Fabrication and characterization of nanoscale elements of a miniaturized gas ionization sensor

In this thesis the nanoscale elements of a Gas Ionization Sensor (GIS) were studied, designed and fabricated. A GIS is working by fingerprinting the ionization breakdown voltage of unknown gases which displays good selectivity even in the very low gas pressure. In GIS, electron impact ionization mechanism leads to the breakdown of gas inside an ionization cell. Since breakdown voltage ( V b ) is a unique quantity of each gas, by measuring this voltage, the existence and type of the unknown gases can be found. To fabricate the GIS, vertically aligned arrays of AgNWs were employed. The AgNWs were synthesized by template-assisted electroplating method. To obtain freestanding metals nanowires without any bundling, Anodized Alumina Oxide (AAO) template with well ordered pore morphology was required. The AAO templates were fabricated using the modified two steps anodization process. By applying various anodization conditions, AAO templates with interpore distance varying from 40nm to 150nm were fabricated. Besides, the dependency of the interpore distance and applied voltage in the AAO was confirmed. The freestanding AgNWs fabricated in the pores of AAO were then used as the cathode in the two parallel plate ionization cell to act as the field amplifier to decrease the field ionization threshold voltage. The GIS was characterized and compared to its AuNWs counterparts. This new device exhibit improvement compared to its previous AuNWs GIS, as the breakdown voltages were further reduced. The reduction of V b was attributed to the lower workfunction of silver compared to that of gold