The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform

Chorng Haur Sow - One of the best experts on this subject based on the ideXlab platform.

  • Blue micro-highlighting in alumina-GO hybrid empowered by Focused Laser Beam
    Journal of Luminescence, 2019
    Co-Authors: Mei Hui Rachel Seah, Eng Soon Tok, Sharon Xiaodai Lim, Chorng Haur Sow
    Abstract:

    Abstract We present a facile and direct method for selectively depositing amorphous aluminium oxide micro-flake or nanoparticles on graphene oxide (GO) by irradiating the GO film with a Focused Laser Beam through a solution containing aluminium cations. Micro-landscapes comprising aluminium oxide (alumina) based compounds directed by the Laser Beam are constructed. The morphology and density of the deposited alumina are engineered through the variation of concentration of the solution used, the power and scanning speed of the Laser. This method facilitates the rapid process of merging Al, O, C into the same matrix and thus resulted in the formation of carbon incorporated amorphous aluminium oxide that exhibits distinctive blue fluorescence upon UV excitation. This process is akin to the act of blue micro-highlighting on the surface of GO film. The GO film proves to be an ideal platform for the mask-free and non-contact micro-patterning process. The fluorescence micropattern is stable and continues to be fluorescence active even after a period of 397 days.

  • Progressive Micromodulation of Interlayer Coupling in Stacked WS2/WSe2 Heterobilayers Tailored by a Focused Laser Beam.
    ACS applied materials & interfaces, 2018
    Co-Authors: Ya Yu Lee, Xinyun Wang, Chorng Haur Sow
    Abstract:

    When a vertically stacked heterobilayer comprising of a WSe2 monolayer on a WS2 monolayer is first fabricated, the heterobilayer behaves like two independent monolayers because of the presence of a large interlayer separation. However, after the stacked heterobilayer is subjected to a Focused Laser treatment, the interlayer separation between the two monolayers becomes progressively reduced which transforms the WS2/WSe2 heterostructure from the noncoupling to the strongly coupling regime. This strong coupling induces the charge transfer between two layers and thus lowers the exciton recombination rate in the individual layer. This changes the optical properties of the heterobilayer from a fluorescence-active species into one where the fluorescence is quenched. The Focused Laser Beam scanning method is therefore able to serve as a localized annealing tool to progressively modulate the interlayer separation and enable the micropatterning of the heterobilayer to achieve distinct regions with different degree...

  • progressive micromodulation of interlayer coupling in stacked ws2 wse2 heterobilayers tailored by a Focused Laser Beam
    ACS Applied Materials & Interfaces, 2018
    Co-Authors: Ya Yu Lee, Xinyun Wang, Chorng Haur Sow
    Abstract:

    When a vertically stacked heterobilayer comprising of a WSe2 monolayer on a WS2 monolayer is first fabricated, the heterobilayer behaves like two independent monolayers because of the presence of a large interlayer separation. However, after the stacked heterobilayer is subjected to a Focused Laser treatment, the interlayer separation between the two monolayers becomes progressively reduced which transforms the WS2/WSe2 heterostructure from the noncoupling to the strongly coupling regime. This strong coupling induces the charge transfer between two layers and thus lowers the exciton recombination rate in the individual layer. This changes the optical properties of the heterobilayer from a fluorescence-active species into one where the fluorescence is quenched. The Focused Laser Beam scanning method is therefore able to serve as a localized annealing tool to progressively modulate the interlayer separation and enable the micropatterning of the heterobilayer to achieve distinct regions with different degree...

  • a Focused Laser Beam a useful and versatile tool for 1d nanomaterials research a review
    Journal of Materials Science & Technology, 2015
    Co-Authors: Sharon Xiaodai Lim, Chorng Haur Sow
    Abstract:

    One-dimensional (1D) nanomaterials have generated considerable interest amongst researchers because of their potential as fundamental building block in future nano- and micro-electronic devices. In this article, we present a review of a Focused Laser Beam system as a versatile tool for the manipulation, structural transformation, micropatterning and chemical modification of 1D nanomaterials. This tool was found to be effective in patterning and modifying various physical and chemical properties of the pristine 1D nanomaterials. It also aids in the fabrication process of heterostructures and 1D nanomaterial based devices. Finally, we present the implementation of the Focused Laser Beam setup as a valuable tool in the study of the origins and photoresponse mechanism of the 1D nanomaterial devices.

  • Spontaneous decoration of Au nanoparticles on micro-patterned reduced graphene oxide shaped by Focused Laser Beam
    Journal of Applied Physics, 2015
    Co-Authors: Yong Wan, Hao Fatt Teoh, Eng Soon Tok, Chorng Haur Sow
    Abstract:

    We report a facile, two-step method for the micro-landscaping of Au nanoparticles(NPs) on reduced graphene oxide (rGO) film en route to micro-patterned Au(NPs)-rGO hybrid functional materials. This method employs a Focused Laser Beam to first locally convert GO to rGO before immersing the micro-patterned GO-rGO film into HAuCl4 solution. The rGO micro-pattern, shaped by the Focused Laser Beam, serves as nucleation sites for the reduction of Au ions. The reduction mechanism that governs the decoration of Au NPs on rGO films is akin to electroless deposition process. In this instance, surface charges that are formed during Laser reduction of GO to rGO provide active nucleation sites for Au3+ ions to form Au NPs when HAuCl4 solution is introduced. The number density, the size, and size distribution of the Au NPs can thus be directly tuned and preferentially anchored onto the rGO micro-pattern by varying the incident Laser power, the scanning speed of the Laser, or the concentration of HAuCl4. The resulting h...

Ya Yu Lee - One of the best experts on this subject based on the ideXlab platform.

  • Progressive Micromodulation of Interlayer Coupling in Stacked WS2/WSe2 Heterobilayers Tailored by a Focused Laser Beam.
    ACS applied materials & interfaces, 2018
    Co-Authors: Ya Yu Lee, Xinyun Wang, Chorng Haur Sow
    Abstract:

    When a vertically stacked heterobilayer comprising of a WSe2 monolayer on a WS2 monolayer is first fabricated, the heterobilayer behaves like two independent monolayers because of the presence of a large interlayer separation. However, after the stacked heterobilayer is subjected to a Focused Laser treatment, the interlayer separation between the two monolayers becomes progressively reduced which transforms the WS2/WSe2 heterostructure from the noncoupling to the strongly coupling regime. This strong coupling induces the charge transfer between two layers and thus lowers the exciton recombination rate in the individual layer. This changes the optical properties of the heterobilayer from a fluorescence-active species into one where the fluorescence is quenched. The Focused Laser Beam scanning method is therefore able to serve as a localized annealing tool to progressively modulate the interlayer separation and enable the micropatterning of the heterobilayer to achieve distinct regions with different degree...

  • progressive micromodulation of interlayer coupling in stacked ws2 wse2 heterobilayers tailored by a Focused Laser Beam
    ACS Applied Materials & Interfaces, 2018
    Co-Authors: Ya Yu Lee, Xinyun Wang, Chorng Haur Sow
    Abstract:

    When a vertically stacked heterobilayer comprising of a WSe2 monolayer on a WS2 monolayer is first fabricated, the heterobilayer behaves like two independent monolayers because of the presence of a large interlayer separation. However, after the stacked heterobilayer is subjected to a Focused Laser treatment, the interlayer separation between the two monolayers becomes progressively reduced which transforms the WS2/WSe2 heterostructure from the noncoupling to the strongly coupling regime. This strong coupling induces the charge transfer between two layers and thus lowers the exciton recombination rate in the individual layer. This changes the optical properties of the heterobilayer from a fluorescence-active species into one where the fluorescence is quenched. The Focused Laser Beam scanning method is therefore able to serve as a localized annealing tool to progressively modulate the interlayer separation and enable the micropatterning of the heterobilayer to achieve distinct regions with different degree...

Xinyun Wang - One of the best experts on this subject based on the ideXlab platform.

  • Progressive Micromodulation of Interlayer Coupling in Stacked WS2/WSe2 Heterobilayers Tailored by a Focused Laser Beam.
    ACS applied materials & interfaces, 2018
    Co-Authors: Ya Yu Lee, Xinyun Wang, Chorng Haur Sow
    Abstract:

    When a vertically stacked heterobilayer comprising of a WSe2 monolayer on a WS2 monolayer is first fabricated, the heterobilayer behaves like two independent monolayers because of the presence of a large interlayer separation. However, after the stacked heterobilayer is subjected to a Focused Laser treatment, the interlayer separation between the two monolayers becomes progressively reduced which transforms the WS2/WSe2 heterostructure from the noncoupling to the strongly coupling regime. This strong coupling induces the charge transfer between two layers and thus lowers the exciton recombination rate in the individual layer. This changes the optical properties of the heterobilayer from a fluorescence-active species into one where the fluorescence is quenched. The Focused Laser Beam scanning method is therefore able to serve as a localized annealing tool to progressively modulate the interlayer separation and enable the micropatterning of the heterobilayer to achieve distinct regions with different degree...

  • progressive micromodulation of interlayer coupling in stacked ws2 wse2 heterobilayers tailored by a Focused Laser Beam
    ACS Applied Materials & Interfaces, 2018
    Co-Authors: Ya Yu Lee, Xinyun Wang, Chorng Haur Sow
    Abstract:

    When a vertically stacked heterobilayer comprising of a WSe2 monolayer on a WS2 monolayer is first fabricated, the heterobilayer behaves like two independent monolayers because of the presence of a large interlayer separation. However, after the stacked heterobilayer is subjected to a Focused Laser treatment, the interlayer separation between the two monolayers becomes progressively reduced which transforms the WS2/WSe2 heterostructure from the noncoupling to the strongly coupling regime. This strong coupling induces the charge transfer between two layers and thus lowers the exciton recombination rate in the individual layer. This changes the optical properties of the heterobilayer from a fluorescence-active species into one where the fluorescence is quenched. The Focused Laser Beam scanning method is therefore able to serve as a localized annealing tool to progressively modulate the interlayer separation and enable the micropatterning of the heterobilayer to achieve distinct regions with different degree...

A. Di Piazza - One of the best experts on this subject based on the ideXlab platform.

  • WKB Electron Wave Functions in a Tightly Focused Laser Beam
    arXiv: High Energy Physics - Phenomenology, 2021
    Co-Authors: A. Di Piazza
    Abstract:

    Available Laser technology is opening the possibility of testing QED experimentally in the so-called strong-field regime. This calls for developing theoretical tools to investigate strong-field QED processes in electromagnetic fields of complex spacetime structure. Here, we propose a scheme to compute electron wave functions in tightly Focused Laser Beams by taking into account exactly the complex spacetime structure of the fields. The scheme is solely based on the validity of the Wentzel-Kramers-Brillouin (WKB) approximation and the resulting wave functions, unlike previously proposed ones [Phys. Rev. Lett. \textbf{113}, 040402 (2014)], do not directly rely on approximations on the classical electron trajectory. Moreover, a consistent procedure is indicated to take into account higher-order quantum effects within the WKB approach depending on higher-and-higher powers of the Planck constant. In the case of a plane-wave background field we show that the found wave functions exactly reduce to the Volkov states, which are then written in a new and fully quasiclassical form. Finally, by using the leading-order WKB wave functions to compute the probabilities of nonlinear Compton scattering and nonlinear Breit-Wheeler pair production, it is explicitly shown that, if additionally the energies of the charges are sufficiently large that the latter are not significantly deflected by the field, the corresponding Baier's formulas are exactly reproduced for an otherwise arbitrary classical electron trajectory.

  • First-order strong-field QED processes in a tightly Focused Laser Beam
    Physical Review A, 2017
    Co-Authors: A. Di Piazza
    Abstract:

    In [Phys. Rev. Lett. \textbf{117}, 213201 (2016)] we have determined the angular resolved and the total energy spectrum of a positron produced via nonlinear Breit-Wheeler pair production by a high-energy photon counterpropagating with respect to a tightly Focused Laser Beam. Here, we first generalize the results in [Phys. Rev. Lett. \textbf{117}, 213201 (2016)] by including the possibility that the incoming photon is not exactly counterpropagating with respect to the Laser field. As main focus of the present paper, we determine the photon angular resolved and total energy spectrum for the related process of nonlinear Compton scattering by an electron impinging into a tightly-Focused Laser Beam. Analytical integral expressions are obtained under the realistic assumption that the energy of the incoming electron is the largest dynamical energy of the problem and that the electron is initially almost counterpropagating with respect to the Laser field. The crossing symmetry relation between the two processes in a tightly Focused Laser Beam is also elucidated.

  • first order strong field qed processes in a tightly Focused Laser Beam
    Physical Review A, 2017
    Co-Authors: A. Di Piazza
    Abstract:

    In a previous article [Phys. Rev. Lett. 117, 213201 (2016)] we have determined the angular resolved and the total energy spectrum of a positron produced via nonlinear Breit-Wheeler pair production by a high-energy photon counterpropagating with respect to a tightly Focused Laser Beam. Here, we first generalize the results in that article by including the possibility that the incoming photon is not exactly counterpropagating with respect to the Laser field. As main focus of the present paper, we determine the photon angular resolved and total energy spectrum for the related process of nonlinear Compton scattering by an electron impinging into a tightly Focused Laser Beam. Analytical integral expressions are obtained under the realistic assumption that the energy of the incoming electron is the largest dynamical energy of the problem and that the electron is initially almost counterpropagating with respect to the Laser field. The crossing symmetry relation between the two processes in a tightly Focused Laser Beam is also elucidated.

  • nonlinear breit wheeler pair production in a tightly Focused Laser Beam
    Physical Review Letters, 2016
    Co-Authors: A. Di Piazza
    Abstract:

    The only available analytical framework for investigating QED processes in a strong Laser field systematically relies on approximating the latter as a plane wave. However, realistic high-intensity Laser Beams feature much more complex space-time structures than plane waves. Here, we show the feasibility of an analytical framework for investigating strong-field QED processes in Laser Beams of arbitrary space-time structure by determining the energy spectrum of positrons produced via nonlinear Breit-Wheeler pair production as a function of the background field in the realistic assumption that the energy of the incoming photon is the largest dynamical energy in the problem. A numerical evaluation of the angular resolved positron spectrum shows significant quantitative differences with respect to the analogous result in a plane wave, such that the present results will be also important for the design of upcoming strong Laser facilities aiming at measuring this process.

Ion Tiginyanu - One of the best experts on this subject based on the ideXlab platform.

  • Design of titania nanotube structures by Focused Laser Beam direct writing
    Journal of Applied Physics, 2013
    Co-Authors: Mihai Enachi, Andrei Sarua, Marion A. Stevens-kalceff, Veaceslav Ursaki, Ion Tiginyanu
    Abstract:

    In this work, we report on electrochemical fabrication of titania films consisting of nanotubes (NTs) and their treatment by Focused Laser Beam. The results of sample characterization by optical and scanning electron microscopy, cathodoluminescence imaging, and Raman scattering scanning spectroscopy are compared to those inherent to specimens subjected to thermal treatment in a furnace. The obtained data demonstrate possibilities for controlling crystallographic structure of TiO2 NTs by Focused Laser Beam direct writing. These findings open new prospects for the design and fabrication of spatial architectures based on titania nanotubes.

  • Design of titania nanotube structures by Focused Laser Beam writing
    CAS 2013 (International Semiconductor Conference), 2013
    Co-Authors: Mihai Enachi, Andrei Sarua, Marion A. Stevens-kalceff, Ion Tiginyanu, L. Ghimpu, Veaceslav Ursaki
    Abstract:

    Matrices of titania nanotubes (TiO2NTs) have been prepared by anodization of Ti foils in ethylene glycol based electrolyte. These matrices were subjected to annealing at various temperatures or exposed to a Focused Laser Beam and were characterized by transmission electron microscopy (TEM), micro-cathodoluminescence (CL) and Raman scattering (RS) spectroscopy. The obtained data demonstrate possibilities to control the crystallographic structure of TiO2NTs by means of Focused Laser Beam writing. These findings open novel prospects for the design and fabrication of titania nanotube structures.