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We have measured the absolute doubly differential angular sputtering yield for 20 keV Kr+ impacting a polycrystalline Cu slab at an incidence angle of θi = 45° relative to the surface normal. Sputtered Cu atoms were captured using collectors mounted on a half dome above the sample, and the sputtering distribution was measured as a function of the sputtering polar, θs, and azimuthal, ϕs, angles. Absolute results of the sputtering yield were determined from the mass gain of each collector, the ion dose, and the solid angle subtended, after irradiation to a total fluence of ∼1 × 1018 ions/cm2. Our approach overcomes shortcomings of commonly used methods that only provide relative yields as a function of θs in the incidence plane (defined by the ion velocity and the surface normal). Our experimental results display an azimuthal variation that increases with increasing θs and is clearly discrepant with simulations using binary collision theory. We attribute the observed azimuthal anisotropy to ion-induced formation of micro- and nano-scale surface features that suppress the sputtering yield through shadowing and redeposition effects, neither of which are accounted for in the simulations. Our experimental results demonstrate the importance of doubly differential angular sputtering studies to probe ion sputtering processes at a fundamental level and to explore the effect of ion-beam-generated surface roughness. [ABSTRACT FROM AUTHOR]

We measured spectra of low energy electrons emitted in the interaction of singly charged Ne+ ions with the Mg surface at incident ion energies ranging from 50 eV to 4 keV. The study examines issues related to the excitation of both the surface and the bulk plasmons of the target. We will also focus on the dynamics of the production of the singlet Ne2p4(1D)3s2 and triplet Ne2p4(3P)3s2 autoionizing states of projectiles scattered in a vacuum. The threshold behavior of the autoionization lines show that double excitation occurs simultaneously in a single scattering. The predominant excitation of the triplet state indicates the importance of charge rearrangement and the electron correlation effects during the collisional excitation. [ABSTRACT FROM AUTHOR]

The unprecedented wide bandgap tunability (∼1 eV) of AlxIn1-xAsySb1-y lattice-matched to GaSb enables the fabrication of photodetectors over a wide range from near-infrared to mid-infrared. In this paper, the valence band-offsets in AlxIn1-xAsySb1-y with different Al compositions are analyzed by tight binding calculations and X-ray photoelectron spectroscopy measurements. The observed weak variation in valence band offsets is consistent with the lack of any minigaps in the valence band, compared to the conduction band. [ABSTRACT FROM AUTHOR]

Vapor-deposited, porous, amorphous, water-ice films, also called amorphous solid water (ASW), crack spontaneously during growth when the film thickness exceeds a critical value (Lc). We measured the Lc during growth of ASW films as a function of growth temperature (Tg=10 K, 30 K, and 50 K) and deposition angle (θ=0°, 45°, and 55°) using a quartz crystal microbalance, an optical interferometer, and an infrared spectrometer. The critical thickness, 1-5 lm under our experimental conditions, increases with Tg and h, an indication of film porosity. We suggest that ASW films undergo tensile stress due to the mismatch between substrate adhesion and contracting forces derived from the incompletely coordinated molecules on the surfaces of the pores. We provide a model to explain the observed dependences of Lc on the Tg and θ in the context of Griffith theory and estimate the tensile strength of low-temperature ASW to be ~25-40 MPa. Our model can be applied more generally to describe fracture of other solids with microporous structures, such as metallic or ceramic materials with voids. Published by AIP Publishing. [ABSTRACT FROM AUTHOR]