Metal-insulator-metal devices have a simple device structure and may have interesting electronic characteristics, including negative differential resistance (NDR) and rewritable resistance memory states. It is postulated these behaviors are due to nanoscopic or molecular switches within the device. The work presented in this thesis includes a combination of physical and chemical alterations and characterization techniques in an attempt to understand the mechanism behind the unusual voltage-controlled behavior in Au-hydridosilsesquioxane (HSQ)-Au junctions. Devices were constructed on macroscopic, mesoscopic, and microscopic scales to determine if a change in size would result in a reduction of the number of switches present. Noise characteristics of the current in macroscopic and microscopic devices were studied to understand the energy profile and timescale of the nanoscale switches. Random telegraph signals (RTS) in macroscopic devices showed complex 1/f statistics, but the scale reduction to microscopic devices resulted in exponential statistics that are indicative of individual isolated fluctuators. Current-voltage (I-V) measurements on macroscopic and microscopic devices revealed that space-charge effects are possibly contributing to the conduction mechanism of Au-HSQ-Au devices. The effect of the interaction of hydrogen with the HSQ was explored. I-V and noise studies in fully deuterated HSQ did not show an isotope effect in macroscopic devices, and proton implantation and electron paramagnetic resonance (EPR) studies revealed that hydrogen is mobile within the HSQ film. Finally, the interfaces of devices were explored. Macroscopic and microscopic Au-HSQ-Au junctions were examined using electron microscopy and X-ray energy dispersive spectroscopy (XEDS), which showed that crystalline gold nanoparticles are present in the macroscopic devices, but not in the microscopic devices. The importance of the Au-HSQ interfaces was examined through modification of the bottom gold electrode using soft lithography with octanethiol. Comparison of the current-voltage curves of modified and unmodified mesoscale devices demonstrated how critical the interfaces are to the appearance of the unusual voltage-controlled behavior in Au-HSQ-Au devices.
展开▼
