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Mechanics of laser-assisted debonding of films (2001)

Tavernier, P. R. ; Clarke, D. R.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 89 (2001), S. 1527-1536

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Films of GaN and ZnO can be separated from the substrates on which they are grown by the use of a laser-assisted debonding process in which a pulsed laser is shone through the substrate and absorbed in the film. Experience shows that the success in separating the films intact and damage free depends sensitively on the laser parameters used and the physical and geometric properties of the films. In this contribution, the mechanics of the laser-assisted debonding of GaN films are presented and used to construct process maps that delineate the conditions for damage-free film separation. The key variable is the nondimensional group ΩEp/(dp2τ), where Ω is a lumped material constant, Ep is the laser pulse energy, dp is the diameter of the illuminated area and τ is the laser pulse length. Experimental observations of UV/excimer laser assisted debonding of GaN films from sapphire substrates are used to illustrate the types of deformations and cracking modes on which the process maps are based. © 2001 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1338519

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Cracking of GaN films (2001)

Etzkorn, E. V. ; Clarke, D. R.

[S.l.] : American Institute of Physics (AIP)

Journal of Applied Physics 89 (2001), S. 1025-1034

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Cracking of thick GaN films grown on sapphire is reexamined on the basis of a combination of microstructural observations of cracking and established mechanics of fracture of films. It is argued that cracking is motivated by tensile growth stresses once a critical thickness is reached. Subsequent growth on the cracked films occurs, perpetuating the cracked structure until the crack surfaces approach one another and touch. Continued film growth buries the crack. Once the crack faces touch, there are conditions under which it is energetically favorable for the cracks to close and heal. Crack healing can be kinetically limited. Whether the crack healing is complete within the growth time depends on several factors including, it is suggested, whether impurities have adsorbed to the surface during growth. Conditions under which cracks that have extended into the sapphire substrate during film growth can act as critical flaws for fracture of the substrate on cooling are also presented. © 2001 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1330243

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Defining and Integrating Sequences in Site Analysis: The Evidence from Hillforts and Other Sites (2001)

Clarke, D. V.

Oxford, UK and Boston, USA : Blackwell Publishers Ltd

Oxford journal of archaeology 20 (2001), S. 0

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ISSN: 1468-0092

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Klassische Archäologie

Notizen: The author sets out at length his personal views on the problems of periodising occupation-sequences on sites of the Iron Age in Britain, with examples from Wheeler to the 1990s.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/1468-0092.00136

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The Cryptococcus neoformans STE11α gene is similar to other fungal mitogen-activated protein kinase kinase kinase (MAPKKK) genes but is mating type specific (2001)

Clarke, D. L. ; Woodlee, G. L. ; McClelland, C. M. ; [weitere]

Oxford, UK : Blackwell Science, Ltd

Molecular microbiology 40 (2001), S. 0

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ISSN: 1365-2958

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Biologie , Medizin

Notizen: Partial sequence analysis of the Cryptococcus neoformans MATα mating type locus revealed the presence of a gene with substantial sequence similarity to other fungal mitogen-activated protein (MAP) kinase kinase kinase (MAPKKK) genes. The C. neoformans gene, designated STE11α, showed the highest degree of similarity to the Neurospora crassa nrc-1, Schizosaccharomyces pombe byr2 and Saccharomyces cerevisiae STE11 genes. A polymerase chain reaction-mediated sib-selection technique was successfully adapted for the purpose of disrupting STE11α. C. neoformans ste11αΔ mutants were found to be sterile, consistent with the phenotypes of ste11 and byr2 mutants in S. cerevisiae and S. pombe respectively. Haploid ste11αΔ mutants were also found to be unable to produce hyphae, suggesting that the C. neoformans gene is functionally conserved when compared with its S. cerevisiae MAPKKK counterpart. Comparison of the wild-type STE11α strain with a ste11αΔ disruptant for virulence using the mouse model showed that the ste11αΔ strain was less virulent, but the difference was only minor. In spite of some of the conserved functions of STE11α, linkage analysis showed that STE11α is only found in mating type α strains. These results demonstrate that, although functionally conserved, the mating pathway in C. neoformans has a unique organization.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1046/j.1365-2958.2001.02375.x

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