Synthesis of Lanthanum Tungsten Oxynitride Perovskite Thin Films

Abstract

Ternary metal‐oxide material systems commonly crystallize in the perovskite crystal structure, which is utilized in numerous electronic applications. In contrast to oxides, there are no known nitride perovskites, likely due to the competition with oxidation, which makes the formation of pure nitride materials difficult and synthesis of oxynitride materials more common. While deposition of oxynitride perovskite thin films is important for many electronic applications, it is difficult to control oxygen and nitrogen stoichiometry. Lanthanum tungsten oxynitride (LaWN3−δOδ) thin films with varying La:W ratio are synthesized by combinatorial sputtering and characterized for their chemical composition, crystal structure, and microstructure. A three‐step synthesis method, which involves co‐sputtering, capping layer deposition, and rapid thermal annealing, is established for producing crystalline thin films while minimizing the oxygen content. Elemental depth profiling results show that the cation‐stoichiometric films contain approximately one oxygen for every five nitrogen (δ = 0.5). Synchrotron‐based diffraction indicates a tetragonal perovskite crystal structure. These results are discussed in terms of the perovskite tolerance factors, octahedral tilting, and bond valence. Overall, this synthesis and characterization is expected to pave the way toward future thin film property measurements of lanthanum tungsten oxynitrides and eventual synthesis of oxygen‐free nitride perovskites.

First-principles calculations of electronic structure and optical and elastic properties of the novel ABX3-type LaWN3perovskite structure

“…Investigation of this novel LaWN 3 ABX 3 -type material based on rst principles can accelerate the future practical synthesis of the piezoelectric and ferroelectric properties of LaWN 3 nitride perovskite using well-established design principles, such as increasing the piezoelectric response in nitride perovskites using morphotropic phase boundaries to better understand the boundary between the polar R3c LaWN 3 and non-polar I4 LaWO x N 3Àx structures. 70,71 In all, this investigation helps accelerate the practical synthesis of R3c LaWN 3 and improve the efficiency by narrowing the scope of specic chemical reaction conditions.…”

Thin Film Synthesis of Semiconductors in the Mg–Sb–N Materials System

“…There are few existing experimental reports on oxygen-containing LaWN3 [16] [17] and TaThN3 [18] perovskites synthesized in bulk form, and a few recent theoretical papers on these and related materials [19] [20]. Several other nitride perovskites have been theoretically predicted [21] [22], and LaWN3 was synthesized in the thin film form by our group [23]. There are also some bulk synthesis reports on antiperovskites, such as Mn3MN (M=Cu, Zn, Ga, Sb) [24] [25] and AE3SbN (AE = Mg, Ca, Sr, Ba) [26] [27], which are perovskites with the cation and anion sites reversed compared to the regular perovskite structure.…”

Influence of Protection Layers on Thermal Stability of Nitride Thin Films

“…[46] The AlN and TiN protective layers were grown for 30-60 min at otherwise equal conditions before and after Zr-N depositions, resulting in 20-40 nm thickness for each material. [47] The resulting samples were cut into 0.5 Â 0.5 00 pieces and used for RTA in flowing N 2 as a function of temperature (500-1200 C) and time (3-24 min), with 3 min chamber purge at 100 C before annealing, 1 min heating time, and 3 min cooling time down to <100 C. [48] The reference AlN, TiN, and AlN/TiN stacks without the Zr-N films were also deposited, and found to be stable under these annealing conditions.…”