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3 Acta Physica Polonica A

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

100%

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

Acta Physica Polonica A

2004

tom 106

nr 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.

Magnetic Properties of FeSeTe Compound Crystallized from Liquid Phase

84%

Lewandowski S. , Berkowski M. , Tarenkov V. , D'yachenko A. , Abal'oshev A. , Abal'osheva I. , Gawryluk D. , Domukhovski V. , Sidorov S. , Boichenko D.

Acta Physica Polonica A

2010

tom 118

nr 2

289-291

We report on measurements of samples with nominal composition FeSe_{0.5}Te_{0.5}, crystallized by the Bridgman method. Magnetic and transport properties of the samples were examined. The measurements confirm the coexistence of ferromagnetism and superconductivity below the superconducting transition temperature. The ferromagnetic contribution to magnetization, estimated at 10%, might be caused by the presence of ferrimagnetic Fe_7Se_8, which occupies about 10% of sample volume. From the Andreev spectroscopy we found superconducting energy gap Δ = 2.6 meV at T = 4.2 K, and from magnetization measurements the critical temperature T_c = 15.8 K. The critical current density in magnetic field H = 4 kOe, determined from magnetization measurements, is j_c = (1-2) × 10^4 A/cm^2 and weakly depends on magnetic field intensity.

Growth and Characterization of YBa_2Cu_3O_{7-δ} Films Deposited by Laser Ablation on CeO_2-Buffered Sapphire

84%

Abal'osheva I. , Zaytseva I. , Aleszkiewicz M. , Malinowski A. , Bezusyy V. , Syryanyy Y. , Gierłowski P. , Abal'oshev O. , Kończykowski M. , Cieplak M.

Acta Physica Polonica A

2014

tom 126

nr 4a

A-69-A-73

In this work we study the growth, by pulsed laser deposition, of YBa_2Cu_3O_{7-δ} (YBCO) films on the CeO_2-buffered R-cut sapphire substrates, with the buffer layer recrystallized prior to the deposition of superconductor. We find that the superconducting critical temperature and the critical current density of the films are very close to similar parameters for the YBCO films grown on lattice-matched single crystalline substrates. It appears that the structural defects in the buffer layer affect the microstructure of YBCO films, resulting in high values of the critical current density, suitable for applications.

Optimization of the Superconducting Properties of Laser Ablated YBa_2Cu_3O_{7-δ} Films on CeO_2-Buffered Sapphire

84%

Abal'osheva I. , Zaytseva I. , Aleszkiewicz M. , Syryanyy Y. , Gierłowski P. , Abal'oshev O. , Bezusyy V. , Cieplak M.

nr 4

805-807

We use pulsed laser deposition to grow YBa_2Cu_3O_{7-δ} (YBCO) superconducting films for microwave applications. The films are grown on R-cut sapphire substrates, with CeO_2 buffer layers, which are re-crystallized at high temperature prior to YBCO growth. Using the atomic force microscopy (AFM) and X-ray diffractometry we determine the optimal temperature for recrystallization (1000°C) and the optimal buffer layer thickness (30 nm). The properties of YBCO films of various thickness, grown on the optimized CeO_2 buffer layers, are studied using several methods, including AFM, magnetooptical imaging, and transport experiments. The YBCO film roughness is found to increase with the increasing film thickness, but the magnetic flux penetration in the superconducting state remains homogeneous. The superconducting parameters (the critical temperature and the critical current density) are somewhat lower than the similar parameters for YBCO films deposited on mono-crystalline substrates.