Defect engineering by ions

Energetic ions interact with materials via ionization and nuclear collisions, creating electronic defects and atom displacements. The amount and the distribution of defects can be controlled by the ion fluence and energy. Therefore ion beam provides an approach for defect engineering. We are using ion beams for the following defect engineering.

  • Strain engineering
  • Defect induced magnetism
  • Tuning the Fermi energy in semiconductors

Strain engineering for oxides

Ion irradiation has emerged as a powerful tool for the efficient control of single-axis lattice expansion in order to fine tune and modulate the otherwise inaccessible complex correlated phases in oxide thin films. We have investigated the fine tuning of the magnetic moment as well as ferromagnetic-paramagnetic and metal-insulator transition temperatures in the NiCo2O4 inverse-spinel oxide by creating oxygen deficiencies caused by high energy He-ion irradiation. Tailoring of oxygen vacancies and consequently a uniaxial tensile strain drives the system towards the colossal increase of the magnetic moment by two-times. The results are corroborated well by spin-polarized electronic structure calculations with density functional theory and X-ray absorption spectroscopic data which show a peak height change and an energy shift of Co-L2,3 and Ni-L2,3 edges driven by the oxygen vacancies. Therefore, a new pathway via ion irradiation can be established to design new functionalities in other complex oxide thin films.

Cooperation partners

(1) Prof. Ying-Hao Chu

National Chao Tung University, Taiwan, ROC

(2) Prof. Xingsen Gao

South China Normal University, PRC

Related Publications

[1] Defect-induced exchange bias in a single SrRuO3 laye

C. Wang, C. Chen, C.-H. Chang, H.-S. Tsai, P. Pandey, C. Xu, R. Böttger, D. Chen, Y.-J. Zeng, X. Gao, M. Helm, S. Zhou

ACS Applied Materials and Interfaces 10, 27472-27476 (2018)
DOI: 10.1021/acsami.8b07918

[2] Enhancing the Magnetic Moment of Ferrimagnetic NiCo2O4 via Ion Irradiation driven Oxygen Vacancies

P. Pandey, Y. Bitla, M. Zschornak, M. Wang, C. Xu, J. Grenzer, D. C. Meyer, Y. Y. Chin, H. J. Lin, C. T. Chen, S. Gemming, M. Helm, Y. H. Chu, S. Zhou

APL Materials 6, 066109 (2018)
DOI: 10.1063/1.5036941


Defect induced magnetism

Recently, unexpected high-temperature ferromagnetism has been observed in a series of materials which do not contain ions with partially filled d or f shells. This emergent ferromagnetism is often called ‘d0 ferromagnetism’, where defects are believed to be responsible in initiating hybridization at the Fermi level and establishing a long-range ferromagnetic coupling. This type of ‘d0 ferromagnetism’ provides a new opportunity for searching high-temperature spintronic materials. By ion irradiation, we have generated defect-induced ferromagnetism in ZnO, TiO2 and SiC. We aim at:

  • Understanding defect induced magnetism at the electronic level
  • Exploring their spintronic applications

Cooperation partners

(1) Prof. Xiaolong Chen

IOP, CAS

(2) Dr. Prof. Elke Arenholz

ALS, Berkeley Lab

Related Publications

[1] Towards diluted magnetism in TaAs

Y. Liu, Z. Li, L. Guo, X. Chen, Y. Yuan, C. Xu, R. Hübner, S. Akhmadaliev, A. V. Krasheninnikov, A. T. N'Diaye, E. Arenholz, M. Helm, S. Zhou

Phys. Rev. Mater. 1, 044203 (2017)

DOI: 10.1103/PhysRevMaterials.1.044203

[2] Interaction between magnetic moments and itinerant carriers in d0 ferromagnetic SiC

Y. Liu, Y. Yuan, F. Liu, R. Böttger, W. Anwand, Y. Wang, A. Semisalova, A. N. Ponomaryov, X. Lu, A. T. N’Diaye, E. Arenholz, V. Heera, W. Skorupa, M. Helm, and S. Zhou

Phys. Rev. B 95, 195309 (2017)

DOI: 10.1103/PhysRevB.95.195309

[3] Defect-induced magnetism in SiC probed by nuclear magnetic resonance

Z. T. Zhang, D. Dmytriieva, S. Molatta, J. Wosnitza, Y. Wang, M. Helm, S. Zhou, H. Kühne

Phys. Rev. B 95, 085203 (2017)

DOI: 10.1103/PhysRevB.95.085203


Tuning the Fermi energy in semiconductors

It is well known that the intentionally generated defects create some electronic states within the semiconductor bandgap and affect the Fermi energy. It has been widely used in practical applications to change the electrical conductivity of semiconductors. We have shown that this effect can be used to tune the ferromagnetic semiconductors regarding their Curie temperature and magnetic anisotropy.

Cooperation partners

(1) Prof. Bryan Gallagher

Univ. Nottingham, UK

(2) Prof. Jianhua Zhao

CAS, China

Related Publications

[1] Switching the uniaxial magnetic anisotropy by ion irradiation induced compensation,

Y. Yuan, T. Amarouche, C. Xu, A. Rushforth, R. Boettger, K. Edmonds, R. Campion, B. Gallagher, M. Helm, H. von Bardeleben, S. Zhou

J. Phys. D: Appl. Phys. 51 145001 (2018)

DOI: 10.1088/1361-6463/aab1db

[2] Precise tuning of the Curie temperature of (Ga,Mn)As-based magnetic semiconductors by hole compensation: Support for valence-band ferromagnetism

S. Zhou, L. Li, Y. Yuan, A. W. Rushforth, L. Chen, Y. Wang, R. Boettger, R. Heller, J. Zhao, K. W. Edmonds, R. P. Campion, B. L. Gallagher, C. Timm, M. Helm

Phys. Rev. B 95, 075205 (2016)

DOI: 10.1103/PhysRevB.94.075205