Thickness Fluctuations Produce Apparent Long-Range Tunneling in Large-Area Junctions: The Case of Polyelectrolyte Multilayers

MALDONADO, LILIANA; HERRERA, SANTIAGO E.; WILLIAMS, FEDERICO J.; TAGLIAZUCCHI, MARIO

JOURNAL OF PHYSICAL CHEMISTRY C

AMER CHEMICAL SOC

Año: 2022 vol. 126 p. 9956 - 9964

1932-7447

The electron-tunneling (ET) current through a barrier of thickness h is generally analyzed with the Simmons model, j ∼exp(-βh), where β is the tunneling decay coefficient. We show that fluctuations in barrier thickness produce apparent β values systematically smaller than the real ones, which may lead to incorrectly postulating long-range electron tunneling. We reached this conclusion by performing the first tunneling studies through polyelectrolyte-multilayer films of different average thicknesses using impedance spectroscopy and EGaIn/Ga2O3 top contacts. We explained these measurements with a model that considers ET through a film with a Gaussian distribution of thicknesses, as observed by atomic force microscopy. It is shown that even relatively small thickness fluctuations can introduce a systematic error in the determination of β and that when the average film thickness and its standard deviation become commensurable, it is impossible to determine β.