Layered self-organized structures on poly(3-octylthiophene) thin films studied by scanning probe microscopy

The morphology and mechanical properties of poly-(3-octylthiophene) P3OT films thin has been studied by scanning force microscopy techniques. On these films we find self-assembled layered structures that appear regardless of the preparation conditions, that is, spin-coating or drop-casting, of the solvent concentration or of the type of substrate. Using the drop-casting method for sample preparation these layered structures are hardly visible due to the high surface roughness, while using spin-coating these structures are the main topographic feature on the surface. These structures have typically one or two layers, even though occasionally up to four layers have been observed. Each layer has a height of 4-5 nm, which is associated to crystalline P3OT domains and lay on the polymer film. The size of these structures increases with increasing concentration of the P3OT in the solvent. We find well differentiated morphological, electrostatic as well as mechanical properties for the self-assembled structures as compared to the rest of the polymer film. Finally, the growth rate of these structures has been studied.     

Partial dewetting of polyethylene thin films on rough silicon dioxide surfaces

The effect of roughness on the dewetting behavior of polyethylene thin films on silicon dioxide substrates is presented. Smooth and rough silicon dioxide substrates of 0.3 and 3.2-3.9 nm root-mean-square roughness were prepared by thermal oxidation of silicon wafers and plasma-enhanced chemical vapor deposition on silicon wafers, respectively. Polymer thin films of approximately 80 nm thickness were deposited by spin-coating on these substrates. Subsequent dewetting and crystallization of the polyethylene were observed by hot-stage optical microscopy in reflection mode. During heating, the polymer films melt and dewet on both substrates. Further observations after cooling indicate that, whereas complete dewetting occurs on the smooth substrate surface, partial dewetting occurs for the polymer film on the rough surface. The average thickness of the residual film on the rough surface was determined by ellipsometry to be a few nanometers, and the spatial distribution of the polymer in the cavities of the rough surface could be obtained by X-ray reflectometry. The residual film originates from the impregnation of the porous surface by the polymer fluid, leading to the observed partial dewetting behavior. This new type of partial dewetting should have important practical consequences, as most real surfaces exhibit significant roughness.     

Behavior and surface energies of polybenzoxazines formed by polymerization with argon,oxygen, and hydrogen plasmas

Polybenzoxazine (PBZZ) thin films can be fabricated by the plasma‐polymerization technique with, as the energy source, plasmas of argon, oxygen, or hydrogen atoms and ions. When benzoxazine (BZZ) films are polymerized through the use of high‐energy argon atoms, electronegative oxygen atoms, or excited hydrogen atoms, the PBZZ films that form possess different properties and morphologies in their surfaces. High‐energy argon atoms provide a thermodynamic factor to initiate the ring‐opening polymerization of BZZ and result in the polymer surface having a grid‐like structure. The ring‐opening polymerization of the BZZ film that is initiated by cationic species such as oxygen atoms in plasma, is propagated around nodule structures to form the PBZZ. The excited hydrogen atom plasma initiates both polymerization and decomposition reactions simultaneously in the BZZ film and results in the formation of a porous structure on the PBZZ surface. We evaluated the surface energies of the PBZZ films polymerized by the action of these three plasmas by measuring the contact angles of diiodomethane and water droplets. The surface roughness of the films range from 0.5 to 26 nm, depending on the type of carrier gas and the plasma‐polymerization time. By estimating changes in thickness, we found that the PBZZ film synthesized by the oxygen plasma‐polymerization process undergoes the slowest rate of etching in CF₄ plasma. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4063–4074, 2004     

Ultrathin films of variable polarity and crystallinity obtained from 1,2-polybutadiene nanoparticle dispersions

Characterization of ultrathin films of different polymer nanoparticles obtained at room temperature via spin-coating of aqueous dispersions and their morphology are described. Very small nanoparticles of semicrystalline 1,2-polybutadiene (PB), noncrystalline poly(1-butene) (PH), and poly(1-butenal) (PHF) were prepared via catalytic emulsion polymerization and subsequent hydrogenation or hydroformylation. The prefabricated nanoparticles were used as building blocks. The thin films obtained are continuous and transparent (n=1.5; κ=0). The properties of these films, formed from different constituents, are analyzed. Atomic force microscopy (AFM) and transmission electron microscopy (TEM) images show that the PB-films are very smooth (rms roughness=10 nm) and polycrystalline. Recrystallization of these PB films reveals that edge-on lamellae are the constituent units. Films with very low roughness values (rms roughness <2 nm) are obtained with PH nanoparticles, due to the soft character of the nanoparticles. The AFM profile of the PHF films reveals that the surface remains structured after drying due to the high degree of the internal cross-linking that occurs in the nanoparticles. Quantification of the films' polarity (I(3)/I(1)=0.89, 1.3, and 2.1 for PHF, PB, and PH, respectively) agrees well with the previous values obtained for the polymer dispersions. Surfactant molecules are desorbed during the film formation; however, these aggregates can be removed by rinsing with water with no undesirable effects observed on the films.     

8－羟基喹啉铝掺杂聚乙烯基咔唑薄膜的光致发光及电致发光

８－羟基喹啉铝掺杂聚乙烯基咔唑薄膜的光致发光及电致发光马於光,唐建国,沈家骢,刘式墉（吉林大学分子光谱与分子结构开放实验室,集成光电子学国家联合重点实验室,长春,１３００２３）关键词聚合物,光致发光,电致发光,８－羟基喹啉铝某些有机染料作为波长转换介...     

Synthesis and structure features of composite silicate and hybrid TEOS-derived thin films doped by inorganic and organic additives

The results of long-term researches of thin films prepared from tetraethoxysilane-derived sols containing inorganic and organic additives are systematized and analyzed. These additives give to films certain physicochemical properties for their application in electronic techniques, optics, power engineering, in biological technologies etc. The influence both inorganic (salts, acids) and organic (polyols, polyionenes, epoxy resin) additives on rheological properties and aggregate stability of sols as well as films surface morphology is minutely considered. The explanations of phenomena during film formation, including spin-coating process, are given. Essential influence of temperature and humidity on films surface morphology is shown. Influence of heat treatment modes on structure and composition of films is analyzed. Recommendations about optimization of thin films sol–gel processing are offered.     

Immobilization of Tris-(8-hydroxyquinoline) aluminum onto P4VP polymer thin films by UV irradiation cross-linking

We report a novel method for the immobilization of Tris-(8-hydroxyquinoline) aluminum (Alq₃) onto poly(4-vinylpyridine) (P4VP) thin polymer films by UV irradiation cross-linking. The polymer films were prepared by spin-coating of P4VP onto cleaned silicon wafer surface followed by UV irradiation. The thicknesses of the polymer thin films were measured by ellipsometry with different irradiation times. The immobilization of Alq₃, orientation and the surface activity were followed using photoluminescence and UV-visible spectroscopy. The surface morphology was investigated by using field emission scanning electron microscopy and atomic force microscopy. Patterning of Alq₃ on P4VP film was obtained using photolithography technique. Our experimental results show that the cross-linked P4VP thin film is a universal surface modifier.     

TOF-GISANS investigation of polymer infiltration in mesoporous TiO2 films for photovoltaic applications

The structure of porous TiO₂ films and TiO₂:poly(N-vinylcarbazole) (PVK) composite films is investigated with time-of-flight grazing incidence small-angle neutron scattering (TOF-GISANS). The TiO₂ films have been prepared by application of a sol–gel process with a diblock copolymer as structure directing agent, and the conductive polymer PVK is infiltrated in the porous network by spin coating and solution casting. The films show a hierarchical pore structure with mesopores 52 nm in size and additional large macropores with a diameter of about 180 nm. By matching the scattering contrast of the TiO₂ with the polymer information about the penetration of the polymer in the pores is determined. Whereas in the PVK film prepared by solution casting the pores are filled to a high degree; in the spin coated film, PVK wets only the TiO₂ pore walls and forms a solid overlying layer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1628–1635, 2010     

Preparation and application of poly(alkoxytitanate) as a TiO2 precursor with high storage stability

Titanium dioxide is a basic material of our daily life. Because of its favourable properties, such as harmlessness, chemical stability, photocatalytic activity, or whiteness it is increasingly applied in both micro and nano particles and thin films and coating. One of the available procedures for film forming is the sol–gel technology, an inexpensive low temperature process with wide possibilities to vary film properties by changing the composition of the precursor solution or other parameters. In the paper a new precursor polymer for TiO₂ film-preparation with high storage and processing stabilities is introduced and applied in thin film forming. The new precursor poly(alkoxytitanate) is prepared by a one step, water-free sol–gel method. A smooth TiO₂ film can be prepared using this precursor by spin-coating followed by H₂-plasma curing. Comparing to a common precursor such as Ti(O–iPr)₄, this precursor has a good solubility in different solvents and a much higher storage stability. The easy to modify precursor end groups enable the tailoring of properties regarding to hydrolysis to both TiO₂ particles and films.     

Protein immobilization on epoxy-activated thin polymer films: effect of surface wettability and enzyme loading

A series of epoxy-activated polymer films composed of poly(glycidyl methacrylate/butyl methacrylate/hydroxyethyl methacrylate) were prepared. Variation in comonomer composition allowed exploration of relationships between surface wettability and Candida antartica lipase B (CALB) binding to surfaces. By changing solvents and polymer concentrations, suitable conditions were developed for preparation by spin-coating of uniform thin films. Film roughness determined by AFM after incubation in PBS buffer for 2 days was less than 1 nm. The occurrence of single CALB molecules and CALB aggregates at surfaces was determined by AFM imaging and measurements of volume. Absolute numbers of protein monomers and multimers at surfaces were used to determine values of CALB specific activity. Increased film wettability, as the water contact angle of films increased from 420 to 550, resulted in a decreased total number of immobilized CALB molecules. With further increases in the water contact angle of films from 55 degrees to 63 degrees, there was an increased tendency of CALB molecules to form aggregates on surfaces. On all flat surfaces, two height populations, differing by more than 30%, were observed from height distribution curves. They are attributed to changes in protein conformation and/or orientation caused by protein-surface and protein-protein interactions. The fraction of molecules in these populations changed as a function of film water contact angle. The enzyme activity of immobilized films was determined by measuring CALB-catalyzed hydrolysis of p-nitrophenyl butyrate. Total enzyme specific activity decreased by decreasing film hydrophobicity.     

Inverse opal photonic crystal of chalcogenide glass by solution processing

Chalcogenide opal and inverse opal photonic crystals were successfully fabricated by low-cost and low-temperature solution-based process, which is well developed in polymer films processing. Highly ordered silica colloidal crystal films were successfully infilled with nano-colloidal solution of the high refractive index As(30)S(70) chalcogenide glass by using spin-coating method. The silica/As-S opal film was etched in HF acid to dissolve the silica opal template and fabricate the inverse opal As-S photonic crystal. Both, the infilled silica/As-S opal film (Δn ~ 0.84 near λ=770 nm) and the inverse opal As-S photonic structure (Δn ~ 1.26 near λ=660 nm) had significantly enhanced reflectivity values and wider photonic bandgaps in comparison with the silica opal film template (Δn ~ 0.434 near λ=600 nm). The key aspects of opal film preparation by spin-coating of nano-colloidal chalcogenide glass solution are discussed. The solution fabricated "inorganic polymer" opal and the inverse opal structures exceed photonic properties of silica or any organic polymer opal film. The fabricated photonic structures are proposed for designing novel flexible colloidal crystal laser devices, photonic waveguides and chemical sensors.     

Computer simulation studies of Newton black films

We study via molecular dynamics simulations thin films (Newton black films, NBF) consisting of water coated with sodium dodecyl sulfate (SDS) surfactants. We analyze in detail the film properties (distribution of particles, pair correlation functions, roughness of the film, tilt angle of the hydrocarbon chain, electron density profiles, and mobility of water molecules) as a function of water content in the film core (i.e., film thickness, H). Our simulations indicate that water is part of the bilayer structure as solvation water. We estimate that around 2.25 water molecules per surfactant are part of this solvation structure. The structural analysis of the NBF shows that the headgroups exhibit a high degree of in-plane ordering. We find evidence for the existence of cavities in the monolayer, where only water is present. The basic structure of the monolayer is conserved down to water contents of the order of 4 water molecules per surfactant (H approximately equal to 11 A). The computed monolayer roughness for the present model is 2.5 A, in good agreement with the experimental data. We find that the roughness is very sensitive to the details of the interatomic potentials. Water mobility calculations emphasize the sluggish dynamics of very thin NBF. Diffusion coefficients of water in the lateral direction strongly decrease with film thickness. We find that the typical mean squared displacement of water in the direction normal to the bilayer is between 9 and 80 A2. Overall, our results indicate that the equilibrium SDS Newton black films studied in the X-ray experiments contain from 2 to 4 water molecules per surfactant.     

旋涂水溶液前驱体制备氧化锌薄膜及其性质

通过旋涂法, 采用Zn(OAc)2·2H2O和聚环氧乙烷(PEO)的水溶液为前驱体在不同的热处理温度下制备了ZnO薄膜. PEO的加入增加了溶液的成膜性, 其较低的热分解温度有利于制得纯净的ZnO薄膜. 文中考察了在不同热处理温度下制备的ZnO薄膜的形貌、结晶性、带隙(Eg)以及电导性. 原子力显微镜(AFM)测试表明在热处理温度为400、450和500 ℃制备的ZnO薄膜的粗糙度均方根值分别为3.3、2.7和3.6 nm. 采用透射电子显微镜(TEM)测试发现ZnO薄膜中含有大量纳晶粒子. 通过测试ZnO薄膜的UV-Vis吸收光谱, 根据薄膜位于373 nm处的吸收带边计算得到ZnO的带隙为3.3 eV. 通过对薄膜的电流-电压(I-V)曲线的测试计算得到在热处理温度为400、450和500 ℃制备的ZnO薄膜的电阻率分别为3.3×109、2.7×109和6.6×109 Ω·cm. 450 ℃时制备的ZnO薄膜的电阻率最小, 主要是由于较高的热处理温度有利于提高薄膜的纯度、密度和吸附氧. 而纯度较高、密度较大的薄膜电阻率比较小; 吸附氧含量增加, 晶界势垒增大, 电阻率增大. 因此在纯度和吸附氧的双重作用下450 ℃时制备的ZnO薄膜的电阻率最小, 而500 ℃时制备的ZnO薄膜的电阻率最大.     

Solventless polymerization: spatial migration of a catalyst to form polymeric thin films in microchannels

This paper reports a simple, additive process to generate patterned polymer films without using any solvent. This process involves a highly efficient catalyst, a Grubbs's catalyst, and a volatile monomer, norbornene. The catalyst and monomers have higher local concentrations inside the microchannels, formed by contacting poly(dimethylsiloxane) stamps to a solid surface, and allow the polymeric thin films to be defined by the microchannels. The patterned thin film serves as an excellent resistant to reactive ion etching, which promises that this process is a complementary, useful alternative to spin-coating and plasma polymerization in microfabrication.     

Synthesis and Characterization of Highly Oriented Sol-Gel (Pb, La) TiO3 Thin Film Optical Waveguides

The preparation and the optical characteristics of highly oriented PLT thin films are investigated. PLT films fabricated on MgO(100) and c-plane sapphire substrates have highly grown in (100) and (111) orientations, respectively. PLT films with high La content have a near cubic structure and weak anisotropy of refractive indices. The optical propagation losses of PLT films decrease as the La content of the films increases due to a complex interaction of surface roughness reduction and a reduction in the anisotropy refractive index. However, optical scattering in thicker sol-gel PLT thin film waveguides occurs by the internal scattering mechanism from the defects and the interfaces rather than by the surface scattering mechanism.     

Growth of organic n-conductors on thin polymer films for use in organic field effect transistors

Thin films of different polymers - poly(styrene) (PS), poly(methylmethacrylate) (PMMA), poly(vinylcarbazole) (PVCz), poly(vinylchloride) (PVC) and poly(vinylidene fluoride) (PVDF) - were deposited by spin-coating or by vapor deposition. On these polymers, thin films of (hexadecafluorophthalocyaninato)-oxovanadium (F₁₆PcVO) were prepared by physical vapor deposition. The growth of these films was monitored in situ by optical spectroscopy. The optical absorbance spectra were analyzed based on the coupling of transition dipoles to obtain information on the intermolecular arrangement of chromophores in the films. In all of these samples, the molecules are oriented with their molecular plane preferentially perpendicular to the substrate surface. This gives the desired overlap of the π-systems for electric conductance parallel to the substrate. Differences in the interactions were detected when deposition temperatures below or above the glass transition temperature of a given polymer were compared. The morphology of the polymer films and the deposited semiconductors were investigated by atomic force microscopy and scanning electron microscopy. The influence of the chosen substrate on the film structure is determined. The optical and electric properties of the films could thereby be influenced and the applicability of such films as active layers in organic thin film transistors is discussed.     

Organic Memristor Based on High Planar Cyanostilbene/Polymer Composite Films

Organic memristors with low power consumption, fast write/erasure speed, and complementary metal-oxide-semiconductor(CMOS) compatibility have attracted tremendous attention to mimic biological synapses to realize neuromorphic computation in recent years. In this paper, organic resistive switching memory(ORSM) based on (Z)-3-(naphthalen-2-yl)-2-(4-nitrophenyl)acrylonitrile(NNA) and polymer poly(N-vinylcarbazole)(PVK) composite film was prepared by spin-coating method. Device performance based on NNA:PVK composite films with different mass fractions of NNA were systematically investigated. The ORSM based on PVK:40%(mass fraction) NNA composite film exhibited non-volatile and bipolar memory properties with a switching ratio(I_on/I_off) of 24.1, endurance of 68 times and retention time of 10⁴ s, a “SET” voltage(V_set) of -0.55 V and a “RESET” voltage(V_reset) of 2.35 V. The resistive switching was ascribed to the filling and vacant process of the charge traps induced by NNA and the inherent traps in PVK bulk. The holes trapping and de-trapping process occurred when the device was applied with a negative or positive bias, which caused the transforming of the conductive way of charges, that is the resistive behaviors in the macroscopic. This study provides a promising platform for the fabrication of ORSM with high performance.     

Solution-processable precursor route for fabricating ultrathin silica film for high performance and low voltage organic transistors

In this paper, we introduce a simple solution spin-coating method to fabricate silica thin film from precursor route in the condition of low temperature and atmospheric environment, which possesses a low leakage current, high capacitance, and low surface roughness. With silica film (~ 50 nm), high performance and low voltage (< 4 V) p-/n-type organic transistors are fabricated. This method shows great potential for industrialization owing to its characteristic of low consumption and energy saving, time-saving and easy to operate.     

Probing structural changes of spin-coated polystyrene film after swelling and precipitation by synchrotron GIUSAXS and AFM

Polystyrene film of about 50 nm in thickness on silicon wafer was obtained by spin-coating in tetrahydrofuran solution. The film exhibits a rough surface as shown by atomic force microscopy images and ellipsometry data. Furthermore, such surface roughness produced a characteristic lateral correlation peak in an “out-ofplane” scan in the synchrotron grazing incidence ultra-small angle X-ray scattering pattern. The film was treated with liquids of solvent and non-solvent sequentially, resulting in a process of swelling and precipitation of the polystyrene film. Such a solvent/non-solvent treatment completely changed the original surface structure of the film. Aggregates of polystyrene of different sizes were observed both in atomic force microscopy and synchrotron grazing incidence ultra-small angle X-ray scattering measurements. The results demonstrate that synchrotron grazing incidence ultra-small angle X-ray scattering is a unique means to investigate large area micro-structural features of thin films supported on smooth surfaces.     

Study of the structure and mechanical properties of hexagonal BaTiO3 thin films prepared by sol鈥揼el processing

Hexagonal barium titanate (HBT) thin films were prepared on borosilicate plate substrates via sol–gel method using the dip-coating process. The structure, texture and morphology of the thin film were analyzed by X-ray diffraction, atomic force microscopy, nanoindentation technique, and transmission electron microscopy. The results showed that the thin film annealed at 700?°C crystallized with BaTiO₃ hexagonal phase and traces of Ba₂TiO₄ (secondary phase). The nanoparticles and the RMS roughness of the sample treated at 700?°C presented high values when compared with those thermally treated at lower temperatures. The hardness and Youngs??modulus of the thin films increased with increasing in grain size, and the thin film annealed at 700?°C with crystallite size about 10?nm presented multiple “pop-in??events during nano-indentation loading curves. The annealing temperature, growth size and surface roughness were discussed in connection with the HBT mechanical properties.