Effect of substrate polishing on the growth of graphene on 3C-SiC(111)/Si(111) by high temperature annealing.

We analyse the effects of substrate polishing and of the epilayer thickness on the quality of graphene layers grown by high temperature annealing on 3C-SiC(111)/Si(111) by scanning tunnelling microscopy, x-ray photoelectron spectroscopy, Raman spectroscopy, low energy electron diffraction and high resolution angle resolved photoemission spectroscopy. The results provide a comprehensive set of data confirming the superior quality of the graphene layers obtained on polished substrates, and the limitations of the growth obtained on unpolished surfaces.

Charge transfer between isomer domains on n+-doped Si(111)-2 × 1: energetic stabilization.

Domains of different surface reconstruction-negatively or positively buckled isomers-have been previously observed on highly n-doped Si(111)-2 × 1 surfaces by angle-resolved ultraviolet photoemission spectroscopy and scanning tunneling microscopy/spectroscopy. At low temperature, separate domains of the two isomer types are apparent in the data. It was argued in the previous work that the negative isomers have a lower energy of their empty surface states than the positive isomers, providing a driving force for the formation of the negative isomers. In this work we show that the relative abundance of these two isomers shows considerable variation from sample to sample, and it is argued that the size of the isomer domains is likely to be related to this variation. A model is introduced in which the electrostatic effect of charge transfer between the domains is computed, yielding total energy differences between the two types of isomer. It is found that the transfer of electrons from domains of positive isomers to negative ones leads to an energetic stabilization of the negative isomers. The model predicts a dependence of the isomer populations on doping that is in agreement with most experimental results. Furthermore, it accounts, at least qualitatively, for the marked lineshape variation from sample to sample observed in photoemission spectra.

Coexistence of negatively and positively buckled isomers on n+-doped Si(111) − 2 × 1.

A long-standing puzzle regarding the Si(111) − 2 × 1 surface has been solved. The surface energy gap previously determined by photoemission on heavily n-doped crystals was not compatible with a strongly bound exciton known from other considerations to exist. New low-temperature angle-resolved photoemission and scanning tunneling microscopy data, together with theory, unambiguously reveal that isomers with opposite bucklings and different energy gaps coexist on such surfaces. The subtle energetics between the isomers, dependent on doping, leads to a reconciliation of all previous results.

Electronic states of CuPc chains on the Au(110) surface.

The electronic properties of Cu-phthalocyanine (CuPc) molecules flat lying along the channels of the Au(110) reconstructed surface have been investigated by means of ultraviolet and x-ray photoelectron spectroscopy. The ordered chains give rise to a highly ordered single-layer structure with a (5x3) symmetry. Although from the core-level analysis not any significant charge transfer between the molecules and the underlying Au surface is observed, the valence band photoemission data bring to light CuPc-induced features localized at the interface. In particular, energy versus momentum dispersion of an interface state reveals a bandwidth of about 90 meV along the enlarged Au channels, where the CuPc chains are formed, with a defined fivefold symmetry well fitting the CuPc intermolecular distance.

[Dialysis and quality of life: identifying and managing critical aspects]. / Terapia dialitica e qualitá di vita: individuare le aree di criticitá per orientare alla metodica più idonea.

Living with a chronic disease is for the patient a ''disease experience'' that also affects the psychosocial sphere and has a negative impact on perceived quality of life. To estimate the effect of dialysis on the perceived quality of life and to identify by means of a specific questionnaire the aspects that are compromised most. From our results it emerged that the examined patients had a sufficiently good total perception of quality of life, even though about 30% of the patients reported critical aspects related to daily life and, in some age groups, also related to dialysis method. This study confirms the importance of developing educational and supportive predialysis programs in order to identify and reduce the critical aspects.

Barrier formation at organic interfaces in a Cu(100)-benzenethiolate-pentacene heterostructure.

The energy level alignment at the metal-organic and organic-organic interfaces of the Cu(100)/benzenethiolate/pentacene heterostructure is studied by photoemission spectroscopy and discussed theoretically using a model that includes, in a consistent way, charge transfer, Pauli repulsion, intrinsic molecular dipoles, and interface screening as a function of coverage. Despite the different nature of the two interfaces, our model provides a unified explanation for the work-function changes at both junctions and enables us to determine the benzenethiolate orientation as a function of coverage.