Impact of lanthanum on the modification of HfO2 films structure

From Doping to Dilution: Local Chemistry and Collective Interactions of La in HfO2

“…In accordance with theoretical calculations on the stabilization of the ferroelectric phase [10][11][12] we suggest the structural incorporation of La into the HfO 2 lattice by a substitution of Hf by La at the Hf site, at least up to a La concentration of about 10%. For higher La concentrations, the formation of a pyrochlore La 2 Hf 2 O 7 phase as reported by Smirnova et al [15] is in accordance with our HAXPES results. However, we cannot confirm the existence of a La 2 O 3 phase in HfO 2 .…”

“…[ 9 ] Perevalov et al concluded from a shape analysis of X‐ray photoelectron spectroscopy (XPS) spectra on the formation of a La 2 O 3 phase, which shall intermix with HfO 2 at a La content of 10%. [ 14 ] Structural investigations by Smirnova et al revealed a pyrochlore La 2 Hf 2 O 7 phase formation above 18% La content, [ 15 ] which is in agreement with observations by Schroeder et al [ 9 ] The XPS spectra of La 2 Hf 2 O 7 showed a similar shape of the La 3 d core level as La 2 O 3 .…”

“…The observed splitting for the 33% sample, however, is comparable to the La 2 O 3 literature values, but our observed satellite intensity is significantly lower. The reported La 3 d spectra of the pyrochlore La 2 Hf 2 O 7 phase [ 15 ] compares well in terms of splitting as well as intensity ratio. Furthermore, our observed plasmon energy is significantly larger than determined by Sunding et al for La 2 O 3 and La 2 (OH) 3 , which reveals a higher electron density in the valence band.…”

Structure, chemistry and luminescence properties of dielectric La Hf1-O films

“…The systematic shift of the reflections indicates the formation of solid solutions [4]. The formation of solid solutions in Hf-M-O systems (M ¼ Al, Sc, or La) was confirmed previously by several methods: GIXRD, XPS, and transmission electron microscopy [4,12,30]. A shift to lower 2q values occurs when La 3þ cations with the ion radius of 1.04 Å substitute in the HfO 2 lattice for Hf 4þ cations with the ion radius of 0.82 Å.…”

Origin of Pr3+ luminescence in hafnium silicate films: combined atom probe tomography and TEM investigations

“…RE ions are frequently used for light-emitting devices due to the variety of electronic levels allowing us to tune optical emission in the UV to IR range [4,5]. Nevertheless, only a few studies have been performed on RE-doped HfSiO x , with particular attention on Er 3+ -doped films [6][7][8][9][10][11]. The structural properties of these materials at the nanoscale level were investigated by transmission electron microscopy (TEM) [7,9], which enabled us to reveal a phase separation between an amorphous SiO 2 and a tetragonal HfO 2 phase caused by high annealing temperature.…”