Role of Intrinsic Electron Trapping in Negative Charging of Amorphous Alumina
Modern computer technology depends on nanoscale electronic devices. These devices rely on extremely thin layers of insulating materials which are in contact with metal or semiconducting electrodes. Many of these layers are amorphous, meaning their atoms are arranged in a disordered structure rather than the regular atomic patterns found in crystals.
We use advanced atomistic computer simulations to investigate how this atomic disorder influences the behaviour of amorphous alumina, a material widely used as an electrical insulator in electronic devices. For these devices to operate reliably, the alumina layer must remain electrically neutral during operation of the device. We find that the disordered atomic structure naturally creates locations where electrons can become trapped. Instead of moving freely through the material, some electrons become localised in deep energy states and require additional energy to escape. As a result, they can persist within the oxide, allowing negative charge to accumulate when a voltage is applied.
By comparing our simulations with experimental measurements, we show that these intrinsic electron traps help explain the long-observed negative charging of amorphous alumina. These findings improve our understanding of the atomic-scale behaviour of disordered materials and provide new insight into the mechanisms responsible for the reliability and long-term degradation of nanoscale electronic devices.
Authors: Jack W. Strand, Kaja H. Hiorth, David Gao, Valeri Afanas’ev, Jaakko Akola, Alexander L. Shluger