Pulsed Laser Evaporation Research Articles

Polymer nano-composite films with inorganic upconversion phosphor and electro-optic additives made by concurrent triple-beam matrix assisted and direct pulsed laser deposition

Abstract The work was to investigate polymer nano-composite films with two inorganic additives: upconversion fluorescent phosphor NaYF4:Yb3+, Er3+ and aluminum doped ZnO (AZO). The films were deposited using a new method of concurrent evaporation of the frozen solution of polymer poly(methyl methacrylate) (PMMA) using the matrix assisted pulsed laser evaporation (MAPLE) and the ablation of the phosphor and AZO targets using the pulsed laser deposition (PLD). Three laser beams, an infrared 1064-nm beam for the MAPLE and two 532-nm beams for the PLD targets, were concurrently used in the process. A new target holder with remote control of the target tilt was designed to provide overlapping of the plumes from the three targets and uniform mixing of the additives in the polymer film. The fabricated nano-composite films were characterized using X-ray diffraction, scanning electron microscopy (SEM), and the measurement of the quantum efficiency (QE) of the upconversion fluorescence. The films retained the crystalline structure of the inorganic additives. The size of the nano-particles varied in the range 10–200 nm. Upconversion QE of the films was an order of magnitude less than that of the bulk phosphor, which can be explained by lesser number of the rare-earth ions in the nano-particles in the polymer film than in the micro-grains of the bulk phosphor. The AZO additive increased QE by 1.6 times to (0.072 ± 0.022) % more likely due to the plasmonic enhancement of the local optical infra-red pump (980 nm) field. The proposed triple-beam triple-target MAPLE/PLD method can be potentially used for making a wide variety of nano-composite films.

Hydroxyapatite thin films grown by pulsed laser deposition and matrix assisted pulsed laser evaporation: Comparative study

Pulsed Laser Deposition (PLD) and Matrix Assisted Pulsed Laser Evaporation (MAPLE) techniques were applied for growing hydroxyapatite (HA) thin films on titanium substrates. All experiments were conducted in a reaction chamber using a KrF* excimer laser source (λ=248nm, τFWHM≈25ns). Half of the samples were post-deposition thermally treated at 500°C in a flux of water vapours in order to restore crystallinity and improve adherence.Coating surface morphologies and topographies specific to the deposition method were evidenced by scanning electron, atomic force microscopy investigations and profilometry. They were shown to depend on deposition technique and also on the post-deposition treatment. Crystalline structure of the coatings evaluated by X-ray diffraction was improved after thermal treatment. Biocompatibility of coatings, cellular adhesion, proliferation and differentiation tests were conducted using human mesenchymal stem cells (MSCs). Results showed that annealed MAPLE deposited HA coatings were supporting MSCs proliferation, while annealed PLD obtained films were stimulating osteogenic differentiation.

Thermal behaviour of sym-octahydroacridines and their corresponding N(10)-oxides

We present and discuss results on the thermal behaviour of 1,2,3,4,5,6,7,8-octahydroacridine (OHA), together with six 9-substituted congeners, i.e. R = –Br, –OCH3, –NH2, –NO2, –OH, and furyl (–C4H3O), and their corresponding N(10)-oxides, under nitrogen atmosphere and with alumina as reference, at a heating rate of 5 °C min−1 from room temperature to 300 °C. Chromatography has been carried out on aluminium sheets, with aluminium oxide 60 F254 neutral (Merck). Melting effects are observed for almost all compounds in their corresponding curves, precisely determined by using a Boetius apparatus. Homolysis of the carbon-substituent bond occurs in most cases, a phenomenon which is consistent with the values of the bond dissociation energy. For all compounds, except for hydroxyl congeners, thermal decomposition started with an endothermic peak. Octahydroacridines readily decompose into volatile products, an effect which correlates with their low melting points, while little amounts of residue remain in place of the aromatic amines compared to the N(10)-oxides. The presence of N–O bonds greatly influences the thermal stability of the compound, in the sense of increasing it compared with the parent amine. Quantitative studies of the decomposition products reveal that the melting points, the 9-position substituent, and N–O bond all play an important role upon the thermal behaviour. Mechanistic/kinetic pathways are also proposed as such results are important in further designing laser processing protocols, i.e. matrix-assisted pulsed laser evaporation (MAPLE) or laser-induced forward transfer (LIFT), for thin film deposition and/or device printing.

Molecular organization in MAPLE-deposited conjugated polymer thin films and the implications for carrier transport characteristics

The morphological structure of poly(3-hexylthiophene) (P3HT) thin films deposited by both Matrix Assisted Pulsed Laser Evaporation (MAPLE) and solution spin-casting methods are investigated. The MAPLE samples possessed a higher degree of disorder, with random orientations of polymer crystallites along the side-chain stacking, π–π stacking, and conjugated backbone directions. Moreover, the average molecular orientations and relative degrees of crystallinity of MAPLE-deposited polymer films are insensitive to the chemistries of the substrates onto which they were deposited; this is in stark contrast to the films prepared by the conventional spin-casting technique. Despite the seemingly unfavorable molecular orientations and the highly disordered morphologies, the in-plane charge carrier transport characteristics of the MAPLE samples are comparable to those of spin-cast samples, exhibiting similar transport activation energies (56 vs. 54 meV) to those reported in the literature for high mobility polymers. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 39–48

Electrically responsive microreservoires for controllable delivery of dexamethasone in bone tissue engineering

A major concern in orthopedic implants is to decrease the chronic inflammation using specific drug therapies. The newest strategies rely on the controlled delivery of antiinflammatory drugs from carrier biointerfaces designed in the shape of 3D architectures. We report on electrically responsive microreservoires (ERRs) acting as microcontainers for antiinflammatory drugs, as potential biointerfaces in orthopedic implants. The ERRs consist in arrays of vertical microtubes produced by laser direct writing using two photon polymerization effects (2PP_LDW) of a commercially available photoresist, IP-L780. A polypyrrole (conductive)/dexamethasone (drug model) (PPy/Dex) mixture was loaded into the ERRs via a simple immersion process. Then, the ERRs were sealed with a poly(lactic-co-glycolic acid)(PLGA) layer by Matrix Assisted Pulsed Laser Evaporation. ERRs stimulation using voltage cycles between −1V and +1V, applied at specific time intervals, at a scan rate of 0.1Vs−1, enabled to control the Dex release. The release time scales were between 150 and 275h, while the concentrations of Dex released were between 450–460nM after three applied voltage cycles, for different microreservoires dimensions. The proposed approach was validated in osteoblast-like MG-63 cell cultures. Cell viability and adhesion assays showed that the Dex-loaded ERRs sustained the cells growth and preserved their characteristic polygonal shape. Importantly, for the electrically-stimulated Dex release, the level of the alkaline phosphatase activity increased twice, the osteogenic differentiation surpassed by 1.6 times and the relative level of osteocalcin gene expression was 2.2 times higher as compared with the unstimulated drug release. Overall, the ERRs were able to accelerate the cells osteogenic differentiation via electrically controlled release of Dex.

Regulation of nanoparticle impact on the growth of MoSex films during pulsed laser evaporation of MoSe2 target

Irradiation of MoSe2 target with intensive laser pulses caused the formation of micro- and nanoparticles. The particles were observed on the target surface and in MoSex films prepared by deposition of the laser-induced plume. Content of nanoparticles on the film surface was markedly larger than that of microparticles. Transport of the plume in vacuum and in a buffer helium (He) gas was studied. The He pressure was high enough to provide effective atom scattering and plume deceleration. For a medium target-substrate distance, the structure of MoSex film was formed due to intensive deposition of atomic flux scattered in the buffer gas. Impact of nanoparticles on the structure was negligible. For a large distance, deposition of the nanoparticles from the plume was assisted by co-deposition of drifting atomic flux. Such deposition resulted in the formation of relatively smooth film containing nanoparticles transferred with plume, as well as the growth of spherical Se particles on the substrate.

RIR-MAPLE deposition of plasmonic silver nanoparticles

Nanoparticles are being explored in many different applications due to the unique properties offered by quantum effects. To broaden the scope of these applications, the deposition of nanoparticles onto substrates in a simple and controlled way is highly desired. In this study, we use resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) for the deposition of metallic, silver nanoparticles for plasmonic applications. We find that RIR-MAPLE, a simple and versatile approach, is able to deposit silver nanoparticles as large as 80 nm onto different substrates with good adhesion, regardless of substrate properties. In addition, the nanoparticle surface coverage of the substrates, which result from the random distribution of nanoparticles across the substrate per laser pulse, can be simply and precisely controlled by RIR-MAPLE. Polymer films of poly(3-hexylthiophene-2,5-diyl) (P3HT) are also deposited by RIR-MAPLE on top of the deposited silver nanoparticles in order to demonstrate enhanced absorption due to the localized surface plasmon resonance effect. The reported features of RIR-MAPLE nanoparticle deposition indicate that this tool can enable efficient processing of nanoparticle thin films for applications that require specific substrates or configurations that are not easily achieved using solution-based approaches.

Deposition of organic dyes for dye-sensitized solar cell by using matrix-assisted pulsed laser evaporation

The deposition of various distinct organic dyes, including ruthenium complex N3, melanin nanoparticle (MNP), and porphyrin-based donor-π-acceptor dye YD2-o-C8, by using matrix-assisted pulsed laser evaporation (MAPLE) for application to dye-sensitized solar cell (DSSC) is investigated systematically. It is found that the two covalently-bonded organic molecules, i.e., MNP and YD2-o-C8, can be transferred from the frozen target to the substrate with maintained molecular integrity. In contrast, N3 disintegrates in the process, presumably due to the lower bonding strength of metal complex compared to covalent bond. With the method, DSSC using YD2-o-C8 is fabricated, and an energy conversion efficiency of 1.47% is attained. The issue of the low penetration depth of dyes deposited by MAPLE and the possible resolution to it are studied. This work demonstrates that MAPLE could be an alternative way for deposition of organic dyes for DSSC.

Emulsion-Based RIR-MAPLE Deposition of Conjugated Polymers: Primary Solvent Effect and Its Implications on Organic Solar Cell Performance.

Emulsion-based, resonant infrared matrix-assisted pulsed laser evaporation (RIR-MAPLE) has been demonstrated as an alternative technique to deposit conjugated polymer films for photovoltaic applications; yet, a fundamental understanding of how the emulsion target characteristics translate into film properties and solar cell performance is unclear. Such understanding is crucial to enable the rational improvement of organic solar cell (OSC) efficiency and to realize the expected advantages of emulsion-based RIR-MAPLE for OSC fabrication. In this paper, the effect of the primary solvent used in the emulsion target is studied, both experimentally and theoretically, and it is found to determine the conjugated polymer cluster size in the emulsion as well as surface roughness and internal morphology of resulting polymer films. By using a primary solvent with low solubility-in-water and low vapor pressure, the surface roughness of deposited P3HT and PCPDTBT polymer films was reduced to 10 nm, and the efficiency of P3HT:PC61BM OSCs was increased to 3.2% (∼100 times higher compared to the first MAPLE OSC demonstration [ Caricato , A. P. ; Appl. Phys. Lett. 2012 , 100 , 073306 ]). This work unveils the mechanism of polymer film formation using emulsion-based RIR-MAPLE and provides insight and direction to determine the best ways to take advantage of the emulsion target approach to control film properties for different applications.

Titanium oxide – reduced graphene oxide – silver composite layers synthesized by laser technique: Wetting and electrical properties

Electrically conductive and highly hydrophobic surface layers are attractive for many practical applications. In this work the functional, wetting and electrical properties of titanium dioxide (TiO2), TiO2/silver (Ag), and TiO2/reduced graphene oxide (rGO)/Ag nanocomposite coatings layers are reported. The functional properties of the layers were correlated with their chemical composition and bonding states between the constituent elements, determined in turn by the synthesis and immobilization process parameters. The nanocomposite coatings were obtained by matrix assisted pulsed laser evaporation, a laser-based environmental friendly thin film deposition technique. The synthesized ternary TiO2/rGO/Ag coatings has optimum performances, highly hydrophobic character and low electrical resistance, attributed to the presence of Ag nanoparticles and to the reduction of the oxygen containing functional groups of the GO platelets during laser irradiation and transfer processes leading to the formation of graphene-like material.

Characterizing the electronic states of the second-row transition metal cations using high-resolution ion mobility mass spectrometry

Reduced mobilities for ground-state and electronic excited-state configurations of the second-row transition metal cations, excluding Tc+, have been measured. These values were obtained using an ion mobility mass spectrometer that utilizes a 2m drift tube to generate high-resolution ion mobility data. Several of these atomic cations have been previously studied and the results obtained here are compared to reduced mobilities reported in the literature. In all cases, ions were generated using pulsed-laser vaporization of either a metal rod or foil target. Presented here for the first time are the reduced mobilities of Y+, Ru+, and Rh+. A discussion of the observed trends in the mobilities of the second-row transition metal series, relative to those measured for the first-row series, is also provided.

Combinatorial MAPLE deposition of antimicrobial orthopedic maps fabricated from chitosan and biomimetic apatite powders

Chitosan/biomimetic apatite thin films were grown in mild conditions of temperature and pressure by Combinatorial Matrix-Assisted Pulsed Laser Evaporation on Ti, Si or glass substrates. Compositional gradients were obtained by simultaneous laser vaporization of the two distinct material targets. A KrF* excimer (λ=248nm, ϿFWHM=25ns) laser source was used in all experiments. The nature and surface composition of deposited materials and the spatial distribution of constituents were studied by SEM, EDS, AFM, GIXRD, FTIR, micro-Raman, and XPS. The antimicrobial efficiency of the chitosan/biomimetic apatite layers against Staphylococcus aureus and Escherichia coli strains was interrogated by viable cell count assay.The obtained thin films were XRD amorphous and exhibited a morphology characteristic to the laser deposited structures composed of nanometric round shaped grains. The surface roughness has progressively increased with chitosan concentration. FTIR, EDS and XPS analyses indicated that the composition of the BmAp-CHT C-MAPLE composite films gradually modified from pure apatite to chitosan.The bioevaluation tests indicated that S. aureus biofilm is more susceptible to the action of chitosan-rich areas of the films, whilst the E. coli biofilm proved more sensible to areas containing less chitosan.The best compromise should therefore go, in our opinion, to zones with intermediate-to-high chitosan concentration which can assure a large spectrum of antimicrobial protection concomitantly with a significant enhancement of osseointegration, favored by the presence of biomimetic hydroxyapatite.

Incidental Ignition of a Pulsed Dye Laser Fiber During Laryngomicrosurgery : A Case Report

Surgical fires require an ignition source, oxidizer, and fuel. The pulsed dye laser (PDL) has been shown to be effective in the treatment of hypertrophic scars and keloids in dermatology. With the increasing number of applications of CO2, laser as ignition source has been associated with operating room fires in the otorhinolaryngologic field. There have been many case reports on PDL-induced fires in dermatology, but until now, there were no reports in the larynx. We describe a 57-year-old patient diagnosed with laryngeal hyperkeratosis treated by PDL-assisted laryngomicrosurgery. In this case, we experienced incidental PDL tip flaring during pulsed dye laser vaporization. Key words: Lasers ㆍ Larynx ㆍ Microsurgery ㆍ Fires

Functionalization of Carbon Nanomaterial Surface by Doxorubicin and Antibodies to Tumor Markers.

The actual task of oncology is effective treatment of cancer while causing a minimum harm to the patient. The appearance of polymer nanomaterials and technologies launched new applications and approaches of delivery and release of anticancer drugs. The goal of work was to test ultra dispersed diamonds (UDDs) and onion-like carbon (OLCs) as new vehicles for delivery of antitumor drug (doxorubicin (DOX)) and specific antibodies to tumor receptors. Stable compounds of UDDs and OLCs with DOX were obtained. As results of work, an effectiveness of functionalization was 2.94 % w/w for OLC-DOX and 2.98 % w/w for UDD-DOX. Also, there was demonstrated that UDD-DOX and OLC-DOX constructs had dose-dependent cytotoxic effect on tumor cells in the presence of trypsin. The survival of adenocarcinoma cells reduced from 52 to 28 % in case of incubation with the UDD-DOX in concentrations from 8.4–2.5 to 670–20 μg/ml and from 72 to 30 % after incubation with OLC-DOX. Simultaneously, antibodies to epidermal growth factor maintained 75 % of the functional activity and specificity after matrix-assisted pulsed laser evaporation deposition. Thus, the conclusion has been made about the prospects of selected new methods and approaches for creating an antitumor agent with capabilities targeted delivery of drugs.

Discovery of Q-BN and Direct Conversion of h-BN into c-BN and Formation of Epitaxial c-BN/Diamond Heterostructures

ABSTRACTWe review the discovery of a new phase BN (named Q-BN) which has been created by nanosecond laser melting in the super undercooled state and quenching rapidly with rates exceeding several billion degrees per second. This phase, sequel to our earlier discovery of Q-Carbon, has amorphous structure from which phase-pure c-BN is formed in the form of nanodots, microcrystals, nanoneedles, and microneedles. Large-area single c-BN are formed by providing a template for epitaxial growth during quenching of super undercooled liquid BN. Since there is a rapid crystal growth from liquid, both n- and p-type dopants can be incorporated into electrically active substitutional sites with concentrations exceeding solubility limits through the phenomenon of solute trapping. We have grown diamond on c-BN by pulsed laser deposition of carbon at 500°C without the presence of hydrogen, and created c-BN and diamond epitaxial composites. We discuss the mechanism of epitaxial c-BN and diamond growth on lattice matching c-BN template under pulsed laser evaporation of amorphous carbon. This discovery on direct conversion of h-BN into phase-pure c-BN at ambient temperatures and pressures in air, represents a seminal contribution to the field of boron nitride, which is quite complementary to our discovery of graphite to diamond conversion. We have bypassed thermodynamics with the help of kinetics and time control. This research represents a major breakthrough for c-BN and diamond based high-power electronic and photonic devices, and host of other applications related to high-speed machining, deep-sea drilling, field-emission displays and biomedical applications.

Functionalized Antimicrobial Composite Thin Films Printing for Stainless Steel Implant Coatings.

In this work we try to address the large interest existing nowadays in the better understanding of the interaction between microbial biofilms and metallic implants. Our aimed was to identify a new preventive strategy to control drug release, biofilm formation and contamination of medical devices with microbes. The transfer and printing of novel bioactive glass-polymer-antibiotic composites by Matrix-Assisted Pulsed Laser Evaporation into uniform thin films onto 316 L stainless steel substrates of the type used in implants are reported. The targets were prepared by freezing in liquid nitrogen mixtures containing polymer and antibiotic reinforced with bioglass powder. The cryogenic targets were submitted to multipulse evaporation by irradiation with an UV KrF* (λ = 248 nm, τFWHM ≤ 25 ns) excimer laser source. The prepared structures were analyzed by infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and profilometry, before and after immersion in physiological fluids. The bioactivity and the release of the antibiotic have been evaluated. We showed that the incorporated antibiotic underwent a gradually dissolution in physiological fluids thus supporting a high local treatment efficiency. Electrochemical measurements including linear sweep voltammetry and impedance spectroscopy studies were carried out to investigate the corrosion resistance of the coatings in physiological environments. The in vitro biocompatibility assay using the MG63 mammalian cell line revealed that the obtained nanostructured composite films are non-cytotoxic. The antimicrobial effect of the coatings was tested against Staphylococcus aureus and Escherichia coli strains, usually present in implant-associated infections. An anti-biofilm activity was evidenced, stronger against E. coli than the S. aureus strain. The results proved that the applied method allows for the fabrication of implantable biomaterials which shield metal ion release and possess increased biocompatibility and resistance to microbial colonization and biofilm growth.

Retraction Note to: Fundamental Discovery of New Phases and Direct Conversion of Carbon into Diamond and hBN into cBN and Properties

We review the discovery of new phases of carbon (Q-carbon) and BN (Q-BN) and address critical issues related to direct conversion of carbon into diamond and hBN into cBN at ambient temperatures and pressures in air without any need for catalyst and the presence of hydrogen. The Q-carbon and Q-BN are formed as a result of quenching from super undercooled state by using high-power nanosecond laser pulses. We discuss the equilibrium phase diagram (P vs T) of carbon, and show that by rapid quenching, kinetics can shift thermodynamic graphite/diamond/liquid carbon triple point from 5000 K/12 GPa to super undercooled carbon at atmospheric pressure in air. Similarly, the hBN-cBN-Liquid triple point is shifted from 3500 K/9.5 GPa to as low as 2800 K and atmospheric pressure. It is shown that nanosecond laser heating of amorphous carbon and nanocrystalline BN on sapphire, glass, and polymer substrates can be confined to melt in a super undercooled state. By quenching this super undercooled state, we have created a new state of carbon (Q-carbon) and BN (Q-BN) from which nanocrystals, microcrystals, nanoneedles, microneedles, and thin films are formed depending upon the nucleation and growth times allowed and the presence of growth template. The large-area epitaxial diamond and cBN films are formed, when appropriate planar matching or lattice matching template is provided for growth from super undercooled liquid. The Q-phases have unique atomic structure and bonding characteristics as determined by high-resolution SEM and backscatter diffraction, HRTEM, STEM-Z, EELS, and Raman spectroscopy, and exhibit new and improved mechanical hardness, electrical conductivity, and chemical and physical properties, including room-temperature ferromagnetism and enhanced field emission. The Q-carbon exhibits robust bulk ferromagnetism with estimated Curie temperature of about 500 K and saturation magnetization value of 20 emu g−1. We have also deposited diamond on cBN by using a novel pulsed laser evaporation of carbon and obtained cBN/diamond composites, where cBN acts as template for diamond growth. Both diamond and cBN grown from super undercooled liquid can be alloyed with both p- and n-type dopants. This process allows carbon to diamond and hBN to cBN conversions and formation of useful nanostructures and microstructures at ambient temperatures in air at atmospheric pressure on practical and heat-sensitive substrates in a controlled way without need for any catalysts and hydrogen to stabilize sp3 bonding for diamond and cBN phases.

Direct conversion of h-BN into c-BN and formation of epitaxial c-BN/diamond heterostructures

We have created a new state of BN (named Q-BN) through rapid melting and super undercooling and quenching by using nanosecond laser pulses. Phase pure c-BN is formed either by direct quenching of super undercooled liquid or by nucleation and growth from Q-BN. Thus, a direct conversion of hexagonal boron nitride (h-BN) into phase-pure cubic boron nitride (c-BN) is achieved by nanosecond pulsed laser melting at ambient temperatures and atmospheric pressure in air. According to the P-T phase diagram, the transformation from h-BN into c-BN under equilibrium processing can occur only at high temperatures and pressures, as the hBN-cBN-Liquid triple point is at 3500 K/9.5 GPa or 3700 K/7.0 GPa with a recent theoretical refinement. Using nonequilibrium nanosecond laser melting, we have created super undercooled state and shifted this triple point to as low as 2800 K and atmospheric pressure. The rapid quenching from super undercooled state leads to the formation of a new phase, named as Q-BN. We present detailed characterization of Q-BN and c-BN layers by using Raman spectroscopy, high-resolution scanning electron microscopy, electron-back-scatter diffraction, high-resolution TEM, and electron energy loss spectroscopy, and discuss the mechanism of formation of nanodots, nanoneedles, microneedles, and single-crystal c-BN on sapphire substrate. We have also deposited diamond by pulsed laser deposition of carbon on c-BN and created c-BN/diamond heterostructures, where c-BN acts as a template for epitaxial diamond growth. We discuss the mechanism of epitaxial c-BN and diamond growth on lattice matching c-BN template under pulsed laser evaporation of amorphous carbon, and the impact of this discovery on a variety of applications.

Amperometric biosensor based on Laccase immobilized onto a screen-printed electrode by Matrix Assisted Pulsed Laser Evaporation

A Laccase-based biosensor for the determination of phenolic compounds was developed by using Matrix Assisted Pulsed Laser Evaporation as an innovative enzyme immobilization technique. and the deriving biosensor was characterized and applied for the first time. Laccase was immobilized onto different substrates including screen printed carbon electrodes and spectroscopic, morphologic and electrochemical characterizations were carried out. A linear range from 1 to 60μM was achieved working at 5.5pH and −0.2V detection potential vs Ag pseudoreference. The limits of detection and quantification were found to be 1 and 5μM, respectively. A good fabrication reproducibility, stability of response and selectivity toward interferents were also found The potential of the developed biosensor was tested in the determination of total polyphenol content in real matrices (tea infusion, ethanolic extract from Muscari comosum bulbs and aqueous solution of a food supplement from black radish root and artichoke leaves) and the results were compared with those obtained by using the Folin–Ciocalteu method.

Additive Growth and Crystallization of Polymer Films

We demonstrated a polymeric thin film fabrication process in which molecular-scale crystallization proceeds with additive film growth, by employing an innovative vapor-assisted deposition process termed matrix-assisted pulsed laser evaporation (MAPLE). In comparison to solution-casting commonly adopted for the deposition of polymer thin films, this physical vapor deposition (PVD) methodology can prolong the time scale of film formation and allow for the manipulation of temperature during deposition. For the deposition of molecular and atomic systems, such a PVD manner has been demonstrated to facilitate molecular ordering and delicately manipulate crystalline morphology during film growth. Here, using MAPLE, we deposited thin films of a model polymer, poly(ethylene oxide) (PEO), atop a temperature-controlled substrate with an average growth rate of less than 10 nm/h. The mechanism of deposition is sequential addition of nanoscale liquid droplets. We discovered that the deposition process leads to the form...