Search

New approaches to synthesize decorative black coatings on metallic surfaces are of significant research and commercial interest to manufacturing industries. In this work, decorative hard black coatings were deposited on a titanium surface by carbon ion implantation at ambient temperature. A 10 keV C+ beam was implanted on a Ti substrate to a fluence of 1–1.25 × 1018 C cm−2. Rutherford backscattering spectrometry and transmission electron microscopy results show that the implantation resulted in a bi-layered coating structure with a ~50 nm amorphous carbon layer at the surface followed by a ~50 nm amorphous titanium carbide intermixing layer deposited on top of a crystalline Ti surface. Raman spectroscopy confirms the formation of carbide intermixing layer and shows that the amorphous carbon layer has 15–20% sp3 content. Nanoindentation measurements show that the surface hardness of the implanted surface has increased by 72%, from 3.7 to 6.6 GPa, upon carbon implantation. Scratch tests further demonstrate a reduction in coefficient of friction in the implanted surface by 25%, signifying an improvement in wear-resistance of the coated materials. Colorimetry measurements reveal that carbon implantation reduces the luminosity of the Ti surface from 77 to 49 and chromaticity from 4.67 to 1.36, confirming incorporation of black color on Ti surface. The results demonstrate that C implantation onto a Ti surface at high fluence results in a black coating with high surface hardness and wear-resistance that can be employed in decorative surface applications for manufacturing industries.

The long term stability of the AlN/Si interface is of paramount importance for reliability and energy efficiency of a wide range of microwave frequency devices. The propagation loss of high power amplifiers, the bandwidth of 5G telecommunication devices, the quantum efficiency of light emitting diodes and conversion efficiency of energy harvesters depend on this interface. We demonstrate that tensile biaxial strain is directly associated with an increase in electromechanical performance by comparing the piezoelectric modulus of different AlN films grown on Si (1 1 1) by three different methods. Only one sample showed a uniquely high d33 of 8.3 pmV−1. However, the d33 degrades almost linearly with storage time to a value of only 4.7 pmV−1 two years after sample preparation, due to the degradation of the interface by pressure-induced phase transformation of the crystalline Si substrate to amorphous Si. Hence, the time-dependent electromechanical performance of AlN is characteristic for the stability of the AlN/Si interface. We show that variations of measured d33 values in literature can directly be attributed to strain variations at the interface. Our AlN/Si interface comparison highlights that device performance for high frequency applications represents a compromise between energy efficiency and reliability.

Epitaxial AlN thin films were implanted with He at 8 keV along the c-axis growth direction with fluences ranging from 1015 to 1017 atoms/cm2. We find that the He implantation generated uniaxial tensile strain along the c-axis for all fluences that increased with fluence. There was an additional (002) X-ray diffraction peak for the highest He fluences of 5 × 1016 atoms/cm2 and 1017 atoms/cm2 that we interpret in terms of He bubble formation. He implantation leads to significant nitrogen (N) site disorder as evidenced by rapid broadening of the E2 (high) Raman mode with increasing fluence due to a reduction of the phonon mean free path. The piezoelectric coefficient, d33, reduces with increasing fluence, and is ~27% of the unimplanted d33 for the highest fluence. This result can be interpreted as implantation-induced nitrogen site disorder that randomises and reduces the Al–N dipoles. Thus, we show that while He implantation induces uniaxial strain, it decreases d33 due to implantation-induced N site disorder.

Modern computing technology is based on silicon. To date, a cost-effective and easy to implement method to obtain isotopically pure silicon is highly desirable for attaining efficient heat dissipation in microelectronic devices and for hosting spin qubits in quantum computing. We propose that it is possible to use a 28Si+ ion beam to obtain an isotopically pure near-surface region in wafer silicon. However, this requires a highly stable, high current, and isotopically pure 28Si ion beam. This work presents and discusses the instrumentation details and experimental parameters involved in generating this required ion beam. Silane is used as the precursor gas and is decomposed in a Penning ion source to generate a 28Si+ ion beam. The influence of key ion source parameters such as the gas flow rate, magnetic field strength, and anode voltage is presented. An isotopically pure 28Si+ ion beam with 10 ± 0.5 μA current on the target is obtained at the GNS Science 40 kV ion implanter. The beam was observed to be stable for at least 8 h and contains less than 700 ppm of other Si isotopes. This high current and high purity provides opportunities to explore efficient modification of the isotopic distribution in a native Si substrate at ambient temperature. The results highlight opportunities offered by using Penning ion source based low energy ion implanters for the synthesis of isotopically modified Si surface regions-a technique also applicable to other materials such as diamonds and diamond-like carbon.

Display Omitted Growth and characterization of CNT based interconnects.Evaluation of the optimal BEOL-compatible metal-CNT interface.Nitrides provide a low contact resistance at the bottom metallization.A Ta-CNT interface has the lowest contact resistance for interconnect applications. Carbon nanotube (CNT) based interconnects with different metal-CNT contacts were prepared and characterized. All investigated contact materials are compatible with the back-end-of-line processing. For interconnect applications the length of the metal-CNT contact interface has to be extremely short, and has to have a low contact resistance. In order to provide a reliable interface between the metal and the CNTs the applied metal should form stable carbides. Indeed, Ta and Ti are beneficial in terms of contact resistance for the top metallization with Ta even outperforming Ti. However, those materials are non-noble metals and hence can oxidize. Besides the metals Ta and Ti, also their metal nitrides were investigated as bottom metallization. They outperform the pure metals since TaN and TiN are more resistant towards oxidation during subsequent processing steps. However, an extremely thin Ta layer also proves beneficial since in this case the formation of a conductive TaC during the CNT growth process is feasible. Unfortunately, insufficiently controlled oxidation processes occur which impairs the reproducibility and hence causes the average via to have a higher resistance.

The following is the accepted manuscript of the original article: Marcel Melzer, Thomas Waechtler, Steve Müller, Holger Fiedler, Sascha Hermann, Raul D. Rodriguez, Alexander Villabona, Andrea Sendzik, Robert Mothes, Stefan E. Schulz, Dietrich R.T. Zahn, Michael Hietschold, Heinrich Lang and Thomas Gessner “Copper oxide atomic layer deposition on thermally pretreated multi-walled carbon nanotubes for interconnect applications”, Microelectron. Eng. 107, 223-228 (2013). Digital Object Identifier: 10.1016/j.mee.2012.10.026 Available via http://www.sciencedirect.com or http://dx.doi.org/10.1016/j.mee.2012.10.026 © 2013 Elsevier B.V. Carbon nanotubes (CNTs) are a highly promising material for future interconnects. It is expected that a decoration of the CNTs with Cu particles or also the filling of the interspaces between the CNTs with Cu can enhance the performance of CNT-based interconnects. The current work is therefore considered with thermal atomic layer deposition (ALD) of CuxO from the liquid Cu(I) β-diketonate precursor [(nBu3P)2Cu(acac)] and wet oxygen at 135°C. This paper focuses on different thermal in-situ pre-treatments of the CNTs with O2, H2O and wet O2 at temperatures up to 300°C prior to the ALD process. Analyses by transmission electron microscopy show that in most cases the CuxO forms particles on the multi-walled CNTs (MWCNTs). This behavior can be explained by the low affinity of Cu to form carbides. Nevertheless, also the formation of areas with rather layer-like growth was observed in case of an oxidation with wet O2 at 300°C. This growth mode indicates the partial destruction of the MWCNT surface. However, the damages introduced into the MWCNTs during the pre treatment are too low to be detected by Raman spectroscopy.

For Cu/carbon nanotube(CNT) hybrid interconnect technology the growth of CNTs on a conductive substrate connected to Cu lines is required. CNTs were grown by catalytic chemical vapour deposition and the effect of a Cu layer beneath was investigated. By electron energy loss spectroscopy (EELS) we found the Cu to diffuse into the catalyst. This influences CNT growth. Therefore, incorporation of a sufficient diffusion barrier between the Cu layer and the substrate is required. As diffusion barriers we used Ta and TaN.

From our glass polishing process of precision optics we know that its physical-chemical nature frequently leads to a complex interaction of several parameters determining the process and the resulting quality. Surface analysis using SIMS and WDX prove that surface and sharp edge polishing of integrated optics chips has to be watched critically in order to obtain useful parts in a reproducible manner.