Permanent polarization and charge injection in thin anodic alumina layers studied by electrostatic force microscopy

Abstract

An electrostatic force microscope (EFM) and a Kelvin probe are used to characterize the charges embedded in thin anodic alumina layers of thickness ranging from 100 to 400 nm. Introducing a method for obtaining self-supported alumina layers, we exhibit the presence of positive charges at the metal/oxide interface of anodic alumina layers. These positive charges, together with the negative charges present at the surface of the anodic layer, induce a true polarization of the layer. The magnitude of this polarization depends on the conditions of preparation of the layers and can be well controlled. As a second step, we show the influence of this polarization on charge injection in these layers with EFM: charges of both signs may be injected in unpolarized layers whereas one cannot inject negative charges in polarized layers, which thus exhibit a diode-like behavior.

Kelvin probe microscopy for reliability investigation of RF-MEMS capacitive switches

“…The result of all these effort, although provided valuable information on the dielectric charging process, were based on the rather uniform contact of MIM capacitors or the average value of many point contacts arising from asperities on the dielectric and suspended electrode surfaces. This drawback has been recently approached in the MOS technology with the aid of EFM Kelvin probe microscopy for the investigation of high-K dielectrics [13][14][15][16]. Here it must be pointed out that in MEMS technology the dielectric surface rough because the thin dielectric film is gown at low temperatures and usually on the tip of an electrolytically deposited metal film.…”

Effect of continuous magnetic field on the growth mechanism of nanoporous anodic alumina films on different substrates

“…However, during alumina growth at the electrolyte/alumina interface, a negative space charge localized on shallow electron traps is accumulated [14][15][16]. This space charge creates non-uniform inner field and consequently affects the growth rate of alumina.…”

Effects of a magnetic field on growth of porous alumina films on aluminum

“…The existence of negative charges that are trapped in a region near the electrolyte/oxide surface and of positive charges that are located mainly near the metal/oxide interface, has been previously observed [9, and references within]. However, the origin of these trapped charges is still discussed controversially in the literature [10]. The experimentally observed space charges were attributed in some recent publications to the electrons which were injected into the oxide layer and which were trapped in deep traps generated by the anions incorporated in the oxide [9].…”

“…The experimentally observed space charges were attributed in some recent publications to the electrons which were injected into the oxide layer and which were trapped in deep traps generated by the anions incorporated in the oxide [9]. In another study it was considered that these traps were related to the defects, that were produced by the mechanical stress in the oxide layer originating from the incorporation of some impurities [10].…”