The influence of nitrogen on the electrical conductivity of planar metal-insulator-metal structures

摘要

The properties of negative differential resistance (NDR), electron emission (EE) and the accompany-ing electroluminescence (EL) in electroformed pla-nar metal films have been extensively reported and reviewed [1]. It is well established that the presence of organic material is essential to the production of NDR in these devices [2] and one possible model for explaining the observed effects is based on a dynamic process of adsorption and desorption of hydrocarbons [3, 4]. Work on the effect of different gases has shown that the presence of oxygen has a detrimental effect on the conduction process [5, 6]. Devices exposed to air at atmospheric pressure lose their conductivity with the application of a voltage. This low conductivity state persists until the devices are reintroduced to vacuum [1,7]. Exposure to air alone, without applying a voltage, does not signifi-cantly alter the first voltage cycle taken after the devices are reintroduced to vacuum. It has also been suggested that there is a strong pressure dependence to the observed conduction process [8]. In this work we investigate the changes in NDR and EL in planar electroformed gold films when the devices are taken from vacuum to atmospheric pressure in a nitrogen atmosphere. The advantage of EL in contrast to EE is that its observation is not mean free path limited. Under vacuum, fluctuations in EE and EL are believed to be correlated and observation of EL is indirect evidence for EE. The effect of electroform-ing and subsequent voltage cycles under nitrogen are also investigated.