Organic-inorganic Thin Films Research Articles

(Invited) Molecular Layer Deposition of Flexible, Transparent and Conductive Hybrid Organic-Inorganic Thin Films

Hybrid organic-inorganic thin film alloys were fabricated by molecular layer deposition (MLD) and atomic layer deposition (ALD) methods using diethyl zinc (DEZ), hydroquinone (HQ), and water (H2O). Sequential exposures of DEZ & HQ for zincone MLD and DEZ & H2O for ZnO ALD led to the linear growth of zincone alloy films. The alloy film composition could be varied by changing the number of MLD cycles and ALD cycles per reactant sequence. The alloy films were found to be highly conductive. Zincone alloys grown with MLD:ALD cycle ratios of 1:1 and 2:2 displayed sheet resistivities in the 10-3Ω cm range. These sheet resistivities were substantially lower than the sheet resistivity for ZnO ALD films. These alloys films may be useful as flexible, transparent and conducting coatings.

Correction to “Conformal Organic-Inorganic Hybrid Network Polymer Thin Films by Molecular Layer Deposition using Trimethylaluminum and Glycidol”

Correction to “Conformal Organic-Inorganic Hybrid Network Polymer Thin Films by Molecular Layer Deposition using Trimethylaluminum and Glycidol”

A Low Dielectric Study on Hybrid Plasma-Polymer Thin Films of Different Ratio Between Toluene and TEOS

Organic-inorganic hybrid co-polymer thin films were deposited on silicon(100) substrates under the several ratio of TEOS (tetraethoxysilane) against toluene by plasma enhanced chemical vapour deposition (PECVD) method. Toluene and TEOS were utilized as organic and inorganic precursors each, and hydrogen and argon were also used as a bubbler and carrier gases, respectively. In order to compare the difference of the electrical and the mechanical properties of the plasma polymerized thin films, we grew the hybrid co-polymer thin films under the conditions of various ratio between toluene and TEOS with fixed RF (radio frequency using 13.56 MHz) powers at 30 W. The as-grown polymerized thin films were in first analyzed by FT-IR and XPS. The result of FT-IR showed that the co-polymer thin films were polymerized with fragmented each precursor. Also, XPS results showed the chemical species and binding energies of each species. Si 2p core-level spectra from the hybrid polymer thin film showed the status of Si oxidation number. Impedance analyzer was utilized for the measurements of I-V curves and capacitance values. Also, the thin films were analyzed for hardness and Young's modulus by nano-indenter.

Hybrid organic/inorganic ambipolar thin film transistor chemical sensor

An ambipolar hybrid organic-inorganic thin film transistor, consisting of pentacene and zinc oxide as semiconductors, is reported. The current-voltage characteristics in different operational modes are studied. The transistor is employed as a chemical vapor sensor, operating at room temperature. In p-channel accumulation mode, which is dominated by hole transport, a decrease of current with the introduction of analyte is observed, while in the n-channel triode mode, in which the current is predominantly contributed by electron transport, an increase in current with analyte delivery is observed. A qualitative model based on dipole interaction is proposed to explain the sensing activity.

Molecular Layer Deposition of Conductive Hybrid Organic-Inorganic Thin Films Using Diethylzinc and Hydroquinone

Conductive hybrid organic-inorganic thin films were fabricated by molecular layer deposition (MLD) methods using diethyl zinc (DEZ) and hydroquinone (HQ). Sequential exposures of DEZ and HQ led to linear MLD film growth. The mass gains measured by quartz crystal microbalance investigations were 52.3 ng/cm2 per MLD cycle. Scanning electron microscope images of focused ion beam milled cross-sections of the MLD film were consistent with a MLD growth of 1.6 Aå per cycle at 150oC. The DEZ/HQ MLD films were conductive based on four-point electrical probe measurements.

Photostability and moisture uptake properties of wood veneers coated with a combination of thin sol-gel films and light stabilizers

Abstract In recent years, there has been increased interest in the use of inorganic UV blocking nanoparticles for photostabilization of wood surfaces. Photostability and moisture uptake properties of wood veneers coated with a combination of hybrid inorganic-organic thin sol-gel films and organic light stabilizers was investigated. The light stabilizers were applied by brushing, and the thin sol-gel films were deposi-ted on the wood surface by dipping in a sol prepared from a mixture of methyltrimethoxysilane, hexadecyltrimethoxysilane, and aluminum isopropoxide precursors. Although the sol-gel film improved the moisture resistance of the wood veneers, it showed mixed results on photostability. Under light and spray conditions in a Weather-Ometer™, specimens treated with a combination of sol-gel thin film and a UV absorber, tris-resorcinol triazine and an acrylic self-crosslink-ing binder, or treated with lignin stabilizer/tris-resorcinol triazine/acrylic self-crosslinking binder showed good overall weathering performance. Under permanent light conditions in the Weather-Ometer™, specimens treated with a combination of sol-gel thin film, a lignin stabilizer, and a water soluble UV absorber – namely: (2-hydroxyphenyl)-benzotriazole – revealed a good overall weathering performance. This study has demonstrated the feasibility of using a combination of organic light stabilizers and sol-gel deposits of hybrid inorganic-organic thin films to improve weathering resistance of softwood substrates.

Effects of atomic layer deposition temperatures on structural and electrical properties of ZnO films and its thin film transistors

Organic-inorganic thin film transistors (OITFTs) with Al/ZnO/PVP structure on Si substrate were fabricated and studied as to their structural and electrical properties. PVP (poly-4-vinylphenol) organic gate insulator was coated on Si substrate by spin coating method. The ZnO was deposited as an active layer by using the atomic layer deposition (ALD) method on PVP/Si substrate at various temperatures ranging from 80 to 140 °C. The structural and electrical properties of ZnO thin films were analyzed by X-ray diffraction and by hall-effect measurement system for optimum process of the OITFT. The grain size and carrier concentration of ZnO films increased, and the resistivity decreased as the deposition temperature increased from 80 to 140 °C. The field effect mobility, on/off current ratio and threshold voltage of OITFTs with ZnO active layer deposited at 100 °C were found to be 0.37 cm2/V·s, 5×102 and 5 V, respectively.

Composite biocompatible hydroxyapatite–silk fibroin coatings for medical implants obtained by Matrix Assisted Pulsed Laser Evaporation

The aim of this study was to obtain biomimetic inorganic–organic thin films as coatings for metallic medical implants. These contain hydroxyapatite, the inorganic component of the bony tissues, and a natural biopolymer – silk fibroin – added in view to induce the surface functionalization. Hydroxyapatite (HA), silk fibroin (FIB) and composite HA–FIB films were obtained by Matrix Assisted Pulsed Laser Evaporation (MAPLE) in order to compare their physical and biological performances as coatings on metallic prostheses. We used an excimer laser source (KrF*, λ = 248 nm, τ = 25 ns) operated at 10 Hz repetition rate. Coatings were deposited on quartz, Si and Ti substrates and then subjected to physical (FTIR, XRD, AFM, SEM) analyses, correlated with the results of the cytocompatibility in vitro tests. The hybrid films were synthesized from frozen targets of aqueous suspensions with 3:2 or 3:4 weight ratio of HA:FIB. An appropriate stoichiometric and functional transfer was obtained for 0.4–0.5 J/cm2 laser fluence. FTIR spectra of FIB and HA–FIB films exhibited distinctive absorption maxima, in specific positions of FIB random coil form: 1540 cm−1 amide II, 1654 cm−1 amide I, 1243 cm−1 amide III, while the peak from 1027 cm−1 appeared only for HA and composite films. Osteosarcoma SaOs2 cells cultured 72 h on FIB and HA–FIB films showed increased viability, good spreading and normal cell morphology. The well-elongated, flattened cells are a sign of an appropriate interaction with the MAPLE FIB and composite HA–FIB coatings.

Polymeric acrylate-based hybrid films containing lead and iron patterned by UV photo-polymerization.

The development and processing of hybrid inorganic-organic thin film materials plays a critical role in advancing interdisciplinary sciences and device manufacturing. Here we present a novel approach to synthesize and deposit acrylate-containing organic/inorganic hybrid films. The material is based on a chemical solution and includes specifically desired metal dopants that are fully integrated into the backbone of the polymer structure. The film can be deposited by simple spin coating, and we confer photosensitive properties to the material making it directly patterned by traditional UV photolithography techniques. Film thickness, chemical characterization, and wet/dry etching capability of the film are also investigated. We believe this innovative material has the potential to be used in a broad range of applications for electronic, photonic, biology, and other interdisciplinary fields.

Sacrificial layers for air gaps in NEMS using alucone molecular layer deposition

A molecular layer deposition approach is reported that produces a new class of hybrid organic–inorganic thin films. These films have very low densities, and display typical atomic layer deposition characteristics: controllable linear growth, conformality, low roughness, and uniform composition. Because of their aluminum content, the alucone films cannot be dry etched with oxygen plasma. In accordance with their molecular structure, the new materials are completely removed in hydrochloric acid solutions. Since they can be etched with accurate control in acidic solutions, these hybrid materials are promising for the fabrication of MEMS/NEMS (Micro/Nano Electro Mechanical Systems) devices. Doubly supported structures with 120 nm air gaps are demonstrated using alucone materials as sacrificial layers.

Sol–gel processing and UVA patterning of epoxy-based hybrid organic–inorganic thin films

Sol–gel processed photosensitive hybrid organic–inorganic films, deposited from 2-(3,4-epoxycyclohexylethyltrimethoxysilane) (EETMOS), have been studied. EETMOS sols have been optimized with respect to several criteria that guarantee a good quality, photosensitivity, and reproducibility of derived films. Photo-sensitivity of EETMOS-based films has been assessed by UVA exposure experiments. Optimized films have been photo-patterned using a mercury lamp or a He–Cd laser source, both emitting in the UVA spectral range. Promising micronic size motives have been laser patterned. The quality of derived motives is discussed with respect to photopolymerization mechanisms and photo-patterning parameters.

Wood surface modification by in-situ sol-gel deposition of hybrid inorganic–organic thin films

Interest in the use of nanoparticles of iron, titanium, aluminum, and zinc oxides in transparent coatings for wood is increasing. Such nano-composite coatings have the potential of not only preserving the natural color of the wood, but also stabilizing the wood surface against the combined degradative effects of sunlight and moisture. The nanoparticles can be used as additives to coating formulations or deposited directly as thin films on a substrate. Thin film deposition can be accomplished by plasma-enhanced chemical vapor or by sol-gel deposition. This paper describes sol-gel deposition of a hybrid inorganic-organic thin film on wood using a mixture of metal-organic precursors and its effect on weathering properties of the wood surface.

Luminescent properties of complexes Y1−xEux(TTA)3(TPPO)2 in nano-TiO2

Abstract A series of HTTA (thenoyltrifluoroacetone) and TPPO (trioctylphosphine oxide) complexes with different molar ratios of Eu3+ to Y3+ has been synthesized. Characterization with XRD, IR, UV, elemental analysis and fluorescence spectroscopy has also been carried out. These results showed luminescence of Eu3+ complex was enhanced after doped with Y3+. The organic–inorganic thin film of complexes Y1−xEux(TTA)3(TPPO)2 in nano-TiO2 was fabricated, and the nano-TiO2 has been used in the luminescence layer to change the luminescence property of complexes Y1−xEux(TTA)3(TPPO)2. It was found that there was an efficient energy transfer process between the ligands and metal ions.

Chemical and Electrical Properties of ZnS Deposited with DEZ and H<sub>2</sub>S by Atomic Layer Deposition Method

ZnS thin films were grown by Atomic Layer Deposition (ALD) method with Diethyl- Zinc (DEZ) and hydrogen sulfide (H2S) for the application of a channel layer of OITFT (Organic-Inorganic Thin-Film Transistor). ZnS has many advantages such as high channel mobility, high deposition rate, transparency at room temperature due to the broad band gap (bandgap of ZnS : 3.7 eV), nontoxic characteristic, low resistivity, and less sensitive about oxidation than ZnO. The deposition rate of the ZnS films in our system was about 1.6 Å/cycle. ZnS film was characterized by AES, XRD, Hall-effect measurement.

Polymerization Kinetics of Methacrylic Groups in Organic-Inorganic Hybrid Polymeric Thin Films

ABSTRACTIn this paper, the polymerization kinetics of unsaturated double bonds (C=C) in TiO2- and ZrO2-doped hybrid polymeric thin films during UV irradiation and thermal curing is studied by monitoring the variation of C=C absorption band at 1630 cm-1 using FT-IR spectroscopic technique. Experimental results showed that polymerization of the unsaturated C=C groups in the TiO2- and ZrO2-doped hybrid polymers can be realized by either photo-irradiation or thermal treatment. The UV-induced polymerization process is much faster than thermal curing, but a full conversion of C=C groups into polyacrylate chains cannot be achieved without thermal treatment. The catalytic effect of TiO2 and ZrO2 on promoting the polymerization of C=C groups was observed, and the time of UV exposure and thermal curing for cross-linking C=C bonds was found to decrease with the increase of the concentration of TiO2 and ZrO2. The activation energy of the hybrid material containing varied concentration of TiO2 and ZrO2 was calculated, and the results indicated that TiO2 is more active than ZrO2 in promoting the polymerization of the unsaturated C=C bonds. Finally, the mechanisms for TiO2 and ZrO2 enhancing the material's photosensitivity (i.e. promoting polymerization of C=C bonds) have been proposed and discussed.

Composition and Functional Properties of Organosilicon Plasma Polymers from Hexamethyldisiloxane and Octamethylcyclotetrasiloxane

ABSTRACTHybrid organic-inorganic thin films with different fractions of silicon oxide were deposited in rf capacitively coupled discharges using pure hexamethyldisiloxane (HMDSO), octamethylcyclotetrasiloxane (D4) or 5 % HMDSO in O2. The deposition in continuous wave (cw) mode was compared with pulsed conditions under which the discharge on-time was 5 ms and the off-time varied from 0.5 to 15 ms. The chemical composition of the films was studied by FTIR, RBS and ERDA. Their optical properties in UV / visible / NIR were determined from spectroscopic ellipsometry and reflectance measurements fitted with a Kramers-Kronig consistent dispersion model based on a parametrization of density of states. Film hardness and reduced modulus were determined from depth sensing indentation tests.

A Highly Photoconductive Poly(vinylcarbazole)/2,4,7-Trinitro-9-fluorenone Sol−Gel Material that Follows a Classical Charge-Generation Model

Highly photoconductive properties are reported for organic-inorganic hybrid sol-gel thin film materials composed of a classical poly(vinylcarbazole)/2,4,7-trinitro-9-fluorenone (PVK/TNF) polymeric mixture, entrapped in a SiO(2) matrix, whose pores have been chemically modified by organic functional groups. The highest photosensitivity obtained, 3.4 x 10(-10) cm Omega(-1) W(-1) at E 22 V microm(-)1, at the optimum molar ratio between the active components, TNF, PVK, and SiO(2), is in the range of the highest values ever reported for any PVK/TNF-based classical photoconductive material. It is demonstrated that the PVK/TNF-based sol-gel films follow Onsager's classical charge-generation model. The analysis of the photocurrent efficiency (Phi) of PVK/TNF-based sol-gel films by such a model provides the primary quantum yield of thermalized pair formation and the initial thermalized pair distance, phi(0) = 0.12 and r(0) = 66.1 Angstrom, respectively, for the optimized sample. As a result of Onsager's analysis, a notorious improvement of the photocurrent generation process was achieved for low TNF concentrations.

Characterization of the Multi-Layer Encapsulation of Thin Films on Ethylene Terephthalate (PET)

In this paper, the inorganic-organic thin film encapsulation layer was newly adopted to protect the organic layer from moisture and oxygen. Using the electron beam, sputter and spin-coater system, the various kinds of inorganic and organic thin-films were deposited onto the Ethylene Terephthalate (PET) and their interface properties between organic and inorganic layer were investigated. In this investigation, the SiON and Polyimide (PI) layer showed the most suitable properties Under these conditions, the WVTR for PET can be reduced from a level of 0.57 g/m2/day (bare substrate) to 1*10−5 g/m2/day after application of a SiON and PI layer. These results indicate that the SiON/PI/SiON/PI/PET barrier coatings have high potential for flexible organic light-emitting diode (OLED) applications.

Silane coating of metal substrates: Complementary use of electrochemical, optical and thermal analysis for the evaluation of film properties

Silane coating is a metal surface pre-treatment introduced as a replacement for chromium treatments. It is supposed to be suited for various metals, including aluminium, steel and galvanised steel. Good corrosion performance has been assigned to these hybrid organic–inorganic thin film deposition systems. The silane molecules contain Si O C n H (2 n+1) groups, which after hydrolysis into reactive silanol groups Si OH form a covalent bonded layer on the metal surface. Curing of these films is considered essential for corrosion protection; during heat treatment, condensation of unreacted silanol groups in the film result in the formation of a Si O Si network with enhanced barrier properties. This contribution gives a chemical and morphological characterisation, obtained with spectroscopic ellipsometry (SE), of BTSE silane coated aluminium as a function of curing. Further, with thermal gravimetric analysis combined with mass spectroscopy (TGA-MS), the mechanism and kinetics of the curing process are explained, and the resulting barrier properties are measured using electrochemical impedance spectroscopy (EIS).

ADVANCED MODELLING OF EPITAXIAL ORDERING OF ORGANIC LAYERS ON CRYSTALLINE SURFACES

A fine balance between weak molecule-molecule interactions and usually only weakly laterally varying molecule-substrate interactions governs the physical structure of organic-inorganic and organic-organic heteroepitaxial thin films. Therefore, it is important to investigate the energetics of realistically large overlayer domains. So far, Potential calculations for large domains of organic overlayers on crystalline substrates were computationally demanding due to the vast number of atoms to be considered. Here, we present a technique which for the first time enables the calculation of both the molecule-substrate interaction potential and the molecule-molecule interaction potential for large molecular domains (up to several thousands of rather large molecules) by utilizing potential energy grid files. This technique does not only allow the investigation of the substrate influence but also full Monte-Carlo based structural optimizations, if applied to 2D crystalline overlayers. Furthermore, it provides an estimate for the energetic gain combined with the differently aligned overlayer domains. In several examples we will discuss the usefulness of this method. As a general result, we will provide evidence that energetically favorable lattice structures in OMBE systems are not restricted to commensurate unit cells or coincident super cells.