Reinhold H. Dauskardt (dauskardt@stanford.edu)

Transportation Vehicle Light-Weighting with

Polymeric Glazing and Mouldings

Organosilicate Films and Coatings

Scott Isaacson, Joe Burg, Siming Dong, Michael Hovish, Florien Hilt

Polymers and Hybrid Nanomaterials

Jeff Yang, Marta Giachino, Qiran Xiao, Linying Cui, Zhenlin Zhao, Yichuan Ding

Membranes for Fuel Cells and Batteries

Daisy Yuen

Complex Multi-Junction Device Structures

Ryan Brock

Photovoltaic and Flexible Electronic Materials

Fernando Novoa, Chris Bruner, Stephanie Dupont, Nick Rolston, Warren Cui,

Brian Watson

Biological Hybrids

Krysta Biniek, Jacob Bow, Chris Berkey, David Kanno

DOE-BES and AFOSR programs on hybrid materials, BA PV

Consortium, Stanford-GCEP program on lightweighting.

Processing and Thermomechanical Reliability of Hybrid Films

light-weight vehicle touch display sensors and PV AR coatingswearable

atmospheric

plasma

Coatings and deposition methods need

improvement

• Vacuum-based techniques: high cost and

inconvenient

• Solution-based techniques: multiple steps, coating

low crosslinking density, solvents pollution

…current polymeric glazings do not meet durability/performance

requirements for near-term implementation

Outline

• Coating Reliability and Lifetimes

• coating characterization techniques for reliability

• accelerated testing and lifetime prediction

• Protective and Transparent Coating Systems

• controlling organosilicate molecular structure

• bi-layers with optimized adhesion and hardness

• strategies for incorporating UV protection

• Anti-Reflection Coating Systems

• single and graded layer strategies

• Transparent and Conducting Films

• applications for sensor and display technologies

Coating Reliability and Evolution of Defects

damage propagates if mechanical stresses are large enough so that

presence of chemical species and photons, damage propagates even if

environment and

stress accelerates

defect evolution

Role of coupled “stress” parameters in coating reliability

and lifetimes:

• mechanical stress

• temperature

• environmental species

• photons (photochemical reactions)

2/ mJGG c

2/ mJGG c

Coating Damage

cohesion or

adhesionmechanical

“driving force”

hn

stress

H2O

diffusion

Limitations of Thin-Film Adhesion Tests

Interface Crack

IndenterPlastic zone

Substrate

Film

Interface Crack

Substrate

Film

MP

PSubstrate

Film

Cavity in Substrate

• Indentation/Scratch Test- complex stress and deformation fields

- principally qualitative results

- (nano) scratch test even less quantitative

• Peel/m-ELT Test- difficult to apply loads

- plastic deformation of film

- temperature complications in m-ELT

• Blister Test- compliant loading system

- environmental effects

- etching/machining of cavity difficult

Major limitations: need detailed film properties, film stress relaxation and film plasticity

principally qualitative results for all above methods!

Quantitative Adhesion/Cohesion and Debond Kinetics

Adhesion/Cohesion

P

substrate

substrate

P

0 1 2 3 4 5 6 710-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

Cra

ck G

row

th R

ate

, d

a/d

t(m

/s)

Strain Energy Release Rate, G (J/m2)

No UV

0 mW/cm2

UV intensity1.2 mW/cm2

0.6

mW/cm2

Degradation Kinetics

(temp/environment /UV effects)

threshold crucial

for reliability

Coating III

Coating IV

Near the interface but

with some deflection

into the PMMA

Fracture between

epoxy and coating

Fracture at interface

between coating and

PMMA

PPG 1 PPG 3 PPG 5 PPG 2 PPG 2* PPG 4* PPG 6*0

50

100

150

200

250

300

Fra

ctu

re E

ne

rgy,

Gc(J

/m2)

Coating III

Coating IV

Coating III

Coating IV

Near the interface but

with some deflection

into the PMMA

Fracture between

epoxy and coating

Fracture at interface

between coating and

PMMA

PPG 1 PPG 3 PPG 5 PPG 2 PPG 2* PPG 4* PPG 6*0

50

100

150

200

250

300

Fra

ctu

re E

ne

rgy,

Gc(J

/m2)

PPG 1 PPG 3 PPG 5 PPG 2 PPG 2* PPG 4* PPG 6*0

50

100

150

200

250

300

Fra

ctu

re E

ne

rgy,

Gc(J

/m2)

Outline

• Coating Reliability and Lifetimes

• coating characterization techniques for reliability

• accelerated testing and lifetime prediction

• Protective and Transparent Coating Systems

• controlling organosilicate molecular structure

• bi-layers with optimized adhesion and hardness

• strategies for incorporating UV protection

• Anti-Reflection Coating Systems

• single and graded layer strategies

• Transparent and Conducting Films

• applications for sensor and display technologies

gas heating

coils

bubbler

bypass line

heated precursor

supply line

bubbler He flow

He and O2 flowdilution He flow

high temperature vaporizer

RF powerplasma

afterglow reactive

species

substratecoating

atmospheric

plasma

showerhead

precursors

Atmospheric Plasma Deposition of Hybrid Films

• higher molecular weight precursors

• higher boiling point

• larger range of material choices

SiSi

O

O

OO

O O

TEOS

BTESE

Innovation in

Precursor Delivery

Dielectric Barrier

Discharge Plasma

• low temperature

• He and N2 plasma gas

• medium temperature

• N2, O2, air plasma gas

Capacitively Coupled

Plasma

Silica Coatings Deposited by Atmospheric Plasma

1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.80

10

20

30

40

50

60

70 fused quartz

TEOS 23 oC

TEOS 135 oC

BTESE 135 oC

TMCTS

(higher plasma power)

TMCTS

Yo

ung

's M

od

ulu

s, E

(G

Pa

)

Density, (g/cm3)

0 100 200 300 400 500 600 700 800 9000

5

10

15

20

25

Ad

he

sio

n E

ne

rgy, G

c (

J/m

2)

Deposition Rate (nm/min)

TEOS 23 oC

TEOS 135 oC

BTESE 135 oC

TMCTS

Cui, Dauskardt, et al., ACS Applied Mat Interfaces, 2012.

SiH

O

HSi O

HSi

O

HSiO

SiSi

O

O

OO

O O

Si

O

O O

O

TEOS BTESE TMCTS

Molecular bridging

Precursors studied:

bridged silica

dense silica

bridged silica

dense silicaCommercial sol-gel polysiloxane

Commercial sol-gel polysiloxane

~100% visible transparency

Single Precursor Method - Hard and Adhesive Bilayer

Integrate layers deposited under different conditions

– carbon-bridged organosilicate bottom layer exhibits excellent adhesion to PMMA

– dense silica top layer exhibits high hardness and scratch resistance

Adhesive organosilicate

Dense silicaCommercial sol-gel polysiloxane

Bilayer

0 5 10 15 200

5

10

15

20

Young's modulus, E (GPa)

Ad

he

sio

n e

ne

rgy t

o P

MM

A,

GC (

J/m

2)

Carbon bridged precursors

C H 2 n S iS i

O

O

O

O

O

O

Cui, Dauskardt, et. al., ACS Nano, 2014.

polymer substrate

tough organosilicate

dense silica

Strategies for Highly Adhesive Multilayer Deposition

Single precursor method

– graded or multi-layers

Multi-precursor method

– graded or multi-layers

– fast deposition

plasma conditions

organic precursor

inorganic precursor

Processing Parameters

polymer substrate

tough silica

dense silica

Integrate multi-layers layers deposited under different conditions

– high toughness carbon-bridged organosilicate bottom layer

– dense silica top layer with high hardness and scratch resistance

– ~100% visible transparency

BTSEC H 2 n S iS i

O

O

O

O

O

O

TEOS

widely used, cheap

1,5-cyclooctadiene

easy ring opening and

network former

Integrate bilayer deposition under single/dual precursors choice

– high adhesion organosilicate bottom layer and dense silica top layer

– ~100% visible transparency

Strategies for Highly Adhesive Multilayer Deposition

Single Precursor Method Dual Precursor Method

Dong, Zhao, Dauskardt, ACS Appl. Mater. Interfaces, 2015.

Cui, Dauskardt, et. al., ACS Nano, 2014.

Outline

• Coating Reliability and Lifetimes

• coating characterization techniques for reliability

• accelerated testing and lifetime prediction

• Protective and Transparent Coating Systems

• controlling organosilicate molecular structure

• bi-layers with optimized adhesion and hardness

• strategies for incorporating UV protection

• Anti-Reflection Coating Systems

• single and graded layer strategies

• Transparent and Conducting Films

• applications for sensor and display technologies

Atmospheric Plasma and Anti-Reflection Coatings (ARC)

• transportation windows

• sensor technologies

• ophthalmic lenses

ArchitectureApplications

Uncoated Surface

Single Layer

Double Layer

Multi-Layer

𝑛𝑠𝑙𝑎𝑟𝑐=

𝑛𝑠𝑢𝑏 ∗ 𝑛𝑎𝑖𝑟

Single Layer Double Layer Multi-Layer

𝑛𝑎𝑖𝑟𝑛𝑠𝑢𝑏𝑠𝑡𝑟𝑎𝑡𝑒

=𝑛21𝑛22

Alternate n1,n2

from DLARC

300 400 500 600 700 800

0

20

40

60

80 Bare Silicon

50 mm/s

70 mm/s

85 mm/s

% R

efle

ctio

n

Wavelength (nm)

300 400 500 600 700 800

0

20

40

60

80 Bare Silicon

75 mm/s

85 mm/s

100 mm/s

% R

eflectio

n

Wavelength (nm)

TaOx

TiOy

Silicon

Metal Oxide ARC

Single Layer ARC

decreasing

thickness

decreasing

thickness

Atmospheric Plasma and Anti-Reflection Coatings (ARC)

Significant AR reduction in both systems

SLARCAverage

Reflectance

AbsoluteReflection Minimum

Silicon 42% 38%

TaOx <7% 1.90%

TiOy <5% 0.3%

Outline

• Coating Reliability and Lifetimes

• coating characterization techniques for reliability

• accelerated testing and lifetime prediction

• Protective and Transparent Coating Systems

• controlling organosilicate molecular structure

• bi-layers with optimized adhesion and hardness

• strategies for incorporating UV protection

• Anti-Reflection Coating Systems

• single and graded layer strategies

• Transparent and Conducting Films

• applications for sensor and display technologies

light-weight vehicle touch display sensors and PV AR coatingswearable

Deposition of Transparent Conducting ZnO Thin Films

- wide bandgap semiconducting material

- high electric conductivity

- high visible transmittance

- abundant resource

- replacement for Indium Tin Oxide (ITO)

Characteristic features of ZnO:

…atmospheric plasma deposition of ZnO films in ambient air

at low temperature on plastics.

Tv = 98%

Tv = 84%

ZnO films with a transmittance above 98% successfully obtained in

ambient air at 25 ºC by atmospheric plasma deposition.

Atmospheric Plasma Deposition of Transparent

Conducting ZnO Thin Films

- Precursor: Diethylzinc (Zn(C2H5)2)

- Substrate: PMMA, PET, PC

Watanabe and Dauskardt, Organic Electronics, 2014

Tv = 84%

Atmospheric Plasma Deposition of Transparent

Conducting ZnO Thin Films

H-impurities as

electron donors

doping

Watanabe and Dauskardt, Organic Electronics, 2014

Visible transmittance ~80% and resistivity as low as 10-1 ohm cm successfully obtained

in ambient air

Precursor: titanium ethoxide on PC substrate

Atmospheric Plasma Deposition of Transparent Conducting

TiNx/TiO2 Hybrid Films

Siming Dong and Dauskardt, Advanced Functional Materials, 2014

Summary• Coating Reliability and Lifetimes

• coating characterization techniques

• accelerated testing and lifetime prediction

• Protective and Transparent Coating Systems

• Anti-Reflection Coating Systems

• single and graded layer strategies

• Transparent and Conducting Films

• sensor and display technologies

Coating III

Coating IV

Near the interface but

with some deflection

into the PMMA

Fracture between

epoxy and coating

Fracture at interface

between coating and

PMMA

PPG 1 PPG 3 PPG 5 PPG 2 PPG 2* PPG 4* PPG 6*0

50

100

150

200

250

300

Fra

ctu

re E

ne

rgy,

Gc(J

/m2)

Coating III

Coating IV

Coating III

Coating IV

Near the interface but

with some deflection

into the PMMA

Fracture between

epoxy and coating

Fracture at interface

between coating and

PMMA

PPG 1 PPG 3 PPG 5 PPG 2 PPG 2* PPG 4* PPG 6*0

50

100

150

200

250

300

Fra

ctu

re E

ne

rgy,

Gc(J

/m2)

PPG 1 PPG 3 PPG 5 PPG 2 PPG 2* PPG 4* PPG 6*0

50

100

150

200

250

300

Fra

ctu

re E

ne

rgy,

Gc(J

/m2)

• current polymeric glazings/windoes do not

meet durability/performance requirements

• hybrid coatings with optimized adhesion

and hardness