Organic-inorganic Thin Films Research Articles

Annealing of thin “Tincone” films, a tin-based hybrid material deposited by molecular layer deposition, in reducing, inert, and oxidizing atmospheres

Molecular layer deposition of hybrid organic–inorganic thin films called “tincones” is achieved using tetrakisdimethylaminotin as the metal precursor and glycerol (GL) as the organic reactant. The GL-based process displays linear growth and self-limiting surface reactions in a broad temperature window ranging from 75 to 200 °C. At higher temperatures, no film growth is possible. The growth per cycle decreases rapidly with increasing temperature from 1.3 Å at 75 °C to less than 0.1 Å at 200 °C. The films are observed to be smooth with scanning electron microscopy and atomic force microscopy. The hybrid organic–inorganic nature of the films is visible in both infrared spectroscopy and x-ray photoelectron spectroscopy. As deposited tincone films are annealed in reducing (H2), inert (He), or oxidizing (O2) atmospheres. In situ x-ray diffraction is employed to study the crystallization of the films during annealing. Tincone films annealed in reducing or inert atmosphere crystallize into a tetragonal SnO phase at 388 and 410 °C, respectively. These temperatures are lower than the crystallization temperature of 480 °C for atomic layer deposition (ALD) tin oxide films annealed in H2. Tincone films annealed in oxygen crystallize into an SnO2 phase at a temperature of 523 °C, which is similar to the crystallization temperature for ALD tin oxide films annealed in He or O2. This reduced temperature for crystallization into SnO for the tincone films is interesting since SnO is one of the few metal oxides known as a p-type semiconductor material.

(Invited) Organic-Inorganic Hybrid Perovskite Tfts with MoO3 Modified Electrodes

: Organic-inorganic hybrid perovskites have attracted substantial attention because of their excellent physical properties, which enable them to serve as the active material in emerging hybrid solar cells. Here, we proposed a new type of thin-film field-effect transistor (TFT) with an organic-inorganic hybrid perovskite channel layer. The organic-inorganic hybrid perovskite material has advantages of a high mobility like that of an inorganic semiconductor and the easy process like an organic layer. A TFT using CH3NH3PbI3 as the semiconducting channel was demonstrated. The effect of the evaporation amount of PbI2 on the crystallization and thickness of CH3NH3PbI3 films was studied. The organic-inorganic hybrid perovskite thin film with an average grain size of 1µm and a smooth surface has been achieved . The MoO3 was adopted as a buffer layer between metal electrodes and the active layer, which remarkably reduced the contact resistance from 705 kΩ·cm to 0.164 kΩ·cm, resulting in the improvement of the interface characteristics and performance of devices. The organic-inorganic hybrid perovskite TFT with the field effect mobility of 3.88cm2/V.s and the subthreshold slope of 1.6 V/dec. was achieved. Fig. 1 shows its transfer curves. This kind of TFT can be processed by cheap, low-temperature techniques, which suggest that it may be suitable for applications that require low cost, a large area, and the flexibility. Molecular engineering of the organic and inorganic components of the hybrids perovskite is expected to further improve device performance for high speed application. Figure 1

Molecular Layer Deposition Using Ring-Opening Reactions: Molecular Modeling of the Film Growth and the Effects of Hydrogen Peroxide.

Novel coating materials are constantly needed for current and future applications in the area of microelectronics, biocompatible materials, and energy-related devices. Molecular layer deposition (MLD) is answering this cry and is an increasingly important coating method for organic and hybrid organic–inorganic thin films. In this study, we have focused on hybrid inorganic–organic coatings, based on trimethylaluminum, monofunctional aromatic precursors, and ring-opening reactions with ozone. We present the MLD processes, where the films are produced with trimethylaluminum, one of the three aromatic precursors (phenol, 3-(trifluoromethyl)phenol, and 2-fluoro-4-(trifluoromethyl)benzaldehyde), ozone, and the fourth precursor, hydrogen peroxide. According to the in situ Fourier-transform infrared spectroscopy measurements, the hydrogen peroxide reacts with the surface carboxylic acid group, forming a peroxyacid structure (C(O)–O–OH), in the case of all three processes. In addition, molecular modeling for the processes with three different aromatic precursors was carried out. When combining these modeling results with the experimental research data, new interesting aspects of the film growth, reactions, and properties are exploited.

Iron-Terephthalate Coordination Network Thin Films Through In-Situ Atomic/Molecular Layer Deposition

Iron terephthalate coordination network thin films can be fabricated using the state-of-the-art gas-phase atomic/molecular layer deposition (ALD/MLD) technique in a highly controlled manner. Iron is an Earth-abundant and nonhazardous transition metal, and with its rich variety of potential applications an interesting metal constituent for the inorganic-organic coordination network films. Our work underlines the role of the metal precursor used when aiming at in-situ ALD/MLD growth of crystalline inorganic-organic thin films. We obtain crystalline iron terephthalate films when FeCl3 is employed as the iron source whereas depositions based on the bulkier Fe(acac)3 precursor yield amorphous films. The chemical composition and structure of the films are investigated with GIXRD, XRR, FTIR and XPS.

Investigation of electrochemical properties of bio-inspired SiOx/PI multilayered thin film anode for lithium ion batteries

The organic-inorganic multilayer thin film composed of SiOx (nonstoichiometric silicon suboxides) and PI (polyimide) has been synthesized by a hybrid sputtering system combining reactive RF sputtering and pulsed laser deposition. SiOx/PI thin films were deposited on a copper foil to investigate its electrochemical properties. The chemical composition of as-deposited SiOx/PI coatings was measured by a FE-EPMA. The overall multilayered structure was observed by a Scanning Electron Microscopy. The SiOx/PI multilayer thin film anode with proper architecture control exhibits higher columbic efficiency during 1st charge/discharge cycle and better capacity retention as compared to pure SiOx thin film anode. The fracture toughness of SiOx/PI multilayer thin film anode is measured via nanoindentation and be compared to the pure SiOx thin film anode. The results show that the multilayer structure reveals a higher fracture toughness, which leads to a better structure stability during the charge/discharge cycling.

Atomic and Molecular Layer Deposition of Hybrid Mo–Thiolate Thin Films with Enhanced Catalytic Activity

AbstractA synthetic route toward hybrid MoS2‐based materials that combines the 2D bonding of MoS2 with 3D networking of aliphatic carbon chains is devised, leading to a film with enhanced electrocatalytic activity. The hybrid inorganic–organic thin films are synthesized by combining atomic layer deposition (ALD) with molecular layer deposition (MLD) using the precursors molybdenum hexacarbonyl and 1,2‐ethanedithiol and characterized by in situ Fourier transform infrared spectroscopy, and the resultant material properties are probed by X‐ray photoelectron spectroscopy, Raman spectroscopy, and grazing incidence X‐ray diffraction. The process exhibits a growth rate of 1.3 Å per cycle, with an ALD/MLD temperature window of 155–175 °C. The hybrid films are moderately stable for about a week in ambient conditions, smooth (σRMS ≈ 5 Å for films 60 Å thick) and uniform, with densities ranging from 2.2–2.5 g cm−3. The material is both optically transparent and catalytically active for the hydrogen evolution reaction (HER), with an overpotential (294 mV at −10 mA cm−2) superior to that of planar MoS2. The enhancement in catalytic activity is attributed to the incorporation of organic chains into MoS2, which induces a morphological change during electrochemical testing that increases surface area and yields high activity HER catalysts without the need for deliberate nanostructuring.

Vectorial method used to monitor an evolving system: Titanium oxide thin films under UV illumination

Under in situ UV illumination, some materials present evolution of their opto-electronic properties that can be monitored by spectroscopy. We present here a mathematical method which can be applied to spectroscopic measurements when an evolving set of data is recorded: the vectorial method. The investigations and quantifications are performed by Infrared spectroscopy and XPS on organic-inorganic thin films prepared by sol-gel. The inorganic part of these hybrid thin films contains Ti oxide-network based whereas the organic part is composed of N,N-dimethylformamide and its hydrolysis products. Under UV illumination, those films exhibit intermediate bandgap behavior due to the photoreduction of Ti(IV) in Ti(III). The role of the solvent in the thin film is underlined during the process of photoreduction together with an understanding of the condensation of the Ti oxide-based network, as these evolutions are critical for the opto-electronic properties of those thin films.

Hydrazinium Salt as Additive To Improve Film Morphology and Carrier Lifetime for High-Efficiency Planar-Heterojunction Perovskite Solar Cells via One-Step Method.

One-step solution process is the simplest method to fabricate organic-inorganic metal halide perovskite thin films, which however does not work well when employed in the planar-heterojunction (PHJ) solar cells due to the generally poor film morphology. Here we show that hydrazinium chloride can be used as an additive in the precursor solution to produce perovskite films featuring higher coverage and better crystallinity. The light absorption ability and charge carrier lifetime are both significantly improved accordingly. Under the optimal additive ratio, the average power conversion efficiency (PCE) of the inverted PHJ perovskite solar cells greatly increases by as much as 70%, and the champion device shows a satisfying PCE of 12.66%. These results suggest that N2H5Cl is a promising additive for fabricating high-efficiency perovskite solar cells via one-step method, which could be of interest in the future commercial solar cell industry.

Molecular Layer Deposition for Applications in Lithium-Ion Batteries

Molecular layer deposition (MLD) of hybrid organic-inorganic thin films called titanicones, vanadicones, tincones, and alucones was investigated for electrode and solid electrolyte applications in lithium-ion batteries. The titanicone, vanadicone and tincone films were studied as electrode materials, both as anodes and cathodes. Novel MLD processes were developed for these materials and were based on an alkylamine metal precursor (TDMAT, TEMAV, TDMASn) and glycerol (GL) as the organic reactant. Linear and self-limited growth could be achieved for these metalcones in a broad temperature range with temperature-dependant growth rates ranging from 0.2 to 1.3 Å/cycle. Film growth was studied in situ with spectroscopic ellipsometry (SE) and infrared spectroscopy (FTIR). The as-deposited films appeared to be electrochemically inactive in all cases. A post-deposition heat treatment up to 500°C in either inert (helium) or oxidizing (air) atmosphere was able to electrochemically activate the films. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) measurements showed that all carbon was removed during calcination in air and that the films crystallized. However, annealing in inert atmosphere conserved the carbon content of the film and thus the films remained amorphous. The performance with increasing charging and discharging rate, and cyclability of the heat-treated MLD electrodes was tested against their respective metal oxide references. The He-annealed metalcones emerged from these tests as the best performing electrodes at higher rates (left and middle figures) and with improved capacity retention and stability during repeated charging and discharging. The transformation of alucone films, deposited with the TMA and ethylene glycol (EG) or GL process, into porous aluminium oxide was examined. Porous, non-conducting materials are interesting for lithium-ion battery research since they may serve as the matrix template for solid composite electrolytes. Calcination in air and water etching proved to be the most successful methods. For the calcination treatment, a clear relation was found between the ramp rate during both heating and cooling and the resulting porosity of the film (right figure). The aging behaviour of the films in ambient atmosphere was also investigated with FTIR and showed that the films deposited with EG decompose in a matter of only a few hours, as opposed to those deposited with GL. Figure 1

Excitation-dependent fluorescence from atomic/molecular layer deposited sodium-uracil thin films

Atomic/molecular layer deposition (ALD/MLD) offers unique possibilities in the fabrication of inorganic-organic thin films with novel functionalities. Especially, incorporating nucleobases in the thin-film structures could open new avenues in the development of bio-electronic and photonic devices. Here we report an intense blue and widely excitation-dependent fluorescence in the visible region for ALD/MLD fabricated sodium-uracil thin films, where the crystalline network is formed from hydrogen-bonded uracil molecules linked via Na atoms. The excitation-dependent fluorescence is caused by the red-edge excitation shift (REES) effect taking place in the red-edge of the absorption spectrum, where the spectral relaxation occurs in continuous manner as demonstrated by the time-resolved measurements.

Synthesis and Fluorescence Properties of a Terbium Complex with Ferrocenylazobenzoic Acid in Nanoparticles

Tb (AUFA)32H2O, a rare earth terbium complex,was synthesized by introducing 4-(11-azobenzene-undecyloxy) ferrocene acid (AUFA) as the ligand. This complex was characterized by elemental analysis, MS, IR, Raman, UV spectroscopy and fluorescence spectrophotometry. The complex exhibited ligand-sensitized green emission, and Tb (AUFA)32H2O had a higher sensitized luminescence efficiency and a longer lifetime than the other terbium complexes (DPC: 2, 6-Pyridinedicarboxylic acid, Aspirin: 2-ethanoylhydroxybenzoic acid). The organic-inorganic thin film of complexe Tb (AUFA)32H2O in nanoTiO2 was fabricated, and the nanoTiO2 has been used in the luminescence layer to change the luminescence property of complexes Tb (AUFA)32H2O. It was found that there was an efficient energy transfer process between the ligands and metal ions. Moreover, In an ITO/PVK/Tb (AUFA)32H2O/Al device, Tb3+ may be excited by intramolecular energy transfer from the ligand, as observed by electroluminescence. The main emitting peak at 545 nm can be attributed to the 5D4→7F5 transition of the Tb3+ ion, and this process results in the enhancement of the green emission from the electroluminescence device.

Atmospheric deposition process for enhanced hybrid organic–inorganic multilayer barrier thin films for surface protection

In this study, organic polymer poly-vinyl acetate (PVA) and inorganic aluminum oxide (Al2O3) have been used together to fabricate a hybrid barrier thin film for the protection of PET substrate. The organic thin films of PVA were developed through roll to roll electrohydrodynamic atomization (R2R-EHDA) whereas the inorganic thin films of Al2O3 were grown by roll to roll spatial atmospheric atomic layer deposition (R2R-SAALD) for mass production. The use of these two technologies together to develop a multilayer hybrid organic-inorganic barrier thin films under atmospheric conditions is reported for the first time. These multilayer hybrid barrier thin films are fabricated on flexible PET substrate. Each layer of Al2O3 and PVA in barrier thin film exhibited excellent morphological, chemical and optical properties. Extremely uniform and atomically thin films of Al2O3 with average arithmetic roughness (Ra) of 1.64nm and 1.94nm respectively concealed the non-uniformity and irregularities in PVA thin films with Ra of 2.9nm and 3.6nm respectively. The optical transmittance of each layer was∼80-90% while the water vapor transmission rate (WVTR) of hybrid barrier was in the range of∼2.3×10−2gm−2day−1 with a total film thickness of∼200nm. Development of such hybrid barrier thin films with mass production and low cost will allow various flexible electronic devices to operate in atmospheric conditions without degradation of their properties.

Organic-Inorganic Hybrid Perovskite with Controlled Dopant Modification and Application in Photovoltaic Device.

Organic-inorganic hybrid perovskite as a kind of promising photovoltaic material is booming due to its low-cost, high defect tolerance, and easy fabrication, which result in the huge potential in industrial production. In the pursuit of high efficiency photovoltaic devices, high-quality absorbing layer is essential. Therefore, developing organic-inorganic hybrid perovskite thin films with good coverage, improved uniformity, and crystalline in a single pass deposition is of great concern in realizing good performance of perovskite thin-film solar cell. Here, it is found that the introduction of suitable amounts of LiI plays a dramatically positive role in enlarging the grain size and reducing the grain boundaries of absorbing layer. In addition, the carrier lifetime and built-in potential of the LiI doped perovskite device are observed to increase. Thus, it leads to about 15% gain in solar cell efficiency comparing to that without the LiI doping. Meanwhile, a hysteresis reduction is observed and 18.16% power conversion efficiency is achieved in LiI doped perovskite device, as well.

Moisture absorption properties of hardwood veneers modified by a sol-gel process

Abstract A new invisible nanolevel coating has been developed based on the sol-gel process for veneer finishes. The sol synthesis and its application as a protective agent is described. It could be demonstrated that a combination of organic light stabilizers and sol-gel deposits is feasible and that the resulting hybrid inorganic-organic thin films decrease moisture uptake of hardwood veneers.

Tailoring a compact and stable Langmuir bi-dimensional PbX-based layered perovskite film at the air-water interface and on solid support.

The present work studies the stability of Langmuir organic-inorganic superlattice materials thin films consisting of layered perovskite-based films with controlled 2D framework as well as to design experimental conditions for increasing the efficiency of the organic-inorganic perovskite motif by mechanical stimulus. Therefore, a whole covering of the air/water interface by a compact and stable lead-based layered perovskite structure is pursued. A 2D layered perovskite-type hybrid structure of the form [(CH3(CH2)19NH3)2(PbX4)], X=Cl, and Br, in which, two-dimensional sheets stabilized by a inner bilayer of organic monoammonium cation matrix, is mechanically tailored by successive compression-expansion cycles. The formation of 2D molecular patterns has been characterized by ΔR, BAM, XRD and XPS.

Aerosol-assisted low pressure plasma deposition of antimicrobial hybrid organic-inorganic Cu-composite thin films for food packaging applications

Abstract An innovative low pressure plasma process for deposition of copper-containing hybrid organic-inorganic thin films was developed. The discharge was fed with an aerosol of an aqueous solution of a copper complex, i.e. bis(ethylenediamine)copper(II) hydroxide and argon. Polymeric films, incorporating inorganic Cu(I) and Cu(II) compounds, were obtained. Morphological and chemical characterizations of the coatings were carried out. Antimicrobial properties were assessed on two species of Pseudomonas spp. In vitro tests were carried out by contact of the optimized films, deposited on square polycarbonate samples (~ 4 cm 2 ), with cell suspensions of 1 × 10 4 CFU/mL for 18 h at 25 °C. It was demonstrated that, the hybrid organic-inorganic thin coatings have potential utilization as active packaging material, showing an antimicrobial effect of up to three orders of magnitude (final microbial concentration 10 5 CFU/mL), compared to control polycarbonate (final microbial concentration 10 8 CFU/mL). Industrial relevance An innovative low pressure plasma process for deposition of copper-based, hybrid organic-inorganic thin films was developed. The optimized thin coatings have potential industrial utilization as active packaging material, being very effective against pseudomonads. Viability of Pseudomonas was reduced by three orders of magnitude (from 10 8 CFU/mL to 10 5 CFU/mL) in the presence of developed films, thus suggesting further investigation of the technique under food packaging conditions.

Thin-film encapsulation of organic electronic devices based on vacuum evaporated lithium fluoride as protective buffer layer

Encapsulation is indispensable for organic thin-film electronic devices to ensure reliable operation and long-term stability. For thin-film encapsulating organic electronic devices, insulating polymers and inorganic metal oxides thin films are widely used. However, spin-coating of insulating polymers directly on organic electronic devices may destroy or introduce unwanted impurities in the underlying organic active layers. And also, sputtering of inorganic metal oxides may damage the underlying organic semiconductors. Here, we demonstrated that by utilizing vacuum evaporated lithium fluoride (LiF) as protective buffer layer, spin-coated insulating polymer polyvinyl alcohol (PVA), and sputtered inorganic material Er2O3, can be successfully applied for thin film encapsulation of copper phthalocyanine (CuPc)-based organic diodes. By encapsulating with LiF/PVA/LiF trilayer and LiF/Er2O3 bilayer films, the device lifetime improvements of ~10 and 15 times can be achieved. These methods should be applicable for thin-film encapsulation of all kinds of organic electronic devices. Moisture-induced hole trapping, and Al top electrode oxidation are suggest to be the origins of current decay for the LiF/PVA/LiF trilayer and LiF/Er2O3 bilayer films encapsulated devices, respectively.

Organic-inorganic hybrid fluorescent sensor thin films of rhodamine B embedded Ag-SBA15 for selective recognition of Hg (II) ions in water

Nowadays, the rapid and effective detection of low doses of heavy metal pollutants in contaminated water is a timely challenge in environmental pollution research. In this study, a rapid and highly sensitive assay for the detection of Hg2+ based on quenching of metal-enhanced fluorescence of rhodamine B (RB) has been fabricated. RB and silver nanoparticle were incorporated into the mesoporous siliceous framework spin cast on a quartz glass through post-synthetic incorporation method. The morphology and crystallinity of mesoporous structure and Ag nanoparticle were characterized by transmission electron microscopy and X-ray diffraction analyses. Photoluminescence assays on the hybrid thin film of RB-Ag-SBA15 showed a high enhancement when compared to the intensity of silver free SBA15-RB in the wavelength of 575nm. The fluorescence of RB-Ag-SBA15 thin film decreased gradually with the increase in the concentration of Hg2+ and the detection limits were 10.54nmol/L. Furthermore, the fluorescence intensity increased linearly with the concentration of Hg2+ in the range from 1.0×10−8mol/L to 10×10−8mol/L, with a response time of a few seconds. In addition, this system offers a high selectivity over interfering cations such as Cd2+and Pb2+. Overall, we have developed an optical assay having a well-ordered mesoporous SBA15 containing Ag-RBfor selective detection of Hg2+ in aqueous solution. The scheme combines the advantages of specific binding interactions between Hg2+ and RB molecule and optical emission properties of RB. The method is suitable for a single-shot and irreversible analytical assay in a quartz glass/microtiter plate.

Ion irradiation induced structural modifications and increase in elastic modulus of silica based thin films

Ion irradiation is an alternative to heat treatment for transforming organic-inorganic thin films to a ceramic state. One major shortcoming in previous studies of ion-irradiated films is the assumption that constituent phases in ion-irradiated and heat-treated films are identical and that the ion irradiation effect is limited to changes in composition. In this study, we investigate the effects of ion irradiation on both the composition and structure of constituent phases and use the results to explain the measured elastic modulus of the films. The results indicated that the microstructure of the irradiated films consisted of carbon clusters within a silica matrix. It was found that carbon was present in a non-graphitic sp2-bonded configuration. It was also observed that ion irradiation caused a decrease in the Si-O-Si bond angle of silica, similar to the effects of applied pressure. A phase transformation from tetrahedrally bonded to octahedrally bonded silica was also observed. The results indicated the incorporation of carbon within the silica network. A combination of the decrease in Si-O-Si bond angle and an increase in the carbon incorporation within the silica network was found to be responsible for the increase in the elastic modulus of the films.

Superhydrophobic organic-inorganic thin films on aluminum by a simple one-step electrochemical process

Superhydrophobic organic-inorganic thin films on aluminum by a simple one-step electrochemical process