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RISS 인기검색어
- 검색키워드
- 저자 : V. J. Kennedy (검색결과 6 건)
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Carbon depth profiling of superconducting YBCO thin films on nanometer scale
V. J. Kennedy,A. Markwitz,A. Bubendorfer,N. Long,N. Dytlewski 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4
Ion beam analysis techniques have been used to probe for carbon contamination in high temperature superconductor thin lms.These techniques provide a powerful tool to detect C with limit of detection close to 0.01 at.% and to measure carbon depth proleson the nanometer scale with a depth resolution of 10 nm at the surface. In the present study, a series of YBa2Cu3O7. d (YBCO) lmshave been formed on MgO substrates by a solgel method. Dierent lm thicknesses and heat treatments were studied. Typicalformation temperatures were 770850.C resulting in thicknesses from 50 to 600 nm. It was found that, depending on the samplepreparation conditions, carbon was incorporated in the lms at a concentration of 0.54.6 at.%. Carbon was homogeneously distributed throughout the films.
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A. Markwitz,V. J. Kennedy,K. Short,M. Rudolphi,H. Baumann 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4
(100) and (111) silicon substrates were implanted with 10 keV Nþ2 ions using plasma immersion ion implantation (PI3). Series ofspecimens were implanted in the uence range from 0.5 to 1.6· 1016 cm. 2 and subsequently annealed at 1000.C (radiation tem-perature) for 60 s with a raster scanned electron beam (EB-RTA) to investigate surface structuring after EB-RTA. Atomic forcemicroscopy (AFM) revealed that the combination of PI3 and EB-RTA resulted in a roughening of the surface on the lower 100 nmscale depending on the nitrogen uence used in the experiments. Similar ion implantation and annealing protocols using an ac-celerator based system in conjunction with EB-RTA showed, however, smooth surfaces on the 3 nm scale. Selected results arepresented providing evidence for the possibility of controlling the surface structuring of implanted surfaces via PI3 process para-meters.
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Surface smoothing of thin HTc YBa2Cu3O7-superconducting films by high-energy iodine ions
A. Markwitz,V. J. Kennedy,A. Bubendorfer,N. Long 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4
A variety of techniques were applied to probe for surface modications and structural changes in thin highTcYBa2Cu3O7. d(YBCO) superconducting lms prepared onto MgO substrates after time of ight heavy ion elastic recoil detection analysis(HERDA).Films have been prepared by ex-situ processing of a spin-coated organic solgel precursor.Evidence is provided for the smoothening of the surface of the films accompanied with an amorphisation of the YBCO lms in the HERDA spot region.Thevirgin surface roughness of 30-50 nm could be reduced to 1-2 nm after bombarding the lm for a short time with pA current.However, large scale surface roughness on the 200 nm scale remained unchanged.Importantly, the integrity of the superconductorlms did not change signicantly during HERDA allowing simultaneous measurements of high resolution Y, Cu, Mg and C depth proles.Further research will utilise the HERDA depth proling capability for carbon and copper since the copper stoichiometry and fraction of carbon as an impurity are crucial for an understanding of the performance of the YBCO films.
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Analysis of heteroepitaxial germanium on gallium arsenide grown by pulsed laser deposition
S. M. Durbin,J. P. Zheng,A. Markwitz,V. J. Kennedy,A. Pun 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4
Interest in the pulsed laser deposition (PLD) technique now extends far beyond growth of multiple component oxides, the area inwhich it rst proved itself. In particular, it shows promise as a viable technique for high-quality crystalline thin lms on substrates with low thermal tolerance. In this paper, we report the PLD growth of single-crystal Ge on (10) GaAs substrates in the tem-perature range of 150550.C. In situ reection high-energy electron diraction shows the formation of a reconstructed surface afteras few as two laser pulses, corresponding to approximately 4% monolayer coverage. Transmission electron microscopy conrms heteroepitaxial growth with good quality interfaces and smooth surfaces, despite the presence of oxygen and carbon impurities.
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Characterisation of polycrystalline gallium nitride grown by plasma-assisted evaporation
S. M. Durbin,V. J. Kennedy,S. I. Liem,R. J. Reeves,A. Markwitz,V. A. Christie 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4
The remarkable success of GaN-based devices despite comparatively large defect densities has prompted many groups to explorepolycrystalline and amorphous GaN thin lms for various device applications. In this paper we present the results of a series of lmgrowths performed using an RF plasma assisted molecular beam epitaxy system. GaN lms were grown on quartz substrates in thetemperature range of 150650.C, and in all cases were found to be polycrystalline and largelyc-axis oriented. Rutherford back-scattering spectroscopy indicates lms have gallium-rich stoichiometry, except for those grown below 200.C. Bandedge photo-luminescence was observed at room temperature even for the lms grown at 150.C, and many lms exhibited a measurable changein resistivity under exposure to ultraviolet radiation.
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Photocatalytic titania coatings
T. Kemmitt,N. I. Al-Salim,M. Waterland,V. J. Kennedy,A. Markwitz 한국물리학회 2004 Current Applied Physics Vol.4 No.2-4
Thin coatings of titania and titania/silica were deposited onto aluminium and anodised aluminium substrates from an aqueous precursor. The titania precursor sol was prepared using a proprietary method, and applied onto cleaned or polished substrates by spray coating. Two-stage heat processing at 160 and up to 650 C densified and crystallised the film. Crack-free, transparent coatings up to 1.00 lm thickcan be produced from a single application using this precursor system. X-ray diffraction was used to identify the crystal phase of the films as anatase, and resonant nuclear reaction (RNRA) experiments were carried out to assess the degree of aluminium migration from the aluminium substrates into the films. Photocatalytic oxidation of an organic dye on the surface was monitored by a novel fluorescence method. Water droplet contact angles were measured on the film surfaces before and after UV illumination to investigate the photoactivated hydrophilicity of the films. The activities were compared with films prepared on glass and ceramic substrates.
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