Temperature dependence of surface roughening during homoepitaxial growth on Cu(001)

URL:http://link.aps.org/doi/10.1103/PhysRevB.64.125427 DOI:10.1103/PhysRevB.64.125427X-ray scattering has been used to study the roughening of the Cu(001) surface during homoepitaxial growth, as a function of temperature. Between 370 and 160 K, the mean-square roughness σ2, obtained from specular reflectivity data, was found to increase as a power law σ2=Θ2β for coverages Θ, ranging from 3 to 96 ML. The roughening exponent β was observed to depend on the temperature of the substrate: it monotonically increases with decreasing temperature from β≈1/3 at T=370K to β≈1/2, at T=200K. At 110 K a smoother growth re-enters in the presence of a large vacancy concentration in the deposited film.Support is acknowledged from the National Science Foundation under contracts ~P.W.S.! DMR-9202528 and~P.F.M. and C.E.B.! DMR-9623827 and the Midwest Superconductivity Consortium ~MISCON! under DOE Grant No. DH-FG02-90ER45427. The SUNY X3 beamline was supported by the DOE, under Contract No. DE-FG02-86ER45231, and the NSLS was supported by the DOE, Division of Material Sciences, and Division of Chemical Sciences. We thank Ian Robinson for the Cu crystal and for valuable discussions

Temperature-dependent vacancy formation during the growth of Cu on Cu(001)

URL:http://link.aps.org/doi/10.1103/PhysRevB.66.195413 DOI:10.1103/PhysRevB.66.195413X-ray diffraction measurements show that a large number of vacancies are incorporated in thin Cu films grown on Cu(001) at low temperatures. At any given deposition temperature between 110 and 160 K, the vacancy concentration cv, obtained from reflectivity data, does not change with the coverage Θ, for 2.5ML<~Θ<~20ML. However, cv is temperature dependent: for 15-ML-thick films, grown at different temperatures, it monotonically decreases with increasing T from cv≈2% at 110 K to zero at T=160K. A different “cv vs T” dependence is observed for films grown at 110 K and then annealed at progressively higher temperatures. Here cv≈2% persists over a broad temperature interval (between 110 and 200 K) and cv exhibits a slower decrease upon heating, reaching zero at 300 K.Support is acknowledged from the National Science Foundation under Contract Nos. ~P.W.S.! DMR-9202528 and ~P.F.M., C.E.B.! DMR-9623827 and the Midwest Superconductivity Consortium ~MISCON! under DOE Grant No. DEFG02-90ER45427. The SUNY X3 beamline is supported by the DOE, under Contract No. DE-FG02-86ER45231 and the NSLS is supported by the DOE, Division of Material Sciences and Division of Chemical Sciences

Vacancy formation in homoepitaxially grown Ag films and its effect on surface morphology

URL:http://link.aps.org/doi/10.1103/PhysRevB.66.075418 DOI:10.1103/PhysRevB.66.075418Synchrotron x-ray diffraction was used to investigate the low-temperature homoepitaxial growth on Ag(001) and Ag(111) surfaces. For both orientations, the Ag films deposited at T=100K were observed to exhibit a 1% surface-normal compressive strain, indicating that an appreciable vacancy concentration (∼2%) is incorporated in the growing film. Concomitantly with the incorporation of vacancies, the growth on Ag(111) leads to the formation of pyramidlike structures with a non-Gaussian distribution of heights, whereas a similar effect was not observed for Ag(001).Support is acknowledged from the National Science Foundation under Contract ~P.W.S.! No. DMR-9202528 and ~P.F.M., C.E.B., W.C.E.! No. DMR-9623827 and the Midwest Superconductivity Consortium ~MISCON! under DOE Grant No. DE-FG02-90ER45427. The SUNY X3 beam line is supported by the DOE, under Contract No. DE-FG02-86ER45231, and the NSLS is supported by the DOE, Division of Material Sciences and Division of Chemical Sciences

Thermal expansion of the Ag(111) surface measured by x-ray scattering

URL:http://link.aps.org/doi/10.1103/PhysRevB.63.113404 DOI:10.1103/PhysRevB.63.113404We have investigated the structure of the Ag(111) surface, for temperatures between 300 and 1100 K (90% of the bulk melting point), using synchrotron x-ray diffraction. Our data show no evidence of the anomalously large surface thermal expansion previously reported by medium-energy ion-scattering [Phys. Rev. Lett. 72, 3574 (1994)]. At all temperatures we find that the interlayer separations at the surface differ from their bulk counterparts by less than 1%, indicating that the surface expands similarly to the underlying bulk crystal. This behavior is in good agreement with results from molecular dynamics simulations.Support is acknowledged from the National Science Foundation under Contract Nos. ~PWS! DMR-9202528 and ~PFM, CEB, WCE! DMR-9623827 and the Midwest Superconductivity Consortium ~MISCON! under DOE Grant No. DE-FG02-90ER45427. The SUNY X3 beam line is supported by the DOE, under Contract No. DE-FG02-86ER45231, and the NSLS was supported by the DOE, Division of Material Sciences and Division of Chemical Sciences

Reconstruction of postexcisional defects for periocular giant carcinoma

Clinic of Plastic and Reconstructive Microsurgery, St. Spiridon Emergency Hospital, Iasi, Romania, Grigore T. Popa University of Medicine and Pharmacy, Iasi, RomaniaIntroduction. The giant basal cell carcinoma is a rare skin malignity, representing only 1% of the basal cell carcinomas. The giant type is defined as the lesion which exceeds 5 cm in diameter. The disease is reported generally in persons in their seventh decade of life, patients with various other pathologies. The excisions within oncological limit lead to large soft tissue defects which, if localized at the periocular region, become a real challenge for the surgeon that has to choose a surgical technique for the reconstruction. Aim of the study. To show some technical solutions to cover soft tissue defects from the periocular level left after excision for giant carcinomas and their results. Materials and methods. The study includes 9 patients, 8 male and one woman, age between 60 to 85 years, with a history of carcinomatous lesions in evolution from 7 to 12 years. All the lesions have dimensions between 5 and 7.5 cm, located in four cases in the external angle of the right eye,two at the upper eyelid and the external angle of the left eye, and, in one case, in theglabellar region with extension at both eyes. In all of the 8 cases the intervention consisted in complete excision (with oncological limit restriction) and covering with regional flaps (in 3 cases Mustarde flap, in 3 cases association of frontal flaps and in 3 cases genian advancement flap, from witch, one anchored in the zygomatic bone). All the reconstructive surgical interventions were performed in one operatory time, only in two cases it was necessary the reintervention after three months for the sectioning of the conjunctival flap (for the eyeprotection). In all 8 cases the nodular form of the basal cell carcinoma was observed. Results. The immediate postoperative evolution was good, without flap vascularisation problems. Long term evolution was good, with full reintegration of the flaps and a pleasant esthetic result. No recurrences were registered 18 months after the intervention. Conclusions. The giant basal cell carcinoma, a rare form of disease, is most often diagnosed at advanced ages. On the face, excision determines the presence of large soft tissue defect. Sometimes the reconstruction represented a real challenge for the surgeon

Vacancy trapping and annealing in noble-metal films grown at low temperature

doi:10.1063/1.1527988We have used synchrotron x-ray diffraction to study the homoepitaxial growth on Cu(001), Ag(001), and Ag(111), at temperatures between 300 and 65 K. The growth on all of these surfaces exhibits a consistent trend towards a large compressive strain that is attributed to the incorporation of vacancies into the growing film below 160 K. In each case, the vacancy concentration is ∼ 2% at 110 K and we have measured the temperature dependence for incorporation on the (001) surfaces as well as the annealing behavior for Cu(001). These results, which suggest new kinetic mechanisms, have important implications for understanding epitaxial crystal growth.Support is acknowledged from the NSF under Contract Nos. ~P.W.S! DMR-9202528 and ~P.F.M!, ~C.E.B! DMR-9623827, MISCON under DOE Grant No. DE-FG02-90ER45427, and the University of Missouri Research Board. The SUNY X3 beam line is supported by the DOE, under Contract No. DE-FG02-86ER45231 and the NSLS is supported by the DOE, Division of Material Sciences and Division of Chemical Sciences. The Advanced Photon Source is supported by DOE Contract No. W-31-109-Eng-38, and the mCAT beam line is supported through the Ames Laboratory Contract No. DOE W-7405-Eng-82