The electrical characteristics of high quality single crystal boron-doped diamond are studied. Samples are synthesized in a high power-density microwave plasma-assisted chemical vapor deposition (CVD) reactor at a pressure of 160 Torr. The boron-doped diamond films are grown using diborane in the feedgas at concentrations of 0-0.25 ppm, and are compared to those grown previously with 1-10 ppm. The boron acceptor concentration is investigated using infrared absorption, and compared to the boron concentration obtained by SIMS. A four point probe is used to study the conductivity. The temperature dependent conductivity is analyzed to determine the boron dopant activation energy.

Current experimental configurations for MW PECVD diamond growth do not allow simple up-scaling towards large areas, which is essential for microelectronic industries and other applications. Another important issue is the reduction of the substrate temperature during diamond growth to enhance the compatibility with wafer processing technologies. Such advantages are provided by MW-linear antenna (LA) plasma applicators, allowing a scalable concept for diamond growing plasmas. In the present work we introduce a novel construction of LA MW applicators designed for nanodiamond growth by using plasmas ranging from continuous wave (CW) to high repetition rates pulsed modes (up to 20 kHz) which advantages are discussed in detail.

Low temperature deposited Interdigitated All Back Contact a-Si:H/c-Si Heterojunction (IBC-SHJ) devices are a promising approach for high efficiency, low cost solar cells on thin wafers. Thin intrinsic a-Si:H films (i-a-Si:H) deposited below 300°C provide excellent surface passivation and high Voc. However, the optical properties of a-Si:H layers and electronic band alignment at the heterointerface are critical to reduce optical losses and transport barriers in IBC-SHJ solar cells. At the front illumination surface, a wide band gap (Eg) i-a-Si:H layer with good passivation is desirable for high Voc and Jsc while at the rear surface a narrower Eg i-a-Si:H layer with good passivation is required for higher FF and Voc as seen in 2D numerical simulation. Various substrate temperature, H2/SiH4 dilution ratio and plasma power conditions were explored to obtain i-a-Si:H with good passivation and desired Eg. All the deposited films are characterized by Variable Angle Spectroscopic Ellipsometry (VASE) to determine Eg and thickness and by Fourier Transform Infrared spectroscopy (FTIR) to estimate hydrogen content and microstructure factor. Passivation qualities are examined by quasi-steady state photoconductance (QSS-PC) measurement. The i-layer Eg, was varied in the range from ~1.65eV to 1.91eV with lifetime >1 ms. Lowest Eg is obtained just prior to the structure transition from amorphous to epitaxial-like growth. The FF of IBC-SHJ devices improved from 20% to 70% as Eg of the a-Si:H rear passivation layer decreased from 1.78 to 1.65 eV.

In this study an electroforming free device structure based on 25nm thin TiO2 thin films is presented. The TiO2 films are deposited on CMOS compatible W plugs. The use of 5nm thick interlayers of Ti and W between the TiO2 and the Pt electrode turn out to be the key step to achieve the forming free performance. In these Pt/Ti/TiO2/W or Pt/W/TiO2/W samples the switching polarity can be repeatedly changed from “eightwise” to “counter-eightwise” in one device by a proper adjustment of the I-V measurement conditions. The most simple explanation for this observation is that the switching interface can be flipped back and forth from the bottom to the top electrode.

The reactivity of silicon nanocrystals (Si-NCs) in near-UV photochemical hydrosilylation was evaluated as a function of size. Results show that Si-NCs with photoluminescence (PL) in the visible spectral region react faster than Si-NCs with near-IR PL. Fourier-transform infrared (FTIR) spectroscopy suggests this difference in reactivity is due to quantum size effects in the exciton-mediated mechanism proposed for this reaction. We have carried out a detailed comparison of Si-NC reactivity in photochemical and thermal hydrosilylation and determined the conditions under which Si-NCs may be size-selected based on their reactivity.

In future technology nodes, 22nm and below, carbon nanotubes (CNTs) may provide a viable alternative to Cu as an interconnect material. CNTs exhibit a current carrying capacity (up to 109 A/cm2), whilst also providing a significantly higher thermal conductivity (SWCNT ~ 5000 WmK) over Copper (106 A/cm2 and ~400WmK). However, exploiting such properties of CNTs in small vias is a challenging endeavor. In reality, to outperform Cu in terms of a reduction in via resistance alone, densities in the order of 1013 CNTs/cm2 are required. At present, conventional thermal CVD of carbon nanotubes is carried out at temperatures far in excess of CMOS temperature limits (400C). Furthermore, high density CNT bundles are most commonly grown on insulating supports such as Al2O3 and SiO2 as they can effectively stabilize metallic nanoparticles at elevated temperatures but this limits their application in electronic devices. To circumvent these obstacles we employ a remote microwave plasma to grow high density CNTs at a temperature of 400C on conductive underlayers such as TiN. We identify some critical factors important for high-quality CNTs at low temperatures such as control over the catalyst to underlayer interaction and plasma growth environment while presenting a fully CMOS compatible carbon nanotube synthesis approach

A novel setup for Raman measurements under small angles of incidence during the parallel plate plasma enhanced chemical vapor deposition of μc-Si:H films is described. The possible influence of disturbances introduced by the setup on growing films is studied. The substrate heating by the probe beam is investigated and reduced as far as possible. It is shown that with optimized experimental parameters the influence of the in-situ measurements on a growing film can be neglected. With optimized settings, in-situ Raman measurements on the intrinsic layer of a microcrystalline silicon solar cell are carried out with a time resolution of about 40 s corresponding to 20 nm of deposited material during each measurement.

The kinetics of slow aggregation of monodisperse TiO2 nanocrystals in the acidic hydrosols at room temperature was studied for months by turbidimetry. The dependence of the initial rate of aggregation on the pH was calculated. The comparison of results obtained by turbidimetry and small angle X-ray scattering permits to suppose that very loose aggregates form at the low pH in HCl solution. The dependencies obtained in this work for room temperature can be taken into consideration at the tuning of TiO2 nanoparticles morphology through thermal treatment of hydrosols.

Bone fractures are one of the most common bone complications. In more severe cases, bone fixation is accomplished using titanium (Ti) implant materials. Unfortunately, the need for revision surgery often arises due to implant loosening and/or deterioration of the implant/bone interface. Rosette nanotubes (RNTs) are a class of self-assembled organic materials obtained through the self-assembly of a guanine-cytosine hybrid base (G∧C motif). These organic materials have been found to increase osteoblast (bone forming cells) adhesion and hydroxyapatite deposition (bone regeneration) on titanium implants as well as on engineered hydrogels. In order to increase the bioactivity of RNTs to enhance bone cell function on Ti implants, two RNT motifs functionalized with different bioactive deca-peptides (A, B) chosen from the knuckle region of bone morphogenic proteins-7 (BMP-7) were synthesized. Their self-assembly process was investigated in water using UV-Vis and SEM techniques.

This study reports on the structural and magnetic characterizations of free-standing bismuth ferrite, BiFeO3, nanoparticles synthesized in polyol medium. Fine tuning of the ferrite magnetic properties was achieved by adding an excess bismuth species or doping with cobalt ions, coupled with thermal annealing. Crystalline Bi1-yCoyFeO3 powders (where ‘y’ ranges from 0.00 to 0.10) were produced after annealing the precursors for one hour at 700οC. The average crystallite size was calculated to be approximately 22 nm. We found that the synthesis under stoichiometric excess of Bi species (up to 10 at.%) promoted a more complete crystallization of the material, i.e., no precursor phases remained. Furthermore, both the saturation magnetization and the coercivity of the synthesized powders were strongly influenced by the concentration of Co. They increased from 0.13 emu/g and 19 Oe to 3.5 emu/g and 1183 Oe for pure BiFeO3 and 10 at.% Co-doped BiFeO3, respectively.

We have studied the effect that applying self-interaction correction (SIC) to oxygen p orbitals has on the magnetic moment formation of three polar ZnO surfaces; all of them being oxygen terminated. For these investigations we have used a multi-code approach. This has allowed us, on the one hand, to relax the surface structure using the pseudopotential code SIESTA. On the other hand, by using the obtained relaxed structures for calculations within the KKR Green’s function formalism, we have been able to apply SIC and use the magnetic force theorem for calculating Heisenberg exchange parameters. The latter contain information about both the strength of the interaction and the interaction mechanism.

Our calculations show that all three surfaces are magnetic. In addition, we find that applying SIC is necessary to correctly describe the top oxygen atom of the (0001)-t and (0001)-h surfaces.

Thin Me-DLC films with different metal contents have been deposited by ECR-CVD (Electron Cyclotron Resonance Chemical Vapour Deposition). Before the growth process, metal nanoparticles were scattered over the substrate surface by dipping it into a dispersion previously sonicated. The concentration of the dispersion (150, 300, 500 and 5000 ppm) controls the metal content into the carbon coating. The morphology of the deposited samples was analysed by SEM (Scanning Electron Microscopy). The metal content in the carbon films has been evaluated by SIMS (Secondary Ion Mass Spectroscopy). The incorporation of low amounts of metal nanoparticles into the hard carbon coating produces an outstanding improvement in the durability of the layer, as detected by pin-on-disc tests. For an optimum chromium content of 300 ppm of nanoparticles in the dispersion, the grown layer exhibits a noteworthy higher wear resistance respect to that of the DLC reference film. More precisely, in this case, the Cr-DLC coating undergoes ten times longer wear process than the reference DLC coating. However, it is important to indicate that in samples grown using more concentrated dispersions (> 300 ppm), a rapid deterioration of the coating is produced and short lifetimes have been detected, attributed to the large contribution of metal to the transfer layer.

In the present study, the strengthening effect of nano-scale twins in body-centered cubic (bcc) crystal was evaluated using micro-sized cantilever type specimen which contained the nanotwinned region (midrib) in ferrous lenticular martensite. The SEM observations of the micro-sized specimen after bending deformation indicated that midrib can act as barriers against dislocations, resulting in slip localization and non-localization across midrib. The load-displacement curve obtained by bending test showed that twin boundaries significantly enhance the critical resolved shear stress of bcc.

Mineral samples of varying petrology, exposed to ion irradiation and subsequently immersed in water or exposed to a humid environment, show up to 60% depletion of specific surface atoms (Mg, Ca, K, and Na) — a depletion that is enhanced 26,000x compared to unirradiated surfaces. Surface depletions of irradiated minerals exposed to water were measured using X-ray photoelectron spectroscopy. Irradiations were performed with 4 keV Ar+ ions at fluences from 1014 – 1019 ion cm-2; samples were subsequently exposed to liquid water or humid air (35º C and 70% RH). Analyses were done before irradiation, after irradiation, and after exposure to water, allowing identification of changes in composition due solely to ion irradiation or combined with water exposure. Before water exposure, we observe no significant change in stoichiometry of the minerals for ion fluences <1018 ions cm-2. We find incongruent depletion of 60% Mg for forsterite after exposure to humidity or three minutes (or more) water immersion. Augite undergoes reduction in the surface concentration of approximately 30% Mg, 40% Ca, and 55% Na after 1.9 x 1017 Ar cm-2 and immersion in HPLC water (pH: 6.8) for three minutes. Depth profiles of the irradiated, water exposed, minerals show that the depth of the depleted region is on the order of the ion range, ~15nm. In addition, preliminary results for albite, anorthoclase, and microcline in water show significant depletions of Na, Na and K, and K, respectively, from the mineral surface.

Ambipolar top-gated field effect transistors (FETs) based on large area Cu catalyzed CVD-grown monolayer graphene interfaced to advanced dielectrics have been constructed and examined both for their material and electrical qualities. Interfacing of the graphene with novel insulators/substrates could be tailored for the particular application and provide for enhanced device functionality. In contrast to graphene FETs using SiO2-based top-gate dielectric, which show asymmetric electron/hole mobility (with larger hole mobility), and Dirac point shifted to positive levels, FETs constructed using advanced AlN show Dirac point almost near neutral levels and near symmetric electron/hole mobility. The DP is shifted likely due to compensation of the intrinsic p-type doping by n-type doping introduced by the AlN deposition and potentially via a contribution of polarization-induced carrier density. Finally, we demonstrate a top-gated graphene FET with the first observation of RF operation with GHz cut-off frequency based on large area CVD graphene.

Thermoelectric (TE) properties of erbium-silicon co-doped InxGa1-xN alloys (InxGa1-xN: Er + Si, 0≤x≤0.14), grown by metal organic chemical vapor deposition, have been investigated. It was found that doping of InGaN alloys with Er atoms of concentration, N[Er] larger than 5x1019 cm-3, has substantially reduced the thermal conductivity, κ, in low In content InGaN alloys. It was observed that κ decreases as N[Er] increases in Si co-doped In0.10Ga0.90N alloys. A room temperature ZT value of ~0.05 was obtained in In0.14Ga0.86N: Er + Si, which is much higher than that obtained in un-doped InGaN with similar In content. Since low In content InGaN is stable at high temperatures, these Er+Si co-doped InGaN alloys could be promising TE materials for high temperature applications.

The present work reports on the defect-selective etching (DSE) for estimating dislocation densities in icosahedral boron arsenide (B12As2) crystals using molten potassium hydroxide (KOH). DSE takes advantage of the greater reactivity of high-energy sites surrounding a dislocation, compared to the surrounding dislocation-free regions. The etch pits per area are indicative of the defect densities in the crystals, as confirmed by x-ray topography (XRT). Etch pit densities were determined for icosahedral boron arsenide crystals produced from a molten nickel flux as a function of etch time (1-5 minutes) and temperature (400-700°C). The etch pits were predominately triangle shaped, and ranged in size from 5-25μm. The average etch pit density of the triangle and oval etch-pits was on the order of 5x107cm-2 and 3x106cm-2 (respectively), for crystals that were etched for two minutes at 550°C.

It is well-known that cadmium and its corrosion product (cadmium oxide) are carcinogenic and toxic. Consequently, efforts to eliminate cadmium from original equipment and repair processes have been on-going. One potential replacement is indium, which is a soft post-transition metal, whose primary use is in the form of indium tin oxide, e.g., in liquid crystal displays (LCDs). The semi-conductive properties of indium oxide alloys make it possible to use these for cadmium brush plating replacement in applications where contact resistance and impedance are critical parameters. Critical requirements of an alternative to cadmium brush plating in a corrosive industrial atmosphere are (1) be sacrificial to mild steel and (2) provide good electrical conductivity. Cadmium oxide remains semi-conductive, while most other pure metal oxides are electrical insulators, such as aluminum oxide, nickel oxide, and zinc oxide, and therefore, fail in meeting the requirement for bonding and grounding. Similar to cadmium oxide, indium oxide is semi-conductive, but indium exhibits other properties such as cold welding. This paper discusses indium- electroplating approaches to overcome the insulating limitation of pure metal plating and to replace cadmium brush plating. Test results are given for the brush-plated indium-tin alloy as compared to cadmium brush plating and conclusions on such replacement feasibility are provided.

An amorphous silicon (a-Si:H) photoconductor array with two distinct integrated amorphous silicon carbon alloy (a-SiC:H) high pass filters is used to detect two of the cell intrinsic fluorophores. The cutoff wavelength of the filters is tuned by the carbon content in the film. The fluorophores of interest – reduced nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) are indicative of the redox state of the cells. Concentrations down to 1 μM for NADH and 50 μM for FAD were detected.

A computational technique is developed to predict the statistics of internal elastic fields of three-dimensional dislocation systems in deforming crystals. The internal elastic fields are computed based on 3D dislocation realizations generated by the method of dislocation dynamics simulation. Preliminary results are presented for the statistical characteristics of the elastic strain, lattice rotation and dislocation density tensor fields. The importance of the current analysis is discussed in the context of direct comparison of simulations with spatially resolved 3D X-ray microscopy measurements of lattice rotation and the dislocation density tensor.