Magnetic properties of amorphous Si films doped with rare-earth elements

Abstract

Amorphous silicon films doped with Y, La, Gd, Er, and Lu rare-earth elements $(a$-Si:RE) have been prepared by cosputtering and studied by means of electron-spin resonance (ESR) and dc magnetization. For comparison purposes the magnetic properties of laser-crystallized and hydrogenated a-Si:RE films were also studied. It was found that the rare-earth species are incorporated in the a-Si:RE films in the ${\mathrm{RE}}^{3+}$ form and that the RE doping depletes the neutral dangling bond ${(D}^{0})$ density. The reduction of ${D}^{0}$ density is significantly larger for the magnetic RE's $({\mathrm{Gd}}^{3+}$ and ${\mathrm{Er}}^{3+})$ than for the nonmagnetic ones ${(Y}^{3+},$ ${\mathrm{La}}^{3+},$ ${\mathrm{Lu}}^{3+}).$ These results are interpreted in terms of an exchangelike interaction ${H}_{\mathrm{int}}\ensuremath{\sim}\ensuremath{-}{J}_{\mathrm{RE}\ensuremath{-}\mathrm{DB}}{\mathbf{S}}_{\mathrm{RE}}{\mathbf{S}}_{\mathrm{DB}}$ between the spin of the magnetic RE's and that of the ${D}^{0}.$ All our Gd-doped Si films showed basically the same broad ESR ${\mathrm{Gd}}^{3+}$ resonance $(\ensuremath{\Delta}{H}_{\mathrm{pp}}\ensuremath{\approx}850\mathrm{Oe})$ at $g\ensuremath{\approx}2.01,$ suggesting the formation of a rather stable RE-Si complex in these films.