This project aims to develop highly sensitive, real-time and low voltage gas ionization sensors. We have successfully fabricated and characterized branched silicon nanowhiskers with extremely sharp tips. Arrays of these sharp tips are used because of their small tip radii and high aspect ratio which allow for high electric fields at low voltages. When the device is biased, the nanowires are at the highest potential and the collector (anode) is at the lowest potential, at this stage the electrons in the outer shell of the gas atoms (molecules) tunnel out due to the large geometrical field enhancement at the tip of these nanostructures. This tunneling effect is a quantum-mechanical process which occurs when a strong electric field is applied. The magnitude of electric field required to ionize these gases is still several hundred million volts per centimeter. Our nanostructures however allow for sub-10 volts ionization of various gaseous pecies which can be used for real-time detection of gasses. This also allows us to design low-power discharge devices such as miniaturized gas ionization sensors and mass spectrometers. The project entails fabrication of high aspect ratio field-intensifying nanostructures, and then tailoring these nanostructures to enable field-ionization of gas molecules at sub-10 volts. The sensor are characterized in a custom-made vacuum chamber with several gas inlets and electrical feedthroughs.
Project end date: 08/19/11