The Effect of the TiOx Line Width on the Tunneling Phenomenon

During the study of novel ultra fast photoconductive switch (PCSS), ultra fine oxidized titanium (TiOx) lines are formed on the surface of titanium (Ti) layer by the atomic force microscope (AFM) tip acting as a selective anodization electrode. The Ti layers are about 3-5nm-thick on the GaAs substrates and formed by magnetron sputtering method. The Ti-TiOx-Ti construction forms metal-insulator-metal (MIM) tunneling junction, and TiOx works as an energy barrier for the electrons. In order to illustrate the effect of the TiOx line width on the tunneling phenomenon and to determine the narrowest TiOx line as well as its forming conditions which can not lead to the breakdown of the tunneling junction, TiOx lines with different widths are fabricated by changing the ambient humidity. The I-V characteristics of tunneling junctions with different TiOx width are measured. The results indicate that the narrowest TiOx line about 16nm fabricated between two electrodes of the PCSS could not lead to the breakdown of the tunneling junction when the voltage between two electrodes is 6V.