AVS-61 JSJur&RPPad_rpedit

next (nano-extended textiles) research group

…Expanding the Influence of Nanotechnology in Textiles

Influence of Polymer Microstructure and Process Temperature on the Formation of Tailored ALD Coatings on

Polymers

Richard P. Padbury and Jesse S. Jur

NC State University

Department of Textile Engineering, Chemistry and Science

Raleigh, NC

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http://www.greatbigcanvas.com/view/nc-state-university-photographs-campus-gateway,rp923/



Outline

• Summary of ALD on polymers

• Section 1: Influence of polymer microstructure on ALD

– Objective: Understand how polymer structure affects the ALD process

• Section 2: Saturation behavior of polymers over broad temperature range

– Objective: Indentify fundamental growth mechanisms based on polymer physics

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Inorganic material toolbox of atomic layer deposition (ALD)

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Pure Elements

Nitrides

Oxides

[1]Puurunen, R. L., Surface chemistry of atomic layer deposition: A case study for the trimethylaluminum/water process. Journal of Applied Physics 2005, 97 (12).

• ALD – Vapor phase technique for forming inorganic coatings on broad range of substrates • ALD on polymers indicates dependence on polymer chemistry • Infiltration and nucleation within carbonyl containing polymers indicates formation of a hybrid coating

• Research Question:

What are the most advantageous material characteristics and optimal vapor phase process parameters to exploit a particular functionality in a polymer for a specific application?



Polymer chemistry and temperature control precursor nucleation

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⁻ Polymer Chemistry

⁻ Temperature

Cross-section TEM of PA-6 infiltrated with trimethylaluminum

Cross-section TEM of trimethylaluminum infiltration in cotton, PP and PA6

Cotton PP PA-6

[2] Sun, Y. et al. Chemical Vapor Deposition (2013)



Experimental Approach

Infiltration Experiments Using In-situ QCM Analysis

A

L

Precursor dose

Polymer film

Precursor Infiltration

QCM data analysis

Diffusion of

precursor molecules

Free Volume

Microstructure

Chemical reaction

Mass uptake (QCM)

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In-situ QCM Analysis of a Typical ALD Process

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[1]

[2]

Vacuum pump

TMA

H2O

N2 Polymer coated quartz crystal

N2 Purge

Direction of flow

Dose Sequence: x(TMA)/N2/H2O/N2)

Electrodes

Exposure

surface

Crystal drawer

Heated

reaction

chamber

QCM exposure

surface facing

down

Piezo-electric

quartz crystal

Top

Bottom



QCM analysis of alumina ALD via TMA/H2O indicates step-wise growth

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ALD Parameters: • Number cycles: 50 • Dose Sequence: TMA/N2/H2O/N2 • Dose times (sec): 0.2/30/0.2/45

• Pressure (Torr): 1 • Temperature (oC): 60

[3] RP Padbury, JS Jur. Effect of Polymer Microstructure on the Nucleation Behavior of Alumina via Atomic Layer Deposition. J. Phys. Chem. C. 118 (32), 18805-18813



Polymers possess nucleation period prior to typical ALD growth

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ALD Parameters:

• Number cycles: 50

• Dose Sequence: TMA/N2/H2O/N2

• Dose times (sec): 0.2/30/0.2/45

• Pressure (Torr): 1

• Temperature (oC): 60

[3] RP Padbury, JS Jur. Effect of Polymer Microstructure on the Nucleation Behavior of Alumina via Atomic Layer Deposition. J. Phys. Chem. C. 118 (32), 18805-18813

PBT = Poly (butyl terephthalate) PPMA = Poly (propyl methacrylate)



Section 1: Influence of polymer microstructure on ALD

• Expected Outcome: – Mass uptake behavior dependent on Tg of each polymer – Steric hindrance due to size of pendant groups

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• Question: How does polymer microstructure influence the ALD process

• Method: Investigate single TMA dose in a series of polymers with varied microstructures

[3] RP Padbury, JS Jur. Effect of Polymer Microstructure on the Nucleation Behavior of Alumina via Atomic Layer Deposition J. Phys. Chem. C. 118 (32), 18805-18813



Larger absorption of TMA in PBT film with lowest Tg

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Infiltration Parameters: • Temperature: 60oC • TMA Dose time (sec): 0.2 • N2 purge time (sec): 1200 • Pressure (Torr): 1

Tg~66oC

Tg~80oC

PET

PBT



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Tg~20oC

Tg~35oC

Tg~65oC

Tg~115oC

Tg~20oC

Tg~35oC

Tg~65oC

Tg~115oC

Infiltration Parameters: • Temperature: 60oC • N2 purge time (sec): 1200 • Pressure (Torr): 1

Larger absorption of TMA in PBMA with lowest Tg

[4] http://pslc.ws/macrog/tg.htm



Absorption of TMA correlated to Tg of polymer film relative to reactor temperature

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Tg~115oC

Tg~65oC

Tg~35oC

Tg~20oC

Free Volume Theory

Infiltration Parameters: • Temperature: 60oC • N2 purge time (sec): 1200 • Pressure (Torr): 1

[6] P. Neogi, Diffusion in Polymers. In New York : Marcel Dekker: 1996.



Free volume distribution influences TMA absorption

13 [5]Dorkenoo, K. D.; Pfromm, P. H.; Rezac, M. E.. Journal of Polymer Science Part B-Polymer Physics 1998, 36 (5), 797-803.



Increased desorption time of TMA as absorption increases

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Dose Sequence: TMA/N2/H2O/N2

Dose times (sec): 0.2/30/0.2/45

Polymer Tg

(oC)

TMA dose

time (sec)

Absorbed

TMA

(ng/cm2)

Desorbed

TMA

(ng/cm2)

Desorption

Time (sec)

PMMA 115 0.2 60 10 50

PEMA 65 0.2 125 75 75

PPMA 35 0.2 375 275 300

PBMA 15 0.2 640 590 450

PET 80 0.2 400 275 75

PBT 66 0.2 2625 2375 120



Precursor infiltration increases desorption time which influences ALD nucleation

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ALD Parameters: • Dose Sequence: TMA/N2/H2O/N2 • Dose times (sec): 0.2/30/0.2/45

• Extended purge: 0.2/480/0.2/45 • Pressure (Torr): 1 • Temperature (oC): 60



• Question: How does temperature affect the infiltration and nucleation behavior of organometallic precursors?

• Method: Investigate infiltration behavior of TMA using an ALD cycle sequence with an eliminated water dose (i.e. multidoses)

• Expected Outcome:

– Mass uptake dependence on temperature and polymer chemistry

– Relationship between mass gains above and below Tg

Section 2: Temperature dependant infiltration in polymers

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[7] RP Padbury, JS Jur. Temperature-Dependent Infiltration of Polymers during Sequential Exposures to Trimethylaluminum. Langmuir 30 (30), 9228-9238



Constant TMA absorption in PMMA despite onset of saturated mass gain

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Infiltration Parameters: • Number cycles: 10 TMA multidoses • Dose Sequence: TMA/N2/H2O/N2

• Dose times (sec): 0.2/60/0/60 • Pressure (Torr): 1



Nucleation behavior of TMA in PMMA influenced by polymer/substrate interface

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• Interface between PMMA and gold plated quartz creates gradient in Tg

[8], [9]

• High concentration of surface

polymer chain ends

[8] Keddie, J. L.; Jones, R. A. L.; Cory, R. A. Interface and surface effects on the glass-transition temperature in thin polymer-films. Faraday Discuss. 1994, 98, 219-230. [9] Xia, W. J.; Mishra, S.; Keten, S. Substrate vs. free surface: Competing effects on the glass transition of polymer thin films. Polymer. 2013, 54, 5942-5951.



PET does not saturate within 10 TMA multidoses

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PET saturates with larger number of TMA doses

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[10] RP Padbury, JS Jur. Systematic study of trimethyl aluminum infiltration in polyethylene terephthalate and its effect on the mechanical properties of polyethylene terephthalate fibers. J. Vac. Sci. Technol. A 33 (1), 01A112



ToF-SIMS confirms bulk infiltration of TMA in PET films

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Cross-section TEM of PET infiltrated with 100 doses of TMA at 100oC

ToF-SIMS depth profile of PET infiltrated with 10 and 50 doses of TMA at 100oC

[10] RP Padbury, JS Jur. Systematic study of trimethyl aluminum infiltration in polyethylene terephthalate and its effect on the mechanical properties of polyethylene terephthalate fibers. J. Vac. Sci. Technol. A 33 (1), 01A112



Nucleation behavior of TMA in PET

22 [7] RP Padbury, JS Jur. Temperature-Dependent Infiltration of Polymers during Sequential Exposures to Trimethylaluminum. Langmuir 30 (30), 9228-9238



Glass transition temperature and polymer free volume influence TMA mass uptake

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Free volume theory

α

β γ

[6] P. Neogi, Diffusion in Polymers. In New York : Marcel Dekker: 1996.



Conclusion

• Series of poly-n-methacrylates and polyesters indicate mass gain dependence on their respective Tg’s

• Polymers with lowest Tg’s relative to reactor temperature possess greatest absorption of TMA

• Larger absorption of TMA increases desorption time which influences nucleation behavior using typical ALD cycle sequence

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Cotton PP PA-6 PET

Surface inorganic Bulk inorganic Sub-surface hybrid Bulk hybrid

Coating morphologies



Graduate Researchers

Postdoctoral Researchers Jesse S. Jur

Assistant Professor N.C. State University

[email protected]

Undergraduates High Schoolers Mannequins

Funding:

mailto:[email protected]



End

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In Situ Quartz Crystal Microgravimetry (QCM)

Electrodes

Exposure

surface

Crystal drawer

Gas injection

Heated

reaction

chamber

QCM exposure

surface facing

down

Piezo-electric

quartz crystal

Top

Bottom

• Principle of QCM relies on the converse piezoelectric effect

• A piezoelectric crystal placed in an alternating electric field will oscillate in a mechanically resonant mode

• Changes in frequency are related to changes in mass

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Motivation: Hybrid Materials

Hybrid Modification

Layer

Organic Materials Inorganic Materials

Benefits:

• Low cost

• Flexibility

• Easy to form

• High throughput

Benefits:

• Excellent thermal

properties

• High dielectric

constants

• Low permeability

• Photocatalytic behavior

• Chemical resistance 100 nm

epoxy

PA-6

Hygiene

Filtration Medical

Benefits:

•United material properties

from each component

•Mix components at

molecular scale increasing

homogeneity

•Overcome mechanical

mismatch between

components

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Rapid saturation of TMA in PA-6

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Infiltration Parameters:

• Number cycles: 10 TMA multidoses

• Dose Sequence: TMA/N2/H2O/N2




Sub-surface infiltration in PA-6

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AVS-61 JSJur&RPPad_rpedit

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