In this paper, a multilayer CNx/TiN composite film on high-speed steel substrate was prepared by using a multi-arc assisted DC reactive magnetron sputtering system. The cross-section observations of the fracture surface reveal that the films show a pure cleavage fracture due to its super-high hardness, and the interfacial strength between the film and substrate is associates with the film thickness, i.e., 2μm is a critical thickness for the present deposition. That is to say, there is no disbonding or cracking at the interface when the film thickness is less than 2μm, while the interfacial failure is generated if the film thickness is larger than 2μm. This direct SEM observation of the fracture surface provides a distinct image for evaluating the mechanical property and also analyzing the failure mechanism of the films.

In this report, we demonstrate the use of helium ion milling for the controllable fabrication of nanostructures in few-layer hexagonal boron nitride (h-BN). Using the direct-write lithographic capabilities of a scanning helium ion microscope (HIM), nanopores with diameters as small as 4 nm and nanoribbons with widths of 3 – 10 nm are etched from suspended h-BN sheets. This ability to pattern h-BN sheets with high-throughput and sub-10 nm precision paves the way for future studies that make use of atomically-thin, nanostructured insulators such as those needed for nanopore sequencing and patterned van der Waals heterostructures.

Subwavelength particles with hyperbolic light dispersion in the constituent medium are a promising alternative to plasmonic, high-refractive-index dielectric, and semiconductor structures in the practical realization of nanoscale optical elements. Hexagonal boron nitride (hBN) is a layered van der Waals material with natural hyperbolic properties and low-loss phonon-polaritons at the same time. In this work, we consider multipole excitations and antennas properties of hBN particles with an emphasis on the periodic arrangement and collective array modes. We analyze excitation of lattice resonances in the antenna array and effect of resonance shifts and overlap with other multipoles supported by particles in the lattice. In such periodic structure, a decrease of reflectance from the array is achieved with appropriate lattice spacing (periods) where the electric and magnetic multipoles overlap, and the resonance oscillations are in phase and comparable in magnitude. We theoretical demonstrate that in this case, generalized Kerker condition is satisfied, and hBN antennas in the array efficiently scatter light in the predominantly forward direction resulting in near-zero reflectance. The resonant lattice Kerker effect with hyperbolic-medium antennas can be applied in developing metasurfaces based on hBN resonators for mid-infrared photonics.

Bioinspired micromanipulators have been made based on gecko dynamic self-cleaning mechanism. Various particles such as spherical SiO2/polystyrene, and short fibrous glass can be captured, transmitted and dropped on glass substrate with precisely predesigned patterns, by using the micromanipulator with the help of atomic force microscope (AFM). It has been demonstrated that particle-pad interface and particle-substrate interface exhibit diverse adhesion behaviors under different z-piezo retracting speed. The particle-substrate adhesion increases faster than the particle-pad adhesion with increasing the detaching velocity, which makes it possible to manipulate the particles by adjusting the retreating speed only. Probability tests was performed to better choose suitable parameters for picking and dropping operations. This work provides a potential solution to manipulation of micro/nano particles for precise assembly.

We propose and demonstrate the photoluminescence enhancement of CsPbBr3 perovskite quantum dot films in the presence of Au nanoparticles. Embedded into a polymer matrix, Au nanoparticle- quantum dot film assemble prepared by an easy spin coating method enabled the photoluminescence enhancement of perovskite quantum dot films up to 78%. The properties of the synthesized perovskite QDs and gold nanoparticles have been analysed using high resolution transmission electron microscopy, X-ray diffraction, energy dispersive X- ray spectroscopy, UV-Vis absorption spectrophotometer, steady state and time-resolved photoluminescence spectrometer.

We report here an experimental study of ultrafast response of the dielectric polarization in (Ba0.8Sr0.2)TiO3 thin films to a strong electric field of a nearly single-cycle THz pulse. The phenomenon of Second Harmonic Generation (SHG) is used as a probe of the polarization in the terahertz pump-optical probe experiment. SHG loops for THz pulses of different amplitudes were obtained. The SHG response is modelled assuming that the ferroelectric material is split into 180-degree domains. It is shown that intuitive model based on forced harmonic oscillator does not fully describe to the observed ultrafast ferroelectric response

Increasing the band gap of cadmium telluride (CdTe) from 1.48 eV to > 2 eV can be achieved by alloying CdTe with ZnTe. Like CdTe, the alloyed films are expected to allow for low cost production, suggesting that Cd1-xZnxTe could be an ideal top cell for mass produced tandem devices. However, the CdCl2 activation of the alloyed films results in a significant loss of Zn, thereby reducing the bandgap. In this study, we demonstrate a novel CdCl2 activation method that does not result in significant Zn loss. By performing the activation step in a closed, inert environment we are able to avoid oxidation of the Zn in the Cd1-xZnxTe film; furthermore, by including sacrificial Zn in the container, an overpressure of ZnCl2 forms limiting the amount of ZnCl2 formed in the film. Both x-ray diffraction, optical measurements, and Auger spectroscopy show that the CdCl2 treatment with no flowing gas minimizes the loss of Zn from the CZT alloy.

Controlling the oxidation state of iron and the crystal structure of iron containing compounds is the key to improved materials such as iron oxide nanoparticles for cancer treatment or heterogeneous catalysis. Iron oxides contain iron in different oxidation states and form different phases for one valence state (α-Fe3+2O2-3, β- Fe3+2O-32, etc.). Chemical vapor synthesis (CVS) allows the reproducible production of pure nanocrystals with narrow size distribution where particle formation and growth take place in the gas phase. Through the controlled variation of synthesis parameters CVS enables the synthesis of diverse iron oxide phases. In this study the energy for the CVS process is supplied by a hot wall furnace and a microwave plasma. The advantage of an plasma reactor as the first CVS stage is the fast and complete precursor decomposition at low temperatures. This results in a larger process window for the hot wall reactor in the second stage. The nanoparticles are examined regarding their structure, surface and valence by XRD and TEM.

The system of quinone molecules encapsulated in the single-wall carbon nanotube (SWCNT) has been proposed as a next-generation cathode electrode material for rechargeable battery. We investigate the complex interaction among the SWCNT, phenanthrene-quinone (PhQ), and Li atoms in the encapsulated system by using our original DFT code. We thereby find that the shape of the SWCNT changes significantly in the relaxed state depending on the extent of Li atoms inserted. The SWCNT shows a circular cylinder shape when no Li exists. With sufficient Li atoms inserted, the SWCNT is flattened. Substantial electron transfer from the PhQs to SWCNT is found. As for the dynamics of Li atoms in insertion or extraction process, we find that the Li atoms can take either of the two paths: one is along the inner wall of the SWCNT and the other is hopping on the PhQs.

The effect of damage induced by plasma etching on the cathodoluminescence intensity of micron-size InP features is studied. At the etched bottom, it is found that the hard mask stripping process is sufficient to recover the luminescence. Within features, the presence of sidewalls reduces luminescence intensity due to additional non-radiative surface recombinations. For a n-doped sample, a carrier diffusion length of 0.84 μm and a reduced nonradiative surface recombination velocity of 2.58 are calculated. Hydrostatic strain within the etched features is measured using the peak shift of the luminescence signal, while in plane strain anisotropy is obtained from its degree of polarization, both with a resolution of about 100 nm.

Bismuth triiodide (BiI3) has been studied aiming the development of lead-free photovoltaic materials. It can also be used as X-ray detectors due to the high density of its elements (bismuth and iodine). We investigate the mechanical stress, hardness, and elastic properties of BiI3 thin films deposited by thermal evaporation. The stress was determined by the bending beam technique using the Stoney equation. The films are tensile with stress of approximately 27 MPa. The hardness and the elastic modulus were determined by nanoindentation technique using a Berkovich diamond tip. The hardness of the films is approximately 0.8 GPa and the reduced Young´s modulus is ∼28 GPa for maximum penetration depth of 10% of the film thickness.

We report single-shot transient absorption (SSTA) measurements of an organic film of 3,3’-Diethyloxatricarbocyanine iodide (DOTCI). In SSTA, the pump-probe time delay is spatially encoded by using a tilted pump pulse. Translation of the sample during SSTA measurements averages over any spatial heterogeneity in the film. We demonstrate that exciton dynamics measured with the single-shot technique agrees with traditional transient absorption measurements of the same film. A signal-to-noise ratio of ∼40 is achieved in 10 s. The ability to measure exciton dynamics in organic films will enable future SSTA measurements of exciton dynamics during the molecular aggregation events that result in film formation.

Ti-based quasicrystals are well known to store a high capacity of hydrogen exceeding the density of liquid hydrogen. This fact is due to that TiZrNi contain a large number of tetrahedral sites formed with Ti and Zr atoms that are chemical affinity with hydrogen. TiZrNi quasicrystal absorbs hydrogen up to host metal ratio (H/M) value near to 2.0. The disadvantage is due to the low equilibrium pressure. To solve this problem, we substituted Ti with a small amount of vanadium (V), with the nominal composition Ti45−x VxZr38Ni17 (x = 5, 10, 15) and synthesized by mechanical alloying. The subsequent annealing in vacuum conditions converted the amorphous into an icosahedral quasicrystal (I-phase) with face-centered cubic (FCC) Ti2Ni-type crystal. As the results, we investigated the discharge capacity for both amorphous and quasicrystal electrodes using three electrodes system (working, reference and counter electrodes) at room temperature. The highest discharge capacities obtained were 81.45 mAh/g recorded for amorphous electrode and 318.4 mAh/g for quasicrystal whose compositions is Ti35V10Zr38Ni17 at discharge current density of 15 mA/g. X-ray diffraction measurement was performed to provide the structural information on materials before and after hydrogenation. Microstructures of the materials were studied using an electron scanning microscope and the chemical compositions were confirmed using an EDX-analysis.

SnS2 has adequate properties for photovoltaic applications in solar cells. For this purpose, we studied the influence of the capping agents pyridine and aniline in the nanoparticles hydrothermal syntheses. These capping agents are suitable for use in hybrid organic- inorganic solar cells. Different ratios of these agents with respect to the metal precursor were tested. Hexagonal and disc-type nanoparticles were obtained. Lower concentrations of capping agent increased the proportion of hexagons, while diminishing their size. The obtained products are adequate in size, dispersion of size, and stabile in suspension in chloroform to use them in hybrid solar cells. Moreover, the use ofpyridine allowed for more stable suspensions, and therefore better results for this application.

Fatigue behaviour of titanium reinforced with TiB particles fabricated by ‘plasma transferred arc solid freeform fabrication’ (PTA-SFFF) technique was investigated. Rotation bending fatigue tests were conducted following the MPIF 56 standard using the staircase method approach. Experimental data is used to calculate the fatigue strength and construct S-N curves, where the results were compared to a powder metallurgy FC0205 as a benchmark material. The titanium samples were found to exhibit superior fatigue behaviour in comparison to the reference FC0205 material, performing well above 1/3 of its ultimate tensile strength with a 90% survival fatigue strength of 244 +/- 98.3 MPa versus 141 +/- 17.4 MPa. Fatigue failure mechanisms of samples were identified by examination of the fracture surfaces through scanning electron microscopy (SEM) as well as using transmission-electron microscopy (TEM) and focused ion beam (FIB) analysis techniques. Fatigue crack propagation was either arrested or deflected when propagation occurred within the vicinity of the TiB intermetallics. Fracture surfaces of the titanium matrix displayed evidence of striations while the TiB intermetallic experience cleavage fracture.

Catalytic behavior of colloidal dispersions of different nanocarbon additives in mineral and synthetic oil has been studied. Oxidation performance of mineral oil and synthetic oil containing detonation nanodiamonds (NDs/DNDs), detonation soot and commercial analogs have been compared with fullerenes and a conventional chemical antioxidant. Degradation characteristics of the oils were determined by total acid number (TAN) and Fourier transform infrared spectroscopy (FTIR). Both fullerenes and DNDs showed antioxidant properties in mineral oil, with DND performance depending on the method of deagglomeration. Antioxidant performance of DNDs and fullerenes in polyalphaolefin (PAO) oil is apparently less effective than in mineral oil.

In this study, the spontaneous formation of hydrogels from a water-soluble and amphiphilic ABA-type block copolymer in an aqueous system was examined. The block copolymers were composed of poly(2-methacryloyloxyethyl phosphorylcholine) (MPC) as the B segment and poly(n-butyl methacrylate) (BMA) as the A segment. A two-step living radical polymerization of the corresponding monomers yielded a well-defined ABA-type block copolymer. By regulating the polymerization degree of each segment, the water solubility and amphiphilic natures of the resulting block copolymer could be controlled. The block copolymers spontaneously formed hydrogels when the composition of water in the medium increased to 80 vol% in the water/ethanol mixture. This was due to molecular aggregation of the block copolymers driven by the hydrophobic interactions between the poly(BMA) segments in the polymer. This hydrogel formation depended on the composition and polymerization degree of the MPC units. The poly(MPC) also showed good biocompatibility, thereby rendering the block copolymers applicable for the immobilization of biological components such as antibodies and enzymes and the encapsulation of cells under mild conditions.

The deposition of uniform, reproducible and compact Sb2S3 thin films were obtained by chemical bath deposition using tartaric acid as a complexing agent. It was found that the thickness of the films increases with the pH of the solution, reaching values of 130 and 170 nm for pH values of 9.5 and 10, respectively. XRD, as well as Raman analysis, showed amorphous Sb2S3 films formed directly from the chemical bath, which crystallized into stibnite after a thermal treatment in N2 with crystallite sizes between 31 and 39 nm. On the other hand, the optical band gap of the Sb2S3 films decreased with an increase in pH, with values of 1.82-2.03 eV for the crystalline ones. An n-type photo-conductivity of 10-6 Ω-1 cm-1 was obtained for the heated films. The evaluation of these films for solar cell applications using CdS as the window layer gave a Voc of 656 mV and a Jsc of 2.66 mA/cm2 under AM1.5G radiation.

The purpose of this research work is to gain a better understanding of the nanostructural properties of Molybdenum (Mo) thin films’ porosity, nanovoid heterogeneity and provide detailed quantitative data on voids volume fractions, sizes, shapes, and their preferred orientations as the growth sputtering pressure changes systematically. This knowledge shall assists in optimizing Mo film nano- and micro-structural properties as desired for solar cells applications. Therefore, two separate series of Mo thin films (∼ 0.7 μm thick) were deposited on high purity (99.999) Al-foil (10 μm thick), and Si/SiO2 substrates using direct-current (DC) planar magnetron sputtering. The sputtering pressure was varied from 0.8 mT to 12 mT, with a sputtering power density of 1.2 W/cm2. High-Resolution Scanning Electron Microscopy (HRSEM) was used to examine the Mo films’ morphology. Whereas, the Mo films’ bulk resistivity was calculated from the films’ thickness and average sheet resistance measurements using Dektak Surface Profilometer, and Four Point Probe method, respectively. Small Angle X-Ray Scattering (SAXS) technique was applied to examine the existence of nanovoids and its heterogeneity in the Mo-coated Al foils (Al/Mo). Moreover, the porosity of the Mo films as a function of sputtering pressure was studied by Transmission Electron Microscopy (TEM) on Mo-coated Si/SiO2 (Si/SiO2/Mo) substrates.

Droplet based microfluidics (digital microfluidics) with Electrowetting on dielectric (EWOD) has gained popularity with the promise of being technology for a true lab-on-chip device with applications spanning across assays/library prep, next-gen sequencing and point-of-care diagnostics. Most electrowetting device architecture are linear electrode arrays with a shared path for droplets, imposing serious limitations -- cross contamination and limited number of parallel operations. Our work is in addressing these issues through large 2D grid arrays with direct addressability providing flexible programmability.

Scaling electrowetting to larger arrays still remains a challenge due to complex and expensive cleanroom fabrication of microfluidic devices. We take the approach of using inexpensive PCB manufacturing, investigate challenges and solutions for scaling electrowetting to large area droplet manipulation. PCB manufactured electrowetting arrays impose many challenges due to the irregularities from process and materials used. These challenges generally relate to preparing the surface that interfaces with droplets -- a dielectric material on the electrodes and the top most hydrophobic coating that interfaces with the droplets. A requirement for robust droplet manipulation with EWOD is thin (<10um) hydrophobic dielectric material which does not break down at droplet actuation voltages (AC/DC, 60V to 200V) and has a no droplet pinning. For this, we engineered materials specifically for large area PCBs.

Traditionally, digital microfluidic devices sandwich droplets between two plates and have focussed on sub-microliter droplet volumes. In our approach, droplets are on an open surface with which we are able to manipulate droplets in microliter and milliliter volumes. With milliliter droplet manipulation ability on our electrowetting device, we demonstrate “digital millifluidics”. Finally, we report the performance of our device and to motivate the need for large open arrays we show an example of running multiple parallel biological experiments.