We demonstrate the charge state of C 60 on a Cu(111) surface can be made optimal, i.e., forming C 60 3À as required for superconductivity in bulk alkali-doped C 60 , purely through interface reconstruction rather than with foreign dopants. We link the origin of the C 60 3À charge state to a reconstructed interface with ordered (4 Â 4) 7-atom vacancy holes in the surface. In contrast, C 60 adsorbed on unreconstructed Cu(111) receives a much smaller amount of electrons. Our results illustrate a definitive interface effect that affects the electronic properties of molecule-electrode contact. DOI: 10.1103/PhysRevLett.104.036103 PACS numbers: 68.43.Àh, 61.05.jh, 68.35.Ct, 73.20.Àr In bulk fulleride A n C 60 (A ¼ Na, K, etc.) [1], an ''optimal doping'' state favoring superconductivity is known to occur for n ¼ 3, with 3 electrons on each C 60 (C 60 3À ). Since C 60 films on metallic surfaces typically involve substrate-to-C 60 electron transfer that partially populates the C 60 lowest unoccupied molecular orbital (LUMO), it has been of great interest to pursue optimally doped C 60 films. Earlier studies show that the electron transfer amount does not simply depend on the substrate work function [2]. This raises the question of the role of the C 60 =metal interface structure. Although strong C 60 -metal interactions are not expected for, e.g., C 60 on noble metal surfaces, there is increasing evidence of C 60 -induced interface reconstruction for C 60 =Auð110Þ [3], C 60 =Ptð111Þ [4], C 60 =Alð111Þ [5], C 60 =Agð100Þ [6], and even for C 60 =Agð111Þ [7] and C 60 =Cuð111Þ [8], etc. The typical scenario is that C 60 tends to dig a ''vacancy'' in the surface. Calculations, including our own, show this geometry increases the adsorption strength that compensates the energy cost of vacancy creation. No studies, however, have discussed how the electronic structure and hence the charge state of a C 60 film are affected by its interface structure. Here, we discovered that a C 60 monolayer on Cu(111) is optimally electron doped purely by interface reconstruction and without intercalating alkali atoms. We convincingly establish the C 60 3À charge state and trace its origin to a reconstructed interface with ordered (4 Â 4) large 7-atom vacancy holes in the surface. The key link between molecular doping and a reconstructed interface indicates the practical needs of tackling the often neglected difficult interface structure problems which could prove essential in understanding the physics and chemistry of thin film materials.Many inconsistencies between experiment and theory in heteroepitaxial systems, such as the charge state of a C 60 film on a surface, are likely rooted in the application of an incorrect interface model. For C 60 =Cuð111Þ, it has been measured to range from 1-3 electrons per C 60 by photoemission spectroscopy (PES) [9]. Calculations predict a much smaller amount, <0:8e À , for an unreconstructed interface [10]. The electronic band structure measured by a recent PES study is also at odds with theoretical analysi...

International audienceIn this paper, we introduce a new spatial modulation (SM) technique using one or two active antennas and multiple signal constellations. The proposed technique, which we refer to as Enhanced SM or ESM, conveys information bits not only by the index(es) of the active antenna(s), but also by the constellations transmitted from each of them. The main feature of ESM is that it uses a primary signal constellation during the single active antenna periods and some other secondary constellations during the periods with two active transmit antennas. The secondary signal constellations are derived from the primary constellation by means of geometric interpolation in the signal space. We give design examples using two and four transmit antennas and QPSK, 16QAM, and 64QAM as primary modulations. The proposed technique is compared to conventional SM as well as to spatial multiplexing (SMX), and the results indicate that in most cases, ESM provides a substantial performance gain over conventional SM and SMX while reducing the maximum-likelihood (ML) decoder complexity

Biaxially stretchable silver nanowire transparent conductors are demonstrated. The silver nanowire film retains its electrical conductivity up to 10% applied strain. We examine the factors limiting stretchability and compare the mechanics of biaxially and uniaxially stretchable systems, which will be useful for exploring biaxially stretchable systems in future. V

Abstract-In this paper, we present three new signal designs for Enhanced Spatial Modulation (ESM), which was recently introduced by the present authors. The basic idea of ESM is to convey information bits not only by the index(es) of the active transmit antenna(s) as in conventional Spatial Modulation (SM), but also by the types of the signal constellations used. The original ESM schemes were designed with reference to single-stream SM and involved one or more secondary modulations in addition to the primary modulation. Compared to single-stream SM, they provided either higher throughput or improved signal-to-noise ratio (SNR). In the present paper, we focus on multi-stream SM (MSM) and present three new ESM designs leading to increasing SNR gains when they are operated at the same spectral efficiency. The secondary signal constellations used in the first two designs are based on a single geometric interpolation step in the signal constellation plane, while the third design also makes use of additional constellations derived through a second interpolation step. The new ESM signal designs are described for MIMO systems with four transmit antennas two of which are active, but we also briefly present extensions to higher numbers of antennas. Theoretical analysis and simulation results indicate that the proposed designs provide a significant SNR gain over MSM.