Short Commuication
Open Access
Polymeric Dye Film Deposition in Vacuum
Kostyantyn Grytsenko1* and Yurii Slominskii2
1Institute of Semiconductor Physics, Laboratory of Semiconductor Molecular Systems, Ukraine
2Institute of Organic Chemistry, Department of Color and Structure of Organic Compounds, Murmanska, Ukraine
2Institute of Organic Chemistry, Department of Color and Structure of Organic Compounds, Murmanska, Ukraine
*Corresponding author: Kostyantyn Grytsenko, Institute of Semiconductor Physics, Laboratory of Semiconductor Molecular Systems, Ukraine. Tel: +38044 5255530; Fax: +38 044 5255530; E-mail:
@
Received: October 26, 2017; Accepted: November 8, 2017; Published: November 10, 2017
Citation: Grytsenko K, Slominskii Y (2017) Polymeric Dye Film Deposition in Vacuum. Nanosci Technol 4(2): 1-4. DOI: 10.15226/2374-8141/4/1/00149
AbstractTop
A new type of evaporable organic molecules containing
unsaturated reactive fragment has been developed for vacuum
deposition of the polymer dye film. The designed molecules contain
the core chromophore for an active optoelectronic function. The
properties of the thin solid films, produced using new evaporationactivation-
polymerization method from the novel compounds possess
enhanced smoothness, hardness and thermal stability. Some dyes
form nano-wires by a self-assembly between the two neighbour gold
strips on the silicone surface.
Keywords: Dye; Vacuum; Evaporation; Activation; Polymerization; Thin Film; Optical Spectra; Annealing
Keywords: Dye; Vacuum; Evaporation; Activation; Polymerization; Thin Film; Optical Spectra; Annealing
Introduction
The development of organic electronics has started at the end
of 20th century. Now the world market of devices based on
functional organic compoundshas been estimated at billions
of dollars. Organic light emitting devices, organic field effect
transistors, various optical and electrical sensors represent just
a short list of the industrial applications of the organic functional
materials. The requirements to organic material vary depending
on the application, but the long term of usage is necessary.
Functional organic layer can be formed from molecules of two
types: a small molecule (dye) or a macromolecule (polymer). The
polymer materials are more robust and have a longer lefe time.
While the polymer film can be deposited by wet method only with
a few exceptions, the dye layer can be made by both wet methods
and vacuum deposition technology. Only some homopolymers
can be deposited by heating, decomposition and secondary
polymerization in vacuum [1]. Widely used in the inorganic
electronics vacuum deposition is not very compatible with wet
methods for in-line production. Moreover, wet methods have some
restrictions for production of multi-layered and multi-component
systems. Using vacuum deposition, there are no restrictions
in wettability of components and layers. The production of the
polymer film by the gas phase deposition provides the benefit
of ease gas processing (small volatile molecules) and stability
of the polymer material. The most vivid example is the di-para-
xylylene gas phase pyrolytic activation-polymerization without
by-products release. The obtained polyparaxylylene films are
characterized with the high thermal and chemical stability and
they have found applications in various industrial products.
Produced by deposition in vacuum, organic solids frequently
appear in the form of mesh, needles,discontinuous aggregates.
The stability of such “films” is not satisfying. It can be improved
by increase of compound molecular weight, but this leads to lose
of evaporability. Therefore, to find a solution to the problem
of producing stable and smooth polymeric films from organic
chromophore by deposition in vacuum is very important for
industrial applications. Previously attempts to polymerize dyes
in plasma were made in Japan, using standard molecules of
phthalocyanine andmerocyanine[2-4]. The deposits were stable
polymers, but their optical absorption was reduced. Authors
emphasized, that the part of the molecules were decomposed.
Later the plasma-assisted dye deposition was performed [5].
Dye molecules were sublimed and introduced to the already
glowing discharge in benzene vapor. Authors reported, that
the part of the dye molecules was damaged. Thus, more dyes
were “polymerized” using plasma with an aim to produce
stable films[6-9]. From IR-spectra authors concluded, that the
dye molecules were incorporated in the “polymer” film, but no
another compound, except dye, was in the plasma. It means, that
the part of the molecules was decomposed to produce “polymer”
matrix.
In general, the energetic species of low temperature plasma destruct chemical bonds in the molecule in the gas phase. Then molecules with opened bonds are condensing on the substrate surface and interacting with each other, producing a “polymer” film. When the classic plasma treats a molecule with the size larger, thanthe small monomer (namely chromophore), it leads to destruction of themolecule in a random way with loss of the chromophore optical properties. Moreover, to ignite the plasma, it is necessary to produce a conductive path in the gas, which leads to ionization and decomposition of the part of the molecules. Therefore, both classic plasma polymerization and standard chromophores are not suitable for production of the polymer film with optoelectronic properties of the pristine molecules.But the attempt to produce polymer films from organic compounds in plasma is still in progress[10,11], indicating the importance of the stable organic functional thin films.
Thus, the new type of the chromophore containing unsaturated group, which is able to open only after evaporation but before the condensation has to be designed. The new technology for selective activation of this unsaturated bond in the gas phase should be created.
In general, the energetic species of low temperature plasma destruct chemical bonds in the molecule in the gas phase. Then molecules with opened bonds are condensing on the substrate surface and interacting with each other, producing a “polymer” film. When the classic plasma treats a molecule with the size larger, thanthe small monomer (namely chromophore), it leads to destruction of themolecule in a random way with loss of the chromophore optical properties. Moreover, to ignite the plasma, it is necessary to produce a conductive path in the gas, which leads to ionization and decomposition of the part of the molecules. Therefore, both classic plasma polymerization and standard chromophores are not suitable for production of the polymer film with optoelectronic properties of the pristine molecules.But the attempt to produce polymer films from organic compounds in plasma is still in progress[10,11], indicating the importance of the stable organic functional thin films.
Thus, the new type of the chromophore containing unsaturated group, which is able to open only after evaporation but before the condensation has to be designed. The new technology for selective activation of this unsaturated bond in the gas phase should be created.
Experimental Details
Deposition of the thin dye films have been performed using UVN-
74 vacuum installation. Base pressure in the chamber was 10-3
Pa. Glass and Si plates have been used for film deposition. Gold
film was deposited on part of the glass and Si plates by thermal
evaporation. Dye powder have been heated in quartz crucible.
The vapor was activated in the gas phase. Growth rate and film
thickness were measured with Sigma quartz thickness monitor.
Film thickness, morphology and nanohardness were studied
using atomic force microscope (AFM) NanoscopeIIIa Dimension
3000TM at room temperature in a tapping mode. Optical spectra
were measured during film heating in the air using Polytec
spectrometer.
Results and Discussion
Creation of comparatively large evaporable and reactive
organic molecule needed special design. The molecule has to
have a special groupthat is not able to react with a neighboring
group during heating up to the evaporation temperature. This
bond has to be opened by activation in the gas phase only, thus
supplying active diradicalsto the substrate surface. They has to be
condensed at room temperature on the substrate surface, interact
with each other to produce a polymeric solid. It was was hardly
possible to calculate the structure of the necessary molecule
due to close values of the energies (E) of the all C=C bonds. The
molecule have to satisfy the following rule:
Eevaporation < Eopening unsaturated bond < Eall other bonds in the molecule
The energy of activation has to be matched with the energy of the unsaturated bond opening.Following this approach, less energetic plasma was tested for polymerization of several comparatively large monomers with unsaturated bond by Grytsenko et al. [12]. It was found that decrease of the discharge power in the monomeric gaseous medium led to the formation of the solid film with the properties close to classic polymer. Stable films of a small merocyanine dye with optical absorption in ultraviolet region were also deposited in plasma. Later various molecules were designed and tested. Ultimately the desired compounds were designed and synthesized [13].
Depending on the molecule structure, activation conditions and substrate material, the solids with different morphologies were produced.Experimental results, obtained using two reactive merocyanine compounds, 1 and 2, are presented in this paper.
Morphology and nano-mechanical properties of the films were varied by changing activation parameters (Figure 1, 2). The films, deposited with the best activation conditions, were smooth at nano-level and showed enhanced nano-hardness. The roughness of the film, deposited with activation by small power classic low temperature plasma was 18 nm, while the roughness of the film from the same dye but deposited with the new activation method was 1,4 nm, (Figure 1). Several dyes have revealed nanowire growth by self-assembly. Figure 1 shows the nanowires (about 30 micrometers ,1 micrometers) lying on the Si surface with both ends attached to the side surfaces of the two neighbor gold strips. Usually the second end of the nanowire is loose [14,15].The additional efforts were necessary to connect the loose end with another surface. The optimal activation conditions were strictly individual for each dye.
Eevaporation < Eopening unsaturated bond < Eall other bonds in the molecule
The energy of activation has to be matched with the energy of the unsaturated bond opening.Following this approach, less energetic plasma was tested for polymerization of several comparatively large monomers with unsaturated bond by Grytsenko et al. [12]. It was found that decrease of the discharge power in the monomeric gaseous medium led to the formation of the solid film with the properties close to classic polymer. Stable films of a small merocyanine dye with optical absorption in ultraviolet region were also deposited in plasma. Later various molecules were designed and tested. Ultimately the desired compounds were designed and synthesized [13].
Depending on the molecule structure, activation conditions and substrate material, the solids with different morphologies were produced.Experimental results, obtained using two reactive merocyanine compounds, 1 and 2, are presented in this paper.
Morphology and nano-mechanical properties of the films were varied by changing activation parameters (Figure 1, 2). The films, deposited with the best activation conditions, were smooth at nano-level and showed enhanced nano-hardness. The roughness of the film, deposited with activation by small power classic low temperature plasma was 18 nm, while the roughness of the film from the same dye but deposited with the new activation method was 1,4 nm, (Figure 1). Several dyes have revealed nanowire growth by self-assembly. Figure 1 shows the nanowires (about 30 micrometers ,1 micrometers) lying on the Si surface with both ends attached to the side surfaces of the two neighbor gold strips. Usually the second end of the nanowire is loose [14,15].The additional efforts were necessary to connect the loose end with another surface. The optimal activation conditions were strictly individual for each dye.
Figure 1: Morphology of the 1 compound deposits on glass, produced
with various (1,2,3) activation conditions, 3 – 3D image of the surface of
the film; 4 - nanowires from compound 2 on Si between two gold strips;
5 – film of compound 1 deposited with low power plasma, 6 - film of
compound 1 deposited with new activation method; marks were made
with AFM tip during hardness measurements.
Figure 2: Load-penetration curves of the films, deposited with different
activation methods: dyes 1 and 2; 1,2,3 – activation conditions.
Optical spectra of the films deposited with activation
contained one monomeric band of the pristine chromophore,
while the films of the same dyes but deposited without activation
contained broadened and red-shifted band. The films, deposited
with the best activation conditions, revealed no transformations
of the optical spectra during heating in air to decomposition
temperature (Figure 3). The decomposition temperature for the
films, deposited with activation was higher, than for the films,
deposited by the classic thermal evaporation. Moreover, the
decomposition temperature of the films exceeded the evaporation
temperatureof the pristine dyes. The enhanced properties of
the films can be explained by the formation of the polymeric
(oligomeric) material. This development is just the first stage of
the research: several types of the much bigger compounds for
polymerization in vacuum, previously unknown, were designed.
The technologies for evaporation-activation-polymerization of
these new reactive chromophores were presently developed and
tested. The second set of the new molecules containing two active
functionalities was designed, in particular, evaporable organic
salts, containing unsaturated group. After their activation upon
evaporation, thin films of cationic dye polymer were obtained.
The molecules, containing core chromophore for photovoltaic,
the unsaturated group and the group for bonding with gold will
be synthesized. The compounds with reactive groups open the
pathways to form a soft matter with enhanced properties, for
example, co-polymerization of two insoluble dyes to produce one
phase solid with no phase separation during heating and so on.
The developed compounds and the deposition technology open
the new direction for creation stable active elements for various
optoelectronic devices on nano- and macro-level.
Figure 3: Optical transmission spectra of the films of the dye 1 (a-c) and 2 (d-f) during heating in air: a,d - films deposited by conventional thermal evaporation, b,c,e,f - – films deposited by activation methods 2 and 3.
Conclusions
The developed evaporable organic compounds with the
reactive group in combination with the activation methods for
selective reaction of this group during the deposition process
lead to the formation of smooth and highly stable thin organic
films. Variations in the activation parameters allow controlled
morphology of the deposited films from the smooth surface at
nano-level to the self-assembled nano-wires in multilayered
nanostructured system.
ReferencesTop
- Gritsenko K P, Krasovsky A M. Thin film deposition of polymers by vacuum degradation. Chemical Reviews. 2003;103(9):3607-3650. doi: 10.1021/cr010449q
- Kashiwazaki N. Iodized Polymeric Yb-Diphthalocyanine Films Prepared by Plasma Polymerization Method. Jap. J. Appl. 1992;31(1) 1892.
- Inagaki N, Tasaka S, Ikeda Y. Plasma polymerization of copper phthalocyanine and application of the plasma polymer films to NO2 gas sensor device. J. Appl. Polymer Sci. 1995; 55(10):1451-1464.
- Inoue M, Morita H, Takai Y, Mizutani T, Ieda M. Photovoltaic Cells of Merocyanine Dye Polymer Thin Films Prepared by Plasma Polymerization Method. Jap. J. Appl. Phys. 1988;27:1059.
- Homilius F, Heilmann A, von Borzyskowski C. Plasma polymer thin films with encapsulated dye molecules and silver nanoparticles. Surface & Coat. Technol. 1995;74-75:594-597.
- Barranco, Groening P. Fluorescent Plasma Nanocomposite Thin Films Containing Nonaggregated Rhodamine 6G Laser Dye Molecules,Langmuir. 2006;22(16):6719-6722. doi: 10.1021/la053304d
- Barranco, Aparicio F, Yanguas-Gil A, Groening P, Cotrino J, González-Elipe A R. Optically Active Thin Films Deposited by Plasma Polymerization of Dye Molecules. Chem. Vap. Deposition. 2007;13(6-7):319-325.
- Blaszczyk-Lezak I, Aparicio F J, Borras A, Barranco A, Alvarez-Herrero A, Fernandez-Rodrıguez M, et al. Optically Active Luminescent Perylene Thin Films Deposited by Plasma Polymerization. J. Phys. Chem. C . 2009;113(1):431-438.
- Aparicio F J, Borras A, Blaszczyk-Lezak I, Groening P, Alvarez-Herrero A, Fernandez-Rodrıguez M, et al. Luminescent and Optical Properties of Nanocomposite Thin Films Deposited by Remote Plasma Polymerization of Rhodamine 6G. Plasma Process. Polym. 2009; 6(1):17-26.
- Palacios J C, Olayo M G, GuillermoJ Cruz, J. A. Chávez-Carvayar. Meyer-NeldelRuleinPlasmaPolythiopheneThinFilms, OpenJ. PolymerChemistry. 2014;4(3):31-37. doi: 10.4236/ojpchem.2014.43004
- Martín M A. Remote plasma assisted fabrication of functional organic and hybrid thin films and supported nanostructures. Ph.D. Thesis, Universidad de Sevilla. 2015.
- Gritsenko K P, Tolstopyatov E M, Yagupolskii L M, Yagupolskii Yu L, Kremlev M M, Slominsky Yu Let al. Plasma polymerisation of complex organic molecules, Conference Ionizing Radiation and Polymers-98. Weinbohla.1998.
- Tolstopyatov E, Grytsenko K, Kolomzarov Yu, Lytvyn P, Navozenko O, Schrader S , et al .Polymeric dye by gas phase deposition, Conference Polymer composites and tribology. Gomel, Belarus. 2013.
- Zhao Y S, Zhan P, Kim J, Sun C, Huang J. Patterned Growth of Vertically Aligned Organic Nanowire Waveguide Arrays. ACS NANO. 2010; 4(3):1630-1636. doi: 10.1021/nn901567z
- Tavares L, Kjelstrup-Hansen J, Thilsing-Hansen K, Rubahn H G. Organic nanofibers integrated by transfer technique in field-effect transistor devices. Nanoscale Research Lett. 2011;6: 319.