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Ferroic domain walls could play an important role in microelectronics, given their nanometric size and often distinct functional properties. Until now, devices and device concepts were mostly based on mobile domain walls in ferromagnetic and ferroelectric materials. A less explored path is to make use of polar domain walls in nonpolar ferroelastic materials. Indeed, while the polar character of ferroelastic domain walls has been demonstrated, polarization control has been elusive. Here, we report evidence for the electrostatic signature of the domain-wall polarization in nonpolar calcium titanate (CaTiO3). Macroscopic mechanical resonances excited by an ac electric field are observed as a signature of a piezoelectric response caused by polar walls. On the microscopic scale, the polarization in domain walls modifies the local surface potential of the sample. Through imaging of surface potential variations, we show that the potential at the domain wall can be controlled by electron injection. This could enable devices based on nondestructive information readout of surface potential., Comment: 30 pages, 12 figures

The understanding of domain structures, specifically domain walls, currently attracts a significant attention in the field of (multi)-ferroic materials. In this article, we analyze contrast formation in full field electron microscopy applied to domains and domain walls in the uniaxial ferroelectric lithium niobate, which presents a large 3.8 eV band gap and for which conductive domain walls have been reported. We show that the transition from Mirror Electron Microscopy (MEM – electrons reflected) to Low Energy Electron Microscopy (LEEM – electrons backscattered) gives rise to a robust contrast between domains with upwards (Pup) and downwards (Pdown) polarization, and provides a measure of the difference in surface potential between the domains. We demonstrate that out-of-focus conditions of imaging produce contrast inversion, due to image distortion induced by charged surfaces, and also carry information on the polarization direction in the domains. Finally, we show that the intensity profile at domain walls provides experimental evidence for a local stray, lateral electric field.

The homoepitaxial growth of Cu on Cu(0 0 1) has been investigated with low-energy electron microscopy (LEEM). The temporal evolution of engineered pyramid-like structures has been monitored for a range of incident Cu fluxes and substrate temperatures. The step velocities have been analyzed in the framework of a novel growth model that contains as the only adjustable parameter the height of the Ehrlich–Schwoebel (ES) barrier. The simultaneous description of all step velocities observed within the flux and temperature range covered by our experiments determines the height of the ES barrier to about 125 meV in this system.

Synchrotron radiation tuned to the Fe 3p–3d transition (hv = 56eV) was used to study Fano type resonant photoemission spectra for a clean CdTe(110) surface sequentially covered in the monolayer (ML) range by Fe atoms and annealed. The results showed that, in the first stage of the deposition, the Fe atoms are mainly involved in the creation of a Cd1−xFexTe ternary crystal (0.2–0.6 ML). At higher coverages (1.2 ML), the contribution of Fe metallic islands becomes visible. CdTe dissociation in the surface region leads to the appearance of Cd Fe interaction at higher Fe deposition (3.6 ML). After deposition of 20 ML, sample annealing in the 300°C range leads to Fe diffusion into the crystal and the measured spectra correspond well to the Cd1−xFexTe calculated spectra.

Valence band of Cd 1-x Fe x Se/Fe in resonant photoemission spectra Resonant photoemission spectra of Fe atoms (3p-3d) were measured for freshly cleaved Cd 0-86 Fe 0.14 Se crystal (110) surface and for the same surface with sequentially deposited Fe atoms in the range 0.3-80 ML. The synchrotron radiation (LURE, Orsay, France) was used to measure valence band density of state distributions and Cd 4d core level for the radiation energy range 50-60 eV, which includes the Fe 3p-3d resonant energy equal to 56 eV. At the lowest stages of Fe atom deposition (up to about 3 ML), Fe atoms replace Cd atoms in the crystal, making a Cd 1-x Fe x Se alloy with a higher x and leaving extra Cd as small islands or clusters. For the next stages of Fe deposition (about 3-10 ML) the dissociated Cd atoms create a Cd-Fe alloy. At higher stages of Fe deposition (above about 10 ML) a Fe thin film is formed.

We review the progress towards developing epitaxial graphene as a material for carbon electronics. In particular, we discuss improvements in epitaxial graphene growth, interface control and the understanding of multilayer epitaxial graphene's (MEG's) electronic properties. Although graphene grown on both polar faces of SiC will be discussed, our discussions will focus on graphene grown on the C-face of SiC. The unique properties of C-face MEG have become apparent. These films behave electronically like a stack of nearly independent graphene sheets rather than a thin Bernal stacked graphite sample. The origins of multilayer graphene's electronic behaviour are its unique highly ordered stacking of non-Bernal rotated graphene planes. While these rotations do not significantly affect the inter-layer interactions, they do break the stacking symmetry of graphite. It is this broken symmetry that leads to each sheet behaving like isolated graphene planes.