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We report the SIMS parameters required for the quantitative analysis of Si1-xGex across the range of 0≤x≤1 when using low energy O2+ primary ions at normal incidence. These include the silicon and germanium secondary ion yield [i.e., the measured ion signal (ions/s)] and erosion rate [i.e., the speed at which the material sputters (nm/min)] as a function of x. We show that the ratio Rx of erosion rates, Si1-xGex/Si, at a given x is almost independent of beam energy, implying that the properties of the altered layer are dominated by the interaction of oxygen with silicon. Rx shows an exponential dependence on x. Unsurprisingly, the silicon and germanium secondary ion yields are found to depart somewhat from proportionality to (1-x) and x, respectively, although an approximate linear relationship could be used for quantification across around 30% of the range of x (i.e., a reference material containing Ge fraction x would give reasonably accurate quantification across the range of ±0.15x). Direct comparison of the useful (ion) yields [i.e., the ratio of ion yield to the total number of atoms sputtered for a particular species (ions/atom)] and the sputter yields [i.e., the total number of atoms sputtered per incident primary ion (atoms/ions)] reveals a moderate matrix effect where the former decrease monotonically with increasing x except at the lowest beam energy investigated (250 eV). Here, the useful yield of Ge is found to be invariant with x. At 250 eV, the germanium ion and sputter yields are proportional to x for all x. [ABSTRACT FROM AUTHOR]

This document is an erratum for an article titled "Non-uniform Gd distribution and magnetization profiles within GdCoFe alloy thin films" published in Applied Physics Letters. The erratum corrects an error in the composition of one of the materials used in the original article. The correct composition is Co30Fe70, not Co70Fe30 as previously stated. The legends and caption for Figure 2 have been updated to reflect the correct composition. The erratum states that all other results, discussions, and conclusions in the original article remain the same. [Extracted from the article]

The N content of a series of GaNSb samples grown by molecular-beam epitaxy is investigated using high-resolution x-ray diffraction (HRXRD) and secondary-ion mass spectrometry. The N contents determined by the two methods agree well at lower N compositions (x < 0.01), and deviate significantly at larger N contents (x > 0.02). Analysis of the HRXRD-determined lattice constant using Vegard's law, underestimates the N content for high N compositions. The underestimation is found to be up to 24% for x = 0.03. The variation of the lattice parameter with N content is modelled by considering the influence of the density of the interstitial N-Sb complex rising with increasing N content. [ABSTRACT FROM AUTHOR]

The O2+ probe-sample conditions and subsequent data analysis required to obtain high depth resolution SIMS depth profiles from Si1− xGe x/Ge quantum well structures (0.6 ≤ x ≤ 1) are presented. For primary beam energies Ep >500 eV and x approaching 1, a significant decrease in the Ge+ ionisation probability resulted in unrepresentative and unquantifiable depth profiles. For Ep ≤ 500 eV, a monotonic increase in the Ge+ signal with x was observed resulting in profiles representative of the sample structure and enabling x to be found. A depth scale was also established using a point-by-point approach taking into account the local erosion rate, which is a function of x. Both the composition and the thickness of the Si1− xGe x and Ge layers were found to be in excellent agreement with those obtained using X-ray and transmission electron microscopy. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Using an O2+ beam at 90 eV, close to the sputtering threshold, we have obtained depth profiles from superficial monolayers on gold. The samples were polymeric copper phthalocyanine (poly(CuPc)) (C32H12N8Cu)n and Co(II)T(o-NH2)PP (5,10,15,20-tetrakis-(2-aminophenyl) porphyrin-cobalt(II)) (C44H28CoN4) monomolecular layers, deposited on gold films on silicon. The layer thicknesses, determined using atomic force microscopy, were ~4.5 nm for the poly(CuPc) and ~1.8 nm for the Co(II)T(o-NH2)PP. The ion signals monitored included: poly(CuPc) layer: 63Cu+, 65Cu+, 30ON+ and 12 C+; Co(II)T(o-NH2)PP layer: 59Co+, 30ON+ and 12 C+. Comparisons between 90 eV and 235 eV profiles from the layers and bare substrates showed that the monomolecular layers are resolvable at 90 eV and distinct from any surface contamination spike. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The use of Shubnikov-de Haas oscillations for determining effective mass is illustrated by a study of the magnetotransport properties of the two-dimensional hole gas in Si1-xGex (x = 0.13, 0.36, 0.95, 0.98) quantum wells. For some samples the data cannot be fitted to standard theoretical curves in which the scattering of charge carriers is described by the conventional Dingle factor. The reasons for the discrepancies between the experiment the theory are: (i) the effect of spin splitting on the amplitude of the peak in the SdH oscillations; (ii) extra broadening of the Landau levels attributable to an inhomogeneous distribution of the carrier concentration; (iii) the coexistence of short and long-range scattering potentials; and, (iv) population of the second energy level in the quantum well. Ways of calculating the effective hole masses m* for all these cases are presented and values of m* are found for the heterostructures studied here. [ABSTRACT FROM AUTHOR]

The thermal stability of thin (110 nm) compressively strained Ge surface channels, grown by reduced-pressure chemical vapor deposition on high quality relaxed Si0.2Ge0.8 reverse-graded buffers, has been investigated using in-situ hydrogen annealing at temperatures up to 650°C. Strain relaxation was observed and found to increase for thicker channels and higher anneal temperatures. For a Ge channel thickness ⩽45 nm, an increased surface roughening was found to dominate the strain relaxation process, which culminated in islanding. For the thicker (⩾45 nm) Ge channels misfit dislocation generation appeared to be the most dominant mechanism. Our results show that low thermal budgets (T < 550°C) should be employed for the fabrication of ~0.65% lattice mismatch strained Ge channels currently being developed for applications in CMOS-based devices and strained Ge-on-insulator platforms. [ABSTRACT FROM AUTHOR]

Secondary-ion-mass spectroscopy (SIMS) analysis of insulators using positive primary beams is routinely performed by compensating the induced charge with a coincident electron beam. In the case of SIMS depth profiling, the established method consists of focusing an electron beam into the SIMS crater with a current well in excess of that of the primary ion beam. In this article we used both caesium and oxygen beams to bombard float glass, and intrinsic and doped diamond samples while varying the electron beam current and the area bombarded by electrons. We have studied how the electron beam to primary ion current density ratio modifies the charging conditions. We demonstrate that, for certain insulating and highly resistive materials, defocusing of the electron beam so as to cover the whole of the sample surface and part of the sample holder is extremely effective. It is also observed that the defocused electron beam works efficiently for an electron to primary ion current density ratio less than 1. We attribute this to the enhancement of surface conductivity through the creation of carriers in the conduction band, and observe similar effects when irradiating the surface with a laser diode. The ability to use a defocused electron beam will significantly aid profiling of insulating and highly resistive materials where alignment of the coincident electron and ion beams is problematic. Defocusing of the electron beam also offers the possible advantage of reducing or eliminating localized electron beam damage of certain material surfaces prior to and during profiling. [ABSTRACT FROM AUTHOR]