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1

Digitale Medien

Epitaxial thin-film ruby as an ion-irradiation damage sensor (1996)

Wen, Q. ; Yu, Ning ; Clarke, D. R.

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

Journal of Applied Physics 80 (1996), S. 3587-3589

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The fluorescence from a thin ruby film, formed by epitaxial growth on a sapphire substrate, is shown to be a sensitive monitor of both the irradiation dose and the strain produced by irradiation of argon ions having an end of range exceeding the thickness of the ruby film. Decreases in fluorescence intensity are detectable for doses in excess of 1012 cm2, whereas no damage is detectable by Rutherford backscattering spectrometry/channeling until doses almost two orders of magnitude larger. Using the systematic shift in fluorescence frequency observed with irradiation, it is concluded that lattice strain accumulates rapidly for doses in excess of 1014 cm2. © 1996 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.363232

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2

Digitale Medien

High-resolution determination of the stress in individual interconnect lines and the variation due to electromigration (1995)

Ma, Qing ; Chiras, S. ; Clarke, D. R. ; [weitere]

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

Journal of Applied Physics 78 (1995), S. 1614-1622

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Large tensile stresses usually exist in metallic interconnect lines on silicon substrates as a result of thermal mismatch. When a current is subsequently passed any divergence of atomic flux can create superimposed stress variations along the line. Together, these stresses can significantly influence the growth of voids and therefore affect interconnect reliability. In this work, a high-resolution (∼2 μm) optical spectroscopy method has been used to measure the localized stresses around passivated aluminum lines on a silicon wafer, both as-fabricated and after electromigration testing. The method is based on the piezospectroscopic properties of silicon, specifically the frequency shift of the Raman line at 520 R cm−1. By focusing a laser beam at points adjacent to the aluminum lines, the Raman signal was excited and collected. The stresses in the aluminum lines can then be derived from the stresses in the silicon using finite element methods. Large variations of stress along an electromigration-tested line were observed and compared to a theoretical model based on differences in effective diffusivities from grain to grain in a polycrystalline interconnect line. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.360255

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3

Digitale Medien

Crystallographic orientation of epitaxial BaTiO3 films: The role of thermal-expansion mismatch with the substrate (1995)

Srikant, V. ; Tarsa, E. J. ; Clarke, D. R. ; [weitere]

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

Journal of Applied Physics 77 (1995), S. 1517-1522

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Expitaxial ferroelectric BaTiO3 thin films have been grown on (001) MgO and MgO-buffered (001) GaAs substrates by pulsed laser deposition to explore the effect of substrate lattice parameter. X-ray-diffraction studies showed that the BaTiO3 films on both MgO single-crystal substrates and MgO-buffered (001) GaAs substrates have a cube-on-cube epitaxy; however, for the BaTiO3 films grown on MgO the spacing of the planes parallel to the substrate was close to the c-axis dimension of the unconstrained tetragonal phase, whereas the BaTiO3 films on MgO/GaAs exhibited a spacing closer to the a-axis dimension of the unconstrained tetragonal phase. The cube-on-cube epitaxy was maintained through the heterostructures even when thin epitaxial intermediate buffer layers of SrTiO3 and La0.5Sr0.5CoO3 were used. The intermediate layers had no effect on the position of the BaTiO3 peak in θ-2θ scans. Together, these observations indicate that, for the materials combinations studied, it is the thermal-expansion mismatch between the film and the underlying substrate that determines the crystallographic orientation of the BaTiO3 film. Preliminary measurements indicate that the BaTiO3 films are "weakly'' ferroelectric. © 1995 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.358902

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4

Digitale Medien

The immunoperoxidase localization of tumour markers in ovarian cancer: the value of CEA, EMA, cytokeratin and DD9 (1991)

HAMMOND, R. H. ; BATES, THELMA D. ; CLARKE, D. G. ; [weitere]

Oxford, UK : Blackwell Publishing Ltd

BJOG 98 (1991), S. 0

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ISSN: 1471-0528

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Medizin

Notizen: Summary. Primary tumours from 40 patients with epithelial ovarian cancer, treated at St Thomas's Hospital over a 10-year period, were studied for the immunocytochemical expression of the following tumour markers in formalin-fixed paraffin embedded material: carcinoembryonic antigen (CEA), epithelial membrane antigen (EMA), cytokeratin (CAM 5.2), and DD9. An indirect immunoperoxidase staining technique was used. All of the tumours were positive for EMA and CAM 5.2, and 30% of them were positive for both CEA and DD9. The absence of CEA and DD9 may be of value in differentiating between metastatic abdominal adenocarcinomas of ovarian origin and those of gastrointestinal origin, but no indication of prognosis was obtained using these epithelial markers. The strong and widespread staining of all of the tumours for EMA suggests that this may be a useful marker for detecting metastatic or recurrent disease by immunoscintigraphy.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1471-0528.1991.tb10315.x

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5

Digitale Medien

Dielectric cracking produced by electromigration in microelectronic interconnects (2000)

Chiras, S. ; Clarke, D. R.

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

Journal of Applied Physics 88 (2000), S. 6302-6312

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The development of stress during electromigration along Al lines, constrained within a dielectric in a coplanar test configuration, is measured. It is shown that, above a certain threshold current density, cracking of the dielectric is induced in the vicinity of the anode. Cracking of the dielectric leads to loss of mechanical constraint on the aluminum conductor which, in turn, leads to increases in electrical resistance with continued current flow. The electromigration-induced stresses are determined from the measured frequency shifts induced in a novel ruby strain sensor embedded immediately beneath the interconnect line on a sapphire substrate. The transparency of the sapphire substrate also facilitated the observation of a hitherto unreported form of dielectric cracking, namely cracking from the interconnect along internal interfaces. The observations of dielectric cracking are in agreement with a recent fracture mechanics model. Analysis of the stress data, together with the results of finite element calculations of the strain energy release rate for crack extension, gives a quantitative estimate of the effective valence Z*(=1.3±0.2) for aluminum. © 2000 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1289044

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6

Digitale Medien

Piezoelectric contributions to the electrical behavior of ZnO varistors (2000)

Verghese, P. M. ; Clarke, D. R.

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

Journal of Applied Physics 87 (2000), S. 4430-4438

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: Internal stresses exist in ZnO varistors as a result of both crystallographic anisotropy in thermal expansion of the constituents and thermal expansion mismatch between phases. Due to the piezoelectric nature of ZnO, these stresses induce a net electric dipole moment that modifies the grain boundary Schottky barriers and causes an alteration of the varistor current–voltage response in the nonlinear regime. We report Raman piezospectroscopic measurements of residual strains in polycrystalline ZnO and develop a stochastic model for the distribution of potential barrier heights based on the distribution of internal stresses. The model provides a physical basis for barrier height distributions used in electrical network simulations of varistor transport behavior. © 2000 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.373088

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7

Digitale Medien

Subnanosecond polarized microfluorimetry in the time domain: An instrument for studying receptor trafficking in live cells (1998)

Martin-Fernandez, M. L. ; Tobin, M. J. ; Clarke, D. T. ; [weitere]

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

Review of Scientific Instruments 69 (1998), S. 540-543

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ISSN: 1089-7623

Quelle: AIP Digital Archive

Thema: Physik , Elektrotechnik, Elektronik, Nachrichtentechnik

Notizen: We describe an instrument designed to monitor molecular motions in multiphasic, weakly fluorescent microscopic systems. It combines synchrotron radiation, a low irradiance polarized microfluorimeter, and an automated, multiframing, single-photon-counting data acquisition system, and is capable of continually accumulating subnanosecond resolved anisotropy decays with a real-time resolution of about 60 s. The instrument has initially been built to monitor ligand–receptor interactions in living cells, but can equally be applied to the continual measurement of any dynamic process involving fluorescent molecules, that occurs over a time scale from a few minutes to several hours. As a particularly demanding demonstration of its capabilities, we have used it to monitor the environmental constraints imposed on the peptide hormone epidermal growth factor during its endocytosis and recycling to the cell surface in live cells. © 1998 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1148691

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8

Digitale Medien

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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9

Digitale Medien

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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10

Digitale Medien

Moisture diffusion along the TiN/SiO2 interface and in plasma-enhanced chemical vapor deposited SiO2 (2000)

Xu, G. ; Clarke, D. R.

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

Journal of Applied Physics 88 (2000), S. 3695-3698

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ISSN: 1089-7550

Quelle: AIP Digital Archive

Thema: Physik

Notizen: The diffusivity of moisture along the TiN/SiO2 interface has been determined by imaging the inward diffusion of 18O and 2D from isotopically labeled water using a secondary ion mass spectroscopy (SIMS) technique. The diffusivity, at room temperature, of the 18O and 2D labeled species along the interface are indistinguishable and have a value of 6.0±2.0×10−13 cm2/s, four orders of magnitude faster than bulk diffusivity of the same species in the plasma-enhanced chemical vapor deposition silica, also determined by SIMS. From 8 to 90 °C, the activation energies for interface and bulk diffusivities of the 2D labeled species are found to be 0.21 and 0.74 eV, respectively. © 2000 American Institute of Physics.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1063/1.1289481

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