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Abstract: The development of transistor manufacturing into the nanoscale regime is accompanied by a continuous awareness concern for contamination control. The ever-increasing demands for analysis sensitivity (in the sub-109 at/cm2 regime) combined with the introduction of new materials (i.e. non-silicon based) put severe challenges on the application of analytical techniques for atomic level contamination monitoring. Since many years, total reflection X-ray fluorescence spectrometry (TXRF) has developed as a preferred technique, ideally suitable due to the excellent reflectivity and flatness of the starting Si substrates. Driven by performance enhancement requirements, many new materials are being introduced at the substrate level (Ge, III/V compounds for higher mobility), gate stack (alternative dielectric materials and gate electrodes for capacitance scaling) and interconnect level (low-k and copper for faster switching). This paper reviews some recent developments in the state-of-the-art TXRF developments for semiconductor applications. Among the focus areas are the expansion of the elemental range (through multi-excitation line selection or multi-excitation source to excite low Z as well as high Z elements in one analysis sweep) and dynamic range (by pre-concentration techniques, synchrotron radiation analysis and detector developments). Further, emphasis is also focused towards quantification issues—whereby the three methodologies (micro-droplet, film and bulk type standards) are critically reviewed. Also, a recent development of sweeping TXRF, suitable for fast screening of large surface areas is being discussed. The applications of TXRF in a semiconductor environment are being reviewed. Finally, the performance of TXRF for the various semiconductor applications is assessed with respected to competitive techniques. [Copyright &y& Elsevier]

• Interface properties are crucial to form dense ODT-SAM on Cu for ASD purposes. • ODT-SAM's ALD inhibition is superior if coating oxidized surfaces. • Selective cupric oxide etching is observed as Cu is coated with ODT-derived SAM. • SAM formation kinetic is hindered if Cu is treated with organic acids. Atomic layer deposition (ALD) combined with self-assembled monolayer (SAM) passivation allows selective deposition on patterned substrates at the nanoscale, enabling bottom-up material fabrication for various applications. Selective chemisorption of 1-octadecanethiol (ODT) on Cu over SiO 2 is exploited to achieve area selective deposition (ASD). Although the essential role played by SAM in preserving a confined material growth at higher ALD cycles is largely accepted, studies elucidating the influence of substrate properties on SAM's ALD inhibition are lacking. In this work, Cu is treated either with acids or oxidizing agents to produce a multiplicity of surfaces, which differ in terms of composition and morphology. Using water contact angle, atomic force microscopy, x-ray photoelectron spectroscopy and cyclic voltammetry measurements, Cu substrates are characterized before and upon ODT deposition. The ODT layers formed on Cu are tested as a passivation means towards Hf 3 N 4 ALD. The results stress the essential contribution of interface properties in forming dense thiol-SAM on metals, which is fundamental to a successful ASD process. It is here demonstrated that ODT on clean Cu cannot block Hf 3 N 4 ALD at 150 °C, whereas on oxidized Cu the same organic layer prevents up to 19 nm Hf 3 N 4 film growth before the Cu passivation is affected. [ABSTRACT FROM AUTHOR]

Ultralow energy (ULE) ion implantation is being increasingly applied to the modification of 2D materials, in particular, for substitutional doping and intercalation of graphene. Implantation-induced defects, whether desired or not, have a strong impact on the properties of graphene. Significant research has been devoted to vacancy-related defects however, disorder induced by ion irradiation in the ULE limit, that is, for energies below the vacancy-formation threshold, remains poorly understood. Here, we focus on that regime and report the formation of defects resulting from the breaking of C–C s p 2 bonds and formation of C-substrate bonds. As a model system we used epitaxial graphene grown on Cu(111) and on Pt(111), subsequently implanted with He, Ne and Ar at energies between 15 eV and 40 eV. The bond defect density is found to increase with increasing energy and atomic number of the implanted element. These findings significantly advance our understanding of disorder induced in graphene by ULE ion implantation, while simultaneously revealing the potential for exploiting such bond defects for physical or chemical functionalization. In particular, these bond defects can be generated with a high degree of selectivity since they occur in the low-energy limit (at least down to 15 eV), significantly below the energies required to form stable vacancies. [Display omitted] • Graphene was implanted at ultralow energies (15–40 eV) with He, Ne and Ar. • C–C bonds in graphene break at energies below the vacancy-formation threshold. • Bond defect density increases with energy and atomic number of implanted elements. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we have studied the effect of boric acid (H3BO3) on the nucleation of nickel (Ni) nanoparticles on titanium nitride (TiN). We linked the potential transients during galvanostatic deposition to the different regimes of Ni deposition. The two most important regimes, i.e. nucleation and growth regime, were found to depend on the H3BO3 concentration. Indeed, by lowering the amount of H3BO3 the particle density increased (nucleation), while it also resulted in an earlier growth termination. Based on these findings, we propose a growth-inhibited nucleation model to explain the impact of H3BO3 on the formation of Ni nanoparticles. During Ni nucleation the surface pH increases due to local H+ reduction, leading to the formation and adsorption of Ni(OH)2 on the Ni particles. As a result, the growth of the particles is inhibited and new nucleation is promoted. The formation of this inhibiting hydroxide is counteracted by the presence of H3BO3 as it buffers the surface pH. Therefore, a higher particle density is obtained at low H3BO3 concentrations. However, when the concentration of H3BO3 is too low, Ni(OH)2 is already formed in the diffusion layer during the nucleation regime as the onset of H2O reduction occurs sooner. This results in the termination of Ni deposition before the nucleation of Ni is complete yielding almost no deposited Ni at the surface at low H3BO3 concentrations. Therefore, an optimum H3BO3 concentration is needed where the degree of growth-inhibition is high while Ni is still deposited for a sufficient amount of time. [Copyright &y& Elsevier]

Protein phosphatase-1 (PP1) is a major protein Ser/Thr phosphatase in eukaryotic cells. Its activity depends on two metal ions in the catalytic site, which were identified as manganese in the bacterially expressed phosphatase. However, the identity of the metal ions in native PP1 is unknown. In this study, total reflection X-ray fluorescence (TXRF) was used to detect iron and zinc in PP1 that was purified from rabbit skeletal muscle. Metal exchange experiments confirmed that the distinct substrate specificity of recombinant and native PP1 is determined by the nature of their associated metals. We also found that the iron level associated with native PP1 is decreased by incubation with inhibitor-2, consistent with a function of inhibitor-2 as a PP1 chaperone. [ABSTRACT FROM AUTHOR]

Abstract: We propose an empirical law correlating the average number of walls and the average diameter in a population of multi-wall carbon nanotubes grown by catalytic chemical vapor deposition. The relationship and its dispersion are derived from the statistical analysis of a database of TEM images of nanotubes collected from more than 60 publications in literature and from our group in the last years. Considering the nanotubes were grown from independent sources in a variety of conditions and tools, it has general validity. The relationship may find applicability in a wide range of fields as it provides a simple model to quickly estimate the number of walls most likely present in a population of nanotubes from only the measure of their average diameter. [Copyright &y& Elsevier]

Abstract: We propose to use carbon nanotube (CNT)–CNT contacts instead of CNT–metal contacts as a route towards low resistance CNT horizontal interconnects. We characterize by electrical transport measurements and Kelvin probe force microscopy the contacts present in CNT horizontal interconnects grown by chemical vapor deposition between titanium nitride electrodes. When two CNTs with diameter around 30nm grow from opposing electrodes and touch each other with their outermost shells, typical contact resistances around 16kΩ are obtained. The corresponding contact resistivity of about 14Ωμm2 is one order of magnitude smaller than the contact resistivity of a CNT touching the TiN surface with its outermost shell. On the other hand, the contact resistance of a CNT grown from a nickel catalyst particle deposited on a TiN electrode is negligibly small when compared to the above mentioned contact resistances. Our results demonstrate that we are able to grow from opposing electrodes CNTs that touch each other with a corresponding high density (up to 1011 cm−2) of CNT–CNT contacts. This may offer an effective solution towards the growth of low resistance CNT horizontal interconnects. [Copyright &y& Elsevier]