Effect of oxygen vacancies and strain on the phonon spectrum of HfO2 thin films
Abstract
The effect of strain and oxygen deficiency on the Raman spectrum of monoclinic HfO2 is investigated theoretically using first-principles calculations. 1% in-plane compressive strain applied to a and c axes is found to blue shift the phonon frequencies, while 1% tensile strain does the opposite. The simulations are compared, and good agreement is found with the experimental results of Raman frequencies greater than 110 cm−1 for 50 nm HfO2 thin films. Several Raman modes measured below 110 cm−1 and previously assigned to HfO2 are found to be rotational modes of gases present in air ambient (nitrogen and oxygen). However, localized vibrational modes introduced by threefold-coordinated oxygen (O3) vacancies are identified at 96.4 cm−1 computationally. These results are important for a deeper understanding of vibrational modes in HfO2, which has technological applications in transistors and particularly in resistive random-access memory whose operation relies on oxygen-deficient HfOx.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jun 08, 2017
- Source ID
- 10.1063/1.4984833
Entities
People
- Alberto Salleo
- Alexander A Demkov
- Annabel R. Chew
- Eilam Yalon
- Eric Pop
- Lingyuan Gao
- Sanchit Deshmukh
Organizations
- Army Research Office
- Division of Electrical, Communications & Cyber Systems
- Stanford University
- United States Department of Energy
- University of Texas at Austin