Deposition and dielectric characterization of strontium and tantalum-based oxide and oxynitride perovskite thin films

• Oxide and oxynitride perovskite films were deposited by magnetron sputtering.
• Reactive gas containing dioxygen and dinitrogen was used.
• Strontium and tantalum based (Sr0.99La0.01)2(Ta0.99Ti0.01)2(O,N)7 films were obtained.
• The permittivity of the epitaxial oxide film is 42 @1 KHz.
• The permittivity of the oriented oxynitride film is 60 @1 KHz.

We have synthesized the composition x = 0.01 of the (Sr1-xLax)2(Ta1-xTix)2O7 solid solution, mixing the ferroelectric perovskite phases Sr2Ta2O7 and La2Ti2O7. Related oxide and oxynitride materials have been produced as thin films by magnetron radio frequency sputtering. Reactive sputter deposition was conducted at 750 °C under a 75 vol.% (Ar) + 25 vol.% (N2,O2) mixture. An oxygen-free plasma leads to the deposition of an oxynitride film (Sr0.99La0.01) (Ta0.99Ti0.01)O2N, characterized by a band gap Eg = 2.30 eV and a preferential (001) epitaxial growth on (001) SrTiO3 substrate. Its dielectric constant and loss tangent are respectively Epsilon' = 60 (at 1 kHz) and tanDelta = 62.5 × 10−3. In oxygen-rich conditions (vol.%N2 ≤ 15%), (110) epitaxial (Sr0.99La0.01)2(Ta0.99Ti0.01)2O7 oxides films are deposited, associated to a larger band gap value (Eg = 4.55 eV). The oxide films permittivity varies from 45 to 25 (at 1 kHz) in correlation with the decrease in crystalline orientation; measured losses are lower than 5.10−3. For 20 ≤ vol.% N2 ≤ 24.55, the films are poorly crystallized, leading to very low permittivities (minimum Epsilon' = 3). A correlation between the dielectric losses and the presence of an oxynitride phase in the samples is highlighted.

Evolution of the permittivity κ and loss tangent tanδ (@1 kHz) of (Sr0.99La0.01)2(Ta0.99Ti0.01)2O7 and (Sr0.99La0.01) (Ta0.99Ti0.01)O2N thin films as a function of the dinitrogen and dioxygen percentages in the reactive sputtering plasma used for the deposition.Figure optionsDownload as PowerPoint slide