ABSTRACT Pure titanium dioxide (TiO 2) and graphene oxide (GO) as well as TiO 2 / GO composite st... more ABSTRACT Pure titanium dioxide (TiO 2) and graphene oxide (GO) as well as TiO 2 / GO composite structures were grown by matrix-assisted pulsed laser evaporation (MAPLE) in a controlled oxygen atmosphere. The MAPLE target dispersions were prepared using distilled water as solvent matrix, with TiO 2 nanoparticles (NPs) and GO platelets serving as host materials. Two laser sources, a free-running IR Er:YAG (λ = 2940 nm, τ fwhm ≅ 350 μs, ν = 10 Hz) and a UV KrF* excimer (λ = 248 nm, τ fwhm ≅ 25 ns, ν = 10 Hz) laser, were used for the transfer and immobilization experiments by infrared (IR)-and ultraviolet (UV)-MAPLE, respectively. The potential physical mechanisms implied in both the IR-and UV-MAPLE processes are discussed, based on numerical simulations of temperature evolution of the distilled water matrix, TiO 2 NPs, and GO platelets. Our results demonstrate the effectiveness of IR-and UV-MAPLE processes for the immobilization of nanoentities onto solid substrates. During IR-MAPLE, the laser radiation is primarily absorbed by the water matrix. The materials transferred to the substrate surface resemble the initial starting materials used for the preparation of the MAPLE target dispersions. Conversely, during UV-MAPLE the UV radiation is mainly absorbed by the nanoentities dispersed in the water matrix. The structural transformation of the nanoentities deposited by UV-MAPLE is significant as compared to the starting materials.
Rare-earth doped TiO2 nanoparticles via colloidal so-gel route have been the focus of intense res... more Rare-earth doped TiO2 nanoparticles via colloidal so-gel route have been the focus of intense research due to their potential optical application in filters, solar cells and light emitters. These applications require the preparation of good quality thin films from the colloids. Therefore different procedures have been used ranging from simple dipping and spin coating to electrophoretic deposition. However, these techniques do not allow a precise, nanometric control of the thickness of the deposited layers required for the targeted applications. In this work we report the successful production of optically active thin films using a non-conventional laser based method, called matrix assisted pulsed laser evaporation (MAPLE). TiO2 nanoparticles doped with Eu have been produced using a colloidal sol gel route [1]. The obtained solutions were frozen in liquid nitrogen to form a solid target further used in the MAPLE experiments. [1] M. Borlaf, et al., J. Phys. Chem. C. B 117, 1556 (2013).
ABSTRACT Nitrogen–doped titanium dioxide (TiO2) thin films were grown on (001) SiO2 substrates by... more ABSTRACT Nitrogen–doped titanium dioxide (TiO2) thin films were grown on (001) SiO2 substrates by reactive pulsed laser deposition. A KrF* excimer laser source (λ = 248 nm, τFWHM ≅ 10 ns, ν = 10 Hz) was used for the irradiations of pressed powder targets composed by both anatase and rutile phase TiO2. The experiments were performed in a controlled reactive atmosphere consisting of oxygen or mixtures of oxygen and nitrogen gases. The obtained thin film crystal structure was investigated by X-ray diffraction, while their chemical composition as well as chemical bonding states between the elements were studied by X-ray photoelectron spectroscopy. An interrelation was found between nitrogen concentration, crystalline structure, bonding states between the elements, and the formation of titanium oxinitride compounds. Moreover, as a result of the nitrogen incorporation in the films a continuous red-shift of the optical absorption edge accompanied by absorption in the visible spectral range between 400 and 500 nm wavelength was observed.
ABSTRACT Titanium oxide/graphene oxide nanocomposite thin films were grown by ultraviolet (UV) ma... more ABSTRACT Titanium oxide/graphene oxide nanocomposite thin films were grown by ultraviolet (UV) matrix-assisted pulsed laser evaporation (MAPLE) technique in controlled oxygen or nitrogen atmospheres. The effect of graphene oxide addition and laser-induced reduction as well as nitrogen doping on the wetting behavior and photoactive properties of titanium oxide thin films was investigated. Hydrophobic to hydrophilic conversion of titanium oxide films takes place progressively as the relative amount of graphene oxide in the MAPLE composite target increases. Nitrogen doping leads to further decrease of the static contact angle of the composite films. The photoactive properties of the synthesized materials were investigated through the evolution of contact angle under UV light irradiation. Wetting properties of both TiO2 and TiO2/GO nanocomposite thin films improved upon exposure to UV light.
Multi-pulse Nd:YAG (lambda = 1.064 mum, tau ~ 100-300 ns, nu = 1-30 kHz laser irradiation of tita... more Multi-pulse Nd:YAG (lambda = 1.064 mum, tau ~ 100-300 ns, nu = 1-30 kHz laser irradiation of titanium at low intensities, below or in some cases just above the single-pulse melting threshold of titanium led to the development of a large variety of surface structures. The morphology evolution was strongly influenced by the number of the subsequent laser pulses as well as the ambient gas. In air the formation of crown-, or dome-shaped micro-structures was evidenced. In vacuum the micro-relief is characterized by smooth polyhedral structures developing in the surface plane. In nitrogen the cumulative laser irradiation induced the growth of uniformly distributed micro-column arrays with a high aspect ratio, protruding above the non-irradiated target surface. Morphological, structural and chemical characterizations of the laser treated surface areas were performed by scanning electron microscopy, X-ray diffractometry, Raman spectroscopy, and wavelength dispersive X-ray spectroscopy. The growth mechanisms which lead to the formation of the specific structures are investigated. Moreover, the potential applications of the laser processed surfaces are discussed.
11th International School on Quantum Electronics: Laser Physics and Applications, 2001
ABSTRACT Thin films of YBa2Cu3O7-x have been obtained on NdGaO3 substrate by pulsed laser deposit... more ABSTRACT Thin films of YBa2Cu3O7-x have been obtained on NdGaO3 substrate by pulsed laser deposition with an excimer KrF* ((lambda) equals 248 nm, (tau) FWHM>= 20 ns laser source from a stoichiometric target. In the present paper we report details of the technology of pulsed laser deposition of high-temperature superconductor thin films, substrates' requirements and high-temperature superconductor thin film characterization. The study of some parameters' intercorrelations for optimization of the technology of the pulsed laser deposition of high-temperature superconductor thin films is also analyzed. Moreover, the contacting technology and techniques of characterization are described.
... For the preparation of the composite MAPLE targets 2.5 μg CdSe/ZnS core–shell QDs were added ... more ... For the preparation of the composite MAPLE targets 2.5 μg CdSe/ZnS core–shell QDs were added to 3 mL of toluene. The obtained solutions were introduced into a special double wall target holder and flash-frozen at −190 °C circulating liquid nitrogen inside the holder walls. ...
ABSTRACT Nanocomposite formed by gold nanoparticles embedded in a titanium dioxide matrix thin fi... more ABSTRACT Nanocomposite formed by gold nanoparticles embedded in a titanium dioxide matrix thin films have been synthesized by a synchronized two laser system. An ArF⁎ excimer (λ=193 nm, τFWHM ∼12 ns) laser and a frequency tripled Nd:Yttrium Aluminium Garnet (YAG; λ=355 nm, τFWHM ∼10 ns) laser were used for the irradiation of titanium dioxide and gold targets. The investigations showed that there exists the possibility for tailoring the optical properties of gold-titanium dioxide nanocomposites by the proper choice of the laser irradiation parameters. The band gap narrowing and additional absorption in the visible spectral region induced by the incorporation of gold in the host TiO2 matrix allows for the design of nanostructured thin films for new generation of photocatalysts or solar energy converters.
Urease thin films were produced by Matrix Assisted Pulsed Laser Evaporation (MAPLE) and Pulsed La... more Urease thin films were produced by Matrix Assisted Pulsed Laser Evaporation (MAPLE) and Pulsed Laser Deposition from two types of targets: frozen water solutions of urease with different concentrations (1–10% m/v) and pure urease pellets. The fluence of the ablating KrF excimer laser was varied between 300 and 2200 mJ/cm2. Fourier transform infrared spectra of the deposited films showed no difference as compared to the original urease. Morphologic studies proved that the films consist of a smooth “base” layer with embedded micrometer-sized droplets. Absorption-coefficient measurements contradicted the traditional “absorptive matrix” model for MAPLE deposition. The laser energy was absorbed by urease clusters leading to a local heating-up and evaporation of the frozen matrix from the uppermost layer accompanied by the release of dissolved urease molecules. Significant enzymatic activity of urease was preserved only during matrix assisted transfer.
We investigated the composition of the surface layer obtained by pulsed Nd:YAG laser (λ=1.064 μm,... more We investigated the composition of the surface layer obtained by pulsed Nd:YAG laser (λ=1.064 μm, τ∼120 ns, ν=1 kHz) irradiation of Ti targets in high pressure nitrogen. The surface morphology, the crystalline state, and the depth distribution of the elements were analysed by scanning electron microscopy, X-ray diffractometry, secondary ion mass spectrometry, X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy.
ABSTRACT Pure titanium dioxide (TiO 2) and graphene oxide (GO) as well as TiO 2 / GO composite st... more ABSTRACT Pure titanium dioxide (TiO 2) and graphene oxide (GO) as well as TiO 2 / GO composite structures were grown by matrix-assisted pulsed laser evaporation (MAPLE) in a controlled oxygen atmosphere. The MAPLE target dispersions were prepared using distilled water as solvent matrix, with TiO 2 nanoparticles (NPs) and GO platelets serving as host materials. Two laser sources, a free-running IR Er:YAG (λ = 2940 nm, τ fwhm ≅ 350 μs, ν = 10 Hz) and a UV KrF* excimer (λ = 248 nm, τ fwhm ≅ 25 ns, ν = 10 Hz) laser, were used for the transfer and immobilization experiments by infrared (IR)-and ultraviolet (UV)-MAPLE, respectively. The potential physical mechanisms implied in both the IR-and UV-MAPLE processes are discussed, based on numerical simulations of temperature evolution of the distilled water matrix, TiO 2 NPs, and GO platelets. Our results demonstrate the effectiveness of IR-and UV-MAPLE processes for the immobilization of nanoentities onto solid substrates. During IR-MAPLE, the laser radiation is primarily absorbed by the water matrix. The materials transferred to the substrate surface resemble the initial starting materials used for the preparation of the MAPLE target dispersions. Conversely, during UV-MAPLE the UV radiation is mainly absorbed by the nanoentities dispersed in the water matrix. The structural transformation of the nanoentities deposited by UV-MAPLE is significant as compared to the starting materials.
Rare-earth doped TiO2 nanoparticles via colloidal so-gel route have been the focus of intense res... more Rare-earth doped TiO2 nanoparticles via colloidal so-gel route have been the focus of intense research due to their potential optical application in filters, solar cells and light emitters. These applications require the preparation of good quality thin films from the colloids. Therefore different procedures have been used ranging from simple dipping and spin coating to electrophoretic deposition. However, these techniques do not allow a precise, nanometric control of the thickness of the deposited layers required for the targeted applications. In this work we report the successful production of optically active thin films using a non-conventional laser based method, called matrix assisted pulsed laser evaporation (MAPLE). TiO2 nanoparticles doped with Eu have been produced using a colloidal sol gel route [1]. The obtained solutions were frozen in liquid nitrogen to form a solid target further used in the MAPLE experiments. [1] M. Borlaf, et al., J. Phys. Chem. C. B 117, 1556 (2013).
ABSTRACT Nitrogen–doped titanium dioxide (TiO2) thin films were grown on (001) SiO2 substrates by... more ABSTRACT Nitrogen–doped titanium dioxide (TiO2) thin films were grown on (001) SiO2 substrates by reactive pulsed laser deposition. A KrF* excimer laser source (λ = 248 nm, τFWHM ≅ 10 ns, ν = 10 Hz) was used for the irradiations of pressed powder targets composed by both anatase and rutile phase TiO2. The experiments were performed in a controlled reactive atmosphere consisting of oxygen or mixtures of oxygen and nitrogen gases. The obtained thin film crystal structure was investigated by X-ray diffraction, while their chemical composition as well as chemical bonding states between the elements were studied by X-ray photoelectron spectroscopy. An interrelation was found between nitrogen concentration, crystalline structure, bonding states between the elements, and the formation of titanium oxinitride compounds. Moreover, as a result of the nitrogen incorporation in the films a continuous red-shift of the optical absorption edge accompanied by absorption in the visible spectral range between 400 and 500 nm wavelength was observed.
ABSTRACT Titanium oxide/graphene oxide nanocomposite thin films were grown by ultraviolet (UV) ma... more ABSTRACT Titanium oxide/graphene oxide nanocomposite thin films were grown by ultraviolet (UV) matrix-assisted pulsed laser evaporation (MAPLE) technique in controlled oxygen or nitrogen atmospheres. The effect of graphene oxide addition and laser-induced reduction as well as nitrogen doping on the wetting behavior and photoactive properties of titanium oxide thin films was investigated. Hydrophobic to hydrophilic conversion of titanium oxide films takes place progressively as the relative amount of graphene oxide in the MAPLE composite target increases. Nitrogen doping leads to further decrease of the static contact angle of the composite films. The photoactive properties of the synthesized materials were investigated through the evolution of contact angle under UV light irradiation. Wetting properties of both TiO2 and TiO2/GO nanocomposite thin films improved upon exposure to UV light.
Multi-pulse Nd:YAG (lambda = 1.064 mum, tau ~ 100-300 ns, nu = 1-30 kHz laser irradiation of tita... more Multi-pulse Nd:YAG (lambda = 1.064 mum, tau ~ 100-300 ns, nu = 1-30 kHz laser irradiation of titanium at low intensities, below or in some cases just above the single-pulse melting threshold of titanium led to the development of a large variety of surface structures. The morphology evolution was strongly influenced by the number of the subsequent laser pulses as well as the ambient gas. In air the formation of crown-, or dome-shaped micro-structures was evidenced. In vacuum the micro-relief is characterized by smooth polyhedral structures developing in the surface plane. In nitrogen the cumulative laser irradiation induced the growth of uniformly distributed micro-column arrays with a high aspect ratio, protruding above the non-irradiated target surface. Morphological, structural and chemical characterizations of the laser treated surface areas were performed by scanning electron microscopy, X-ray diffractometry, Raman spectroscopy, and wavelength dispersive X-ray spectroscopy. The growth mechanisms which lead to the formation of the specific structures are investigated. Moreover, the potential applications of the laser processed surfaces are discussed.
11th International School on Quantum Electronics: Laser Physics and Applications, 2001
ABSTRACT Thin films of YBa2Cu3O7-x have been obtained on NdGaO3 substrate by pulsed laser deposit... more ABSTRACT Thin films of YBa2Cu3O7-x have been obtained on NdGaO3 substrate by pulsed laser deposition with an excimer KrF* ((lambda) equals 248 nm, (tau) FWHM>= 20 ns laser source from a stoichiometric target. In the present paper we report details of the technology of pulsed laser deposition of high-temperature superconductor thin films, substrates' requirements and high-temperature superconductor thin film characterization. The study of some parameters' intercorrelations for optimization of the technology of the pulsed laser deposition of high-temperature superconductor thin films is also analyzed. Moreover, the contacting technology and techniques of characterization are described.
... For the preparation of the composite MAPLE targets 2.5 μg CdSe/ZnS core–shell QDs were added ... more ... For the preparation of the composite MAPLE targets 2.5 μg CdSe/ZnS core–shell QDs were added to 3 mL of toluene. The obtained solutions were introduced into a special double wall target holder and flash-frozen at −190 °C circulating liquid nitrogen inside the holder walls. ...
ABSTRACT Nanocomposite formed by gold nanoparticles embedded in a titanium dioxide matrix thin fi... more ABSTRACT Nanocomposite formed by gold nanoparticles embedded in a titanium dioxide matrix thin films have been synthesized by a synchronized two laser system. An ArF⁎ excimer (λ=193 nm, τFWHM ∼12 ns) laser and a frequency tripled Nd:Yttrium Aluminium Garnet (YAG; λ=355 nm, τFWHM ∼10 ns) laser were used for the irradiation of titanium dioxide and gold targets. The investigations showed that there exists the possibility for tailoring the optical properties of gold-titanium dioxide nanocomposites by the proper choice of the laser irradiation parameters. The band gap narrowing and additional absorption in the visible spectral region induced by the incorporation of gold in the host TiO2 matrix allows for the design of nanostructured thin films for new generation of photocatalysts or solar energy converters.
Urease thin films were produced by Matrix Assisted Pulsed Laser Evaporation (MAPLE) and Pulsed La... more Urease thin films were produced by Matrix Assisted Pulsed Laser Evaporation (MAPLE) and Pulsed Laser Deposition from two types of targets: frozen water solutions of urease with different concentrations (1–10% m/v) and pure urease pellets. The fluence of the ablating KrF excimer laser was varied between 300 and 2200 mJ/cm2. Fourier transform infrared spectra of the deposited films showed no difference as compared to the original urease. Morphologic studies proved that the films consist of a smooth “base” layer with embedded micrometer-sized droplets. Absorption-coefficient measurements contradicted the traditional “absorptive matrix” model for MAPLE deposition. The laser energy was absorbed by urease clusters leading to a local heating-up and evaporation of the frozen matrix from the uppermost layer accompanied by the release of dissolved urease molecules. Significant enzymatic activity of urease was preserved only during matrix assisted transfer.
We investigated the composition of the surface layer obtained by pulsed Nd:YAG laser (λ=1.064 μm,... more We investigated the composition of the surface layer obtained by pulsed Nd:YAG laser (λ=1.064 μm, τ∼120 ns, ν=1 kHz) irradiation of Ti targets in high pressure nitrogen. The surface morphology, the crystalline state, and the depth distribution of the elements were analysed by scanning electron microscopy, X-ray diffractometry, secondary ion mass spectrometry, X-ray photoelectron spectroscopy (XPS), and Auger electron spectroscopy.
Uploads
Papers by E. György