A comprehensive study on the structural evolution of HfO₂thin films doped with various dopants

Abstract

Quantitative phase analysis is first performed on doped Hafnia films to elucidate the structural origin of unexpected ferroelectricity.

Si Doped Hafnium Oxide—A “Fragile” Ferroelectric System

“…A split of the peak at 35°, the broadened peak at 51°, and features around 60° and 75° suggests that a tetragonal phase is formed for high Si content and the cubic Fm3m phase can be excluded. [24] The results of the Rietveld refinement in Figure 7d show clearly that the incorporation of silicon in the hafnium oxide films leads to a continuous decrease of the monoclinic phase www.advelectronicmat.de fraction accompanied by an increasing amount of tetragonal phase fraction. Therefore, Rietveld refinement is performed to determine the different phase fractions of the patterns (similar to what was reported by Park et al).…”

“…[24] For Gd-doped HfO 2 , no variation of the dopant content throughout the film thickness is visible, whereas for Aldoped HfO 2 , the Al dopants diffused to the interfacial region. [24] For Gd-doped HfO 2 , no variation of the dopant content throughout the film thickness is visible, whereas for Aldoped HfO 2 , the Al dopants diffused to the interfacial region.…”

“…[24] For Gd-doped HfO 2 , no variation of the dopant content throughout the film thickness is visible, whereas for Aldoped HfO 2 , the Al dopants diffused to the interfacial region. [24] It is worth noting that different precursors and oxygen sources were used for the ALD depositions, so that different impurity levels [25,26] or microstructures [27] cannot be excluded, which may affect the distribution of the dopant atoms. [24] It is worth noting that different precursors and oxygen sources were used for the ALD depositions, so that different impurity levels [25,26] or microstructures [27] cannot be excluded, which may affect the distribution of the dopant atoms.…”

“…[24] It was suggested that Gd and Al can diffuse faster than Si in HfO 2 thin film due to the higher oxygen vacancy concentration. [24] Si is tetravalent, resulting in minimal oxygen vacancy generation in the HfO 2 lattice. Since previous studies showed negligible impurity levels and similar microstructures, Park et al proposed the different valences of the dopants and the corresponding oxygen vacancy generation as a possible explanation for the differences in dopant diffusion for different dopant species.…”

Polarization switching behavior of Hf–Zr–O ferroelectric ultrathin films studied through coercive field characteristics

“…In other words, ferroelectric domains are isolated from each other in the film, and the number of ferroelectric domains changes with parameters such as metal composition and film thickness. In the reports utilizing high-resolution TEM observation, 66,67) it is found that orthorhombic, monoclinic, and tetragonal crystals are tightly bonded while maintaining smooth interfaces. Because the orthorhombic crystal is a metastable phase, 3) it may be stable when it is surrounded by stable phases.…”