The low limit of the deposition temperature for atomic layer deposition (ALD) of noble metals has been studied. Two approaches were taken; using pure oxygen instead of air and using a noble metal starting surface instead of Al2O3. Platinum thin films were obtained by ALD from MeCpPtMe3 and pure oxygen at deposition temperature as low as 200 °C, which is significantly lower than the low-temperature limit of300 °C previously reported for the platinum ALD process in which air was used as the oxygen source. The platinum films grown in this study had smooth surfaces, adhered well to the substrate, and had low impurity contents. ALD of ruthenium, on the other hand, took place at lower deposition temperatures on an iridium seed layer than on an Al2O3 layer. On iridium surface, ruthenium films were obtained from RuCp2 and oxygen at 225 °C and from Ru(thd)3 and oxygen at 250 °C, whereas no films were obtained on Al2O3 at temperatures lower than 275 and 325 °C, respectively. The crystal orientation of the ruthenium films was found to depend on the precursor. ALD of palladium from a palladium β-ketoiminate precursor and oxygen at 250 and 275 °C was also studied. However, the film-growth rate did not saturate to a constant level when the precursor pulse times were increased.

Ruthenium thin films were grown by atomic layer deposition (ALD) from tris(2,2,6,6-tetramethyl-3,5-heptanedionato)-ruthenium [Ru(thd) 3 ] and oxygen, at temperatures between 325 C and 450 C. All the films were polycrystalline metallic ruthenium as analyzed by X-ray diffraction (XRD). Impurity contents of the films (< 2.9 at.-% H, < 1.9 at.-% C, and < 5.5 at.-% O) were nearly independent of the Ru(thd) 3 pulse time as analyzed by time of flight elastic recoil detection analysis (TOF-ERDA). The films had resistivities below 20 lX cm and they adhered well to a thin Al 2 O 3 film on glass. Growth rates of 0.36 per cycle were obtained at a deposition temperature of 350 C. The gaseous reaction by-products were analyzed in situ by quadrupole mass spectrometry (QMS).

Magnesium fluoride is an ultraviolet (UV) transparent material which is widely used in optical applications over a wide wavelength range. We have developed a novel atomic layer deposition (ALD) process for depositing magnesium fluoride thin films for the first time. MgF2 films were grown at 250-400 degrees C using Mg( thd)(2) and TiF4 as precursors. The crystallinity, morphology, composition, thicknesses and refractive indices of the films were analyzed by X-ray diffraction/ reflection ( XRD/XRR), transmission electron microscopy ( TEM), atomic force microscopy ( AFM), field emission scanning electron microscopy ( FESEM), time-of-flight elastic recoil detection analysis ( TOF-ERDA), and UV-vis spectrophotometry. Electrical properties were also measured. The growth rate was temperature dependent decreasing from 1.6 A cycle 21 at 250 degrees C to 0.7 angstrom cycle(-1) at 400 degrees C. The films were polycrystalline at 250 - 400 degrees C. The refractive indices were between 1.34 - 1.42 and the permittivity 4.9. The impurity levels were below 0.6 at.% in the films deposited at 350 - 400 degrees C

Time-of-flight elastic recoil detection (ToF-ERD) analysis software has been developed. The software combines a Python-language graphical front-end with a C code computing back-end in a user-friendly way. The software uses a list of coincident time-offlight-energy (ToF-E) events as an input. The ToF calibration can be determined with a simple graphical procedure. The graphical interface allows the user to select different elements and isotopes from a ToF-E histogram and to convert the selections to individual elemental energy and depth profiles. The resulting sample composition can be presented as relative or absolute concentrations by integrating the depth profiles over user-defined ranges. Beam induced composition changes can be studied by displaying the eventbased data in fractions relative to the substrate reference data. Optional angular input data allows for kinematic correction of the depth profiles. This open source software is distributed under the GPL license for Linux, Mac, and Windows environments.

Metal fluorides, like CaF 2 , are interesting dielectric materials which are optically transparent over a wide wavelength range down to the vacuum ultraviolet regime. In addition, CaF 2 has a low refractive index and is therefore an attractive material for optical filters. In this study thin films of calcium fluoride were deposited by atomic layer deposition (ALD) at a temperature range of 300-450 °C using TiF 4 as a new convenient fluoride precursor. Ca(thd) 2 was used as a calcium precursor. Films were analyzed by X-ray diffraction/reflection (XRD/XRR), field emission scanning electron microscopy (FESEM), timeof-flight elastic recoil detection analysis (TOF-ERDA), and UV-vis spectrophotometer. The growth rate of the film was 1.6 Å/cycle, which is 4 times higher than that published before for CaF 2 ALD. All films were polycrystalline and the impurity levels were low. The refractive index was 1.43 and the permittivity 6.6. This novel ALD process using the new fluoride precursor TiF 4 is likely more general and applicable also to other metal fluorides.

Carbon nanotubes (CNT) are known to be materials with potential for manufacturing sub-20 nm high aspect ratio vertical interconnects in future microchips. In order to be successful with respect to contending against established tungsten or copper based interconnects, though, CNT must fulfil their promise of also providing low electrical resistance in integrated structures using scalable integration processes fully compatible with silicon technology. Hence, carefully engineered growth and integration solutions are required before we can fully exploit their potentialities. This work tackles the problem of optimizing a CNT integration process from the electrical perspective. The technique of measuring the CNT resistance as a function of the CNT length is here extended to CNT integrated in vertical contacts. This allows extracting the linear resistivity and the contact resistance of the CNT, two parameters to our knowledge never reported separately for vertical CNT contacts and which are of utmost importance, as they respectively measure the quality of the CNT and that of their metal contacts. The technique proposed allows electrically distinguishing the impact of each processing step individually on the CNT resistivity and the CNT contact resistance. Hence it constitutes a powerful technique for optimizing the process and developing CNT contacts of superior quality. This can be of relevant technological importance not only for interconnects but also for all those applications that rely on the electrical properties of CNT grown with a catalytic chemical vapor deposition method at low temperature.

No abstract

Nanopore technology has been extensively investigated for analysis of biomolecules, and a success story in this field concerns DNA sequencing using a nanopore chip featuring an array of hundreds of biological nanopores (BioNs). Solid-state nanopores (SSNs) have been explored to attain longer lifetime and higher integration density than what BioNs can offer, but SSNs are generally considered to generate higher noise whose origin remains to be confirmed. Here, we systematically study low-frequency (including thermal and flicker) noise characteristics of SSNs measuring 7 to 200 nm in diameter drilled through a 20-nm-thick SiN x membrane by focused ion milling. Both bulk and surface ionic currents in the nanopore are found to contribute to the flicker noise, with their respective contributions determined by salt concentration and pH in electrolytes as well as bias conditions. Increasing salt concentration at constant pH and voltage bias leads to increase in the bulk ionic current and noise therefrom. Changing pH at constant salt concentration and current bias results in variation of surface charge density, and hence alteration of surface ionic current and noise. In addition, the noise from Ag/AgCl electrodes can become predominant when the pore size is large and/or the salt concentration is high. Analysis of our comprehensive experimental results leads to the establishment of a generalized nanopore noise model. The model not only gives an excellent account of the experimental observations, but can also be used for evaluation of various noise components in much smaller nanopores currently not experimentally available.