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We introduce a novel time-resolved photoemission-based near-field illumination method, referred to as femtosecond normal-incidence photoemission microscopy (NI-PEEM). The change from the commonly used grazing-incidence to normal-incidence illumination geometry has a major impact on the achievable contrast and, hence, on the imaging potential of transient local near fields. By imaging surface plasmon polaritons in normal light incidence geometry, the observed fringe spacing directly resembles the wavelength of the plasmon wave. Our novel approach provides a direct descriptive visualization of SPP wave packets propagating across a metal surface. [ABSTRACT FROM AUTHOR]

In spite of its large lattice mismatch, Bi grows epitaxially in (111) orientation and almost free of defects on Si substrates. On Si(111), the Bi film is under compressive strain of less than 2% and shows a 6-7 registry to the Si(111)-(7 × 7) substrate. On Si(001), the compressive lattice strain of 2.3% results in the formation of an array of misfit dislocations with a periodicity of 20 nm. We studied the cooling process of ultrathin bismuth films deposited on Si(111) and Si(001) substrates upon excitation with short laser pulses. With ultrafast electron diffraction, we determined the thermal boundary conductance σK from the exponential decay of the transient film temperature. Within the error bars of 7%, the experimentally determined thermal boundary conductances are the same for both substrates and thus independent of the presence of a periodic array of misfit dislocations and the different substrate orientation. [ABSTRACT FROM AUTHOR]