Key words ZnO thin films, Mg-doped, modified pechini method, band gap, photoluminescence spectra.ZnO thin films with different Mg doping contents (0%, 3%, 5%, 8%, 10%, respectively) were prepared on quartz glass substrates by a modified Pechini method. XRD patterns reveal that all the thin films possess a polycrystalline hexagonal wurtzite structure. The peak position of (002) plane for Mg-doped ZnO thin films shifts toward higher angle due to the Mg doping. The crystallite size calculated by Debey-Scherrer formula is in the range of 32.95-48.92 nm. The SEM images show that Mg-doped ZnO thin films are composed of dense nanoparticles, and the thickness of Mg-doped ZnO thin films with Mg doped at 8% is around 140 nm. The transmittance spectra indicate that Mg doping can increase the optical bandgap of ZnO thin films. The band gap is tailored from 3.36 eV to 3.66 eV by changing Mg doping concentration between 3% and 10%. The photoluminescence spectra show that the ultraviolet emission peak of Mg-doped ZnO thin films shifts toward lower wavelength as Mg doping content increases from 3% to 8%. The green emission peak of Mg-doped ZnO thin films with Mg doping contents were 3%, 8%, and 10% is attributed to the oxygen vacancies or donor-acceptor pair. These results prove that Mg-doped ZnO thin films based on a modified Pechini method have the potential applications in the optoelectronic devices.
A mathematical model representing the relation between pulling up speed, time and aspect ratio is reported, accordingly the axially pull-up electrochemical etching method for fabricating nanoprobes is proposed. The tungsten probes with predetermined shape and aspect ratio according to the model were successfully produced with this method. Then the probes were installed inside a micromanipulation system to manipulate the carbon nanotubes and measure their current-voltage (I-V) characteristics. The probe fabrication and application experiments demonstrated the reasonability and reliability of the model and method developed in this note.
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