[en] Anodic oxidation of Al film on silicon substrate in three different electrolytes is investigated through j-t curves and photoluminescence (PL) of the grown porous anodic alumina (PAA) under same voltage. Their growth is analyzed with three typical stages according to j-t curve. The influence of the electrolyte on color centers is shown through comparison of the PL spectra of Si-based PAA fabricated in different electrolytes. From sulfuric, oxalic to phosphoric acids, The PL shows blueshift behavior with different electrolytes due to mechanical stress and concentration of defect centers, while the change of PL intensity reduced for decreasing of the contrast across barrier layer, which is helpful to understand PL mechanism and growth mechanism of porous anodic alumina

[en] Formation mechanism of alumina nanotubes and their array was analysed on the basis of voids in both anodic porous alumina membrane and the tube walls of alumina nanotubes. Circular, crack-like, and wheel-like voids were observed and considered to be responsible for the formation of aluminian nanotubes and their array. Based on microstructural observation of individual alumina nanotubes, the morphology of the tube wall filled with the voids was experimentally determined, which will help to understand the formation mechanism of alumina nanotubes. Our observations and analyses give further information on self-organized mechanism of anodic porous alumina membrane

[en] Rectifying undoped and nitrogen-doped ZnO/p-Si heterojunctions were fabricated by plasma immersion ion implantation and deposition. The undoped and nitrogen-doped ZnO films were n type (n∼10¹⁹ cm^-3) and highly resistive (resistivity ∼10⁵ Ω cm), respectively. While forward biasing the undoped-ZnO/p-Si, the current follows Ohmic behavior if the applied bias V_forward is larger than ∼0.4 V. However, for the nitrogen-doped-ZnO/p-Si sample, the current is Ohmic for V_forward<1.0 V and then transits to J∼V² for V_forward>2.5 V. The transport properties of the undoped-ZnO/p-Si and the N-doped-ZnO/p-Si diodes were explained in terms of the Anderson model and the space charge limited current model, respectively

[en] ZnO nanoporous films consisting nanocrystals on ITO-coated glass substrates were prolongedly electrodeposited under pulse voltages in zinc nitrate solution at room temperature. Their structures were found to be determined by experimental parameters, especially, the voltage and the deposition time. On the basis of the structural characterization, the growth mechanism was proposed as a combined growth process: the competitive growth between lateral overgrowth and nanovoid formation. The structural evolvement is believed to be due to the decrease of surface potential with deposition time, leading to the formation of a quasi-two-layer structure. The revealed mechanism here could be helpful to understand the growth and corresponding properties of ZnO films as well as their nanostructures. -- Highlights: → ZnO nanoporous films were prolongedly electrodeposited under pulse voltages. → The film consists of a quasi-two-layer structure. → Competitive growth between lateral overgrowth and nanovoid formation. → Decrease of surface potential with deposition time.

[en] Visible bands arising from N-related defects are investigated by dynamic cathodoluminescence (CL) and Gaussian deconvolution. The intensity of the red band increases while that of the ultraviolet (UV) band decreases. The intensity of the yellow band also decreases but only slightly as a function of the electron bombardment cycle. The CL behavior of N-doped ZnO after post-annealing in N₂ at high temperature reveals that the N-related defects cannot be easily compensated. The results also confirm the assignment of the N-related defects and are in agreement with the theoretical prediction about Zn-N bonding. Our data provide some clues to the mechanism of the conversion of ZnO into p-type by nitrogen doping

[en] ZnO film with (1 0 0) orientation was produced on silicon substrate and doped with nitrogen using plasma immersion ion implantation. The effects due to N doping were investigated using cathodoluminescence (CL). In the heavily nitrogen-doped ZnO film, the intensity of ultraviolet (UV) band decreases and that of the visible band increases as a function of the electron bombardment cycle i.e. time. Based on the X-ray photoelectron spectroscopy (XPS) analysis, the unstable Zn-N bond is responsible for the CL behavior and the experimental results agree well with the first-principle calculation. Our work is helpful to our understanding of the role of p-type dopants in ZnO

[en] Germanium oxide thin films on silicon substrate were produced using pulsed laser deposition method under adjusted substrate temperature and oxygen pressure. There existed two PL bands observed in our samples, violet and blue bands. We attributed both of them to the neutral oxygen vacancy (NOV) but of different types: GeGe and GeSi, respectively. Fourier transform infrared spectra (FTIR) measurements in our samples not only proved the GeOSi vibration but also assigned the peaks around 1000-bar cm-1 in Si-Ge oxide system qualitatively

[en] Al-based anodic porous alumina membranes with ordered nanopore arrays are fabricated for exploring the template synthesis of carbon nanotubes and nanowires. Via the polymerization of acrylonitrile in the ordered nanopores of the membranes and subsequent heating, the polymer structure was converted into a quasi-graphitic structure. Atomic force microscopy observations revealed that the quasi-graphitic nanostructures are located in the pores of the porous alumina membrane, displaying a hexagonal symmetry. Raman scattering investigation confirmed the formation of carbon nanotubes in the nanopores. With further mild, controlled treatment in aqueous alkali and acidic solution, individual alumina nanotubes (ANTs) coaxially wrapping the carbon nanotubes and nanowires are obtained, as evidenced by transmission electron microscopy observations

[en] Cu oxide nanowire array on Si-based SiO₂ nanoscale islands was fabricated via nanochannels of Si-based porous anodic alumina (PAA) template at room temperature under a pulse voltage in a conventional solution for copper electrodeposition. X-ray diffraction and X-ray photoelectron spectroscopy showed that the main composite of the oxide nanowire is Cu₂O. The nanowires had a preferential growth direction (1 1 1) and connected with the nanoscale SiO₂ islands, which was confirmed by Transmission Electron Microscopy (TEM). Such Si-based nanostructure is useful in the nanoelectrics application. The growth mechanism of Cu oxide nanowires in Si-based PAA template was discussed. The formation of Cu₂O is due to the alkalinity of the anodized solution. However, the oscillations of the potential and current during the experiment trend to bring on a small amount of copper and CuO in the nanowires

[en] Si-based nano-island arrays were fabricated on porous anodic alumina by two methods. In the first method, a thick silicon film was first deposited onto the surface with highly ordered bowl array prepared by anodizing an Al foil, followed by the formation of a polycrystalline silicon nano-island array on the surface close to the bowl array after dissolving aluminum. In the second method, porous anodization was performed on an Al thin film on Si and a SiO₂ nano-island array was subsequently formed electrochemically. Time-resolved atomic force microscopy and photoluminescence were used to investigate the growth process as well as the mechanism of the growth process. Our proposed mechanism as well as assumptions made to formulate the model were found to be in agreement with the experimental results