A Low Voltage Gas Ionization Sensor based on Sparse Gold Nanorods

We report fabrication and characterization of a gas ionization sensor using a sparse array of vertically aligned gold nanorods (AuNR). Our device displayed improved sensitivity compared to the carbon nanotube (CNT) film counterpart, since the room temperature breakdown voltages (V_b) of the tested gases were further reduced. With AuNRs configured as the cathode, V_b was unaffected by gas pressure within a wide range (10^-5 < P < 0.1 torr), suggesting that the breakdown process does not follow Townsend´s criterion. At higher and lower pressures, Vh increased. The field-emission (FE) and field-ionization (FI) properties of the AuNRs were also studied, and the latter showed measurable pressure dependency in a certain voltage range. The lowering of V_b as well as enhanced FE and FI actions, were attributed to the high field-amplification factor of atomically sharp features on AuNR tips covered by a thin alumina scale.