basic principles of x-ray reflectivity in thin films - felix jimenez-villacorta [compatibility...
TRANSCRIPT
-
7/28/2019 Basic Principles of X-ray Reflectivity in Thin Films - Felix Jimenez-Villacorta [Compatibility Mode].pdf
1/12
BasicPrinciples
of
X
ray
ReflectivityinThinFilms
FlixJimnezVillacorta
02-24-2011
-
7/28/2019 Basic Principles of X-ray Reflectivity in Thin Films - Felix Jimenez-Villacorta [Compatibility Mode].pdf
2/12
Outline
Xraydiffraction
Xraydiffractioninthinfilms:highanglevslowangle
XRR
as
structural
characterization Diffusescattering:specularvsoffspecular
reflectivity
Summary
-
7/28/2019 Basic Principles of X-ray Reflectivity in Thin Films - Felix Jimenez-Villacorta [Compatibility Mode].pdf
3/12
William Lawrence Bragg
William Henry Bragg
-
7/28/2019 Basic Principles of X-ray Reflectivity in Thin Films - Felix Jimenez-Villacorta [Compatibility Mode].pdf
4/12
Xray
diffraction
Bragg slaw:anglewhere
constructiveinterferenceofscatteredXraysproducesadiffractionpeak:
n =BC+CD=2dhklsinwhered
hklisthevectordrawnfrom
theoriginoftheunitcelltointersectthecrystallographicplane.
-
7/28/2019 Basic Principles of X-ray Reflectivity in Thin Films - Felix Jimenez-Villacorta [Compatibility Mode].pdf
5/12
Highangle
vs
Low
angleProbing ranges in x-ray
diffraction on thin filmsn = 2dsin = 2dhklsin n = 2tsin
~ 1/d
2=
k i k fQ
2=
k i k fQ
k (incident)
k(diffracted)
Q
d
High (high Q) = Lowd Low (lowQ) = High d
-
7/28/2019 Basic Principles of X-ray Reflectivity in Thin Films - Felix Jimenez-Villacorta [Compatibility Mode].pdf
6/12
Xray
Reflectivity
0 1 2 3 41E-6
1E-4
0,01
1
2c
2
m2
Log(Reflectivity)
Grazing incidence (degree)
8 nm
15 nm
0 20 40 60 80
0,000
0,001
0,002
W (8 nm) // Si
(/2d)2
2
222
2
=
dmc
44
22 116)(
zyx
z
el
qqq
qQR =
Reflectivity
(background)
Ateveryinterface,aportionofxraysisreflected.Interferenceofthesepartialyreflectedxraybeamscreatesareflectometrypattern.
Kiessigfringes
-
7/28/2019 Basic Principles of X-ray Reflectivity in Thin Films - Felix Jimenez-Villacorta [Compatibility Mode].pdf
7/12
Xray
Reflectivity
0 1 2 3 4
1E-7
1E-6
1E-5
1E-4
1E-3
0.01
0.1
1
10
Grazing incidence angle (degree)
Log(Reflectivity)
CoSi2(15 nm) // Si
* Flat surface Vacuum/CoSi2
=0
* Rough interface CoSi
2/Si
no roughness
5A
10 A
Xrayreflectivitycanbeusedfor: Layerthicknessofthinfilmsandmultilayers. Surfaceandinterfaceroughness. Surfacedensitygradientsandlayerdensity.
-
7/28/2019 Basic Principles of X-ray Reflectivity in Thin Films - Felix Jimenez-Villacorta [Compatibility Mode].pdf
8/12
Xray
Reflectivity
Special case: bilayers and multilayers
Bilayer:2oscillationfrequenciesareevidenced
0 1 2 3
1E-6
1E-5
1E-4
1E-3
0.01
0.1
1
10
Grazing incidence (degree)
Log(Reflectivit
y)
CuO2 (5,5 nm) // Cu (45 nm) // Si
Cu
thickness
CuO2thickness
Multilayer:n1Kiessigfringesbetween2BraggPeaks
1 2 310
100
1000
10000
100000
Intensity(c.p.s.)
2-Theta
CoSN2
-
7/28/2019 Basic Principles of X-ray Reflectivity in Thin Films - Felix Jimenez-Villacorta [Compatibility Mode].pdf
9/12
Diffusescattering
Specular vs off-specular reflectivity
Specularcontributionofthediffusescattering Sameoscillationsthanreflectivitycurve
Longitudinaldiffusescattering
-
7/28/2019 Basic Principles of X-ray Reflectivity in Thin Films - Felix Jimenez-Villacorta [Compatibility Mode].pdf
10/12
Diffusescattering
0 1 2 3 4 5
10
100
1000
10000
100000
1000000
Intensity
2 theta ()
XRR specular
long. diff (=0.05)
long. diff (=0.1)
Off Specular XRR - (s2 - Au Cold)
0 1 2 3 4 5
10
100
1000
10000
100000
1000000
Off Specular XRR - (s6 - Au Hot)
Intensity
2 theta
XRR specular
long. diff. (=0.05)
long. diff. (=0.1)
Longitudinaldiffusescattering
FeRhthinfilms+cap
Um+1(x,y)
Um (x,y)
Um (x,y)hm
ideal
zm+1
zm
Q qzQ = qz
-
7/28/2019 Basic Principles of X-ray Reflectivity in Thin Films - Felix Jimenez-Villacorta [Compatibility Mode].pdf
11/12
Diffusescattering
Transversediffusescan(rockingcurve)
0 1 2
Log[
Intensity
(arb.
units)]
scan
=7000 A=2000 A=500 A
Yoneda Wingsc c
Specular
Various : Large lateral correlation at interfaceSpecular peak
Yoneda wings : each time iorf=c
-
7/28/2019 Basic Principles of X-ray Reflectivity in Thin Films - Felix Jimenez-Villacorta [Compatibility Mode].pdf
12/12
Summary
Ateveryinterface,aportionofxraysisreflected.Interferenceofthesepartialyreflectedxraybeamscreatesareflectometrypattern.
Xrayreflectivityisausefultechinqueforstructural
characterization
of
thin
films.
Information
about
the
thickness
andtheroughnessofsuchsamplescanbeobtained.
Diffusescatteringofxraysgivealsoinformationabouttheroughness,correlationlength(fractalparameters)insurfaces
andinterfaces.