V3Si by Thermal
Diffusion of SiH4 into V
S.M. Deambrosis*^, G. Keppel*, N. Pretto^,
V. Rampazzo*, R.G. Sharma°*, F. Stivanello* and V. Palmieri*^
* INFN - Legnaro National Labs
^ Padua University, Science faculty, Material Science Dept
° Interuniversity Accelerator Center, New Delhi
Padova University, Material Science Dept
1) Theory
2) Literature review
V3Si
3)Technique choice
reasons
Nomogram
Multilayer
films
Cosputtering
Thermal
diffusion
Reactive
sputtering
Used system
4) Method
5) Work in progress
6) Conclusions
V Substrate
preparation
V3Si obtainment
Samples caracterization
Nomogram
At T = 4.2 K,
f = 500 MHz,
s = 4,
on Δ and ρn
ρn (μΩcm)
RBCS depends
Ideal
R BCS ~ 1 nΩ
~ 10 μΩcm
Tc (K)
18
Theory
Thermally diffused V3Si multilayer films
S. De Stefano, A Di Chiara, G. Peluso, L. Maritato*, A. Saggese* and R. Vaglio*
Naples University, *Salerno University
Cryogenics 1985 Vol 25 April
V and Si layers sequentially deposited by Electron-beam evaporation
Tc measured by a 4-terminal resistive method
Tcmax = 16,2 K
Tc < 0,1 K
Tc vs Annealing T (600-900°C for 1h)
Literature
Preliminary results on cosputtering of V3Si films by the facing-target
magnetron technique
Y. Zhang, V. Palmieri, R. Preciso, W. Venturini, Legnaro National Laboratory, ITALY
sample5-9
0.35
Schematic
diagram of the facing-target magnetron.
0.30
Si target
RR
RRR
V target
0.25
0.20
Superconducting
transition of a V 3Si
sample
0.15
0.10
0.05
0.00
13.5
14.0
14.5
15.0
K
15.5
16.0
16.5
Literature
Reactive sputtered V3Si films
Y. Zhang, V. Palmieri, W. Venturini, R. Preciso, Legnaro National Laboratory - INFN, Italy
Tc (K)
After
annealing
Before
annealing
Surface of two annealed samples
under SEM: Grain size, (a) 0.2m,
(b) 0.5m
a
b
Literature
Thermal diffusion of V3Si films
Y. Zhang, V. Palmieri, W. Venturini, F. Stivanello, R. Preciso, Legnaro National Laboratory, ITALY
Diffusion
Parameters:
V
Silane
pressure
Heat power
Temperature
Diffuse in
silane
Anneal in
vacuum
1.2·10-4mbar
300W
900ºC
20h
40h
Bulk Vanadium, sample No.13-2
4.5
4.0
AC inductive measurement:
Tc ~ 16.0K
ΔTc < 0.4K
3.5
3.0
2.5
14.5
K
15.0
15.5
16.0
16.5
17.0
Literature
V3Si by Thermal
Diffusion of SiH4 into V?
• Very simple technique (RF applications!)
• Promising old results
• There is room to improve the film quality by higher
thermal diffusion temperature or by longer annealing
time in vacuum.
Technique Choice Reasons
Laboratory Procedure
• Used system
• V Substrate preparation
• V3Si obtainment
• Samples caracterization
Method
Vacuum System
Vacuum system
SiH4 Gas Cabinet
Controllers
Method
Heating System
V substrates
Nb
Method
Substrate Chemical Etching
Sample
Reactant mixture
T (°C)
t (s)
Erosion
rate
Method
V Substrate: Optical Microscope
HF, HNO3, H3PO4 1:1:2
50°C, 7,8 m
HF, HNO3 1:4
20°C, 73,8 m
HF, HNO3, H3PO4 1:1:1
60°C, 36,2 m
HNO3, H2O, NH4F 25:12:1
30°C, 46,5 m
Method
V Substrate: Profilometer
HF, HNO3, H3PO4 1:1:2
50°C, 7,8 m
HF, HNO3 1:4
20°C, 73,8 m
HF, HNO3, H3PO4 1:1:1
60°C, 36,2 m
HNO3, H2O, NH4F 25:12:1
30°C, 45,5 m
Method
V3Si obtainment
Vacuum
p ~ 10-8 mbar
V substrate heating
To get SiH4 decomposition and
Silicon diffusion
Silanization
Film growth
(p (SiH4) ~ 10-3-10-4 mbar)
Annealing in vacuum
To get rid of hydrogen
Method
SEM
Process T = 850°C, p (SiH4) = 5,0x 10-4 mbar
Silanization t = 10h Annealing t = 20h
V3Si
V
Method
XRD
Process T = 825°C, p (SiH4) = 5,0x 10-4 mbar
Relative Intensity
Silanization t = 10h Annealing t = 20h
Angle (2θ)
Method
A Superconductive Transition Curve
V3Si 5N: 850°C, 1,0x10 -3 mbar, 10h+20h
V3Si (Tc = 15,4 K)
V (Tc = 5,0 K)
Method
Tc vs Process T
Tc (°C)
p(SiH4)=5,0 x 10-4mbar, silanization t=10h, ann t=20h
Cu Contaminations?
T (°C)
Method
6 GHz Cavities
1. Spinning Technique
2. Surface Treatments
• Mechanical polishing
• Chemical polishing
Method
Mechanical Polishing
Used media:
SiC
ZrO2
Method
V 6 GHz cavity: Mechanical Polishing
Before the treatment
After:
SiC 120h + ZrO2 96h
Method
V 6 GHz cavity: Chemical Polishing
Used recipe:
Method
Work in progress
• Parameters optimization: T, t and p (SiH4)
• Use of the best results to coat 6 GHz V cavities to
test sistematically RF properties
• Plasma used to try to avoid the presence of hydrogen
• Different sperimental method to prepare V3Si:
multilayer obtained altermatively depositing V and Si
Conclusions
• Thermal diffusion technique
•T, t and p(SiH4) change trying to improve V3Si films
properties
• Good preliminary results: Tc ~ 15 K and Tc ~ 0,4 K
Preliminary results on cosputtering of V3Si films by the facing-target
magnetron technique
Y. Zhang, V. Palmieri, R. Preciso, W. Venturini, Legnaro National Laboratory, ITALY
Cosputtering technique: Deposition T > 500°C + sometimes annealing (800°C)
Composition (RBS, EDS): composition ratio V/Si linerly dependent on the
Target Voltage Ratio
Tc: four probe DC resistivity measurement
Literature
Reactive sputtered V3Si films
Y. Zhang, V. Palmieri, W. Venturini, R. Preciso, Legnaro National Laboratory - INFN, Italy
Reactive sputtering of V-Si films by a DC facing target magnetron
configuration in SiH4 atmosphere
Surface: SEM
Composition: EDS
Superconducting properties: DC four probe technique
Important parameters:
•T
•Deposition rate
•SiH4 partial pressure
Literature