solvent-less synthesis of organic photonic nanocomposite ... · physics: basics and applications...

Solvent-less synthesis of organic photonic nanocomposite thin films by remote plasma assisted vacuum deposition.

Institute of Materials Science of Seville

Spanish National Research Council (CSIC)-University of Seville, Spain

Francisco J. Aparicio fjaparicio@icmse.csic.es http://www.sincaf.icmse.csic.es/

Plasma deposition of heterogeneous nanostructures with photoactivity

International School on Low Temperature Plasma Physics: Basics and Applications

October 8th 2016

The 1D morphology enables the modulation of the longitudinal or radial composition and structure

Core@shell Hierarchical nanostructures Nanotrees Segmented NWs Homojunctions Heterojunctions Multibranched NWsQDs and MNPs decorated NWs

Enhanced properties / multifunctional systems

Advanced materials for electronics photonics, catalysis, sensing, enegygeneration

WHY 1D NWs, NRs, NBs, NFs??

QDs decorating TiO2 NTs

Single Wire Solar Cells

Briseno et al. JACS 2010, Nano Letters 2011

Examples of Plasma Generated NanoStructures

Silicon QDs; Silicon nanograss.Silicon Solar CellsCheng JMC 2010Xiao J. Phys. D: Appl. Phys. 2011

Low temperature growth of CNTs and CNFsVertical alignment Kato CVD 2006, Science 2003

Graphene

nansheetsand carbon

nanowalls

Ostrikov

Nanoscale

Water repellentCNT-NanocarpetsOstrikov APL 2009

Atmospheric-pressure plasma jetsto improve wound and cancer treatment. Levchenko et al.

Soft organic nanostructures by plasma processingRossi Small 2007

OUTLINE

PECVD of Nanostructured Thin FilmsAd‐species MobilityShadowing

PECVD of 1D HomostructuresMetal Catalyst NanoparticlesPlasma sheath

1D Heterostructures Core@Shell Metal@MetalOxideNanofibersNanorods

1D Heterostructures Core@Shell Oganic@MetalOxide

OUTLINE

PECVD REACTOR (MW-ECR)

TiC12H28O4

REMOTE CONFIGURATION

Pressure 10-2-10-3 torr

Journal of The Electrochemical Society (2007), 154, 152

PECVD of Homogenous Nanostructured Thin Films

Titanium tetraisopropoxide

TiO2 Micro/Nanostructures

Antireflective coatings

Self cleaning surfaces

Separation Membranes

Solar Cells (Grätzel)

Biomaterials

Gas and Humidity Sensors

TiO2: White photoactive compound,Amorphous, or crystalline structure (anatase, rutile)

Controlled Refractive index

High biocompatibility Low cost Good stability and adhesion

High transparency in the visible

TiO2 Micro/Nanostructures

Antireflective coatings

Self cleaning surfaces

Separation Membranes

Solar Cells (Grätzel)

Biomaterials

Gas and Humidity Sensors

TiO2: White photoactive compound,Amorphous, or crystalline structure (anatase, rutile)

Most important processes taking place during the thin film formation

Plasma

formation of highly reactive species

100%O2‐298K 10%O2 25ºC

Pure O2 Discharge Ar/O2 DischargeColumnar or dense compact structures can be obtained depending on the plasma gas composition

100%O2 25ºC

Plasma Chemistry

Growth Mode

Nanostructure

298 K 100% O2 10% O2

Deposition rate (nm/min) 5 2.4

Journal of The Electrochemical Society 154 (2007) 152

100%O2‐298K 10%O2 25ºC

Pure O2 Discharge Ar/O2 DischargeColumnar or dense compact structures can be obtained depending on the plasma gas composition

100%O2 25ºC

298 K 100% O2 10% O2

Deposition rate(nm/min) 5 2.4

Journal of The Electrochemical Society 154 (2007) 152

Key Factors:

Shadowing

Ad‐species mobility

Progress in Materials Science 76 (2016) 59

Glancing Angle Deposition (GLAD)in a Physical Vapour Deposition (PVD) system

TiO2 by e‐ beam evaporation

Ballistic Models

P < 10‐4 torrmean free path > source‐substrate distance

Directional deposition flux

J. Am. Chem. Soc. 130 (2008), 14755Progress in Materials Science 76 (2016) 59

Non‐Directional deposition flux

A minimum thickness threshold is required to induce the columnar growth

Surface roughness Shadowing effect Microporous and Mesoporous Materials 160 (2012) 1.

100%O2 25ºC

Monte Carlo Simulation by increasing the diffusion rate (D) of ad‐species

Microporous and Mesoporous Materials 160 (2012) 1.

High diffusion rates preclude the columnar growth by shadowing

Isotropic flow

Normal Columnar growth

400 500 600 700 800 900

100% O2

TiO*Ti*,TiO*

O2+, O, Ti, TiO

400 500 600 700 800 900

10% O2

Ar*, H*

More intense fragmentation

Reactive species Ti(high sticking coefficient)

Low surface mobility at the growing surface

Lack of Ti or O2 emission lines

The precursor is just partially decomposed TiOXCYHZ

High surface mobility at the growing surface

Columnar Growth Dense Thin films

100% O2

Plasma generation of high‐sticking‐coefficient species

(low mobility)

Shadowing

Columnar Growth

e10% O2

TiOXCYHZ (high mobility)

Dense Structure

100%O2 25º C 100%O2 250º C

At high deposition temperature the microstructure is controlled by the development of the crystalline phase

Crystal Growth & Design 9 (2009) 2869

10%O2 25 ºC

10%O2 250 ºC

At high deposition temperature the microstructure is controlled by the development of the crystalline phase

Crystal Growth & Design 9 (2009) 2869

Microporous and Mesoporous Materials 118 (2009) 314–324

Crystallization

OUTLINE

How can we promote the development of 1D nanostructures?

Rev. Mod. Phys. 77 (2005) 489Advances in Physics 62 (2013) 113

PECVD of 1D Nanostructures

Surface inhomogeneitiesare used to induce the development 1D supported NS

Shadowing effects Diffusion rate of the

ad‐species

Heterogeneous catalytic reactions.

(metal nanoparticles)

Inhomogeneities in the plasma sheath.

Plasma induced surface reaction

Key Factors:

Vapour deposition

CVD and PECVD

Rev. Mod. Phys. 77 (2005) 489 and Advances in Physics 62 (2013) 113

Metallic nanoparticles the preferred nucleation seed for the growth of 1D nanostructures

Advances in Physics 62 (2013) 113 J. Vac. Sci. Technol. B 31 (2013) 050801

Silicon Nanowires

Carbon nanotubes

The vapor–liquid–solid process:Thermal growth of metal-catalyzed semiconductorNanowires (CVD and PECVD processes)

1 Thermal activated catalytic dissociation (DIS) of the source gas on the surface of the metal particles(Substrate temperature > 300 ºC)

2 Surface diffusion (SD) of generated ad-species

3 Incorporation (INC) of the ad-species into the growing structure.

LAP: loss of adsorbed particles at interaction with atomic hydrogen

Journal of applied physics 104 (2008) 073301 J. Appl. Phys. 94 (2003) 6005

PECVD of 1D NanostructuresM

The vapor–liquid–solid process:Thermal growth of metal-catalyzed semiconductorNanowires (CVD and PECVD processes)

1 Thermal activated catalytic dissociation (DIS) of the source gas on the surface of the metal particles(Substrate temperature > 300 ºC)

2 Surface diffusion (SD) of generated ad-species

3 Incorporation (INC) of the ad-species into the growing structure. Plasma Effects:

*Ionization/activation of the incoming species*Local surface heating of the Nanoparticles.

Higher dissociation and diffusion LAP: loss of adsorbed particles at interaction with atomic hydrogen

Journal of applied physics 104 (2008) 073301 J. Appl. Phys. 94 (2003) 6005

PECVD of 1D NanostructuresM

Plasma sheath effects

Phys. D: Appl. Phys. 40 (2007) 2308

Surface inhomogeneities modulates the drop of potential along the plasma sheath

Focalization of the ion current

OUTLINE

Metallic substrates Organic fibers

Thin films

1D Nanostructures

D < 100 nm (2D)

NANOPOROS500nm500nm

Template assisted growth on

PECVD: From Thin Films to Heterogeneous 1D Nanostructures

Core@ShellNanostrucutres

Metallic substrates Organic fibers

Thin films

1D Nanostructures

D < 100 nm (2D)

NANOPOROS500nm500nm

Template assisted growth on

PECVD: From Thin Films to Heterogeneous 1D Nanostructures

Core@ShellNanostrucutres

PECVD on Metallic Substrates

500nmCrystalline TiO2 250º C growth on a silver layer

The film microstructure is completely different on the silver covered zone than on the bare silicon substrate.

J. Phys. D: Appl. Phys. 44 (2011) 174016

Amorphous TiO2

Crystalline TiO2 (250º C)500nm

500nmAmorphous TiO2 (130º C)on Si Preferential growth on

Metallic nanoparticles

J. Phys. D: Appl. Phys. 44 (2011) 174016

Preferential Growth on Metal NanoParticles (MNP)

Conductive nanoparticles

Local inhomogeneities in the electrical field of the plasma sheath.

Focusing of the positive ion current to the metal nanoparticle

Metal induced catalytic processes

Shadowing (neutral species)

Preferential Growth on Metal NanoParticles (MNP)

Growth of Metal@Metal‐Oxide Nanofibers

1) Plasma oxidation a silver Membrane at > 130 ºC

Nanotechnology 17 (2006) 3518Plasma Process. Polym. 4 (2007) 515

Formation of supported core@shell (metal/oxide(Ag@TiO2)) NanoFibers (NF)

2) Plasma deposition of TiO2 > 130 ºC

2‐step process

SEM micrographs from a silver foil after different times of oxygen plasma treatment at 130º C. a) 20 min exposure, b) 60 min exposure, c) 120 min exposure, and d) high magnification image from sample (c).

Plasma oxidation induce the formation of heterogeneous structures

Internal stress at the Ag/Ag2O/AgO interfaces

Molar volumes of silver oxide and metallic silver, are in an ratio of 1:1.6:1.6 for Ag, Ag2O, and AgO,

Prolonged plasma oxidation pre‐treatment

Detection of Ag nanoparticles in the outer shell

Short Plasma TiO2 deposition

Diffusion of Ag to the outer shell at least the first growth

stages

Diffusion of Ag essential for the NF growth

Non Fiber formation

In‐situ XPS Analysis

Ag2O + TiO(CxHy) Ag + TiO2 + CO2 + H2OAg2O + TiO(Ti) Ag + TiO2

TiO2 Ag

Single fibre growth Stages

Proposed chemical reactions

Plasma oxidation pre‐treatment

Heterogeneous metallic and a oxidized Ag structures

PECVD TIO2 deposition is enhanced at the Ag2O NPs

plasma sheath inhomogeneities+

The presence of Ag2O

Ag2O + TiO(CxHy) Ag + TiO2 + CO2 + H2OAg2O + TiO(Ti) Ag + TiO2

Stress accumulated in the external layers of the oxygen‐plasma‐treated silver is released by the formation

of a silver wire

NFs only develop at 130º C

TiO2 deposition occurs preferentially on the wire walls and significantly at its tip

plasma sheath effects

Migration of Ag and Ag Plasma oxidation

Generalization of the formation of M@MOx (M: Ag, Au @MOx: Si, Ti, Zn) 1D NS

Metal@Metal Oxide NanoStructuresGrowth on Metal

layers

Ag@TiO2/SiO2

Ag@SiO2

Au@TiO2

Ag@ZnO

J. Phys. D: Appl. Phys. 44 (2011) 174016

Growth of Metal@Metal‐Oxide Nanorods

Supported Ag@TiO2 NanoRods

DC‐ sputtering of Ag NanoParticles

J. Phys. D: Appl. Phys. 44 (2011) 174016

Supported Ag@TiO2 nanoRods

Plasma Oxidation at 130 ºC

Non Plasma O2 oxidation at 130 ºC provides a more regular distribution

J. Phys. D: Appl. Phys. 44 (2011) 174016

DC‐ sputtering of Ag NanoParticles

Plasma Process. Polym. 11 (2014) 164

TEM and ToF‐SIMS characterization of Ag@TiO2 NanoRods

J. Phys. D: Appl. Phys. 44 (2011) 174016Plasma Process. Polym. 11 (2014) 164

Plasma deposition of TiO2 > 130 ºC

Supported Ag@TiO2 and Ag@ZnO NanoRods

SEs BSEAg

limited amount of silver available

inhomogeneous inner core formed by the agglomeration of small nuclei silver

3D reconstruction of the Ag@ZnONanoRods

HAADF-STEM 3D tomographic reconstruction

J. Mater. Chem. 22 (2012) 1341

Supported Ag@ZnO NanoRods

SEs BSEAg@ZnO

Ag Nanoparticles in the Nanorod shells

Do they paly a key roll?

Used precursor Diethylzinc (ZnEt2)

Nanotechnology 23 (2012) 255303

In situ XPS during exposure of a silver layer to oxygen and ZnEt2

(1) Heating the metallic silver layer under oxygen plasma.

(2a) Exposure of the oxidized silver layer to the ZnEt2 precursor at room temperature chemically reduce the oxidized silver layer, rendering metallic silver andleading to the formation of a ZnO overlayer

(2b) Heating at 132º C in oxygen did not induce any significant change either in the chemical state of the different elements or in the relative intensity of the peaks.(2c) Upon exposure to an oxygen plasma at 132 ºC in (2c), silver becomes reoxidized and a complete reversal of the Zn=Ag intensity ratio occurred. the silver oxide is very mobile and

diffused to cover the ZnO surface were become reoxidazed

‐plasm

a expe

In situ XPS during exposure of a silver layer to oxygen and ZnEt2

(3)‐(6) plasma depositions of ZnO at 132 ºC produced an increase in the amount of deposited ZnO, while surface silver remained oxidized as in (2c).

plasma sheath effects / shadowing effects

Plasma regenerated AgOx/ZnEt2 surface reactionsPlasma oxidation

i) The oxidized silver layer act as nucleation points for the NRs formation

ii) the diffusion of silver or silver oxide to the outer shell contribute to growth of the nanostructure

iii) and IV) most silver has been removed from the substrate layer to decorate the ZnOphase.

R The Growth direction is driven by the precursor flow

mean free path similar to the dispenser‐substrates distance

Tilted and zig‐zag structures

NanoRods Photoactivity

TiO2 and ZnO: Wide band gap semiconductor with photoactive response under UV illumination

Energy Environ. Sci. 5 (2012) 7491

When a semiconductor is irradiated by light of sufficient energy, electrons are excited from the valence band of the semiconductor to the conduction band

Photo‐generation of charge carriers

photocurrents of TiOx thin films during an on–offUV light irradiation cycle

NanoRods Photoactivity

The generated photocarriers migrate to the surface where they are able to reduce and oxidize adsorbed electron acceptors and donors by interfacial charge transfer

Application example: Hydrophilic‐ Super hydrophilic conversion under UV illumination

One of the proposed mechanisms

Applications: Self cleaning sistems. Microfluidics Lab‐on‐a‐chip

θ<90ºHydrophilic

θ>90ºHydrophobic

θ>150ºSuperhydrophobic

γ: Interfacial Energy per unit area (surface tension)SV: Solid-VapourLV: Liquid-VapourSL: Solid-Liquid

In flat materials the contact angel depends on the surface composi on → γSL

Nanorods Photoactivity

Macroscopically, the wettability of solids can be determined bymeasuring the contact angle, which is defined as the angle between the solid surface and the tangent line of the liquid at the contact point between the three phases

tsThe surface structure also has a strong impact on the wettability

Θa: “Apparent” contact angleΘs: Material contact angler: roughness factor (Wenzel)fs: fraction of liquid in contact with the solid

Wenzel Model: Applicable when the liquid penetrates into thegrooves of the rough surface

Cassie and Baxter Model: the liquid does not penetrates and to vapor pockets underneath the liquid are formed

Contac angle increase due to the microstructure

Hydrophilic material → Smaller CAHydrophobic material → Larger CA

Super hydrophobic Ag@TiO2 NanoRods

Fast Superhydrophobic /Superhydrophilicconversion under UV illumination

Dense films

Au‐NP NanoRods with photoactivity in the visible range

Fast Superhydrophobic /Superhydrophilic conversion under UV illumination

Super hydrophobic Ag@ZnO NanoRods

J. Mater. Chem. 22 (2012) 1341

OUTLINE

Hybrid ONW@MetalOxide Nanowires

Plasma Source

Gas input DEZ input

Quartz balance

Thermal evaporator

Pumping system

Rotating sample holder

Growing process

a) Nucleation

b) ONW

c) Core@shell

ZnO Plasma conditions:T = RT – 200oCp = 10‐3 – 10‐6 mbarP = 400 – 800WGases: Ar, O2, H2

Metallic NP or columnar TiO2

Adv. Funct. Mater. 23 (2013) 5981

PECVD of Organic NanoWires (ONW)

Ag NPs on Si(100)

PtOEP NWs

Self-assembly by π-stacking

Physical Vapour deposition of ONW

Langmuir 26 (2010) 5763

Organic Nanowires (ONW)

Zinc phthalocyanine

Columnar ZnOthin film growth on a flat substrate

Hybrid Nanowires

ONW@ZnO

Adv. Funct. Mater. 23 (2013) 5981

Conformal growth of the semiconductor shell over the organic core

Adv. Funct. Mater. 23 (2013) 5981

Hybrid nanowires with different inorganic shells

Adv. Funct. Mater. 23 (2013) 5981 Scientific Reports 6 (2016) 20637

Hybrid nanowires with different inorganic shells

10%O2‐298K

100%O2‐298KThin film on a flat substrate

Adv. Funct. Mater. 23 (2013) 5981 Scientific Reports 6 (2016) 20637

Vertical alignment due to plasma sheath

Charge accumulation at the ONW tips Coulomb Repulsion

Alignment of the flexible ONW

Growth of a rigid inorganic shell

Adv. Funct. Mater. 23 (2013) 5981

Hybrid ONW@MetalOxide Nanowires Photoactivity

Initial WCA

Dense TiO2 films < 90º

Ag@TiO2 Nanorods 150 º

ONW@TiO2Nanowires

180 º

Fast Superhydrophobic/Superhydrophilicconversion under UV illumination

Hybrid ONW@MetalOxide NanowiresNan

esfor liquid‐liq

uid sepa

NANOMEMBRANE

Fluidic separation based in nanometric structures.

Applications:

Microbiology (pharmaceutical industry)

Food industry

Water filtration

Nanoelectronics (sensing, microfluidics cells ).

PLoS ONE 9 (2014) e89712 Thermal Science 19 (2015) 1267

ONW@TiO2 Oxide over metallic filters

esfor liquid‐liq

uid sepa

nMaster Thesis, José Mª Román Cabrerizo, University of Seville

ONW@TiO2 Oxide over metallic filters Nan

esfor liquid‐liq

uid sepa

nMaster Thesis, José Mª Román Cabrerizo, University of Seville

Water and Diiodomethane

mixture

Filtered Diiodomethane

Principles of Fluorescence Spectroscopy 3rd Ed (Lakowicz)

Fluorescence microscopy of the organic core

Photoluminesce spectra of different hybrid systems

The organic core preserve the

photofunctionalproperties

Photonics effects

Stronger emission at the NW tips

erOptical Fiber Working principle

The contrast between the refractive index of the core and shell enables the efficient confinement of the light propagation to the high refractive index material

Critical angle for total reflection θ = arcsin(n1/n2)

Photoluminescence of the inner organic core

Luminescent nano‐optical‐fibers

Luminescent organic core @ high refractive index shell

High refractive index shell Low refractive index coreAdv. Funct. Mater. 23 (2013) 5981

Hybrid systems with different shell

Inorganic Nanotubes

Fabrication of Inorganic nanotubes by annealing

Scientific Reports 6 (2016) 20637

Inorganic NanotubesPh

Photoluminescence of ZnO nanotubes

Photo‐response to environmental O2

Scientific Reports 6 (2016) 20637

The Nanotechnology on Surfaces group

http://www.sincaf.icmse.csic.es/

Tenured ScientistsAna Borras Angel Barranco

20072013

F.J. Aparicio2010

Manuel Macias Montero

2015Maria Alcaire

Alejandro Nicolas Filippin

Agustin R. Gonzalez‐Elipe

Group Leader

solvent-less synthesis of organic photonic nanocomposite ... · physics: basics and applications...

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