UNIVERSITÀ DEGLI STUDI DI PADOVASCIENCE FACULTY

MATERIAL SCIENCE DEGREE

INFN – LABORATORI NAZIONALI DI LEGNARO

MORPHOLOGY OF NIOBIUM FILMS SPUTTERED AT MORPHOLOGY OF NIOBIUM FILMS SPUTTERED AT DIFFERENT TARGET DIFFERENT TARGET –– SUBSTRATE ANGLESUBSTRATE ANGLE

DIEGO TONINI

�� WhatWhat isis the the effecteffect of target of target –– substrate substrate angle on the film properties?angle on the film properties?

�� HowHow the film the film morphologymorphology variesvaries changingchangingtarget target –– substrate angle? substrate angle?

2 QUESTIONS…

DEPOSITIONS MADE AT DIFFERENT TARGET –SUBSTRATE ANGLE

CRYSTAL STRUCTURE

SUPERCONDUCTINGPROPERTIES

TC MEASURE

RRR

MAGNETO-OPTICAL

ELECTROCHEMICALIMPEDANCE

SPECTROSCOPY

AFM IMAGING

THICKNESS

TEXTURE ANALYSIS

X-RAYDIFFRACTION

FILM MORPHOLOGY

• 7 substrates coated in the same run

• Almost identical processconditions for each sample

MULTI-ANGLE SAMPLE HOLDER

DC MAGNETRON SPUTTERING

• LOWER TC AND RRR INCREASING TARGET –SUBSTRATE ANGLE

PULSED MAGNETRON SPUTTERING

• BETTER PROPERTIES FOR PULSED CURRENT DEPOSITION

• THERE IS STILL THE SAME ANGLE DEPENDENCE OF TCAND RRR

DC MAGNETRON SPUTTERING WITH SUBSTRATE HEATING

Substrate temperature kept at 600°C duringprocess

1. Better properties

2. Less angle sensitivity

0 15 30 45 60 75 900

5

10

15

20

25

RR

R

deposition angle (degrees)

0 15 30 45 60 75 908.2

8.4

8.6

8.8

9.0

9.2

9.4

9.6

TC (K

)

deposition angle (degrees)

20 40 60 80 100 120 1400

20

40

60

80

100

321222310220

211200

110

75 degrees

60 degrees

45 degrees

30 degrees

15 degrees

Rel

ativ

e In

tens

ity

2 Theta (degrees)

XRD SPECTRA OF FILM DEPOSITED AT DIFFERENT TARGET – SUBSTRATE ANGLE

ESTIMATED GRAIN DIMENSION

)2()cos(9.0

θθλ∆⋅

=D

15 30 45 60 75

60

80

100

120

140

crys

talli

te d

imen

sion

(Ang

stro

m)

deposition angle (degrees)

d110 OF CRYSTAL PLANES

λθ nd hkl =sin2 )(

15 30 45 60 75

1,0

1,2

1,4

1,6

1,8

2,0

2,2

2,4

2,6

2,8

3,0

d 110 (

Ang

stro

m)

deposition angle (degrees)

TEXTURE ANALYSIS

DC MAGNETRON SPUTTERING

0 gradi

75 gradi60 gradi45 gradi

30 gradi15 gradi

PULSED MAGNETRON SPUTTERING

0 gradi

75 gradi60 gradi45 gradi

30 gradi15 gradi

TEXTURE ANALYSISDC VS PULSED MAGNETRON SPUTTERING

0 15 30 45 60 75 90

0

10

20

30

40

50Φ

max

cou

nts

(deg

rees

)

deposition angle (degrees)

DC PULSED

ATOMIC FORCE MICROSCOPY TOPOGRAPHIC IMAGES

15 gradi 30 gradi 45 gradi

60 gradi 75 gradi 90 gradi

0 15 30 45 60 75 900

2

4

6

8

10

12

14

16

18

20

roug

hnes

s (n

m)

deposition angle (degrees)

ATOMIC FORCE MICROSCOPY DC MAGNETRON SPUTTERING

0 15 30 45 60 75 900

2

4

6

8

10

12

14

16

18

20

roug

hnes

s (n

m)

deposition angle (degrees)

Variable thickness Uniform thickness

I campioni depositati in corrente pulsata sono sistematicamente più rugosi

ATOMIC FORCE MICROSCOPY PULSED MAGNETRON SPUTTERING

ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY

)cos()( 0 tVtV ω=

)cos()( 0 ϕω −= tItI

)cos()cos(

)()(

0 ϕωω−

==t

tZ

tItV

Z

ϕjeZZ 0=

ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY NYQUIST PLOT

0 2 4 60

2

4

6porous electrodeideally flat electrode

Im(Z

) /a

rbitr

ary

units

Re(Z) / arbitrary units

FLAT ELECTRODE:

Real part of impedance representsRs at any frequency

Immaginary part does not vary withfrequency

NYQUIST PLOT IS A VERTICAL LINE

POROUS/ROUGH ELETRODE:

The apparent capacity Cdl dependson frequency because the penetration length of electric fieldinside the pores raises whendecreasing frequency.

NYQUIST PLOT IS A 45°INCLINED LINE

ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY DC MAGNETRON SPUTTERING

VARIABLE FILM THICKNESS

Up to 45°there is porouselectrode behaviour

Film deposited at higher angles are less thick so resistence is greaer

COMPARISON BETWEEN FILM WITH DIFFERENT THICKNESS AND FILM WITH CONSTANT THICKNESS

Films with the same thickness havethe same resistance

There is a maximum in capacity at 60°target – substrate angle

ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY DC MAGNETRON SPUTTERING

Films with the same thickness –measures in passivaton condition

Imposed potential to create a passivation layer on the film

Oxide tichkness depends onlyon applied potential

Oxide growth follows niobiumfilm morphology

Capacity shows the sameangle dependence of non oxidized films

ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY DC MAGNETRON SPUTTERING

100×−=∆ pulsedac

pulsedac

contac

CCC

R

ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY PULSED MAGNETRON SPUTTERING

MAGNETO-OPTICAL ANALYSIS

OFHC copper substrate (not electropolished)

Target – substrate angle: 0°

Good connectivity respect tovortex penetration

Target – substrate angle: 45°

Vortex penetrate along substratediscontinuity

SIMULATION OF THIN FILM GROWTH

0°

15°

30°

45°

60°

75°

85°

CONCLUSIONS s.c. and transport properties

0 15 30 45 60 75 90

7.8

8.0

8.2

8.4

8.6

8.8

9.0

9.2

9.4

9.6

TC (K

)

deposition angle (degrees)

DC PULSED HEATED

0 15 30 45 60 75 900

5

10

15

20

25

RR

R

deposition angle (degrees)

DC PULSED HEATED

Properties depend on target – substrate angle

Pulsed magnetron sputtering and heating of the substratereduce the angle dependence

CONCLUSIONS Crystal structure

FilmsFilms depositeddeposited at at higherhigher anglesangles tendtend towardstowardsamorphizationamorphization

Lattice Lattice parameterparameter hashas a a maximummaximum at 60at 60°°target target ––subtrate anglesubtrate angle

(110) crystal (110) crystal planesplanes of the of the growinggrowing film film orientorientalongalong niobiumniobium atomsatoms arrivalarrival directiondirection

ThisThis effecteffect isis reducedreduced usingusing pulsedpulsed magnetron magnetron depositiondeposition

CONCLUSIONSmorphology

0 15 30 45 60 75 90

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

norm

aliz

ed in

tens

ity

deposition angle

Impedance spectroscopy AFM simulated

There is a maxmum in roughness between 60°and 75°target – substrate angle

This is not a thickness effect but is due to deposition dynamics

Fine.Fine.