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