YBaCuO films obtained by excimer laser ablation

Walmsley, D.G.; Sakeek, H. F.; Morrow, Thomas; Rowan, C.; Turner, Robert

doi:10.1016/0921-5107(92)90096-r

Cited by 11 publications

(2 citation statements)

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“…At first sight it seems to imply that initially there are atomic products, including Y, from the ablation process and these are subsequently oxidized to YO in the oxygen-surrounded plume. There is a correlation between the YO emission intensity in the spectrum and the quality of the films obtained under the same conditions: higher Tc and lower normal-state resistance accompany high YO spectral content [4,5]. Production of YO in the plume ensures that the stoichiometric oxygen content can more readily be achieved in the YBCO film.…”

Section: Resultsmentioning

confidence: 88%

Absorption and emission spectra of the YBCO laser plume

Morrow¹,

Sakeek²,

Astal³

et al. 1994

J Supercond

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The plasma produced during laser ablation deposition of thin film YBCO has been studied by optical emission spectroscopy. There is evidence of increased YO band emission in the range 590-625 nm as the ambient oxygen gas pressure confining the plume is increased in the range 30-200 m Torr. Temporal profiles show that close to the target the plume is insensitive to ambient oxygen pressure. It is deduced that the optical emission here is excited by electron impact excitation. Further away from the target there is evidence that two distinct processes are at work. One is again electron excitation; the emission from this process decreases with distance because the expanding plmne cools and collisions become less frequent in the expanding gas. The second is driven by oxidation of atomic species expelled at high speeds from the target. The main region of this activity is in the plume sheath where a shock front ensures heating of ambient O2 and reaction of monatomic plasma species to form oxide in an exotherrnic reaction. Spatial mapping of the emission demonstrates clearly how increasing oxygen gas pressure confines the plasma and enhances the emission intensity from the molecular YO species ejected from the target in a smaller region close to the target. Ba + is observed as a dominant species only very close to (within 1 mm of) the target. Absorption spectra have been taken in an attempt to examine ground state and cool species in the plume. They reveal the quite surprising result that YO persists in the chamber for periods up to 1 msec. This suggests an explanation for the recent report of off-axis laser deposition in terms of simple condensation. Previously, quasi-ballistic transfer of material from target to substrate has been considered the only significant process.

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Section: Resultsmentioning

confidence: 88%

Absorption and emission spectra of the YBCO laser plume

Morrow¹,

Sakeek²,

Astal³

et al. 1994

J Supercond

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“…[2][3][4] Both the nature of the laser-generated plasma and the deposition atmosphere significantly influence the film characteristics. 5,6 A further understanding of the plasma processes, in addition to its intrinsic interest, opens the way to reliable control of the film deposition process.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive study of the film surface temperature and plasma thermokinetics during La1.85Sr0.15CuO4 deposition by laser ablation

Buzea

Wang

Nakajima

et al. 1999

Journal of Applied Physics

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Articles you may be interested inTime relaxation of flux rotation and dimensional crossover in La 1.85 Sr 0.15 Cu O 4We report a comprehensive study of the film surface temperature (T S ) variation during La 1.85 Sr 0.15 CuO 4 deposition by laser ablation as a function of the process parameters ͑oxygen pressure and target-substrate distance͒. For high O 2 pressures, T S ͑measured with an infrared pyrometer͒ follows a decreasing exponential law, while for lower oxygen pressures the experimental data suffer a departure from the theoretical curve. The observed deviation suggests the existence of nonsteady thermal processes in the plume during deposition. The modifications of plume kinetics along with the characterization of deposited films provide important information and a better understanding of the pulsed-laser deposition process.

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