The use of gold cluster focused ion beams produced by a liquid metal ion gun in a TOF-SIMS mass spectrometer is shown to dramatically enhance secondary ion emission of phospholipids and peptides. The method has been successfully tested with cells grown onto plastic slips and with mouse brain slices, without any treatment of the samples. Very reliable time-of-flight mass spectra are acquired with a low primary ion dose of a few 10(7) ions, and high lateral resolution molecular ion images are obtained for heavy ions of great biological interest. This approach offers new opportunities in pharmacological and biological research fields by localizing compounds of interest such as drugs or metabolites in tissues.
Ar cluster sputtering of organic multilayers such as organic light-emitting diode model structures and Irganox delta layers is studied with time-of-flight secondary ion mass spectroscopy in the dual beam mode. Results for sputtering yield volumes and depth resolution are presented for Ar clusters with sizes from 500 to 5000 atoms in the energy range from 2.5 to 20 keV. The sputtering yield volume shows a linear dependence on the energy per atom for all materials in this study with a material-dependent threshold below 1 eV/atom. The sputtering yield volume at a given energy per atom increases with the cluster size. At constant beam energies, the sputtering yield volume decreases slightly with increasing cluster size. The depth resolution is investigated for the two model systems as a function of energy and cluster size, and it will be shown that the depth resolution depends mainly on the sample roughening. The depth resolution is approximately proportional to the depth of the impact crater at a given cluster size and energy. The optimum depth resolution achieved is in the range of 4-5 nm and is fairly constant with depth. At very low energies per atom close to the threshold energy, ripple formation is observed that leads to a fast degradation of the depth resolution with depth. This can be completely eliminated by fast sample rotation. Finally, the perspective of 3D analysis of organic devices with high depth resolution in the dual beam mode will be discussed. Figure 1. a) Sputtering yield volume of HTM-1 versus energy/atom for sputtering with Ar cluster sizes from 500 to 5000. b) Sputtering yield volume of HTM-1 for Ar cluster energies from 2.5 keV to 20 keV as a function of the cluster size.
SynopsisThe course of intermolecular reactions induced by peroxide decomposition in linear polyethylene has been determined and compared with similar reaction systems in which the substrate is a lowmolecular-weight alkane. Efficiency of intermolecular coupling is 40% for an alkane and 25-30% for the polymer system. Competing reactions, which reduce coupling efficiency, are mainly disproportionation of the initially formed radicals and to a minor extent further reactions involving the products from the peroxide decomposition. The low efficiencies found are similar to those well studied when initial radicals are produced by radiolysis in polymer and alkane systems.
We studied the structural and electrical properties of TiO 2 thin films grown by thermal oxidation of e-beam evaporated Ti layers on Si substrates. Time of flight secondary ion mass spectroscopy (TOF-SIMS) was used to analyse the interfacial and chemical composition of the TiO 2 thin films. Metal oxide semiconductor (MOS) capacitors with Pt or Al as the top electrode were fabricated to analyse electrical properties of the TiO 2 thin films. We show that the reactivity of the Al top contact affects electrical properties of the oxide layers. The current transport mechanism in the TiO 2 thin films is shown to be Poole-Frenkel (P-F) emission at room temperature. At 84 K, FowlerNordheim (F-N) tunnelling and trap-assisted tunnelling are observed. By comparing the electrical characteristics of thermally grown TiO 2 thin films with the properties of those grown by other techniques reported in the literature, we suggest that, irrespective of the deposition technique, annealing of as-deposited TiO 2 in O 2 is a similar process to thermal oxidation of Ti thin films.
Articles you may be interested inMatrix effects on secondary ion emission from a room-temperature ionic liquid, 1-ethyl-3-methylimidazolium bis[trifluoromethanesulfonyl]imide Ion and electron bombardment-related ion emission during the analysis of diamond using secondary ion mass spectrometryThe secondary ion emission behavior of 10 different thiols ͑8 alkanethiols, with nϭ4 -18 C atoms, TSA, and MCP͒ was investigated. In particular, we determined the generated negative secondary ion species X i Ϫ , their yields Y, the corresponding damage cross section (X i Ϫ ), and the activation energy for desorption E D (X i Ϫ ) ͑from the temperature behavior͒ of these secondary ions. The results supply important information on the analytical capabilities of secondary ion mass spectrometry ͑e.g., sensitivity and ultimate lateral resolution͒, as well as on the capabilities and limits of ion beam induced modification of these molecular overlayers. By comparing spectra and yields for different thiols bonded in the same way to the same substrate, these results give some additional insight into the ion formation process. A comparison of the activation energy for desorption E D (X i Ϫ ) with the corresponding damage cross section (X i Ϫ ) supplies insight into the energy distribution within the impact cascade.
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