Rare Earth Oxide Films Research Articles

Rare earth oxide films: their preparation and optical properties

The results of investigations into the production methods of Gd(2)O(3), Eu(2)O(3), Er(2)O(3), Yb(2)O(3) films are presented. A description of the optical properties contains the optical constants n and k of the films evaporated by an electron-beam gun in the 0.2-9-microm wavelength range. Interpretations of the IR absorption bands is given.

Properties of rare earth oxide films

We investigated the properties of rare earth oxide films produced by the vacuum evaporation of rare earth metallic films and their oxidation in an oxygen atmosphere; we also studied the silicon-rare earth oxide interface. The rare earth oxide films were characterized by good insulating properties: an electrical resistivity of more than 10 12 Ω cm, a dielectric permittivity of 7–20, a dielectric dissipation factor of 0.01 or less and a breakdown field strength of (2–6) × 10 6 V cm −1. The behaviour of the effective surface charge density curve at flat-band voltages for scandium, yttrium and lanthanum to lutetium was found to be identical with that of the thermal neutron capture cross section for these elements. The presence of a deep level located some 0.3–0.38 eV below the conduction band edge was observed in fast surface state spectra of Si/Ln 2O 3 structures (Ln  Sc, Y, La, Gd, Er). On heating an Si/Y 2O 3/Al structure at 423 K for 20 min with a gate voltage of +5 V we observed a shift in the capacitance-voltage curve of approximately 2.5 V towards more negative voltages; for the same conditions but with a gate voltage of −5 V the shift was about 1 V in the opposite direction.

On `non-stoichiometric phases' in thin films of rare-earth oxides

Kaul & Saxena [Acta Cryst. (1977), A33, 992-996] have reported the existence of long-range and short-range order in a non-stoichiometric phase 'LnO x ' (Ln = rare earth). It is shown that the experiments they are describing are indeed the oxidation of the rare-earth hydride LnH2 into the rare-earth cubic C-type sesquioxide. The interpretation they give of their experiments is to be discarded entirely.

Influence of Trivalent Rare-Earth Oxide Layer on Kerr Effects in EuO Films

The effects of a dielectric overlayer on Kerr magneto-optic properties in thick EuO films were examined. The dielectric film serves not only as a passivation layer, but also to increase the Kerr effects. A series of thin Eu2O3 films were vacuum deposited on a thick EuO film, followed by in situ measurements of the reflectivity and the transverse Kerr effects using a polarized light (with the electric field vector in the plane of incidence) at 45° angle of incidence in the wavelength region from 0.4 to 0.8 μ. As the dielectric (Eu2O3) thickness increases the characteristic reflectance minimum of EuO shifts toward longer wavelengths, accompanied by decreasing reflectivity. This shift agrees well with calculated reflectances using optical constants of Eu2O3 film and EuO. The minimum reflectance of ∼0.04% occurs at 0.675 μ for a dielectric thickness of ∼500 Å. The transverse Kerr effects also depend strongly upon the dielectric thickness. The maximum Kerr effects occur at the wavelength of minimum reflectance For example, corresponding to the minimum reflectance of ∼0.04%, a maximum transverse Kerr effect of ∼+140% occurs at this wavelength. This value can be compared with ∼25% in bulk crystal at 0.575 μ and ∼80% in thin EuO film on a mirror substrate at 0.525 μ, which is the largest value reported in the literature. Preparations and optical properties of several other rare-earth oxide films are also presented.

On the recrystalization behaviour of rare earth oxide thin films

Abstract Abstract Recrystallization behaviour of thin rare earth oxide films Er2O3, HO2O3 and Dy2O3 has been investigated. Recrystallization is induced in these films by the electron beam heating in local areas (pulse annealing) in the electron microscope. In these films recrystallization resembles that observed in the bulk specimens and is also similar to the recrystallization behaviour observed in the case of metals.