Vapor-Phase Processing: The Next Revolution in Paper Manufacturing? Or Functional Paper: From Hydrophobic to Phosphorescent – What Properties are Possible?
Mark D. Losego Assistant Professor of Materials Science and Engineering, Georgia Tech www.losegolab.gatech.edu
Renewable Bioproducts Institute (RBI) Annual Executive Meeting 2016 School of Materials Science & Engineering
Losego Lab – www.losegolab.gatech.edu
Outline • Introduction to Atomic Layer Deposition
• State-of-the-Art in ALD Manufacturing • ALD: Near-Term Opportunities for Paper Manufacturing • Vapor-Phase Modification: Immediate Opportunities for Paper Manufacturing • Summary School of Materials Science & Engineering
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The Losego Lab
• We do Materials Synthesis* including thin film deposition (PVD, CVD, ALD), polymerization, surface functionalization, and electrochemical processing. • Our primary interests are in materials systems that (a) combine organic and inorganic components or (b) use 3-dimensionality to enhance functionality.
Chemical Synthesis & Vacuum Processing
Plasmonic Sensing Materials for National Security
Solar Fuels
Ferroelectrics
Capacitors Materials for Microelectronics
Materials for Renewable Energy
DSSCs Functional Textiles
Molecular Catalysis
Nano-scale heat transport
Conductive Oxides
Solar Fuels Vapor Barriers
0.5 mm
Vapor Barriers MOF on Textile
Tungsten Photonic Structure *Note: We design and build all of our own deposition tools (hardware & software) for maximum adaptability. ALD Reactor
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Film on Foil Capacitors
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Atomic Layer Deposition: An Introduction to the Basics
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Definition Atomic layer deposition (ALD) is a vapor-phase thin film deposition technique that proceeds via a sequential set of surface reactions that are self-limiting. Precursors chemicals are delivered in the gas phase. Precursors are delivered sequentially (NOT concurrently).
Precursors only react with solid surfaces, not with other precursors in the gas phase. Precursors do not react with themselves.
School of Materials Science & Engineering
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Atomic Layer Deposition Purge Dose Precursor Precursor (Metal Organic (Inert Gas or Purge) Metal Halide) Surface Reaction + Byproduct Removal
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Atomic Layer Deposition Dose Purge Co-Reactant Precursor (Oxidant (Inert Gas or Reductant) Purge)
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Atomic Layer Deposition Dose DoseCo-Reactant Precursor (Metal (Oxidant Organic oror Reductant) Metal Halide)
ETC…
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Virtues of ALD 1. Provides highly conformal coatings, even over complex nanostructured 3D architectures
Ritala, M. et al., Chem. Vap. Dep. 5 7 (1999)
2. Provides very high precision and reproducibility in film thickness. (deposition rates of ≈ 1 Å / cycle)
Losego & Arpin, Nat. Comm. 4 2630 (2013)
3.8 nm
50 cycles
Spagnola et al. J. Mater. Chem. 20 4213 (2010)
3. Potential for low process temperatures compatible with polymer substrate. (Many oxide ALD processes < 150°C) Nylon
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0.5 mm
1 mm
Losego Lab – www.losegolab.gatech.edu
Triyoso et al. JVSTB 23 288 (2005)
Tungsten- Coated Nylon
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Nuances of ALD
Subsurface!
Nylon
Refractive Index
1. ALD is NOT like the cartoons! 1 cycle does not necessarily equal 1 atomic layer. For example, TMA/H2O cycles are ~1/3 of a layer. 2. Subsurface deposition occurs for many polymeric systems.
Ligands block sites!
Deposition Temperature
3. Film density and organic content can change with temperature.
Platinum ALD
Al:ZnO ALD
4. Nucleation can be a problem. Delay!
5. Byproducts can cause problems. Mackus, Bol, and Kessels, Nanoscale 6 10941 (2014) School of Materials Science & Engineering
Losego Lab – www.losegolab.gatech.edu
Elam & George, Chem. Mater. 15 1020 (2003)
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All Sorts of Materials Can Be Deposited by ALD…
Miikkulainen, Leskala, Ritala, Puurunen J. Appl. Phys. 113, 021301 (2013) School of Materials Science & Engineering
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An ALD Reactor in the Losego Lab
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A Commercial ALD Reactor (Beneq)
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So this is just a research curiosity?
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We all (probably) own something manufactured by ALD
Starting with the 45 nm node (circa 2007), all integrated circuits have been manufactured using ALD to deposit the transistor’s gate oxide. (400,000,000+ transistors in this IC)
2007 School of Materials Science & Engineering
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State-of-the-Art in ALD Manufacturing
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Challenges to ALD Manufacturing
1. Low Throughput Research systems like our flow tube reactors can take 2 min / cycle, which equates to 1.5 days to deposit 0.1 mm. -Can be overcome by increasing pumping speeds, using batch processing –
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Large Batch ALD Manufacturing Used in semiconductor industry (ICs and PVs) -ALD used for gate oxides since 2007
2007
• About 4 s per cycle • 1.5 nm/min or 0.1 mm/hr • Up to 500 wafers per batch Skarp, ECS Trans. 33 447 (2010). Shown: Applied Materials (USA) and Beneq (Finland) School of Materials Science & Engineering
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Challenges to ALD Manufacturing
1. Low Throughput Research systems like our flow tube reactors can take 2 min / cycle, which equates to 1.5 days to deposit 0.1 mm. -Can be overcome by increasing pumping speeds, using batch processing –
2. Non-Continuous Processing Research reactors that use temporal dose/purge steps are not readily adaptable to a continuous process -Continuous ALD systems use spatial separation of precursors –
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Continuous Manufacturing: Spatial ALD
Precursor Zone
Purge Zone
Coreactant Zone
Levitech (Netherlands)
Lotus Applied Technologies (USA)
Poodt et al., JVSTA. 30 010802 (2012). School of Materials Science & Engineering
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Continuous ALD Manufacturing
Eastman Kodak (USA) Poodt et al., JVSTA. 30 010802 (2012). School of Materials Science & Engineering
ASTRaL (Finland)
Losego Lab – www.losegolab.gatech.edu
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Outlook for ALD Manufacturing 1. A number of companies are developing ALD systems for manufacturing 2. Large batch ALD systems are already used for manufacturing ICs and PVs 1. Spatial ALD reactors are coming and could revolutionize paper & textile manufacturing (Next 5 to 10 years) School of Materials Science & Engineering
Losego Lab – www.losegolab.gatech.edu
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Atomic Layer Deposition: Opportunities for Paper Modification
School of Materials Science & Engineering
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Electrically Conductive Paper Before
After
Light Bulb!
Conformal Coating
Micrograph from a cotton ball School of Materials Science & Engineering
Losego Lab – www.losegolab.gatech.edu
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Color Changing Paper?
In collaboration with the Reynolds Group at GT School of Materials Science & Engineering
Losego Lab – www.losegolab.gatech.edu
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Newspaper That Resists UV Degradation
ALD coatings of TiO2 or ZnO act like sunscreen and prevent the UV degradation of mechanically pulped papers like newsprint.
Hanson, Oldham, & Parsons J. Vac. Sci. Technol. A, 30 01A117 (2012) School of Materials Science & Engineering
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Single-Cycle Vapor Modification: An Immediate Opportunity for Paper
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Single Cycle Vapor Phase Modification 1. Evacuate chamber 2. Fill chamber with reactive, volatile precursor. 3. Wait for reaction 4. Evacuate chamber.
Paper
5. Vent and remove. Pump
Precursor
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Gaseous Precursors Get EVERYWHERE (Or “Look, Mom, No Surface Tension!”)
We are able to convert cellulosic fibers from hydrophilic to hydrophobic using a single exposures cycle that takes < 1 min. (a) Cotton
(b) Paper
This effect is irrespective of the cellulose’s form factor because gaseous precursors can diffuse everywhere! (c) Denim School of Materials Science & Engineering
(d) Cardboard Losego Lab – www.losegolab.gatech.edu
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Water Repellent Paper
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Water Repellent Cardboard
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Potential to Introduce More Functionality Fluorescence
Hydrophobicity
Organics
Anti-Bacterial
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Oxides
Erbium, Europium
Iron, Cobalt
Magnetism
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Summary Burgeoning opportunities in vapor-phase modification of paper-based products. Roll-to-roll atomic layer deposition has the potential to revolutionize paper and textile manufacturing. (Who will seize this opportunity?) An even more immediate opportunity is to use single-cycle (or few cycle) vapor phase processing techniques to enhance the properties of FINISHED paper products. -Water Repellency -Anti-Bacterial -Phosphorescence / Fluorescence -Magnetism School of Materials Science & Engineering
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Acknowledgments The Losego Group @ Georgia Tech
Research Funding
ACS Petroleum Research Fund Doctoral New Investigator Program under Award Number 55526DNI10.
Brandon Piercy (Graduate Student) Collen Leng (Graduate Student) Daniel Yin (Undergraduate) Derek Henry (Undergraduate) Shawn Gregory (Undergraduate) Andrew Short (Undergraduate) School of Materials Science & Engineering
Georgia Tech Startup Funds
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School of Materials Science & Engineering
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“Ideal” ALD The ALD “Temperature Window” • Provide sufficient precursor to saturate the surface • Purge sufficiently long to remove all excess precursor
*Sometimes thisetwindow only19,a 161 few degrees Kalanyan, Losego a. Chem. Vap. is Deposition (2013).
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• Work within a temperature window where ONLY surface reactions are thermodynamically favored.
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