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We describe a solid-state Br atom source for surface etching, kinetics, and reaction dynamics studies. Pulsed laser irradiation of crystalline KBr, near the bulk absorption threshold at 6 eV, produces hyperthermal Br atoms in dense plumes. The Br atom density and velocities may be controlled by choice of laser pulse power and photon energy. Single and multiple pulse excitation of KBr produces Br and Br* in controllable quantities and velocities, thus providing an attractive ultrahigh vacuum compatible solid-state radical atom source. The solid-state atom source is in principle extendable to other halogens using other alkali halides and perhaps other materials.

The quantum efficiency (QE) of Cu is found to increase dramatically when coated by a CsI film and then irradiated by a UV laser. Over three orders of magnitude quantum efficiency enhancement at 266 nm is observed in CsI/Cu(100), indicating potential application in future photocathode devices. Upon laser irradiation, a large work function reduction to a value less than 2 eV is also observed, significantly greater than for similarly treated CsBr/Cu(100). The initial QE enhancement, prior to laser irradiation, is attributed to interface interaction and the intrinsic properties of the Cs halide film. Further QE enhancement following activation is attributed to formation of inter-band states and Cs metal accumulation at the interface induced by laser irradiation.

We explore the use of plasmonic Ag nanorod arrays featuring enhanced photoemission as high-brightness photocathode material. Silver nanorod arrays are synthesized by the direct current electrodeposition method and their dimensionality, uniformity, crystallinity, and oxide/impurity content are characterized. The yielded arrays exhibit greatly enhanced two-photon photoemission under 400 nm femtosecond pulsed laser excitation. Plasmonic field enhancement in the array produces photoemission hot spots that are mapped using photoemission electron microscopy. The relative photoemission enhancement of nanorod hot spots relative to that of a flat Ag thin film is found to range between 102 and 3 × 103.

Thin films of CsBr and KBr were deposited on Cu(100) to investigate photoemission properties of these potential photocathode materials. After prolonged laser ultraviolet irradiation photoemission, quantum efficiency increases by factors of 26 and 77 for KBr/Cu(100) and CsBr/Cu(100) photocathodes, respectively. Immediately following thin film deposition, a decrease in work function is observed, compared to bare Cu, in both cases. Quantum efficiency enhancements are attributed to the decrease in photocathode work function, and photo-induced processes that introduce defect states into the alkali halide bandgap. Our results suggest that KBr, a relatively stable alkali-halide, also has potential for photocathode applications.

Photoemission electron microscopy is used to study copper diffusion through a ruthenium thin film. The photoemission electron microscopy images display a large contrast between Cu and Ru due to the differences in work function, making photoemission electron microscopy an ideal methodology to study thin film diffusion in real time. Between 175 and 290°C, Cu mainly diffuses through defect sites in the thin Ru film. Uniform diffusion of Cu through the Ru film begins at approximately 300°C. The results are confirmed by x-ray photoemission spectroscopy depth profiling and scanning electron microscopy–energy dispersive x-ray spectroscopy analysis.

β-FeOOH nanorods of dimensions of 15nm diameter and 200nm length were prepared by aqueous synthesis. Charge carrier dynamics following femtosecond excitation display three time scales. The first is a subpicosecond decay of initially excited carriers to the band edge followed by trapping or nonradiative decay within 2ps. The trapped electrons and holes persist for significantly longer times (at least tens of picoseconds), similar to previous results from α-Fe2O3 materials. The short carrier lifetimes in these materials are attributed to fast trapping to Fe d-d and midgap states.

We report photoelectron emission microscope observations of the thermal martensitic transformation in a CuZnAl shape memory alloy. The phase transformation appears at 48°C during heating and at 42°C upon cooling. The transformation is marked by a sharp change in photoelectron intensity, as well as a significant displacement and reorientation of surface features. The difference in the photoelectron intensity before and after the transformation is attributed to a change in work function of about 0.2eV. Photoemission electron microscopy provides real-time information on microstructural changes and phase-dependent electronic properties.