Lateral electronic transport in 2D arrays of oxidized Si nanocrystals on quartz:Coulomb blockade effect and role of hydrogen passivation

摘要

We report on the lateral transport in a single two-dimensional (2D) array of Si nanocrystals of different sizes grown by low pressure chemical vapor deposition (LPCVD) of silicon on a quartz substrate and subsequent oxidation at high temperature. The initial nanocrystal size in the z-direction was 5 nm, while it was reduced to ~3 nm after oxidation. The nanocrystals in the x-y plane were connected by grain boundaries and/or by very thin silicon oxide barriers, while a thin oxide layer was formed on their surface. The electrical measurements showed that current in the film is mainly governed by thermionic emission over the barriers (grain boundaries or dielectric barriers) at high temperatures and by tunneling at lower temperatures. Charge traps at the interfaces of the silicon nanocrystals with the oxide and at the grain boundaries cause considerable hysteresis in the current-voltage characteristics. Hydrogen passivation of the charge traps reduces considerably the hysteresis effect and the activation energy of the thermionic emission, while revealing a clear Coulomb gap.