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Study of Excimer Laser Irradiation Effects on Properties of Crystalline YBaCuO Thin Films

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Abal'oshev A., Abal'osheva I., Lewandowski S., van der Beek C., Konczykowski M., Rizza G., Barbanera S.

Acta Physica Polonica A

2004

vol. 106

issue 5

681-685

The influence of UV laser irradiation on the physical properties of epitaxial YBa_2Cu_3O_{7-δ} thin (<1μm) films fabricated by laser ablation was studied. The samples were irradiated by pulsed excimer laser beam at different incident energy densities E_{ir}≤130 mJ/cm^2, i.e. 2-3 times below the ablation threshold of YBaCuO. The analysis of the sample cross-section using transmission electron microscope shows that such irradiation forms a disordered layer on the top of the crystalline film. Sample surface amorphization was observed also by atomic force microscope. Due to strong UV irradiation absorption in YBaCuO this surface layer acts like a protective cover for the sample interior. Only a small reduction of superconducting critical temperature T_c was observed. Both transport measurements in normal state and magneto-optical studies in superconducting state indicate that between the disordered layer and the bottom non-modified part of the film there exists a wide transitional region with reduced carrier concentration.

X-ray Characterization of Films Formed by Pulsed Laser Deposition on Cold Substrates from YBaCuO Targets

100%

Pełka J., Paszkowicz W., Gierłowski P., Lewandowski S., Zieliński M., Barbanera S., Knapp M.

Acta Physica Polonica A

2002

vol. 101

issue 5

787-794

Grazing-incidence X-ray diffraction supplemented with atomic force microscopy and secondary ion mass spectroscopy were applied to the characterization of films deposited by laser ablation on cold substrates from YBaCuO targets and subsequently irradiated with additional laser pulses of lower energy density. Evolution of X-ray diffraction pattern was observed as a function of irradiation dose. For the as-deposited films the pattern was typical of the amorphized solids. For the films irradiated with doses higher than the threshold, the pattern was enriched with the diffraction peaks, whose general features, like peak positions, widths and relative intensities were almost independent of the dose. The size of the crystallites was deduced from the peak widths to be not smaller than 12-16 nm. Comparison of the pattern with patterns of known phases indicates that, apart of the amorphous component, a structure with an admixture of some new metastable or high temperature phase(s) is formed during the process of pulsed laser annealing. The atomic force microscopy observations revealed that the surface roughness shows a pronounced minimum at low irradiation doses. The secondary ion mass spectroscopy investigation confirms that the strongest chemical changes (increase in concentration of yttrium and copper) due to irradiation with higher doses are observed in the near-surface film material.

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2 Acta Physica Polonica A

1 2004

1 2002

2 Barbanera S.

2 Lewandowski S.

1 Abal'oshev A.

1 Abal'osheva I.

1 Gierłowski P.

1 Knapp M.

1 Konczykowski M.

1 Paszkowicz W.

1 Pełka J.

1 Rizza G.

1 Zieliński M.

1 van der Beek C.

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Study of Excimer Laser Irradiation Effects on Properties of Crystalline YBaCuO Thin Films

X-ray Characterization of Films Formed by Pulsed Laser Deposition on Cold Substrates from YBaCuO Targets