Upper critical field and Raman spectra of MgB{sub 2} thin films irradiated with low energy oxygen ion

Journal Article · Sun Nov 01 00:00:00 EDT 2009 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.3256154· OSTI ID:21361910

Wang, J; Li, J; Zheng, D N ^[1]; Zhuang, C G; Wang, Y Z; Feng, Q R ^[2]

---

1. National Laboratory for Superconductivity, Institute of Physics and National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, P.O. Box 603, Beijing 100190 (China)
2. Department of Physics, Peking University, Beijing 100871 (China)

The structure, upper critical field, and Raman spectrum of epitaxial MgB{sub 2} thin films irradiated by 300 keV O{sub 2}{sup +} ions have been investigated. Lattice parameter c expands after irradiation. There is a significant increase in upper critical field in the moderately irradiated films, while the critical temperature is reduced slightly. The values of critical field at zero temperature exhibit a maximum for samples with a moderate irradiation level for the applied magnetic field both perpendicular and parallel to the film surface. The temperature dependence of the anisotropy parameter, which is defined as the ratio of the upper critical field with the field parallel to the film surface and perpendicular to the film surface, reveals that oxygen ion irradiation mainly affects the sigma band at a low irradiation level. With increasing irradiation level, pi band scattering is strongly enhanced, and finally both bands are in the dirty limit. A broad peak centered around 570 cm{sup -1} is observed in the Raman spectrum of the unirradiated films, and the peak position has a visible redshift in the irradiated samples. In particular, high-frequency spectral structures appear and become dominant, while the E{sub 2g} broad band diminishes gradually with increasing irradiation fluence. The results are discussed by considering the disorder-induced change in carrier scattering within and between the sigma and pi bands and a violation of the Raman selection rules due to oxygen ion irradiation.

• OSTI ID: 21361910
• Journal Information: Journal of Applied Physics, Vol. 106, Issue 9; Other Information: DOI: 10.1063/1.3256154; (c) 2009 American Institute of Physics; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANISOTROPY
CRITICAL FIELD
CRITICAL TEMPERATURE
EPITAXY
ION BEAMS
LATTICE PARAMETERS
MAGNESIUM BORIDES
OXYGEN IONS
RAMAN SPECTRA
RED SHIFT
SCATTERING
SELECTION RULES
SUPERCONDUCTORS
TEMPERATURE DEPENDENCE
THIN FILMS
ALKALINE EARTH METAL COMPOUNDS
BEAMS
BORIDES
BORON COMPOUNDS
CHARGED PARTICLES
CRYSTAL GROWTH METHODS
FILMS
IONS
MAGNESIUM COMPOUNDS
MAGNETIC FIELDS
PHYSICAL PROPERTIES
SPECTRA
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE