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Banerjee D, Dey CC, Kumar R, Modak B, Hazra S, Datta S, Ghosh B, Thakare SV, Jha SN, Bhattacharyya D. Comprehensive study on the origin of orthorhombic phase stabilization in Gd-doped HfO 2 and DFT calculations. Phys Chem Chem Phys 2023; 25:21479-21491. [PMID: 37539659 DOI: 10.1039/d3cp00062a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/05/2023]
Abstract
In recent times, ultra-thin films of hafnium oxide (HfO2) have shown ferroelectricity (FE) attributed to the orthorhombic (o) phase of HfO2 with space group Pca21. This polar o-phase could be stabilized in the doped thin film of the oxide. In the present work, both polar and non-polar o-phases of HfO2 could be stabilized in Gd-doped bulk polycrystalline HfO2. Rietveld analysis of XRD data shows that the relative population of o-phases in the presence of the monoclinic (m) phase of HfO2 increases with increasing Gd-content. The local environment around the host atom has been investigated by time differential perturbed angular correlation (TDPAC) spectroscopy, synchrotron based X-ray near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) measurements showed a reduction in grain size with increasing Gd-dopant indicating a solute drag effect. It could be established that the segregation of the Gd-dopant in the grain boundary is a thermodynamically favorable process and the solute drag effect plays an important role in nucleation of the o-phase in bulk HfO2. Stabilization of Gd in both Pbca and Pca21 phases of HfO2 was supported by defect formation energy calculations using density functional theory (DFT). The present study has important implications in future applications of HfO2 in ferroelectric devices and in understanding the role of dopants in stabilizing the o-phase of HfO2 in the bulk.
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Affiliation(s)
- D Banerjee
- Radiochemistry Division (BARC), Variable Energy Cyclotron Centre, Kolkata 700064, India.
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - C C Dey
- Applied Nuclear Physics Division, Saha Institute of Nuclear Physics, Kolkata 700064, India
- Homi Bhabha National Institute, Anushaktinagar, Mumbai 400094, India
| | - Ravi Kumar
- Atomic & Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
| | - Brindaban Modak
- Chemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India
| | - Snehamoyee Hazra
- Department of Condensed Matter and Materials Physics, S. N. Bose National Centre for Basic Sciences, JD Block, Sector-III, Salt Lake City, Kolkata 700106, India
| | - Subarna Datta
- Material Science Section, Physics Group, Variable Energy Cyclotron Centre, 1/AF, Bidhan Nagar, Kolkata 700064, India
| | - Barnali Ghosh
- Department of Condensed Matter and Materials Physics, S. N. Bose National Centre for Basic Sciences, JD Block, Sector-III, Salt Lake City, Kolkata 700106, India
| | - S V Thakare
- Radiopharmaceutical Division, Bhabha Atomic Research Centre, Mumbai 400085, India
| | - S N Jha
- Beamline Development and Application Section, Bhabha Atomic Research Centre, Mumbai 400085, India
| | - D Bhattacharyya
- Atomic & Molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India
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