Cornell X-ray Experiment Details - University of Chicago...Cathode 1: K-Sb deposition on Si...
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Cornell X-ray Experiment Details
Transcript of Cornell X-ray Experiment Details - University of Chicago...Cathode 1: K-Sb deposition on Si...
Cornell X-ray Experiment Details
Unload the chamber
Source holder in detail Front view
Backside view, Connections
Sb
K
Cs
Picture was taken before the change, sources are from previous run, Sb bead was used already.
Chamber inside in detail
QCM, directly attached on sample holder, no water cooling
Movable anode, also served as source blocker
Sample holder
RF graphene evaporator
Chamber inside in detail
RF graphene evaporator
Source exchange
Sb sources wired on copper pins and inserted in to holes to be fixed on the holder.
K, Cs sources, clamped at both sides and bended to insert into the holder
The two holes, made of macor tubes
Source company- Cs, K Phase diagram (Bi-Cs)
Alkali and alkali earth metals form many stable, high melting intermetallic compounds with nontoxic metals (bismuth).
s
http://www.alvatec.com/products/
GISAXS: Grazing Incidence Small Angle X-ray Scattering XRR: X-ray Reflectivity
GIXRD: Grazing Incidence X-ray Diffraction
In XRR scan, incidence angle (αi) = exit angle (αf), scan range: 0 - 4o In GISAXS and GIXRD, αi =1.8o, fringes due to x-ray scattering was recorded.
X-ray Techniques used for Bi-alkali Photocathode Study
Experiment performed at: NSLS X21 (BNL) & CHESS G3 (Cornell)
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CHESS Cathode Growth Process (Yo-Yo)
9 Silicon Substrate (p-type)
Sb (5 nm) (150 oC)
K (15 nm) (150 oC)
Cs (100 nm) (150 oC)
Sb (5 nm) (150 oC)
K (50 nm) (150 oC)
Silicon Substrate (p-type)
Sb (5 nm) (25 oC)
K (16 nm) (150 oC)
Cs (6 nm) (150 oC)
Sb (6 nm) (25 oC)
K (53 nm) (150 oC)
Cs (26 nm) (150 oC)
Sb (3 nm) (25 oC)
B33 Glass Substrate
Sb (5 nm) (25 oC)
K (16 nm) (150 oC)
Cs (6 nm) (150 oC)
Sb (6 nm) (25 oC)
K (53 nm) (150 oC)
Cs (26 nm) (150 oC)
Sb (3 nm) (25 oC)
Cathode 2 Cathode 3 Cathode 1
Sb, K, Cs deposited at 150 oC Sb deposited at Room Temperature, K & Cs at 150 oC
* All thicknesses are from QCM estimation, the K,
Cs deposition thicknesses are determined by QE
Cathode 1: K-Sb deposition on Si substrate
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X-ray reflectivity Electron density profile
αi (degree)
I (a.
u.)
Thickness (Å)
ρ p
rofi
le (
Å-3
)
0 0.5 1 1.5 2 2.5 3 3.5 410
-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
Inte
nsity (
a.u
.)
Angle (deg)
-30 -20 -10 0 10 20 30 40 50 60 700
0.2
0.4
0.6
0.8
1
1.2
1.4
depth (A)
ele
ctr
on d
ensity (
A-3
)
0 0.5 1 1.5 2 2.5 310
-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
Inte
nsity (
a.u
.)
Angle (deg)
-50 0 50 100 150 200 2500
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
depth (A)
ele
ctr
on d
ensity (
A-3
)
Silicon Substrate (p-type)
Sb (5 nm) (150 oC)
Silicon Substrate (p-type)
Sb (5 nm) (150 oC)
K (15 nm) (150 oC)
Uniform KxSb on Si
0 0.5 1 1.5 2 2.5 310
-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
Inte
nsity (
a.u
.)
Angle (deg)-50 0 50 100 150 200 250 3000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
depth (A)
ele
ctr
on d
ensity (
A-3
)0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8
10-7
10-6
10-5
10-4
10-3
10-2
10-1
100
Inte
nsity (
a.u
.)
Angle (deg)
-100 0 100 200 300 400 500 600 7000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
depth (A)ele
ctr
on d
ensity (
A-3
)
Cathode 1: K-Sb deposition on Si substrate (continued)
X-ray reflectivity Electron density profile
αi (degree) Thickness (Å)
Uniform KxSb on Si
I (a.
u.)
ρ p
rofi
le (
Å-3
)
Silicon Substrate (p-type)
Sb (5 nm) (150 oC)
K (15 nm) (150 oC)
Sb (5 nm) (150 oC)
Silicon Substrate (p-type)
Sb (5 nm) (150 oC)
K (15 nm) (150 oC)
Sb (5 nm) (150 oC)
K (50 nm) (150 oC)
Uniform KxSb? Sb also diffuses in to the compound?
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Cathode 2: K-Sb deposition on Si substrate
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0 0.5 1 1.5 2 2.5 310
-6
10-4
10-2
100
102
104
Inte
nsity (
a.u
.)
Angle (deg)
-60 -40 -20 0 20 40 600
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
depth (A)
ele
ctr
on d
ensity (
A-3
)
0 0.5 1 1.5 2 2.5 3 3.5 410
-6
10-4
10-2
100
102
104
Inte
nsity (
a.u
.)
Angle (deg)
-50 0 50 1000
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
depth (A)
ele
ctr
on d
ensity (
A-3
)
0 0.5 1 1.5 2 2.5 3 3.5 410
-6
10-4
10-2
100
102
104
Inte
nsity (
a.u
.)
Angle (deg)
-50 0 50 100 1500
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
depth (A)
ele
ctr
on d
ensity (
A-3
)
X-ray reflectivity Electron density profile
αi (degree) I (
a.u
.)
Thickness (Å)
ρ p
rofi
le (
Å-3
)
Silicon Substrate (p-type)
Silicon Substrate (p-type)
Sb (5 nm) (25 oC)
Silicon Substrate (p-type)
Sb (5 nm) (25 oC)
K (16 nm) (150 oC)
Uniform KxSb on Si
0 0.5 1 1.5 2 2.5 310
-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
Inte
nsity (
a.u
.)
Angle (deg)
-50 0 50 100 150 200 2500
0.2
0.4
0.6
0.8
1
1.2
1.4
depth (A)
ele
ctr
on d
ensity (
A-3
)
Cathode 2: K-Sb deposition on Si substrate (continued)
X-ray reflectivity Electron density profile
αi (degree) Thickness (Å)
I (a.
u.)
ρ p
rofi
le (
Å-3
)
Silicon Substrate (p-type)
Sb (5 nm) (25 oC)
K (16 nm) (150 oC)
Sb (6 nm) (25 oC)
Silicon Substrate (p-type)
Sb (5 nm) (25 oC)
K (16 nm) (150 oC)
Sb (6 nm) (25 oC)
K (53 nm) (150 oC)
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 210
-6
10-5
10-4
10-3
10-2
10-1
100
Inte
nsity (
a.u
.)
Angle (deg)
-100 0 100 200 300 400 500 6000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
depth (A)
ele
ctr
on d
ensity (
A-3
)
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-60 -40 -20 0 20 40 600
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
depth (A)
ele
ctr
on d
ensity (
A-3
)
0 0.5 1 1.5 2 2.5 310
-6
10-4
10-2
100
102
104
Inte
nsity (
a.u
.)
Angle (deg)
Cathode 3: K-Sb deposition on B33 glass substrate
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X-ray reflectivity Electron density profile
αi (degree) I (
a.u
.)
Thickness (Å)
ρ p
rofi
le (
Å-3
)
0 0.5 1 1.5 2 2.5 3 3.5 410
-6
10-4
10-2
100
102
104
Inte
nsity (
a.u
.)
Angle (deg)
-60 -40 -20 0 20 40 60 80 1000
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
depth (A)
ele
ctr
on d
ensity (
A-3
)
0 0.5 1 1.5 2 2.5 3 3.5 410
-6
10-4
10-2
100
102
104
Inte
nsity (
a.u
.)
Angle (deg)
-100 -50 0 50 100 150 2000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
depth (A)
ele
ctr
on d
ensity (
A-3
)
Uniform KxSb on glass
B33 glass Substrate (p-type)
B33 glass Substrate
Sb (5 nm) (25 oC)
B33 glass Substrate
Sb (5 nm) (25 oC)
K (16 nm) (150 oC)
0 0.5 1 1.5 2 2.5 310
-7
10-6
10-5
10-4
10-3
10-2
10-1
100
101
Inte
nsity (
a.u
.)
Angle (deg)
-100 -50 0 50 100 150 200 2500
0.2
0.4
0.6
0.8
1
1.2
1.4
depth (A)
ele
ctr
on d
ensity (
A-3
)
Cathode 3: K-Sb deposition on glass substrate (continued)
X-ray reflectivity Electron density profile
αi (degree) Thickness (Å)
I (a.
u.)
ρ p
rofi
le (
Å-3
)
B33 glass Substrate
Sb (5 nm) (25 oC)
K (16 nm) (150 oC)
Sb (6 nm) (25 oC)
B33 glass Substrate
Sb (5 nm) (25 oC)
K (16 nm) (150 oC)
Sb (6 nm) (25 oC)
K (53 nm) (150 oC)
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.810
-5
10-4
10-3
10-2
10-1
100
101
Inte
nsity (
a.u
.)
Angle (deg)
-100 0 100 200 300 400 500 6000
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
depth (A)
ele
ctr
on d
ensity (
A-3
)
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XRR Preliminary Results (continue updating)
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Sb, K, Cs deposited at 150 oC Sb deposited at Room Temperature, K & Cs at 150 oC
Silicon Silicon Glass
Thickness (Å) Roughness (Å) Thickness (Å) Roughness (Å) Thickness (Å) Roughness (Å)
Substrate - 4.04±0.67 - 4.84±0.02 - 4.94±0.02
Sb on Substrate 49.76±0.22 1.90±0.12 50.53±0.21 3.37±0.03 52. 39±0.28 3.40±0.03
K-Sb on Substrate 163.73±0.78 4.83±0.11 110.41±0.41 3.67±0.04 116.55±0.56 3.80±0.03
Sb-K-Sb on Substrate
225.08±0.59 4.60±0.09 165.47±0.53 4.11±0.09 175.97±0.77 4.21±0.08
K-Sb-K-Sb on Substrate
544.18±1.16 7.63±0.06 543.13±2.25 5.17±0.15 530.66±2.33 2.82±0.35
Cs-K-Sb-K-Sb on Substrate
Sb-Cs-K-Sb-K-Sb on Substrate
- -
Cs-Sb-Cs-K-Sb-K-Sb on Substrate
- -
XRR Preliminary Summary
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All the simulation is based on one homogeneous Sb or KxSb layer code. Similar thickness and roughness indicates the growth of K-Sb/substrate on Si and glass may follow the same growth mechanism. During first KxSb deposition, cathode 1 has thicker KXSb film than cathode 2 and 3; at the end, cathode 1 has the same KXSb film thickness as cathode 2 and 3. They have the same thickness Sb deposition, the final thickness seems to be determined solely by Sb thickness. Uniform electron density profile indicates the formation of pure alkali antimonide (KxSb) compound. The absolute electron density value may be not very accurate. Further understanding and optimization of the code is under going. Electron density value is strongly determined by the accuracy of the critical angle. In the future, the alignment may be addressed. Electron density of bulk K (19e) is 0.26/A3, Electron density of bulk Sb (51e) is 1.69 /A3, electron density of bulk Si (14e) is 0.70/A3, it is possible that the KxSb (with rich K) electron density is lower than Si. XRR roughness is different from AFM roughness. During XRR experiment in our experiment, the 2-cm long surface was covered with X-ray at small angle.
