhancement of 1s σ *
E
G razing
incidence
N ormal
incidence
N
G
* s *
O
O s
E
π orbital
σ orbital
E
sp2
θ=20º
θ=90º
Polarization dependence -NEXAFS
C K-edge NEXAFS spectra of single-crystal
graphite at various incident angles (θ )
R.A. Rosenberg et al., Phys.
Rev. B 33, 4034 (1986).
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② NEXAFS
Au mesh
試 I(h)
①XPS
I0 (h)
Synchrotron
radiation ring
A
A
hν=700 eV
Hot filament system
X-ray gun
QMS
Analyzer
Ion gun
Hot
filament
system
Ultra high vacuum chamber
Base pressure of the UHV chamber was ~8×10-8 Pa
Experimental
I(h)
I0 (h)
All the experiments were
performed at the BL-11A beam
line of the Photon Factory. BN/Ni(111)
07.0 A
10.0 V 9
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NEXAFS -Spectral change by atomic deuterium treatment
400 410 420 430 440In
ten
sity
(arb
. u
nit
)
N K-edge
Photon Energy / eV
Before
After
188 192 196 200 204
Inte
nsi
ty (
arb
. u
nit
)
B K-edge
Photon Energy / eV
π*B
π*A σ* Before
After
Experimental results-NEXAFS
Interaction change between
film and substrate by
deuterium adsorption
1.Formation of B-D bond or
2. Interaction change between film and
substrate by deuterium adsorption or
3.Resultant of these two phenomena. 10
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Spectral change between π*A
and σ*showing similar
polarization dependence like
π*A & π*B .
185 190 195 200 205 210
Inte
nsit
y (
arb
. u
ni )
Photon Energy / eV
angle ( ) = 20
angle ( ) = 35
angle ( ) = 55
B
D
Out of plane orientation – B-D bonds are perpendicular to the surface
Out of plane orientation was used for DV-Xα calculation
Spectral change between π*A & σ*
Formation of B-D bond
E SR
Polarization dependence NEXAFS
Before
After
Before
After
Before
After
B K-edge
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BN film- B27N27H18
Unoccupied
states
Vacuum
π*
σ* 0.5
0.5
One H on B site
One H on N site
Two H on adjacent B&N site
DV-Xα Calculation
Slater’s transition theory
☆Minimal basis set :
•2s & 2p for B&N
•1s for H
▲Model clusters :
optimization :
Win MOPAC / AM1
Model clusters Calculation method
B
N
H
( A molecular orbital calculation method)
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1. One H attached to B site
DV-Xα Calculation- NEXAFS
B 1s to LUMO
π* σ*
B-Without H
B-With H
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N-With H
N-Without H
2. One H attached to N site N 1s to LUMO
π* σ*
DV-Xα Calculation- NEXAFS
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XPS-Spectral change by atomic deuterium treatment
188 190 192 1940
1
2
3
4
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Additional component appeared at low BE
Before
After
B 1s
396 398 400 4020
1
2
3
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Broadening to high BE
Before
After
N 1s
Experimental results-XPS
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188 190 192 1940
1
2
3
4
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Before
After
B 1s
396 398 400 4020
1
2
3
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Before
After
N 1s
XPS calculation
XPS-Spectral change by atomic deuterium treatment
Cluster
Chemical shift ( eV)
Hydrogenated sites Neighboring sites
B 1s N 1s B 1s N 1s
B27N27H18+HB -0.7 N/A N/A -0.4
B27N27H18+HN N/A +2.2 -2.0 N/A
B27N27H18+2HBN -1.6 +2.2 N/A N/A
DV-Xα Calculation- XPS
B-D
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187 188 189 190 191 192 193 194 195
Binding Energy / eV
Inte
nsit
y (
arb
. u
ni )
BD
A
A* Rtop
Degree of deuteration was estimated to be 29 % considering only B site.
NEXAFS and XPS results imply that atomic deuterium adsorption
occurred on B site more preferentially than on N site
,100 topD
D
RAB
B
Degree of deuteration (%) =
Degree of deuteration
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Deuterium ion
X-ray
(N excitation)
X-ray
(B excitation)
Why PSID ?
NEXAFS and XPS spectroscopic methods are not considered to
be methods of directly detecting hydrogen from the surface
Photon stimulated ion desorption ( PSID)
PSID can be employed to study hydrogen adsorption sites on a BN film
Time of flight mass spectrometer
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PSID yield () spectra for D+ ion
Clear increase at the B
K-edge
0
40
80
120
160
184 188 192 196
395 400 405 410
B
Photon Energy / eV
N
D+
des
orp
tio
n y
ield
(
arb
. u
nit
)
Electron excited to
* state
B-D anti bonding
state
does not show clear increase in the N K-edge
N sites adsorbed by deuterium was smaller than B 19
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Why H/D prefers to adsorb on B site ??
Explanation is based on the frontier orbital theory
0.00
0.05
0.10
0.15
0.20
0.25
-20 -10 0 10 20
P
DO
S o
f B
Ground state
Energy / eV
B site
H
1st H atom
0.0
0.1
0.2
0.3 N 2s
N 2p
-20 -10 0 10 20
PD
OS
of
N
Energy / eV
N site
π* σ* π* σ* B site- without H N site- without H
Wu et el J. Chem. Phys.,
121 (17), 8481 (2003).
H atom chemisorbs
on the BN
The HOMO of H interacts
with the LUMO of the BN
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H
2nd H atom
H attached to B –Neighboring B&N
Neighboring B site
Ground state
Neighboring N site
Neighboring N site
Neighboring B site
-20 -10 0 10 200.0
0.1
0.2
0.3
Energy / eV
N 2s
N 2p
N P
DO
S
0.0
0.1
0.2
0.3
B P
DO
S
B 2s
B 2p
Why H/D prefers to adsorb on B site ??
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2H attached to adjacent B&N Zohu et al : Most stable
configuration
NEXAFS calculation : PDOS of B1s/N1s to LUMO transition
Clear spectral change in π* observed for B and N sites 22
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The hydrogenation properties of a h-BN thin film were investigated
as a model material of BN nanomaterials for chemisorption-based
hydrogen adsorption.
The degree of the deuteration was estimated to be 29 % from the
spectral change of the B 1s XPS spectra.
The XPS and NEXAFS spectra of h-BN on Ni(111) were interpreted
using the DV-Xα method, considering the core-hole effect.
The results for the B and N sites implied that deuteration mainly
occurs on B sites. The PSID results support the idea that B sites of BN
are preferentially adsorbed by atomic deuterium
Finally, I concluded that atomic hydrogen is preferentially adsorbed
on B sites in a single hydrogen adsorption mechanism on BN material.
Summary
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Selective adsorption of atomic hydrogen
on a h-BN thin film
Outline
1. Introduction
2. Sample preparation & Deuteration.
3. TOF
4. NEXAFS- Experiment & Calculation.
5. XPS-Experiment & Calculation.
6. PSID.
7. Why H/D prefers to adsorb on B site ?
Kaveenga Rasika Koswattage
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the "forever fuel" that we can never run out of
HYDROGEN
It’s abundant, clean, efficient, and can be derived from diverse domestic resources.
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Light-duty vehicles
Light storage system
Storing hydrogen in light storage system is required Materials at nano scale
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Carbon nanotubes (CNTs) are allotropes of
carbon(同素异形体)(graphite 石墨,diamond钻石, Fullerene)with a cylindrical
nanostructure. Nanotubes have been
constructed with length-to-diameter ratio of
up to 28,000,000:1,which is significantly
larger than any other material.
Discovered in 1991 by the Japanese electron microscopist Sumio Iijima.
Carbon nanotubes
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(a) (b)
Crystal structures: (a). Hexagonal boron nitride (h-BN) (b). Graphite.
Boron nitride (BN) nanomaterials
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Transportation Fuel cell power technology Renewable
Sustainable
Light-duty vehicles
Light storage system
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CNT
US DOE on board hydrogen system has proposed to achieve 5 wt % hydrogen storage by
Introduction
H2 H2
H2 H2 H2 H H
H H H
Quality of the sample problems
Contamination
Defects
Diameter dependence.
Single wall /Multi wall
1996 1998 2000 2002 2004 2006 2008
0.01
0.1
1
10
SW-CNT- Physisorption BNNT- Physisortption .
SW-CNT- Chemisorption
Hyd
rogen
up
tak
e /
wt%
Year
DOE target
Hydrogenation by ,
chemisorption >
physisorption
Nikitin et al. Nano
Letters, 8, 162 (2008).
Physisorption Chemisorption
Reported hydrogen uptakes …..
BNNT One of the
promising
candidates
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Volumetric and gravimetric hydrogen density of some selected hydrides.
Hydrogenation by chemisorption > physisorption
A. Zuttel et al, Phil. Trans. R. Soc. A 368, 3329 (2010)
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For graphite
Hydrogenation degree at saturation coverage of atomic hydrogen
adsorption and desorption of hydrogen as a function of temperature were
reported.
Formation of C-H bonds at the surface under atomic hydrogen treatment
employing X-ray photoelectron spectroscopy (XPS) was reported.
A. Nikitin et al, Ruffieux et al C-H
Hydrogenation
degree = 0.370.05
Saturation coverage of atomic hydrogen adsorption values estimated by
XPS and other techniques ( TDS) are coincides .
T. Zecho et al , A. Nikitin et al.
C-H
H adsorbed on neighbor carbon
bending of C–H bonds
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2. Hydrogen adsorption on BN is site selective
BN nano-materials
This suggestion/coverage for hydrogen adsorption has not been
experimentally verified
1. Hydrogenation on BNNT > CNT Ex: R. Ma et al ,J. Am. Chem.
Soc. 124 (26) ,7672 (2002).
H
B N
Wu et al., J. Chem. Phys.
121, 8481 (2003).
V.A Margulis et al.,
springer , 275 (2007).
H atom prefers
to adsorb on the
top site of the B
H atom prefers
to adsorb on the
top site of the N
Two hydrogen atoms adsorbed on-top sites
of adjacent B and N atoms Z. Zhou et al., J. Phys. Chem. B
110, 13363 (2002).
Hydrogenation was examined using thin film of h-BN
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Ni(111)
substrate
·lattice constant
·atomic distance
lattice
matching
h-BN 2.51 Å
Ni(111) 2.49Å -0.4 %
Pd(111) 2.76Å 10 %
Pt(111) 2.89Å 15.2 %
Borazine
(B3N3H6)
N N B
B B
H
H H
H
H
H N
Ni(111) ~800 ℃
Precursor gas
Well ordered
Highly commensurate
Perfect lattice match
BN film on Ni(111) substrate
Chemical Vapor Deposition
Thin film of h-BN on a Ni(111) substrate was selected for the investigation
h-BN on a Ni(111)
pressure of
1×10-4 Pa
W. Auwarter et al., Surf. Sci.,
429, 229 (1999).
Nagashima et al., Phys.
Rev. B 51, 4606 (1995).
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F
BK EhE
X-ray Photoelectron spectroscopy (XPS)
XPS spectra of clean HOPG (a) and H treated
HOPG with H saturated coverage (b).
A. Nikitin et al., Surf. Sci. 602, 2575 (2008).
(a)clean HOPG
(b).H treated
HOPG
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180 188 196 204 212 220 228
Vacuum
*
Core level
σ*
Unoccupied
levels
Excitation
Energy
Photon Energy / eV
Ab
sorp
tion I
nte
nsi
ty
Synchrotron
Radiation
*
σ*
Photon Energy (eV)
Ab
sorp
tion
in
ten
sity
(ar
b. un
its.
)
NEXAFS
σ*
*
(a) (b)
Continuum States
Eπ*
Eσ*
IP
IP
FL
ValenceBand σ*
(b). A typical B – Kedge NEXAFS spectrum of
bulk h-BN which shows two features, π* and σ*.
(a). Schematic representation of the processes involved in NEXAFS for unsaturated
compounds with double or triple bonds.
Near-edge X-ray absorption fine structure (NEXAFS)
I. Shimoyama et al., J. Elec. Spec. Relat. Phenom.
137, 573 (2004).
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Grazing incidence : Enhancement of 1s *
Normal incidence : Enhancement of 1s σ *
E
G razing
incidence
N ormal
incidence
N
G
* s *
O
O s
E
π orbital
σ orbital
E
sp2
θ=20º
θ=90º
Polarization dependence -NEXAFS
C K-edge NEXAFS spectra of single-crystal
graphite at various incident angles (θ )
R.A. Rosenberg et al., Phys.
Rev. B 33, 4034 (1986).
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X-ray gun
QMS
Analyzer
Ion gun
Hot filament
system
Ultra high vacuum chamber
Base pressure of the UHV chamber was ~8×10-8 Pa
Experimental
All the experiments were performed at the BL-11A beam line of the Photon Factory.
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QMS
Ion gun
Hot filament system
XPS-
analyzer
Manipulator
SR
I0 Monitor
(Au mesh)
Experimental chamber set up for the experiment at the BL-11A
Bending magnet beamline
Energy range of 70 eV – 1900 eV
Max. photon flux of 1012 photons/sec
Resolving power 500 - 4000
Experimental
BL- 11A at KEK-PF
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Ni(111)
STEP 1. Ar+ sputtering-
{Ni(111) substrate}
STEP 2. Heated Ni(111) substrate to ~800 ℃
STEP 3.
Introducing borazine
Borazine (B3N3H6)
N N B
B B
H
H H
H
H
H N
Sample preparation
Chemical Vapor Deposition
pressure of
1×10-4 Pa
Nagashima et al., Phys. Rev. B 51, 4606 (1995).
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Hot filament system
BN/Ni(111)
07.0 A
10.0 V
2 3 4 5 6 7 8
800
1000
1200
1400
1600
1800
2000
T
emper
ature
/ C
Current / A
Degree of dissociation of a hot filament
system as a function of temperature Filament temperature as a function of current
C. Eibl et al, J. Vac. Sci. Technol. A 16, 2979 (1998).
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2. NEXAFS
Au mesh
I(h)
1. XPS
I0 (h)
Synchrotron
radiation ring
A
A
hν=700 eV
I(h)
I0 (h)
Spectroscopic measurements…………..
Schematic diagram of the
experimental arrangement
for ion TOF measurements
CFD
MCA
Pre-AMP
TAC 1/312
Divider
RF cavity
( 500 MHz) AMP
STOP
START
3. TOF
Experimental
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Thin film of BN on Ni(111)
Ni (111)
BN thin film
IN1s IB1s
INi3s
t
Composition ratio & Thickness
0
500
hv = 192.1 ,
H+
D +
0
D +
H+
Sample annealed
at 200 C Supposed to
be due to
water
hν =
192.1 eV
sN
sB
sB
sN
I
I
hν
hν
N
B
1
1
1s1B
1s1N
)(
)(
][
][
s
s
)/exp(
)/exp(1
)(
)(
BNin 3s Ni
BNin 1s B
Ni
B
Niin 3s Ni
BNin 1s B
3s Ni
1s B
3s Ni
1s B
s
s
t
t
n
n
hν
hν
I
I
XPS spectrum of as-deposited
BN film on Ni(111)
Equations for estimation of Composition ratio & Thickness
Thickness of the BN film was estimated to be 6.6 Å
[B]/[N] was estimated to be 0.98
C 1s
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Sample annealed at 200 C
TOF spectrum after deuterium treatment
Supposed to be
due to water
hν = 192.1 eV
After deuterium treatment
K.R. Koswattage et al., J. Chem. Phys., 135, 014706 (2011).
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NEXAFS -Spectral change by atomic deuterium treatment
400 410 420 430 440In
ten
sity
(arb
. u
nit
)
N K-edge
Photon Energy / eV
Before
After
188 192 196 200 204
Inte
nsi
ty (
arb
. u
nit
)
B K-edge
Photon Energy / eV
π*B
π*A σ* Before
After
Experimental results-NEXAFS
Interaction change between
film and substrate by
deuterium adsorption
1.Formation of B-D bond or
2. Interaction change between film and
substrate by deuterium adsorption or
3.Resultant of these two phenomena.
K.R. Koswattage et al., J. Chem. Phys., 135, 014706 (2011).
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Spectral change between π*A
and σ*showing similar
polarization dependence like
π*A & π*B .
185 190 195 200 205 210
Inte
nsit
y (
arb
. u
ni )
Photon Energy / eV
angle ( ) = 20
angle ( ) = 35
angle ( ) = 55
B
D
out of plane orientation – B-D bonds are perpendicular to the surface
out of plane orientation was used for DV-Xαcalculation
Spectral change between π*A & σ*
Formation of B-D bond
E SR
Polarization dependence NEXAFS
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BN film- B27N27H18
Unoccupied
states
Vacuum
π*
σ* 0.5
0.5
One H on B site
One H on N site
Two H on adjacent B&N site
DV-Xα Calculation
Slater’s transition theory
☆Minimal basis set :
•2s & 2p for B&N
•1s for H
▲Model clusters :
optimization :
Win MOPAC / AM1
Model clusters Calculation method
( A molecular orbital calculation method)
B
N
H
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1. One H attached to B site
DV-Xα Calculation- NEXAFS
B 1s to LUMO
π* σ*
B-Without H
B-With H
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N-With H
N-Without H
2. One H attached to N site N 1s to LUMO
π* σ*
DV-Xα Calculation- NEXAFS
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3. One H attached to B site-Neighbouring B and N
Neighbouring B
Neighbouring N
DV-Xα Calculation- NEXAFS
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4. One H attached to N site-Neighbouring B and N
Excitation Energy / eV
Excitation Energy / eV
188 192 196 200 204 208
400 404 408 412
Inte
nsi
ty (
arb
. u
nits
) B 2p
B 2s
N 2p
N 2s
Neighbouring B
Neighbouring N
DV-Xα Calculation- NEXAFS
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Cluster dependence B
N
H
B48N48H24
B12N12H12
DV-Xα Calculation- NEXAFS
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B48N48H24 B12N12H12
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XPS-Spectral change by atomic deuterium treatment
188 190 192 1940
1
2
3
4
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Additional component appeared at low BE
Before
After
B 1s
396 398 400 4020
1
2
3
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Broadening to high BE
Before
After
N 1s
Experimental results-XPS
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Cluster
Chemical shift ( eV)
Hydrogenated sites Neighboring sites
B 1s N 1s B 1s N 1s
B27N27H18+HB -0.7 N/A N/A -0.4
B27N27H18+HN N/A +2.2 -2.0 N/A
B27N27H18+2HBN -1.6 +2.2 N/A N/A
DV-Xα Calculation- XPS
188 190 192 1940
1
2
3
4
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Before
After
B 1s
396 398 400 4020
1
2
3
Inte
nsi
ty (
arb
. u
nit
)
Binding Energy / eV
Before
After
N 1s
XPS calculation
XPS-Spectral change by atomic deuterium treatment
B-D
NEXAFS and XPS results imply that atomic deuterium
adsorption occurred on B site more preferentially than on N site
187 188 189 190 191 192 193 194 195
Binding Energy / eV
Inte
ns
ity
( a
rb .
un
i )
BD
A
A* Rtop
Degree of deuteration was estimated to be 29 % considering only B site.
,100 topD
D
RAB
B
Degree of deuteration (%) =
Degree of deuteration
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Deuterium ion
X-ray
(N excitation)
X-ray
(B excitation)
Why PSID ?
NEXAFS and XPS spectroscopic methods are not considered to
be methods of directly detecting hydrogen from the surface
Photon stimulated ion desorption ( PSID)
PSID can be employed to study hydrogen adsorption sites on a BN film
Time of flight mass spectrometer
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Single bunch
SR
PF- Storage
ring
CFD
MCA
Pre-AMP
TAC 1/312
Divider
RF cavity
( 500 MHz)
AMP
STOP
START
TOF-MS measurement system
Schematic diagram of the experimental arrangement for ion TOF measurements
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PSID yield () spectra for D+ ion
Clear increase at the B
K-edge
0
40
80
120
160
184 188 192 196
395 400 405 410
B
Photon Energy / eV
N
D+
des
orp
tio
n y
ield
(
arb
. u
nit
)
Electron excited to
* state
B-D anti bonding
state
does not show clear increase in the N K-edge
N sites adsorbed by deuterium was smaller than B
K.R. Koswattage et al., J. Appl. Surf. Sci., 258, 1561 (2011).
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Why H/D prefers to adsorb on B site ??
Explanation is based on the frontier orbital theory
0.00
0.05
0.10
0.15
0.20
0.25
-20 -10 0 10 20
P
DO
S o
f B
Ground state
Energy / eV
B site
H
1st H atom
0.0
0.1
0.2
0.3 N 2s
N 2p
-20 -10 0 10 20
PD
OS
of
N
Energy / eV
N site
π* σ* π* σ* B site- without H N site- without H
Wu et el J. Chem. Phys.,
121 (17), 8481 (2003).
H atom chemisorbs
on the BN
The HOMO of H interacts
with the LUMO of the BN
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H
2nd H atom
H attached to B –Neighboring B&N
Neighboring B site
Ground state
Neighboring N site
Neighboring N site
Neighboring B site
-20 -10 0 10 200.0
0.1
0.2
0.3
Energy / eV
N 2s
N 2p
N P
DO
S
0.0
0.1
0.2
0.3
B P
DO
S
B 2s
B 2p
Why H/D prefers to adsorb on B site ??
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2H attached to adjacent B&N Zohu et al : Most stable
configuration
NEXAFS calculation : PDOS of B1s/N1s to LUMO transition
Clear spectral change in π* observed for B and N sites
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The hydrogenation properties of a h-BN thin film were investigated
as a model material of BN nanomaterials for chemisorption-based
hydrogen adsorption.
The degree of the deuteration was estimated to be 29 % from the
spectral change of the B 1s XPS spectra.
The XPS and NEXAFS spectra of h-BN on Ni(111) were interpreted
using the DV-Xα method, considering the core-hole effect.
The results for the B and N sites implied that deuteration mainly
occurs on B sites. The PSID results support the idea that B sites of BN
are preferentially adsorbed by atomic deuterium
Finally, I concluded that atomic hydrogen is preferentially adsorbed
on B sites in a single hydrogen adsorption mechanism on BN material.
Summary
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6th International conference of DV-Xα was held in Korea .
Awarded best research in poster and oral section.