S.M. Deambrosis*^, G. Keppel*, N. Pretto^, V. Rampazzo*, R.G. Sharma°*, F. Stivanello* and V....
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Transcript of S.M. Deambrosis*^, G. Keppel*, N. Pretto^, V. Rampazzo*, R.G. Sharma°*, F. Stivanello* and V....
S.M. Deambrosis*^, G. Keppel*, N. Pretto^, V. Rampazzo*, R.G. Sharma°*, F. Stivanello* and V. Palmieri*^
Padova University, Material Science Dept
* INFN - Legnaro National Labs ^ Padua University, Science faculty, Material Science Dept
° Interuniversity Accelerator Center, New Delhi
V3Si by Thermal Diffusion of SiH4 into V
1) Theory
2) Literature review
3)Technique choice reasons
4) Method
5) Work in progress6)
Conclusions
Multilayer films
Cosputtering
Reactive sputtering
Thermal diffusion
Nomogram
Samples caracterization
Used system
V Substrate preparation
V3Si obtainment
V3Si
18
Tc (K)
ρn
(μΩ
cm)
Nomogram
Theory
IdealR BCS ~ 1 nΩ
At T = 4.2 K,
f = 500 MHz,
s = 4,
RBCS depends
on Δ and ρn
~ 10 μΩcm
Thermally diffused V3Si multilayer films S. De Stefano, A Di Chiara, G. Peluso, L. Maritato*, A. Saggese* and R. Vaglio*
Naples University, *Salerno UniversityCryogenics 1985 Vol 25 April
V and Si layers sequentially deposited by Electron-beam evaporation
Tc vs Annealing T (600-900°C for 1h)
Tc measured by a 4-terminal resistive method
Literature
Tcmax = 16,2 K
Tc < 0,1 K
Annealing t = 1 h
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
Schematic diagram of the facing-target magnetron.
V target Si target
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
13.5 14.0 14.5 15.0 15.5 16.0 16.5
sample5-9
RR
K
Superconducting transition of a V3Si sample
RR
R
Literature
6.0
9.0
12.0
15.0
18.0
10.0 15.0 20.0 25.0 30.0Silicon content ( % at. )
800oC
500oC
Reactive sputtered V3Si films Y. Zhang, V. Palmieri, W. Venturini, R. Preciso, Legnaro National Laboratory - INFN, Italy
a bSurface of two annealed samples under SEM: Grain size, (a) 0.2m, (b) 0.5m
Before annealing
After annealing
Tc (K
)
Literature
Thermal diffusion of V3Si filmsY. Zhang, V. Palmieri, W. Venturini, F. Stivanello, R. Preciso, Legnaro National Laboratory, ITALY
Silane pressure
Heat power Temperature
Diffuse in silane
Anneal in vacuum
1.2·10-
4mbar300W 900ºC 20h 40h
Diffusion Parameters:
2.5
3.0
3.5
4.0
4.5
14.5 15.0 15.5 16.0 16.5 17.0
Bulk Vanadium, sample No.13-2V
K
AC inductive measurement:Tc ~ 16.0K ΔTc < 0.4K
Literature
Technique Choice Reasons
• Very simple technique (RF applications!)
V3Si by Thermal Diffusion of SiH4 into V?
• There is room to improve the film quality by higher thermal diffusion temperature or by longer annealing time in vacuum.
• Promising old results
Laboratory Procedure
• Used system
• V Substrate preparation
• V3Si obtainment
• Samples caracterization
Method
Vacuum System
Method
Vacuum system
Controllers
SiH4 Gas Cabinet
Heating System
Method
Nb
V substrates
Substrate Chemical Etching
Method
Sample Reactant mixture T (°C) t (s)
Erosion rate
V Substrate: Optical Microscope
HF, HNO3, H3PO4 1:1:2
50°C, 7,8 m
HF, HNO3, H3PO4 1:1:160°C, 36,2 m
HNO3, H2O, NH4F 25:12:1
30°C, 46,5 m
HF, HNO3 1:420°C, 73,8
m
Method
HF, HNO3, H3PO4 1:1:250°C, 7,8 m
HF, HNO3 1:420°C, 73,8 m
HF, HNO3, H3PO4 1:1:160°C, 36,2 m
HNO3, H2O, NH4F 25:12:130°C, 45,5 m
V Substrate: Profilometer
Method
V3Si obtainment
Vacuum p ~ 10-8 mbar
V substrate heatingTo get SiH4 decomposition and
Silicon diffusion
SilanizationFilm 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
Method
V
V3Si
XRD
Method
Angle (2θ)
Rel
ativ
e In
tens
ity
Process T = 825°C, p (SiH4) = 5,0x 10-4 mbar
Silanization t = 10h Annealing t = 20h
A Superconductive Transition Curve
Method
V3Si 5N: 850°C, 1,0x10-3 mbar, 10h+20h
V3Si (Tc = 15,4 K)
V (Tc = 5,0 K)
Tc vs Process T
Method
T (°C)
Tc(°
C)
p(SiH4)=5,0 x 10-4mbar, silanization t=10h, ann t=20h
Cu Contaminations?
• Mechanical polishing
• Chemical polishing
6 GHz Cavities
1. Spinning Technique
2. Surface Treatments
Method
Mechanical Polishing
SiC
Used media:
ZrO2
Method
Before the treatmentAfter:SiC 120h + ZrO2 96h
V 6 GHz cavity: Mechanical Polishing
Method
V 6 GHz cavity: Chemical Polishing
Used recipe:
Method
• Parameters optimization: T, t and p (SiH4)
Work in progress
• Use of the best results to coat 6 GHz V cavities to test sistematically RF properties
• Different sperimental method to prepare V3Si: multilayer obtained altermatively depositing V and Si
• Plasma used to try to avoid the presence of hydrogen
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
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
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
Reactive sputtering of V-Si films by a DC facing target magnetron configuration in SiH4 atmosphere
Surface: SEMComposition: EDSSuperconducting properties: DC four probe technique
Important parameters:•T•Deposition rate•SiH4 partial pressure
Literature
Reactive sputtered V3Si films Y. Zhang, V. Palmieri, W. Venturini, R. Preciso, Legnaro National Laboratory - INFN, Italy