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The growth and rupture of conductive filaments act a crucial part in the reliability of resistive switching behaviors. The random growth and rupture of conductive filaments are the primary reason for the instability of set/reset reproducibility. Hence, we propose a method that embedded carbon quantum dots (CQDs) in polymethylmethacrylate (PMMA) to fabricate the Ag/PMMA&CQDs/FTO resistive switching device. Five different concentrations of CQDs are embedded in PMMA to regulate the resistive switching properties, and the resistive memory characteristics of the optimal group are systematically studied. The optimal group exhibits excellent switching repeatability, low set/reset voltages, and stable forming voltage, which is much better than PMMA without CQDs. Furthermore, we employ the COMSOL software to build a simulation model for exploring the influence of CQDs on the internal electric field of PMMA, which proved that the introduction of CQDs might have a favorable effect on the orderly growth of conductive filaments. [ABSTRACT FROM AUTHOR]

We report electrical conductivity measurements of polymethyl-methacrylate filled by onion-like carbon particles with a primary particle size of ≈5 nm. We show that the conductivity σ is exceptionally high even at very low loadings and that its low-temperature dependence follows a Coulomb gap regime at atmospheric pressure and an activated behavior at a pressure of 2 GPa. We interpret this finding in terms of the enhancement under the applied pressure of the effective dielectric permittivity within the aggregates of onion-like carbons, which improves the screening of the Coulomb interaction and reduces the optimal hopping distance of the electrons. [ABSTRACT FROM AUTHOR]

Down conversion Ce3+-Yb3+ co-doped YAG phosphors are used to enhance concentrator monocrystalline silicon solar cells. The coating of polymethyl methacrylate (PMMA) mixed with the phosphors is deposited on the surface of the solar cells by spin-coating method. It is found that the solar cells with the phosphor coating always have higher conversion efficiency than the bare solar cells under different illumination intensities. This is attributed to the down conversion effect of the phosphors and the reduced reflection (especially in the wavelength range 350–550 nm). The reflection of the light emitted from the phosphor's particles at the air/PMMA interface also contributes to the improvement. The relative growth in the conversion efficiency of the solar cells with the phosphor coatings increases with the illumination intensity from 4.86% under 100 mW cm−2 to 6.04% under 400 mW cm−2 because the increase in the emission from the phosphors is faster than that of the illumination intensity when the illumination intensity increases. [ABSTRACT FROM AUTHOR]

We report the development of a microcavity drum sealed by suspended graphene. The drum is fabricated by using a low-pressure dry-transfer technique, which involves vacuum de-aeration between a graphene sheet and a substrate and raising the temperature to above the glass transition of the supporting poly(methyl methacrylate) film, which serves to increase the real contact area. The result is a suspended graphene sheet with a maximum diameter of 48.6 µm. The Raman spectrum of the suspended graphene has a 2D/G ratio of 1.79 and a few D peaks, which suggests that the material is high-quality single-layer graphene. The dry-transfer technique yields a vacuumsealed microcavity drum 1.1 µm deep up to 4.5 lm in diameter. The Raman shift indicates that the suspended graphene is subjected to a tensile strain of 0.05%, which is attributed to the pressure difference between the evacuated cavity and the exterior gas. [ABSTRACT FROM AUTHOR]

In this work, nonvolatile bipolar resistive switching behaviors based on the MoS2 quantum dots (QDs) embedded in the insulating polymethylmethacrylate (PMMA) were reported with the device configuration of Au/PMMA/PMMA:MoS2 QDs/PMMA/fluorine doped tin-oxide. The device exhibits the reversible switching performances with the excellent read endurance and data retention capability. The related carrier transport behaviors were predominated by Schottky emission and Ohmic conductions in OFF and ON states, respectively. Importantly, a conductance quantization effect was evidently observed in this MoS2 QD-based memory device. Combined with the energy band evolution, these phenomena were elucidated in views of electrons trapping/de-trapping and quantum tunneling effects of nanoscale MoS2 QDs. This work also suggests the potential application of MoS2 QDs in next generation ultra-high-density data storage. [ABSTRACT FROM AUTHOR]

We investigate the heteroepitaxial Si0.5Ge0.5 quantum dot site-selection on a patterned Si(001) substrate by continuously varying the underlying substrate pattern morphology from pit-in-terrace to quasi-sinusoidal. The pit-in-terrace morphology leads to well-ordered quantum dots centered in the pits over a wide range of pattern wavelengths. However, for quasi-sinusoidal morphology, when the pattern wavelength is twice the intrinsic lengthscale, quantum dots suddenly bifurcate and shift to form in every saddle point, with high uniformity in size and site occupancy. We compare our results with existing models of quantum dot formation on patterned surfaces. [ABSTRACT FROM AUTHOR]

Poly(3-hexylthiophene-2,5-diyl) (P3HT) can generate nanoporous structures with variable pore diameters ranging from 150 to 600 nm from spin-coated blends with polystyrene (PS). In the present study, we observe the effect of the addition of polymethylmethacrylate (PMMA) to P3HT:PS blends to increase the pore-to-pore dimensions up to the micrometer scale. The phase separation in the ternary blend can be directly visualized by replacing the commercial (non-emissive) PS with a boron-dipyrromethene functionalized PS to distinctively locate the red-emitting P3HT and the green-emitting PS phases. In particular, in the ternary blend with high PMMA contents, we observe that PS acts as a compatibilizing agent at the interface between the P3HT and PMMA phases. After selective removal of the PS and PMMA phases using acetone, we demonstrate that, in these P3HT structured thin films, iridescence can be observed as they exhibit angle dependent reflectivity which is further emphasized when covered with a thin metal layer. The metal covered nanostructured P3HT films display bright color switching properties with blue and red emission at low and high reflection angles, respectively. [ABSTRACT FROM AUTHOR]

We investigate the mechanical strength of boron nitride nanotube (BNNT) polymerinterfaces by using in situelectron microscopy nanomechanical single-tube pull-out techniques. The nanomechanical measurements show that the shear strengths of BNNT-epoxy and BNNT-poly(methyl methacrylate) interfaces reach 323 and 219MPa, respectively. Molecular dynamics simulations reveal that the superior load transfer capacity of BNNT-polymer interfaces is ascribed to both the strong van der Waals interactions and Coulomb interactions on BNNT-polymer interfaces. The findings of the extraordinary mechanical strength of BNNT-polymer interfaces suggest that BNNTs are excellent reinforcing nanofiller materials for light-weight and high-strength polymernanocomposites. [ABSTRACT FROM AUTHOR]

Quartz-enhanced conductance spectroscopy is developed as an analytical tool to investigate dynamic nanomechanical behaviors of polymerwires, in order to determine the glass transitiontemperature (Tg). A polymethyl methacrylate (PMMA) microwire with a diameter of 10 µm was bridged across the prongs of a quartz tuning fork (QTF). With the advantage of QTF self-sensing as compared with micro-cantilevers or other resonators, the resonance frequency and Q factor can be directly determined by means of its electrical conductance spectra with respect to the frequency of the external excitation source (dI/dV vs f), and therefore, no optical beam is required. The Tg of the PMMA microwire was determined by the maximum loss modulus of the QTF, calculated from the resonance frequency and the Q factor as a function of temperature. The measuredTg of the PMMA is 103 °C with an error of ±2 °C. Both heating/cooling and physical aging experiments were carried out, demonstrating that the technique is both reversible and reproducible. [ABSTRACT FROM AUTHOR]

We have demonstrated an electrically injected ultra-low threshold (8.9 nA) room temperature InGaN/GaN based lateral nanowire laser. The nanowires are triangular in shape and survived naturally after etching using boiling phosphoric acid. A polymethyl methacrylate (PMMA) and air dielectric distributed mirror provide an optical feedback, which together with one-dimensional density of states cause ultra-low threshold lasing. Finite difference eigen-mode (FDE) simulation shows that triangular nanowire cavity supports single dominant mode similar to TE01 that of a corresponding rectangular cavity with a confinement factor of 0.18. [ABSTRACT FROM AUTHOR]

The pyro-electrohydrodynamic (EHD) manipulation of liquids has been discovered and demonstrated recently as a high resolution printing technique avoiding the use of nozzles and external electrodes. The activation of the pyro-electric effect is usually achieved on ferroelectric crystals by an external heating source or by an infrared laser. Here, we show an original modality for triggering the pyro-EHD process through a light-absorbing polymer nanocomposite thin layer deposited on the ferroelectric substrate, thus overcoming some limitations of the previous configuration. Significant simplification and compactness of the set-up is achieved thanks to the nanocomposite coating, since a commercial low-cost white-light halogen lamp can be adopted to trigger the pyrojetting process from a liquid reservoir. Remarkably, high resolution is achieved in dispensing very high viscous liquids. Practical demonstrations in polymer optical microlenses direct printing using polydimethylsiloxane and poly(methyl methacrylate) are finally reported to validate the approach in handling high-viscous polymers for practical applications. [ABSTRACT FROM AUTHOR]

We investigated the transitions of conformations and their effects on emission properties of poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) single molecules in PMMA matrix during thermal annealing process. Total internal reflection fluorescence microscopy measurements reveal the transformation from collapsed conformations to extended, highly ordered rod-like structures of MEH-PPV single molecules during thermal annealing. The blue shifts in the ensemble single molecule PL spectra support our hypnosis. The transition occurs as the annealing temperature exceeds 100 °C, implying that an annealing temperature near the glass transition temperature Tg of matrix is ideal for the control and optimization of blend polymer films. [ABSTRACT FROM AUTHOR]

Scalably grown and transferred graphene is a highly promising material for organic electronic applications, but controlled interfacing of graphene thereby remains a key challenge. Here, we study the growth characteristics of the important organic semiconductor molecule para-hexaphenyl (6P) on chemical vapor deposited graphene that has been transferred with polymethylmethacrylate (PMMA) onto oxidized Si wafer supports. A particular focus is on the influence of PMMA residual contamination, which we systematically reduce by H2 annealing prior to 6P deposition. We find that 6P grows in a flat-lying needle-type morphology, surprisingly independent of the level of PMMA residue and of graphene defects. Wrinkles in the graphene typically act as preferential nucleation centers. Residual PMMA does however limit the length of the resulting 6P needles by restricting molecular diffusion/attachment. We discuss the implications for organic device fabrication, with particular regard to contamination and defect tolerance. [ABSTRACT FROM AUTHOR]

We have demonstrated the laser ablation of PMMA using dual-color waveform synthesis of the fundamental (ω) and its second-harmonic (2ω) of a femtosecond Ti:Sapphire laser. A modest and yet clear modulation (~22%) in ablated area versus relative phase between the 2ω and ω beams with a power-ratio of 15% (28/183mW) is revealed. This is explained qualitatively by the dependence of ablation on multiphoton ionization of which the rate is related to the relative phase of the synthesized waveform. At higher peak power ratios, the modulation decreases rapidly, as the two-photon-ionization rate of the 2ω dominates over that of the three- to four- photon ionization of the ω beam. This technique demonstrates the feasibility of phase-controlled laser processing of materials. [ABSTRACT FROM AUTHOR]

The investigation of a simple and self-assembling method for realizing polymeric micro-bottle resonators is reported. By dispensing precise amounts of SU-8 onto a cleaved optical fiber, employed as mechanical support, bottle microcavities with different shapes and diameters are fabricated. The balancing of surface energy between glass fiber and polymeric microresonator with surface tension of SU-8 confers different shape to these microstructures. Planar single-mode SU-8 based waveguide, realized on polymethylmethacrylate, is chosen for exciting the micro-bottle resonators by evanescent wave. The reliability of the fabrication process and the shape of the bottle microcavities are investigated through optical analysis. We observe whispering gallery modes in these resonant microstructures by a robust coupling with single mode planar waveguides around 1.5 im wavelength. The resonance spectra of micro-bottle resonators and the spectral characteristics, such as Quality-factor (Q factor) and free spectral range, are evaluated for all the realized microstructures. SU-8 micro-bottle resonators show high Q-factors up to 3.8 x 104 and present a good mechanical stability. These features make these microcavities attractive for sensing and/or lasing applications in a planar platform. [ABSTRACT FROM AUTHOR]

A mathematical model is proposed to describe bulk longitudinal waves in a nonlinearly elastic thin-walled cylindrical shell. The equation of motion for the longitudinal displacement is derived. In case of the homogeneous shell, this equation is reduced to the doubly dispersive equation for the linear longitudinal strain component and provides a solitary wave solution. Results of the first experimental observation of the bulk strain soliton in a duct-like shell are presented, and both the wave amplitude and velocity are estimated. [ABSTRACT FROM AUTHOR]

A facile technique is presented which enables high-resolution electron beam lithography on irregularly-shaped, non-planar or fragile substrates such as the edges of a silicon chip, thin and narrow suspended beams and bridges, or small cylindrical wires. The method involves a spin-free dry-transfer of pre-formed uniform-thickness polymethyl methacrylate, followed by conventional electron beam writing, metal deposition, and lift-off. High-resolution patterning is demonstrated for challenging target substrates. The technique should find broad application in micro- and nanotechnology research arenas. [ABSTRACT FROM AUTHOR]

Single molecule (SM) chips could serve as the fundamental devices in quantum information processing. In this context, a chip with the non-polar SMs of squaraine-derived rotaxanes embedded in a polar poly(methyl methacrylate) matrix was realized and the SM fluorescence hysteresis induced by the electric field was observed at room temperature. Here, we presented a model considering both of the electron transfer and space charge relaxation processes to explain the fluorescence hysteresis effect, and the model-based simulations agreed reasonably well with the experimental results. [ABSTRACT FROM AUTHOR]

Polymer materials, such as polymethylmethacrylate (PMMA), are widely used as insulators in vacuum. The insulating performance of a high-voltage vacuum system is mainly limited by surface flashover of the insulators rather than bulk breakdown. Non-thermal plasmas are an efficient method to modify the chemical and physical properties of polymer material surfaces, and enhance the surface insulating performance. In this letter, an atmospheric-pressure dielectric barrier discharge is used to treat the PMMA surface to improve the surface flashover strength in vacuum. Experimental results indicate that the plasma treatment method using Ar and CF4 (10:1) as the working gas can etch the PMMA surface, introduce fluoride groups to the surface, and then alter the surface characteristics of the PMMA. The increase in the surface roughness can introduce physical traps that can capture free electrons, and the fluorination can enhance the charge capturing ability. The increase in the surface roughness and the introduction of the fluoride groups can enhance the PMMA hydrophobic ability, improve the charge capturing ability, decrease the secondary electron emission yield, increase the surface resistance, and improve the surface flashover voltage in vacuum. [ABSTRACT FROM AUTHOR]

Room temperature single photon emitters are very important resources for photonics and emerging quantum technologies. In this work, we study single photon emission from defect centers in 20nm zinc oxide (ZnO) nanoparticles. The emitters exhibit bright broadband fluorescence in the red spectral range centered at 640nm with polarized excitation and emission. The studied emitters showed continuous blinking; however, bleaching can be suppressed using a polymethyl methacrylate coating. Furthermore, hydrogen termination increased the density of single photon emitters. Our results will contribute to the identification of quantum systems in ZnO. [ABSTRACT FROM AUTHOR]

This study investigated dynamic friction during oblique impact of a golf ball by evaluating the ball's angular velocity, contact force, and the contact area between the ball and target. The effect of the contact area on the angular velocities was evaluated, and the results indicated that the contact area plays an important role in dynamic friction. In this study, the dynamic friction force F was given by F=µN+µn dA/dt, where µ is the coefficient of friction, N is the contact force, dA/dt is the time derivative of the contact area A, and n is a coefficient associated with the contact area. [ABSTRACT FROM AUTHOR]

We report a method to significantly enhance the mass sensitivity of a quartz crystal microbalance (QCM) device in which Polymethyl Methacrylate (PMMA) micropillars were fabricated on QCM surface to form a two-degrees-of-freedom vibration system. PMMA micropillars were fabricated using nanoimprinting lithography technology. The QCM-micropillar coupled system exhibits a unique resonant frequency, near which the mass sensitivity of QCM can be enhanced by several orders of magnitude. Both numerical simulation and theoretical analysis were conducted to understand this improvement. Thereafter, ultrahigh sensitivity of the QCM-micropillar system was demonstrated by detecting a 1H, 1H, 2H, 2H-perfluorooctyl-trichlorosilane single monolayer film [ABSTRACT FROM AUTHOR]

In this paper, we have systematically studied the evolution of Raman spectrum of graphene with the thickness of SiO2 capping layer on Si substrate. We find that, for both monolayer and bilayer graphenes, the intensities of D, G, and 2D bands, together with the intensity ratio of 2D to G Raman bands (I2D/IG), oscillate quasi-periodically with SiO2 thickness increasing. The origin of the observed phenomena is theoretically analyzed. Our result shows that one must pay enough attention to the SiO2 thickness when using the Raman footprints, especially the commonly used I2D/IG, to identify the graphene layers transferred onto SiO2/Si substrate. [ABSTRACT FROM AUTHOR]

Insulating, polymethylmethacrylate (PMMA), and semiconducting, poly(3-hexylthiophene) (P3HT), nanometer thick polymers/Au nanoparticles based hybrid multilayers (HyMLs) were fabricated on p-Si single-crystal substrate. An iterative method, which involves, respectively, spin-coating (PMMA and P3HT deposition) and sputtering (Au nanoparticles deposition) techniques to prepare Au/HyMLs/p-Si Schottky device, was used. The barrier height and the ideality factor of the Au/HyMLs/p-Si Schottky devices were investigated by current-voltage measurements in the thickness range of 1-5 bilayers. It was observed that the barrier height of such hybrid layered systems can be tuned as a function of bilayers number and its evolution was quantified and analyzed. [ABSTRACT FROM AUTHOR]

A simple process is developed to curl graphene membranes through thermal annealing. The resulting curled graphene ribbons displayed enhanced photocurrent response compared to flat graphene ribbons. The annealing temperature, the thickness of the graphene, and the type of poly-methyl methacrylate used were the three key factors that influenced the morphology of graphene during thermal annealing. Each of the factors has been systematically investigated, and the transition from flat to curled graphene ribbons was observed. This work has shown a facile method to alter graphene morphology and to develop promising graphene structures for future optoelectronics. [ABSTRACT FROM AUTHOR]

The clean removal of a poly(methyl methacrylate) (PMMA) film on graphene has been an essential part of the process of transferring chemical vapor deposited graphene to a specific substrate, influencing the quality of the transferred graphene. Here we demonstrate that the clean removal of PMMA can be achieved by a single heat-treatment process without the chemical treatment that was adopted in other methods of PMMA removal. The cleanness of the transferred graphene was confirmed by four-point probe measurements, synchrotron radiation x-ray photoemission spectroscopy, optical images, and Raman spectroscopy. [ABSTRACT FROM AUTHOR]

We have derived a general formula for sensitivity optimization of gravimetric sensors and use it to design a high sensitivity gravimetric sensor using unidirectional carbon fiber epoxy composite (CFEC) guiding layer on (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-xPT) single crystal substrate. The normalized maximum sensitivity (|Smf|λ)max exhibits an increasing tendency with the decrease of (h/λ)opt. For the CFEC/[011]c poled PMN-0.29PT sensor configuration with λ = 24 μm, the maximum sensitivity |Smf|max can reach as high as 1230 cm2/g, which is about 3 times that of a traditional SiO2/ST quartz configuration gravimetric sensor. [ABSTRACT FROM AUTHOR]

Three different blends containing side-chain azobenzene polyesters and poly(methyl methacrylate) homopolymers have been prepared for recording volume holographic polarization gratings using 488 nm light pulses. The final azo content in the blends has been decreased down to 0.2 wt. %, and their morphologies have been investigated by transmission electron microscopy. Stable and rewritable polarization gratings have been recorded, and 20 gratings have been multiplexed using 2 ms pulses of low energy (4 mJ/cm2). The equilibrium values of the diffraction efficiency were higher than 5 × 10-5. [ABSTRACT FROM AUTHOR]

Channel access resistance (Rsd) effects on the charge carrier mobility (μ) and low-frequency noise (LFN) in a polymethyl-methacrylate (PMMA) passivated tin-oxide nanowire (SnO2-NW) field effect-transistor were investigated. To this end, the Y function method was employed for direct electrical parameters extraction without Rsd influence. Numerical simulation was used to evaluate gate-to-channel capacitance (Cgc) accounting for the electrostatic gate coupling effects through PMMA passivation layer. Furthermore, LFN measurements were carried out to study the SnO2/dielectrics interface. The carrier number fluctuation (CNF) noise model was found appropriate to interpret LFN data provided Rsd influence is included. [ABSTRACT FROM AUTHOR]

An organic floating-gate memory device using CdSe quantum dots (QDs) as a charge-trapping element was fabricated. CdSe QDs were localized beneath a pentacene without any tunneling insulator, and the QD layer played a role as hole-trapping sites. The band bending formed at the junction between pentacene and QD layers inhibited back-injection of holes trapped in CdSe into pentacene, which appeared as a hysteretic capacitance-voltage response during the operation of the device. Nearly, 60% of trapped charge was sustained even after 104 s in programmed state, and this long retention time can be potentially useful in practical applications of non-volatile memory. [ABSTRACT FROM AUTHOR]

A pentacene-based organic metal-insulator-semiconductor memory device, utilizing single walled carbon nanotubes (SWCNTs) for charge storage is reported. SWCNTs were embedded, between SU8 and polymethylmethacrylate to achieve an efficient encapsulation. The devices exhibit capacitance-voltage clockwise hysteresis with a 6 V memory window at ± 30 V sweep voltage, attributed to charging and discharging of SWCNTs. As the applied gate voltage exceeds the SU8 breakdown voltage, charge leakage is induced in SU8 to allow more charges to be stored in the SWCNT nodes. The devices exhibited high storage density (∼9.15 × 1011 cm-2) and demonstrated 94% charge retention due to the superior encapsulation. [ABSTRACT FROM AUTHOR]

Nonvolatile memory devices based on CuInS2 (CIS) quantum dots (QDs) embedded in a polymethylmethacrylate (PMMA) layer were fabricated using spin-coating method. The memory window widths of the capacitance-voltage (C-V) curves for the Al/CIS QDs embedded in PMMA layer/p-Si devices were 0.3, 0.6, and 1.0 V for sweep voltages of ±3, ±5, and ±7 V, respectively. Capacitance-cycle data demonstrated that the charge-trapping capability of the devices with an ON/OFF ratio value of 2.81 x 10-10 was maintained for 8 x 10³ cycles without significant degradation and that the extrapolation of the ON/OFF ratio value to 1 x 106 cycles converged to 2.40 x 10-10, indicative of the good stability of the devices. The memory mechanisms for the devices are described on the basis of the C-V curves and the energy-band diagrams. [ABSTRACT FROM AUTHOR]

High-voltage vacuum insulator failure is generally due to surface flashover rather than insulator bulk breakdown. To study the characteristic of surface flashover channel, a diagnosis system to obtain the images of flashover channel is fabricated using a high speed frame camera, and results are presented by an investigation into the flashover of poly-methyl methacrylate insulator with gap spacing of 170 mm in vacuum under 180 ns quasi-square pulses. It is obtained that after formation of the flashover channel, the impedance of the flashover channel is inductive and the waveform of the measured voltage is determined by the inductance of the flashover channel directly. [ABSTRACT FROM AUTHOR]

We report the production of graphene folds induced by femtosecond laser ablation. A single laser pulse irradiation on graphene produced an ablated spot featuring in its proximity circumferentially periodic graphene folds. The graphene fold structure was constructed through folding of a single layer graphene segment. We investigated the laser fluence effect on the graphene fold structure. We also performed ablation on suspended graphene and verified that interaction with the underlying substrate is required for the formation of graphene folds. We expect this one-step folding method may provide a controlled process to explore properties of graphene folds. [ABSTRACT FROM AUTHOR]

Microlens arrays on curvilinear surfaces are highly desirable for wide field-of-view imaging and sensing systems. However, it is technically challenging to fabricate these structures. This letter reports a simple method to machine close-packed microlenses on curvilinear surfaces as inspired by the insect eyes, which involves a femtosecond-laser-based microfabrication and a thermomechanical bending process. Over 7600 hexagonal-shaped microlenses with a diameter of 50 μm were fabricated on a hemispherical poly (methyl methacrylate) shell, which is similar to the compound eyes of insects. The optical performances of the microlens array were demonstrated by the abilities of high-resolution imaging and large view-angle focusing. [ABSTRACT FROM AUTHOR]

We demonstrate laser direct growth of few layer graphene on a silicon substrate. In our study, a continuous wave laser beam was focused on a poly(methyl methacrylate) (PMMA)-coated silicon wafer to evaporate PMMA and melt the silicon wafer. Carbon atoms, decomposed from PMMA, were absorbed by the molten silicon surface, and then separated from silicon in the cooling process to form few-layer graphene. This Si-catalyzed method will provide a new approach and platform for applications of graphene. [ABSTRACT FROM AUTHOR]

Polymer coatings endow ultra-high-Q dielectric resonators with nonlinear properties, impacting numerous applications. However, minimal research combining microcavities with polymer-nanoparticle coatings to tune or tailor the optical properties of the system has been performed. One challenge is maintaining the high performance of the optical device while in the presence of nanoparticles. In the present work, a toroidal microcavity is coated with a polymethylmethacrylate thin film containing thiol-functionalized gold nanoparticles. The thiol-functionalization ensures that the nanoparticles are uniformly distributed throughout the film. The quality factors of these devices are above 5 × 106 and are in good agreement with the theoretical predictions. [ABSTRACT FROM AUTHOR]

A low-operating voltage and stable pentacene field-effect transistor (FET) employing thin low-dielectric constant gate layer of poly (methyl methacrylate) (PMMA) dissolved in propylene carbonate (PC) has been realized. This device exhibiting high field-effect mobility, a threshold voltage of -1 V, and a small sub-threshold slope at operating voltages below -3 V is compared with an FET cast from PMMA film dissolved in a low dipole moment solvent. The negligible hysteresis and excellent electrical stability of FETs under gate bias stress with the use of PC are traceable to the low density of trap states in PMMA bulk and at the interfaces. [ABSTRACT FROM AUTHOR]

A mixture of ZnO nanoparticles and polymethylmethacrylate was used as an active layer in a nonvolatile resistive memory device. Current-voltage characteristics of the device showed nonvolatile write-once-read-many-times memory behavior with a switching time on the order of μs. The device exhibited an on/off ratio of 104, retention time of >105 s, and number of readout of >4 × 104 times under a read voltage of 0.5 V. The emission, cross-sectional high-resolution transmission electron microscopy (TEM), scanning TEM-high angle annular dark field imaging, and energy dispersive x-ray spectroscopy elemental mapping measurements suggest that the electrical switching originates from the formation of conduction paths. [ABSTRACT FROM AUTHOR]

We investigate buckling phenomenon during shape recovery in a poly(methyl methacrylate) upon immersing in ethanol (chemo-responsive) and heating (thermo-responsive). The underlying mechanism is revealed and the influential factors are discussed. Such buckling phenomenon is generic and applicable to all materials during shape recovery when certain conditions (as discussed here) are satisfied. [ABSTRACT FROM AUTHOR]

The memory effects and the carrier transport mechanisms of write-once-read-many-times (WORM) memory devices fabricated using poly(3-hexylthiophene) (P3HT) molecules embedded in a polymethylmethacrylate (PMMA) polymer layer on a flexible substrate were investigated. Current-voltage (I-V) curves at 300 K for Al/P3HT:PMMA/indium-tin-oxide WORM device showed a permanent memory behavior with an ON/OFF ratio of 104. The estimated retention time of the ON state of the WORM device was more than 10 years. The carrier transport mechanisms of the WORM memory devices are described using several models to fit the experimental I-V data. [ABSTRACT FROM AUTHOR]

Poly(methyl methacrylate) (PMMA) substrates were ablated through a fast femtosecond (fs) laser scanning process to create patterns for enhanced protein binding. Typically, two patterns with lines and grids were produced and the protein binding was evaluated by studying the adsorption of fluorescein isothiocyanate (FITC)-labeled bovine serum albumin (BSA). It was found that the adsorption of FITC-BSA was increased up to tenfold on both patterns compared with the untreated PMMA surface, indicating the potential application of the fs laser ablated PMMA surfaces as protein assay substrates. [ABSTRACT FROM AUTHOR]

Microdisk lasers with active region made of type-II GaSb/GaAs quantum dots on the GaAs substrate have been demonstrated. A microdisk cavity with diameter of 3.9 μm was fabricated from a 225-nm-thick GaAs layer filled with GaSb quantum dots. Lasing at wavelengths near 1000 nm at 150 K was achieved for this microdisk. A high threshold characteristic temperature of 77 K was also observed. It is found that the lasing wavelength matches closely with the first-order whispering-gallery mode of the cavity as obtained from the finite-element method simulation. [ABSTRACT FROM AUTHOR]

In this letter, we report the experimental results on plasmonic waves excited on a silver film coated with dye-doped poly(methyl methacrylate) nanogratings, which are characterized by leakage radiation microscopy. Various patterns of the surface plasmon-coupled emission are demonstrated with the structured nanogratings. Plasmonic waves of anisotropic wave-numbers and Bragg mirror effect are both observed in this configuration. Mechanism of the experimental results is discussed from the viewpoint of coupling between adjacent stripe loaded surface plasmons. Our work has potential application in the development of plasmon lasers. [ABSTRACT FROM AUTHOR]

The inherent material properties of silica reduce the susceptibility of silica optical microcavities to many nonlinear phenomena, enabling the development of devices with improved stability. However, large nonlinear coefficients can be leveraged to create microcavities with additional functionality. Therefore, devices with controllable nonlinear behavior are of interest. In the present research, silica microcavities are coated with polystyrene or polymethylmethacrylate to form hybrid microresonators. Using these devices, the thermally induced nonlinear optical behavior is investigated. By precisely controlling the optical field overlap with the polymer film, an environmentally stable device, in which the resonant frequency is independent of the input power, is demonstrated. [ABSTRACT FROM AUTHOR]

A hybrid resistance switching device consisting of ZnO nanorods embedded in an insulating polymethylmethacrylate (PMMA) heterostructure sandwiched between a transparent conductive film and an Al electrode is proposed. The current-voltage characteristics of the device are discussed in terms of the formation and rupture of its conductive filaments. The hybrid device shows stable electrical bistable behaviors after more than 200 resistance-switching cycles. The hybrid ZnO nanorod/PMMA device presented in this work has potential applications in the field of bistable random access memory devices. [ABSTRACT FROM AUTHOR]

An efficient, low-cost, and highly photostable second-order distributed feedback (DFB) laser, fabricated by thermal nanoimprint lithography and based on a polymer active film containing a perylenediimide derivative, is reported. It shows a photostability half-life of 3.1×105 pump pulses (>8 h), when pumped at the same spot of the film. This value is the highest reported to date for organic DFB lasers measured under ambient conditions. The device emits at 573 nm, matching the second low-loss transmission window of poly(methylmethacrylate) (460-590 nm), thus offering potential for applications in data communications based on polymer optical fibers. [ABSTRACT FROM AUTHOR]

We quantify guest molecule aggregation and its effect on the photoconductive properties of guest-host thin films, depending on the guest concentration and host material. A high-performance anthradithiophene (ADT) derivative served as a guest, while functionalized benzothiophene (BTBTB) and polymethylmethacrylate (PMMA) were chosen as hosts. Aggregates exhibited redshifted optical absorption and photoluminescence (PL) spectra, as well as reduced PL quantum yields. Propensity toward guest aggregation differed for PMMA and BTBTB hosts. Photocurrents dramatically increased as the percentage of aggregated guest molecules increased due to considerably higher charge carrier mobility in the aggregates. At low guest concentrations, BTBTB films outperformed PMMA films. [ABSTRACT FROM AUTHOR]

Organic bistable devices (OBDs) fabricated utilizing ZnO quantum dots (QDs) embedded in a poly(methyl methacrylate) (PMMA) layer were fabricated by using a spin-coating technique. Transmission electron microscopy images revealed that 5-nm-diameter ZnO QDs were formed inside the PMMA polymer layer. Current-voltage (I-V) measurements on Al/ZnO QDs embedded in PMMA layer/indium-tin-oxide devices at 300 K showed electrical bistability. The maximum ON/OFF ratio of the current bistability for the OBDs was as large as 4×104. Carrier transport mechanisms for the OBDs are described by using several models to fit the experimental I-V data. [ABSTRACT FROM AUTHOR]

Interfaces between inorganic materials and anharmonic polymers have potentially intriguing thermal transport behavior. The low thermal conductivity of amorphous polymers limits significant interfacial effects to polymer film thicknesses of only a few nanometers. We use time-domain thermoreflectance to directly measure interfacial effects in the thermal conductance of spun-cast poly(methyl methacrylate) (PMMA) thin films and PMMA brushes “grafted-from” the substrate. PMMA brushes are expected to have polymer chains partially aligned perpendicular to the substrate, yet only a modest increase (13%) in thermal conductivity is observed over spun-cast layers. [ABSTRACT FROM AUTHOR]