Low-frequency excess noise in YBCO thin films near the transition temperature

ABSTRACTWe have prepared high-quality superconducting YBa2Cu3O7−δ (YBCO) thin films on Si(100) with TiN as a buffer layer using in-situ multitarget deposition system. Both TiN and YBCO thin films were deposited sequentially by KrF excitner laser ( λ = 248 nm ) at substrate temperature of 650°C. Thin films were characterized using X-ray diffraction (XRD), four-point-probe ac resistivity, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Rutherford backscattering (RBS). The TiN buffer layer was epitaxial and the epitaxial relationship was found to be cube on cube with <100> TiN // <100> Si. YBCO thin films on Si with TiN buffer layer showed the transition temperature of 90–92K with Tco (zero resistance temperature) of ∼84K. We have found that the quality of the buffer layer is very important in determining the superconducting transition temperature of the thin film. The effects of processing parameters and the correlation of microstructural features with superconducting properties are discussed indetail.

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Study of Low-Frequency Excess Noise Transport in Ga-Face and N-Face GaN Thin Films Grown on Intermediate-Temperature Buffer Layer by RF-MBE

phys stat sol (a) ◽

10.1002/1521-396x(200208)192:2<466::aid-pssa466>3.0.co;2-2 ◽

2002 ◽

Vol 192 (2) ◽

pp. 466-471 ◽

Cited By ~ 2

Author(s):

W.K. Fong ◽

B.H. Leung ◽

J.Q. Xie ◽

C. Surya

Keyword(s):

Thin Films ◽

Buffer Layer ◽

Low Frequency ◽

Intermediate Temperature ◽

Excess Noise

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Effect of Cationic Substitution on Raman Spectra of SrBi2Ta2O9Ceramics and Thin Films

MRS Proceedings ◽

10.1557/proc-784-c3.29 ◽

2003 ◽

Vol 784 ◽

Cited By ~ 2

Author(s):

W. Perez ◽

R. R. Das ◽

P. S. Dobal ◽

Y. I. Yuzyuk ◽

P. Bhattacharya ◽

...

Keyword(s):

Thin Films ◽

Transition Temperature ◽

Lattice Mismatch ◽

Ferroelectric Properties ◽

Low Frequency ◽

X Ray Diffraction ◽

Ionic Radii ◽

Cationic Substitution ◽

Factor Substitution ◽

Raman Modes

ABSTRACTIn the present work micro-Raman spectroscopy has been used to understand the lattice dynamics of cation substituted SBT ceramics and thin films. Different concentrations of Ca and V were introduced into SBT lattices. Incorporation of Ca ion at Sr-site was confirmed by decrease in the lattice parameters calculated from x-ray diffraction data. The lowest Raman modes at 27 cm-1and 58 cm-1showed upward shift with increasing Ca concentration and was attributed to the lower mass and lower ionic radii of Ca. The temperature dependant Raman studies revealed the increase of the phase transition temperature with increased Ca content, and was attributed to the decrease in tolerance factor. Substitution of smaller cation at Sr site in SBT compound has increased lattice mismatch between SrO and TaO2planes inside the stable perovskite unit of SrTa2O7which has pronounced influence on ferroelectric properties of SBT. Substitution of vanadium at Ta-site of SBT did not influence the low frequency Raman modes of SBT. However, it showed a pronounced influence on the O-Ta-O stretching modes by splitting the mode frequency at 810 cm-1. The transition temperature of SBT was reduced with increasing vanadium contents.

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Low frequency impedance and structural properties of YBCO thin films

Vacuum ◽

10.1016/0042-207x(92)90198-6 ◽

1992 ◽

Vol 43 (1-2) ◽

pp. 131-134 ◽

Cited By ~ 1

Author(s):

BG Murray ◽

MS Raven ◽

EE Inameti ◽

YM Wan

Keyword(s):

Thin Films ◽

Structural Properties ◽

Low Frequency ◽

Ybco Thin Films

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Study of low-frequency excess noise in GaN thin films deposited by RF-MBE on intermediate-temperature buffer layers

IEEE Transactions on Electron Devices ◽

10.1109/16.954483 ◽

2001 ◽

Vol 48 (10) ◽

pp. 2400-2404 ◽

Cited By ~ 18

Author(s):

Bong-Hung Leung ◽

Wai-Keung Fong ◽

Chang-Fei Zhu ◽

C. Surya

Keyword(s):

Thin Films ◽

Low Frequency ◽

Intermediate Temperature ◽

Buffer Layers ◽

Excess Noise

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Observation of Kosterlitz‐Thouless Transition and Conductivity Fluctuation in Superconducting Ybco Thin Films

MRS Proceedings ◽

10.1557/proc-169-863 ◽

1989 ◽

Vol 169 ◽

Author(s):

Q. Y. Ying ◽

H. S. Kwok

Keyword(s):

Thin Films ◽

Transition Temperature ◽

Power Law ◽

Mean Field ◽

Superconducting Thin Films ◽

Ybco Thin Films ◽

The Mean ◽

Conductivity Fluctuation ◽

Field Transition

AbstractKosterlitz‐Thouless properties of laser deposited high Tc superconducting thin films of YBa2Cu3O7‐x were examined. The exponent of the power law dependence of V on I showed a “universal jump” at Tc. ID like conductivity fluctuation was also found at temperatures slightly above the mean‐field transition temperature Tco, which may be the result of imperfections of the sample.

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STUDY OF LOW-FREQUENCY EXCESS NOISE IN Ga-POLARITY GaN EPITAXIAL LAYERS

Fluctuation and Noise Letters ◽

10.1142/s0219477501000445 ◽

2001 ◽

Vol 01 (04) ◽

pp. R163-R174 ◽

Cited By ~ 1

Author(s):

J. Q. XIE ◽

W. K. FONG ◽

B. H. LEUNG ◽

C. F. ZHU ◽

C. SURYA ◽

...

Keyword(s):

Thin Films ◽

Flicker Noise ◽

Substantial Reduction ◽

Power Spectra ◽

Low Frequency ◽

Buffer Layers ◽

Excess Noise ◽

Rf Plasma ◽

Noise Power ◽

Scattering Rate

We report detailed investigations of low-frequency excess noise in Ga -polarity GaN thin films deposited by RF-plasma assisted molecular beam epitaxy. The noise properties of the GaN thin films deposited with and without the intermediate-temperature buffer layers (ITBL) are studied in detailed to examine the effects of the ITBL on the noise. Substantial reduction in the flicker noise levels are observed for samples grown on ITBLs with a Hooge parameter of 3×10-4, which is believed to be the lowest, to date, reported for GaN material. At low-temperatures, Lorentzian bumps originating from the generation-recombination processes are observed. Detailed studies of the temperature dependencies of the voltage noise power spectra have led to the formulation of a model for the observed low-frequency fluctuations. The model stipulates that the phenomenon arises from the thermally activated trapping and detrapping of carriers. The process results in the correlated fluctuations in the carrier number and the Coulombic scattering rate. Quantitative computation shows that number fluctuation dominates in our samples. Numerical evaluation of the deep-levels indicates substantial reduction in the trap density for the Ga -polarity GaN films.

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Electrical Noise in Ultra Thin Giant Magnetoresistors

MRS Proceedings ◽

10.1557/proc-574-365 ◽

1999 ◽

Vol 574 ◽

Cited By ~ 5

Author(s):

A. Lisauskas ◽

S. I. Khartsev ◽

A. M. Grishin ◽

V. Palenskis

Keyword(s):

Transition Temperature ◽

Low Frequency ◽

Epitaxial Films ◽

Excess Noise ◽

Ferromagnetic Phase ◽

Sharp Change ◽

Voltage Fluctuations ◽

Characteristic Peak ◽

Ferromagnetic Phase Transition ◽

Resistance Fluctuations

AbstractWe report measurements of low frequency 1/f excess noise for the series of La0.75Sr0.25MnO3 (LSMO) giant magnetoresistive thin epitaxial films with thickness of 42, 50, 100, and 600 Å. Fabricated manganite films experience semiconductor-normal metal (paramagnetic-ferromagnetic) phase transition with the temperature change. The transition manifests itself by the sharp change of resistivity and characteristic peak of magnetoresistivity. Thickness decrease results in lowering the transition temperature and increasing of resistivity. The noise spectra has 1/fa behavior with a ≈ 1± 0.2. The voltage fluctuations spectral density shows quadratic dependence on current indicating that observed noise is caused by the resistance fluctuations. Noise level, temperature coefficient of resisistvity and magnetoresistance increase for thin films. Therefore, the operation point (transition temperature) can be tailored from 330 K to 220 K by changing only the film thickness while the performance of temperature and magnetic field LSMO sensors can be maintained almost constant in thickness range down to 100 Å.

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