Prof Peter Kelly

Surface Engineering Group,

Manchester Metropolitan University, UK

Functional Films by Magnetron

Sputtering Processes

Magnetron Sputtering

Versatile PVD technique for high quality coatings

Metals, alloys, oxides, nitrides, multi-layers, etc.

Magnetron discharge driven in DC, pulsed DC, HiPIMS, RF,

MW, AC modes

Von Ardenne

Teer

Coating

s

BOC

Magnetrons:

Rectangular, circular, or cylindrical

10s of mm diameter up to several m in length

Variable field strength – variable ICD to growing film

Multi-source systems – vertically opposed, in-line,

web coating, indexed, etc.

Valmet General

Industrial Applications of Magnetron Sputtering

Wear resistant coatings on cutting

tools/components

Low friction coatings

Corrosion resistant coatings

Decorative coatings

Architectural & automotive glazing

Anti-reflective/Anti-static (AR/AS)

Transparent conductive oxides (TCO’s)

Microelectronics

Data storage media

Case Study 1: Photocatalytic and Superhydrophilic

Titania Coatings

Photocatalytic and Superhydrophilic Applications

‘Self-Cleaning’ Surfaces

Anti-fogging surfaces

Photocatalytic and Superhydrophilic applications of TiO2

Building

materials

Antibacterial

surfaces

Anti-

fogging

surfaces

Self-cleaning

windows

o Road pavements;

o Exterior tiles;

o Exterior paint

o Eye glasses;

o Mirrors;

o Car side-view

mirrors

o Implants;

o Medical instruments;

o Indoor tiles

Highest activity shown by anatase:

• Requires elevated temperatures for formation;

• Requires UV light for activation;

• Dopants investigated to promote visible light activity

Reactively Sputtered Doped-Titania Coatings

To vacuum pumps

Piezo

valve

Reactive

gas supply

Fibre optic cable

Rotating

substrate

holder

Pinnacle

Plus

RF Bias

Pinnacle

Plus

Ti W

Reactaflo

OEM

system

As-deposited coatings analysed by SEM, EDX, micro-Raman spectroscopy.

Selected coatings annealed in air at 400 or 600 OC and re-analysed

Constant power to

2x Ti targets: 1kW

pulsed DC

Power to dopant

target varied in

range 60 to 180W DC

Substrates – floating

OEM control for O2

MFC control for N2

Rotating substrate

holder

Ti

target

Ti target

Dopant

metal

target

Ar + O2 OEM

Control (+ N2, MFC)

Blanking plate

Raman Spectroscopy Analysis of PDC Doped Titania

Coatings

200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

Raman shift / cm-1

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

Co

un

ts

200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500

Raman shift / cm-1

0

10000

20000

30000

40000

50000

60000

70000

80000

90000

Co

un

ts

2.44 at% Mo annealed at 400ºC:

Anatase

10.03 at% W annealed at

600 ºC: Mixed anatase/rutile

A

A A

A

A

A A

A

R R

As-deposited PDC

coatings are amorphous

Photocatalytic Activity Tests: Decomposition of

Methylene Blue

Methylene blue: heterocyclic aromatic

dye: C16H18ClN3S

Often used as a model organic

compound to measure photo-reactivity

UV-visible spectrum shows strong

absorption peak at 662 nm

Changes in peak height used to

monitor the photocatalytic degradation

of MB by doped- and un-doped titania

coatings

C16H18ClN3S + 25.5O2 → HCl + H2SO4 + 3HNO + 16CO2 + 6H2O

TiO2 + hu ≥ 3.2eV

0

0.02

0.04

0.06

0.08

0.1

0.12

550 600 650 700 750

Inte

ns

ity,

arb

. u

nit

s

Wavelength, nm

0h 1h

2h 3h

4h 5h

ka = ln(A0/At)

Calculation of first order constant of MB

decomposition:

Comparison of relative activity

0

0.2

0.4

0.6

0.8

1

1.2

TiO2 0.7at% Nb 2.4at% Mo 5.9at% W

Ph

oto

cata

lyti

c A

cti

vit

y I

nd

ex

UV Light Fluorescent Light

Annealed at 400oC Annealed at

600oC

27% 33%

37% 46%

*Fl light activities normalised to same integrated power flux as UV light source

Optimising Dopant Levels:

W-doped coatings (PDC/annealed)

5500

5520

5540

5560

5580

5600

5620

5640

0

2

4

6

8

10

12

0 2 4 6 8 10 12 14 16

Surf

ace

are

a, m

m2

Ka

x 1

0-5

, s-1

Tungsten contest, at%

UV light

Fluorescent light

Surface area

Band gap, eV

2.98

3.00

3.02

3.05

3.09

3.09

3.12

3.16

Annealed at 600oC

M Ratova, G West, P Kelly, Coatings 3 (2013) 194-207.

Lorret, O.; Francová, D.; Waldner, G.; Stelzer, N.,

Applied Catalysis B: Environmental 2009, 91, 39-46.

Antimicrobial effect of doped TiO2:

Fluorescent light

1.E+00

1.E+02

1.E+04

1.E+06

1.E+08

0 4 8 12 16 20 24

Bac

teri

al c

ou

nt

(cfu

/cm

-2)

Irradiation time (hours)

SS Light SS Dark Mo Light Mo Dark

Mo-doped

Escherichia coli

W-doped

Escherichia coli.

0

1

2

3

4

5

6

7

8

0 24 48

Bac

teri

al c

ou

nt

(lo

g 10 c

fu m

l-1)

Irradiation time (hours)

SS dark SS light Ti-W dark Ti-W light TiO₂ light

Potential Applications:

Beer bottle filling lines

In collaboration with Panimolaboratorio - Bryggerilaboratorium Ab (PBL), a company

devoted to research and development in malting and brewing on behalf of Finnish

industry

Acknowledgement: Kaisa Tapani, PBL

New Development:

HiPIMS (high power impulse magnetron sputtering)

-1200

-1000

-800

-600

-400

-200

0V

olt

age,

v

50 Hz, 0.5 kW, 100 µs Pulse

Time

-1500

-1000

-500

0

500

0.0E+00 2.0E-06 4.0E-06 6.0E-06 8.0E-06 1.0E-05T

arg

et

vo

ltag

e,

V

Timebase, s

Pulsed DC:

350kHz, 50% duty

Peak currents can be 1000A, peak powers can be in MW range

50 – 1000 Hz, 100 – 200 ms pulses, duty 1-10%

New Development:

HiPIMS (high power impulse magnetron sputtering)

HiPIMS may offer the opportunity to produce optimum

structures/properties without substrate heating/post deposition annealing

Deposition of Photocatalytic TiO2 onto PET using

HiPIMS

Pulsed DC

100kHz, 50% duty

1.5 kW ave. power

HIPIMS Huettinger

200Hz, 200 ms pulse

1.5 kW ave. power

GT West, PJ Kelly, P Barker, A Mishra and JW Bradley, Plasma Process. Polym, 6 (2009) S543-S547

100nm of TiO2 deposited onto 100mm of

PET at same time-average power

Raman Spectroscopy Analysis of HiPIMS

Titania Coatings

Photocatalytic Results: PDC & HiPIMS

At% W: 0 3.8 4.6 5.9 7.1 0 5.7 0

Ka x

10

-5, s

-1

Band Gap Measurements: Tauc Plots

Pulsed DC HiPIMS

0

1

2

3

4

5

6

TiO2 W80 HiPIMS W-HiPIMS

Ka

x 1

0-5

, S-1

UV FL Vis

To 10.0

M Ratova, G West, PJ Kelly, ‘HiPIMS Deposition of Tungsten-doped Titania Coatings for Photocatalytic Applications’, Vacuum

102 (2014) 48-50

Water Contact Angle

TiO2 as deposited (38o)

ka = 3.3x10-5, s-1

HiPIMS

W80 annealed at 600oC (15o)

ka = 9.9x10-5, s-1

Pulsed DC

Case Study 1: Summarising Comments

Photocatalytic doped-titania coatings have been produced by

magnetron sputtering techniques

Performance assessed in terms of dye degradation, antimicrobial

assays, band gap shifts and contact angle measurements

Wide variation in results

Performance is sensitive to: Dopant material and content (Mo and W most active)

Crystalline structure (annealing temp/dep’n process)

Alternative materials for visible light activity (Bi complex oxides)

Many potential industrial/medical applications

Bottling line trials underway

HiPIMS allows single stage processing on polymeric substrates

Ability to deposit active coatings at low temps opens up new

opportunities

PJ Kelly, et al, ‘Structural formation and photocatalytic activity of magnetron sputtered titania and doped-titania

coatings’, Molecules, 19 (2014) 16327-16348.

Case Study 2: Comparison of Tribological and Anti-

Microbial Properties of CrN/Ag, ZrN/Ag,

TiN/Ag, and TiN/Cu Nanocomposite Coatings

Staphylococci

1µm

Transition Metal Nitride Coatings

TiN, ZrN, CrN, TiAlN, etc.

High hardness, resistance to corrosion and wear and attractive

appearance

Industrial applications

Protection of cutting and forming tools

Decorative items

Source: Tecvac

Source: Newform Source: Teer Coatings Ltd

To vacuum pumps

Piezo

valve

Reactive

gas supply

Fibre optic cable

Rotating

substrate

holder

MDX/SP20

MDX

MDX/SP20

Ti Ag

Reactaflo

OEM

system

Deposition of TiN/Ag Nanocomposite Coatings

Ti and Ag sputtered simultaneously in Ar/N

gas. TiN forms, but AgN is unstable

TiN/Ag Nanocomposite Coatings

PJ Kelly, et al, ‘A Study of the Anti-Microbial and Tribological Properties of TiN/Ag Nanocomposite Coatings’, Surf.

Coat. Technol., 204 (2009) 1137-1140

Ag nanoparticles

TiN-10at%Ag TiN-16at%Ag

Coating Properties

Decreasing hardness and

friction with increasing Ag or Cu,

but also increasing wear rate

Unlubricated sliding wear test

Antimicrobial Activity

Zone of inhibition

– Silver/copper ion release

NBT (nitro-blue tetrazolium) assays

– Contact kill. Tests antimicrobial effectiveness after incubation

Bacteria used:

– Pseudomonas aeruginosa (P. aeruginosa, a gram negative rod

shaped bacterium with flagellum),

– Staphylococcus aureus (S. aureus, a gram positive 1 µm

diameter coccal bacterium)

Zone of Inhibition Colony forming units

0

20

40

60

TiN4.60%

10.80%16.70%

Co

lon

y f

orm

ing

un

its

cm

-2

S. aureus

P. aeruginosa

Increasing silver content

a: TiN; b:4.6% Ag;

c: 10.8% Ag,; d: 16.7% Ag

No ZOI observed (zone of inhibition)

For NBT assays, S. aureus colonies were present on all

the surfaces, but the number of colony forming units

decreased significantly with increasing silver content.

Microbiology Results: Staphylococcus aureus

a) b)

c) d)

ZoI – All Coatings

Pseudomonas aeruginosa

ZoI surrounding

CrN/10.2%Ag against P.

aeruginosa cells

TiN/Ag ZrN/Ag CrN/Ag TiN/Cu

Case Study 2: Summary

Nanocomposite transition metal nitride coatings have been

produced with varying Ag and Cu contents

Decreased friction coefficients in wear tests

Also decreased hardness and increased wear rates

Coatings can combine enhanced tribological properties with

antimicrobial activity, but results are coating and organism

specific

PJ Kelly, et al, ‘Comparison of Tribological and Anti-Microbial Properties of CrN/Ag, ZrN/Ag, TiN/Ag, and TiN/Cu

Nanocomposite Coatings,’ Surf. Coat. Technol., 205 (2010) 1606-1610

Conclusions

PVD processes are extremely versatile and successful

Magnetron sputtering now process of choice in many cases

Continuous development over ~20 years has provided improvements in properties/process

Unbalanced magnetrons

Closed field multiple magnetron systems

Pulsed magnetron sputtering

HiPIMS

Applications of magnetron sputtering will continue to grow

Versatility

Reliability

Scaleability

Clean process