Epitaxial BaTiO3 films with embedded metallic Ni nanocrystal （Ni-BaTiO3） were successfully fabricated on SrTiO3 （001） single-crystalline substrate through the laser molecular beam epitaxial （L-MBE） technique.Hig...Epitaxial BaTiO3 films with embedded metallic Ni nanocrystal （Ni-BaTiO3） were successfully fabricated on SrTiO3 （001） single-crystalline substrate through the laser molecular beam epitaxial （L-MBE） technique.High resolution transmission electron microscopy （HRTEM） and electron energy loss spectrum （EELS） with Kramers-Kronig analysis methods were employed to characterize the microstructures,elementary distribution and the electron structure of these films.HRTEM results suggested that the structure of BaTiO3 was tetragonal with lattice parameters of a=0.399 nm and c=0.403 nm.Energy dispersive X-Ray spectroscopy （EDX） confirmed metallic Ni nanocrystal embedded successfully in BaTiO3 epitaxial films.The Ni-BaTiO3 composite films were compound of the epitaxial BaTiO3 （110） layers alternating with Ni NCs array （111） layers.Furthermore,the existence of the misfit dislocations induced by the embedding of Ni nanoparticles was also clearly demonstrated by the HRTEM images.The Ni L2,3 edges of EELS revealed that Ni NCs in their metallic state were embedded uniformly in the BaTiO3 matrix.A chemical shift of about 7 eV regarding L3 edges in the Ni EELS was also observed.The optical band gap of BaTiO3 in these films was about 3.84 eV,higher than 3.55 eV for pure BaTiO3 films at room temperature.展开更多
In this work ITO thin film annealing was carried out using a CW CO2 laser beam for ITO thin film annealing over a 1 cm2 area with a temperature higher than 250°C to obtain ITO grains with excellent structural qua...In this work ITO thin film annealing was carried out using a CW CO2 laser beam for ITO thin film annealing over a 1 cm2 area with a temperature higher than 250°C to obtain ITO grains with excellent structural quality thin films. The obtained ITO films were characterized for crystallization, surface morphology, electrical and optical properties, which has theoretical significance and application value. ITO thin films are deposited on glass substrates by sputter coater system (RF) from a high density target (In2O3-SnO2, 90-10 wt%). After deposition, ITO thin films have been irradiated by CW CO2 laser (λ = 10.6 μm) with power ranging from 1 to 10 watt. These films were annealed at temperatures 250°C, 350°C, and 450°C in the air for 20 minutes using different laser power. The main incentive was to develop a low temperature process for ITO thin films, which typically required a 350°C anneal to crystallize and achieve optimum optical and electrical properties. The XRD results showed that 350°C temperature laser annealing could crystallize ITO with a strong (222) preferred orientation and its grain size increased from 29.27 nm to 48.63 nm. The structure, optical transmission, energy gap, resistivity and sheet resistance of the ITO thin films were systematically investigated as a function of laser post annealing temperature. It was found that the lowest resistivity was 2.9 × 10-4 Ω-cm and that sheet resistance was 14.5 Ω/sq. And the highest optical transmittance (98.65%) of ITO films was obtained at 350°C annealing temperature.展开更多
Laser spark obtained by using a conical optics is much more appropriate to form conducting channels in atmosphere. Only two types of lasers are actively considered to be used in forming high-conductivity channels in a...Laser spark obtained by using a conical optics is much more appropriate to form conducting channels in atmosphere. Only two types of lasers are actively considered to be used in forming high-conductivity channels in atmosphere, controlled by laser spark： pulsed sub-microsecond gas and chemical lasers （CO2, DF （deuterium fluoride））, short pulse solid-state and UV （ultraviolet） lasers. Main advantage of short pulse lasers is their ability in forming of super long ionized channels with a characteristic diameter of- 100 mm in atmosphere along the beam propagation direction. At estimated electron densities below 1,016 cm3 in these filaments and laser wavelengths in the range of 0.5-1.0 mm, the plasma barely absorbs laser radiation. In this case, the length of the track composed of many filaments is determined by the laser intensity and may reach many kilometers at a femtosecond pulse energy of-100 mJ. However, these lasers could not be used to form high-conductivity long channels in atmosphere. The ohmic resistance of this type a conducting channels turned out to be very high, and the gas in the channels could not be strongly heated （〈 1 J）. An electric breakdown controlled by radiation of femtosecond solid-state laser was implemented in only at a length of 3 m with a voltage of 2 MV across the discharge gap （670 kV/m）. Not so long ago scientific group from P.N. Lebedev physical institute has improved that result, the discharge gap （-1m） had been broken under KrF laser irradiation when switching high-voltage （up to 390 kV/m） electric discharge by 100-ns UV pulses. Our previous result -16 m long conducting channel controlled by a laser spark at the voltage -3 MV was obtained more than 20 years ago in Russia and Japan by using pulsed CO2 laser with energy -0.5 kJ. An average electric field strength was 〈 190 kV/m. It is still too much for efficient applications.展开更多
基金Funded by National High Technology Research and Development Program of China (863 Program)
文摘Epitaxial BaTiO3 films with embedded metallic Ni nanocrystal （Ni-BaTiO3） were successfully fabricated on SrTiO3 （001） single-crystalline substrate through the laser molecular beam epitaxial （L-MBE） technique.High resolution transmission electron microscopy （HRTEM） and electron energy loss spectrum （EELS） with Kramers-Kronig analysis methods were employed to characterize the microstructures,elementary distribution and the electron structure of these films.HRTEM results suggested that the structure of BaTiO3 was tetragonal with lattice parameters of a=0.399 nm and c=0.403 nm.Energy dispersive X-Ray spectroscopy （EDX） confirmed metallic Ni nanocrystal embedded successfully in BaTiO3 epitaxial films.The Ni-BaTiO3 composite films were compound of the epitaxial BaTiO3 （110） layers alternating with Ni NCs array （111） layers.Furthermore,the existence of the misfit dislocations induced by the embedding of Ni nanoparticles was also clearly demonstrated by the HRTEM images.The Ni L2,3 edges of EELS revealed that Ni NCs in their metallic state were embedded uniformly in the BaTiO3 matrix.A chemical shift of about 7 eV regarding L3 edges in the Ni EELS was also observed.The optical band gap of BaTiO3 in these films was about 3.84 eV,higher than 3.55 eV for pure BaTiO3 films at room temperature.
文摘In this work ITO thin film annealing was carried out using a CW CO2 laser beam for ITO thin film annealing over a 1 cm2 area with a temperature higher than 250°C to obtain ITO grains with excellent structural quality thin films. The obtained ITO films were characterized for crystallization, surface morphology, electrical and optical properties, which has theoretical significance and application value. ITO thin films are deposited on glass substrates by sputter coater system (RF) from a high density target (In2O3-SnO2, 90-10 wt%). After deposition, ITO thin films have been irradiated by CW CO2 laser (λ = 10.6 μm) with power ranging from 1 to 10 watt. These films were annealed at temperatures 250°C, 350°C, and 450°C in the air for 20 minutes using different laser power. The main incentive was to develop a low temperature process for ITO thin films, which typically required a 350°C anneal to crystallize and achieve optimum optical and electrical properties. The XRD results showed that 350°C temperature laser annealing could crystallize ITO with a strong (222) preferred orientation and its grain size increased from 29.27 nm to 48.63 nm. The structure, optical transmission, energy gap, resistivity and sheet resistance of the ITO thin films were systematically investigated as a function of laser post annealing temperature. It was found that the lowest resistivity was 2.9 × 10-4 Ω-cm and that sheet resistance was 14.5 Ω/sq. And the highest optical transmittance (98.65%) of ITO films was obtained at 350°C annealing temperature.
文摘Laser spark obtained by using a conical optics is much more appropriate to form conducting channels in atmosphere. Only two types of lasers are actively considered to be used in forming high-conductivity channels in atmosphere, controlled by laser spark： pulsed sub-microsecond gas and chemical lasers （CO2, DF （deuterium fluoride））, short pulse solid-state and UV （ultraviolet） lasers. Main advantage of short pulse lasers is their ability in forming of super long ionized channels with a characteristic diameter of- 100 mm in atmosphere along the beam propagation direction. At estimated electron densities below 1,016 cm3 in these filaments and laser wavelengths in the range of 0.5-1.0 mm, the plasma barely absorbs laser radiation. In this case, the length of the track composed of many filaments is determined by the laser intensity and may reach many kilometers at a femtosecond pulse energy of-100 mJ. However, these lasers could not be used to form high-conductivity long channels in atmosphere. The ohmic resistance of this type a conducting channels turned out to be very high, and the gas in the channels could not be strongly heated （〈 1 J）. An electric breakdown controlled by radiation of femtosecond solid-state laser was implemented in only at a length of 3 m with a voltage of 2 MV across the discharge gap （670 kV/m）. Not so long ago scientific group from P.N. Lebedev physical institute has improved that result, the discharge gap （-1m） had been broken under KrF laser irradiation when switching high-voltage （up to 390 kV/m） electric discharge by 100-ns UV pulses. Our previous result -16 m long conducting channel controlled by a laser spark at the voltage -3 MV was obtained more than 20 years ago in Russia and Japan by using pulsed CO2 laser with energy -0.5 kJ. An average electric field strength was 〈 190 kV/m. It is still too much for efficient applications.
