Identification of the ferroelectric switching process and dopant-dependent switching properties in orthorhombic HfO2: A first principles insight

Abstract

The origin of the ferroelectric polarization switching in orthorhombic HfO2 has been investigated by first principles calculations. The phenomenon can be regarded as being the coordinated displacement of four O ions in the orthorhombic unit cell, which can lead to a saturated polarization as high as 53 μC/cm2. We show the correlation between the computed polarization reversal barrier and the experimental coercive fields.

Prediction of new metastable $$\hbox {HfO}_{2}$$ HfO 2 phases: toward understanding ferro- and antiferroelectric films

“…Despite the value of these earlier HfO 2 structure prediction studies [15,25], two problems are clear. The first problem is the relevance of the predicted structures from the viewpoint of structural energetics.…”

“…However, precise identification of the phase(s) in these films is problematic due to experimental limitations such as the broadness of the thin-film diffraction spectra, unknown film texture and strain fields, and possible presence of multiple phases within a single film. Even the most conclusive phase determination to date [3], combining multiple characterization techniques, has had to rely on a pre-postulated set of possible structural candidates, which in turn has relied on a prior theoretical structure prediction study identifying possible metastable phases [15]. While the detailed investigation in Ref.…”

“…This discovery is of great interest to the semiconductor industry and has led to intensive experimental [3][4][5][6][7][8][9][10][11][12][13][14] and theoretical [9,[15][16][17][18][19][20][21][22] research, because these materials are believed to avoid the problems typical for the traditional ferroelectric materials (such as lead zirconate titanate) during integration into microelectronic devices. However, precise identification of the phase(s) in these films is problematic due to experimental limitations such as the broadness of the thin-film diffraction spectra, unknown film texture and strain fields, and possible presence of multiple phases within a single film.…”

“…Ref. [15] has predicted both polar (potential ferroelectric) and nonpolar metastable HfO 2 structures, and some of these predictions have later been used during the experimental analysis of Ref. [3].…”

“…Applied to HfO 2 , it has identified two new nonpolar structural candidates (space groups P−1, P2 1 /m), and confirmed that the polar (Pca2 1 , hereforth referred to as o-FE) structure previously observed [28] in doped ZrO 2 could also appear in HfO 2 . More recently, Huan et al have used [15] a minima hopping method to identify low-energy metastable phases in HfO 2 , specifically focusing on the possible identity of the ferroelectric phase(s). Minima hopping is a widely used structure prediction method [29,30] comprising a series of short molecular dynamics and structural relaxation runs.…”