Al-doped ZnO thin film (AZO) is regarded as a potential candidate to replace the expensive ITO thin film and is the
central issue in current research in the field of transparent conductive film because of its properties of high conductivity,
low level of pollution, high transmittanceand and low fabrication cost. In this paper, c-axis preferred growth AZO films
were fabricated on sapphire (0001) substrate by the pulsed laser deposition at different substrate temperatures (Ts). The
scanning electron microscope (SEM), X-ray diffraction (XRD) and the four-point probe (FPP) were used to measure the
thin film microstructure and electrical characteristics. SEM results show that the surfaces of all AZO films are very flat
and have no droplets on them, expect the film grown at room temperature. The grain sizes of AZO gradually decrease
with increse of Ts. X-ray diffraction spectra show that the quality of the crystallization of thin films gradually is
improved with increase of Ts. The results measured by FPP show that with increase of temperature, sheet resistance first
decreases then increases.
Al-doped ZnO thin film(AZO) has become a type of material which is the first choice to replace the expensive ITO thin
film and is the central issue in current research in the field of transparent conductive film because of its properties of high
conductivity, high transmittance, low level of pollution, and cheap. In this paper, AZO films were produced by the RF
magnetron sputtering under the different growth temperatures condition. The atomic force microscope (AFM), X-ray
diffraction (XRD), visible-UV spectrophotometer and the four-point probe (FPP) were used to measure the thin film
microstructure, optical properties and electrical characteristics. AFM results show that the film with the smoother surface
and the more uniform size distribution grains are obtained by increasing substrate temperature. X-ray diffraction spectra
show that with increase of the temperature, the quality of the crystallization of thin films gradually is improved and the
the optimum growth temperature is 600 °C. Optical transmission spectra show that the AZO films have high
transmittance and band gap of thin films decreases with increasing temperature. The results measured by FPP show that
with increase of temperature, sheet resistance decreases.
Er-doped nanocrystalline Si thin films were fabricated by pulsed laser ablation in high-purity Ar gas with different gas pressures at room temperature and post-annealing technology under different temperature in nitrogen. Scanning electron microscopy(SEM), x-ray diffraction(XRD) and Raman were employed to picture the microstructure of films. The SEM photographs showed that the morphology of film was transformed from the uniform nanoparticles in size to the web-like structure with the increase of gas pressure, which was attributed to the different collision cooling process of ablated particles. Raman and XRD spectra showed that the introduction of Ar gas could effectively improve the crystallinity degree of the samples and Si nanoparticle size could be controlled by adjusting the post-annealing temperature which was critical for improving the luminescent intensity of Er3+ ion. More uniform and higher crystallinity degree Er-doped Si thin films could be obtained at lower annealing temperature.
To investigate nucleation area and transport dynamics of Si nanoparticles, nanocrystalline silicon films were prepared by pulsed laser ablation. Subsequently, the additional laser beam as energy source was introduced, which crossed vertically the plasma plume from the top down in front of the target at a distance of 0.5 cm under same experiment condition. In this region, due to collision between the photon and the plasma plume, the transport of Si nanoparticles was impacted by the cross-laser beam. The Raman and x-ray diffraction spectra (XRD), scanning electron microscopy (SEM) images of the films showed that Si nanoparticles were formed in a certain range, and the average size of Si nanoparticles monotonically decreases with the increase of distance. Obviously, the range of Si nanoparticles deposited in substrates became narrower due to the influence of additional laser beam. Experimental results were analyzed in terms of the nucleation area model.
In He, Ne or Ar gas under a deposition pressure of 10Pa, nanocrystalline silicon films were prepared by pulsed laser ablation, which the deposition time was 5, 7, 13, 15, 69 and 350min, respectively. A Lambda Pyhsik XeCl excimer laser (wavelength 308nm, pulse duration 15ns, laser fluence 4J/cm2, repetition rate 1Hz) was used, and the distance between Si target and the substrate was 3cm. The Raman spectra indicate that the films are nanocrystalline. Scanning electron microscopy images show that the discrete nanoparticles are first formed, more and more nanoparticles are obtained with increasing of deposition time, and then some nanoparticles start to aggregate and form continuous film, and finally the film ruptures due to the stress. It is the complicated interaction between nanoparticles as-formed in the film and those produced subsequently to lead to the phenomena mentioned above. The morphology of the films deposited in different ambient gases is compared. The result shows that aggregation between nanoparticles, film-formation and rupture take place in a lighter gas earlier than those in a heavier gas. This is related to the different growing rate of the films deposited in different gases.
In this paper, vertical-cavity surface-emitting laser (VCSEL) with pillar structure which has potential applications in optical communication and optical interconnect is theoretically analyzed, the calculation model that used to discuss the modal performance of cylinder VCSEL with oxidized aperture is established by using vector field model. The numerical simulations show oscillating wavelength and threshold gain against inner and outer radius of laser, the layer refractive index and pair number of Bragg mirror, thickness, position and oxidized material’s refractive index of oxidized aperture, in detail. According to the standard that oscillating wavelength should approach to the designed one and threshold gain should be as low as possible, we give the appropriate range of parameters discussed in the paper.
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