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We have employed atomic layer deposition to produce uniform films of $$\hbox {Bi}_{2}\hbox {Se}_{3}$$, which is a 3D topological insulator (TI), over 5 cm $$\times $$ 5 cm $$\hbox {SiO}_{2}$$-coated Si substrates. The crystalline properties of the films were characterized via Raman spectroscopy, x-ray diffraction, cross-sectional transmission microscopy, and atomic force microscopy, which confirmed the high quality of the films. The TI properties were examined using Hall bridge structures and recording magnetoresistance at 1.9 K. A weak anti-localization effect was observed at low field, from which a phase coherent length of 242 nm and prefactor $$\alpha $$ value of 1 were determined, indicating desirable topological properties. This approach for film growth provides a path for integrating a 3D topological insulator with silicon integrated circuit technology.

Potassium iron hexacyanoferrate, or Prussian blue (PB), is investigated as a cathode material for nonaqueous divalent calcium ion batteries. PB is an attractive prospect due to its high specific capacity, nontoxicity, low cost, and simple synthesis. Charge/discharge performances are examined at current densities of 23 mAg−1, 45 mAg−1, 90 mAg−1, and 125 mAg−1 that produced reversible specific capacities ranging from 150 mAhg−1 (at 23 mAg−1 current density) to over 120 mAhg−1 (at 125 mAg−1 current density). These are the highest storage capacities to date for a divalent calcium ion cathode over extended period of charge/discharge cycling and are comparable in performance to monovalent intercalating ions.

Traditionally, emphasis has been placed on durable, long-lasting electronics. However, electronics that are meant to intentionally degrade over time can actually have significant practical applications. Biodegradable, or transient, electronics would open up opportunities in the field of medical implants, where the need for surgical removal of devices could be eliminated. Environmental sensors and, eventually, consumer electronics would also greatly benefit from this technology. An essential component of transient electronics is the battery, which serves as a biodegradable power source. This work involves the fabrication, characterization, and modeling of a magnesium-based biodegradable battery. Galvanostatic discharge tests show that an anode material of magnesium alloy AZ31 extends battery lifetime by over six times, as compared to pure magnesium. With AZ31, the maximum power and capacity of the fabricated device are 67 μW and 5.2 mAh, respectively, though the anode area is just 0.8 cm2. The development of an equivalent circuit model provided insight into the battery's behavior by extracting fitting parameters from experimental data. The model can accurately simulate device behavior, taking into account its intentional degradation. The size of the device and the power it produces are in accordance with typical levels for low-power transient systems.

Calcium cobalt hexacyanoferrate (CaCoHCF) was synthesized and tested as a cathode material for rechargeable batteries, using divalent cations (Mg2+, Ca2+, Ba2+). CaCoHCF demonstrated reversible specific capacity and coulombic efficiency (in parentheses) of 45.49 mAh/g (99.18%) for Mg2+, 55.04 mAh/g (99.2%) for Ca2+, and 44.09 mAh/g (99.42%) for Ba2+, at a current density of 25 mA/g. Of the three ions, Ca2+ resulted in the highest absolute specific capacity as well as high specific capacity utilization. The cathodes were also subjected to rate capability measurements using current densities of 50 mA/g (30 cycles) and 0.1 A/g (100 cycles). Upon addition of 2 mL water to the non-aqueous electrolyte, the fraction of theoretical specific capacity increased to 0.55 for Mg2+, 94.8% for Ca2+, and 95.53% forBa2+. This increase has been interpreted as the ability of the cathode material to intercalate and de-intercalate more ions due to the electrostatic shielding provided by water molecules between the host lattice and the guest cations. An empirical relationship between the cation size and specific capacity utilization is presented.Calcium cobalt hexacyanoferrate (CaCoHCF) was synthesized and tested as a cathode material for rechargeable batteries, using divalent cations (Mg2+, Ca2+, Ba2+). CaCoHCF demonstrated reversible specific capacity and coulombic efficiency (in parentheses) of 45.49 mAh/g (99.18%) for Mg2+, 55.04 mAh/g (99.2%) for Ca2+, and 44.09 mAh/g (99.42%) for Ba2+, at a current density of 25 mA/g. Of the three ions, Ca2+ resulted in highest absolute specific capacity as well as high specific capacity utilization. The cathodes were also subjected to rate capability measurements using current densities of 50 mA/g (30 cycles) and 0.1 A/g (100 cycles). Upon addition of 2 mL water to the non-aqueous electrolyte, the fraction of theoretical specific capacity increased to 0.55 for Mg2+, 94.8% for Ca2+, and 95.53% forBa2+. This increase has been interpreted as the ability of the cathode material to intercalate and de-intercalate more ions due to the electrostatic shielding provided by water molecules between the host lattice and the guest cations. An empirical relationship between the cation size and specific capacity utilization is presented.

Both WS2 and SnS are 2-dimensional, van der Waals semiconductors, but with different crystal structures. Heteroepitaxy of these materials was investigated by growing 3 alternating layers of each of these materials using atomic layer deposition on 5 cm × 5 cm substrates. Initially, WS2 and SnS films were grown and characterized separately. Back-gated transistors of WS2 displayed n-type behavior with an effective mobility of 12 cm(2) V(-1) s(-1), whereas SnS transistors showed a p-type conductivity with a hole mobility of 818 cm(2) V(-1) s(-1). All mobility measurements were performed at room temperature. As expected, the heterostructure displayed an ambipolar behavior with a slightly higher electron mobility than that of WS2 transistors, but with a significantly reduced hole mobility. The reason for this drop can be explained with transmission electron micrographs that show the striation direction of the SnS layers is perpendicular to that of the WS2 with a 15 degree twist, hence the holes have to pass through van der Waals layers that results in drop of their mobility.

One-compartment hydrogen peroxide fuel cells with Co, Cu, and Fe phthalocyanine (PC) and iron nitride (FexN) as cathodes and Ni anode have been investigated as sustainable energy sources. The cells were operated under acidic conditions and at room temperature. The potentials for onset of the catalytic currents in these cells were determined via cyclic voltammograms. The reduction current onset potentials of FePC, CoPC, CuPC and FexN were 0.56 V, 0.42 V, 0.51 V and 0.57 V, respectively. Potential-current linear sweep voltammetry was utilized to determine the open circuit potentials (OCP) and the power densities the fuel cells. The OCPs for Co, Cu, and Fe phthalocyanines and FexN were 0.47 V, 0.57 V, 0.56 V and 0.58 V, respectively. The maximum output power densities of FePC and CoPC, CuPC, and FexN were 3.41 mW cm−2, 0.39 mW cm−2, 0.39 mW cm−2 and 0.76 mW cm−2, respectively. These power densities are suitable for powering micro-devices.

To accommodate the global shift towards increased energy production from renewable sources, further advancements in storage technology are needed to mitigate the intermittent nature of wind and solar. Aqueous zinc ion intercalation batteries (ZIBs) offer an inexpensive and safe alternative to the traditional lithium ion battery (LIB), making them a prime candidate for large scale storage. Metal hexacyanoferrates have been shown to be suitable cathode materials for ZIBs, allowing for the reversible insertion/extraction of the doubly charged zinc ion. In this work, we report on the performance of a cathode material composed of mixed manganese-cobalt hexacyanoferrate nanoparticles for a rechargeable ZIB. The cathode exhibits a reversibly capacity of 111 mAh/g at 25 mA/g and good capacity retention after extended cycling at 100 rnA/g. X-ray diffraction and SEM imaging reveal nanoparticles with a rhombohedral structure and sizes on the order of 20 - 60 nm. The combination of the nontoxic hexacyanoferrate cathode, with the aqueous zinc ion electrolyte offers a promising system for large scale energy storage.

Tin selenide (SnSe) is a two-dimensional, layered metal chalcogenide material. It has a direct band gap, hence has a great potential for next generation of opto- and photovoltaic devices. Uniform, smooth and high quality SnSe thin films were grown over large areas (5cm x 5cm) Si/SiO 2 substrates using Atomic Layer Deposition (ALD). Films were grown over a temperature range of 350°C to 450°C, which exhibit p- type semiconductor characteristics. Structural and optical properties of the as-grown films were investigated using X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). These analyses show growth of 2 dimensional, orthorhombic phase films. Back-gated transistors show p-type conductance, with an average hole mobility of 10 cm2/V.s and I on /I off ratio of ~105. Magnetic analysis shows a paramagnetic behavior.

Transition metal dichalcogenides (TMDCs) are a family of materials whose crystalline structure consists of a layer of transition metal atoms sandwiched between 2 layers of chalcogenide atoms. Some of these materials can be grown in 2D hexagonal phase and show tunability of their electrical and magnetic properties based on layer thickness. One aspect of these materials that has received little attention is their magnetic properties. Hence, we have investigated magnetic properties of CoSe and NiSe (both 2D semiconductors), and their heterostructure. The reason for choosing these intrinsically ferromagnetic transition metal atoms based TMCs was to examine how reduction from the bulk to 2D films would influence the magnetic activity of these samples. In order to produce large area films, we have employed atomic layer deposition (ALD) for growth of uniform, few layer-thick films. First the composition and crystal structure of these films are characterized, and then their magnetic properties analyzed. We have found that thin films of both these materials show mostly paramagnetic behavior.

In our modern scenario with increasing population use of energy resources such as fuels from crude oil increases and the amount of resources decreases as the time increases. So, in near future there will be limited amount of fuel to overcome this problem the project focus on the zero-fuel consumption. The working principle is based on the electromagnetism. Here the hollow cylinder contains coil which produce the magnetic field and at top of the piston is made up of the ferrous rod. When the current is supplied due to pulls force of the solenoid the ferrous rod gets pulled with great amount of force. Thus, the reciprocating motion is achieved, and some IC engine components and electronic circuits are used to control the motion.

The influence of the precursors, namely potassium ferrocyanide and potassium ferricyanide on the particles sizes of Prussian Blue (PB) and Prussian Green (PG), under identical reaction conditions have been investigated. It was found that the particle sizes influence the gravimetric capacity utilization of these materials as cathodes for aqueous potassium (K + ) ion batteries. The PG particle sizes were on the order of 50–75 nm, whereas PB particles size were on the order of 2–10 microns. The PG cathodes demonstrated a reversible capacity of 121.4 mAhr/g, with a coulombic efficiency of 98.7% compared to PB cathodes which demonstrated 53.8 mAhr/g, with a coulombic efficiency of 100%. We interpret the increased capacity of PG batteries relative to PB batteries as being a result of the smaller particle size of PG, which results in greater accessibility of the cathode to K+ ions.

Potassium barium hexacyanoferrate (K2BaFe(CN)6) was investigated as a cathode material for reversible Ca2+ ion insertion/extraction type rechargeable battery using non-aqueous electrolytes. The electrochemical performance of K2BaFe(CN)6was evaluated using cyclic voltammetry and galvanic cycling at ambient temperature. It is shown that addition of water led to significant enhancement in intercalation and de-intercalation of Ca2+ ions, leading to improved charge/discharge capacity. The enhancement in performance is attributed to formation of solvation spheres around the intercalating Ca2+ ions which provide screening from the electrostatic charges of the BaFe(CN)6 lattice. A reversible capacity of 55.8 mA hr g−1 and a coulombic efficiency of 93.8% was demonstrated at the end of 30 charge/discharge cycles.

Chemical modification of graphene by covalently functionalizing its surface potentially allows a wider flexibility in engineering electronic structure, in particular the local density of states of the carbon atoms bound to the modifier that can result in opening of the band gap. Such binding can involve covalent hydrogenation of graphene to modify hybridization of carbon atoms from sp2 to sp3 geometry [1] , [2] , [3] . Methods have also been developed to functionalize graphene covalently with molecular species [4] , [5] , [6] , [7] , [8] . Among these, perfluorophenylazide (PFPA) functionalization of graphene is well-developed using a nitrene intermediate. Films of this molecule also act as adhesion layers that allow production of long ribbons of exfoliated graphene [7] , [8] , [9] . We have developed a theory to predict electrical properties of PFPA functionalized graphene and compared it to experimental results. Conductivity of these PFPA functionalized ribbons of exfoliated graphene show good agreement with our theory.

Physical properties of graphene depend on the number of atomic layers in the film, presence of structural defects and impurities. Low-voltage, aberration-corrected, high-resolution transmission electron microscopy (HRTEM) has proven to be an excellent tool for structure analysis of graphene films. However, experimental observations of graphene films by HRTEM exhibit several challenges due to low contrast and sensitivity of graphene to intense electron beams. While a majority of electron scattering effects in graphene are purely kinematic, the contrast interpretation still requires computer simulations for reliable structure identification. In this paper, we present HRTEM contrast simulations of graphene films based on multislice algorithms and compare them to experimental results. The effects of stacking sequence, number of layers, and presence of impurities have been analyzed in conjunction with imaging conditions.

We have employed first-principles density functional calculations using Quantum ESPRESSO software to study the carrier conductance in few-layer thick 2D WSe2 semiconducting films. The results of this simulation are then compared to the experimental results where the films were grown via atomic layer deposition. The contact resistances were determined using the transfer line method. A comparison of experimental and simulated carrier conductance values shows a good agreement.

Diatoms are single-celled algae that possess silica shells called "frustules" decorated with periodic structures ordered at the micro- and nanoscale. Diatom biosilica containing metabolically inserted germanium is used to fabricate an electroluminescent (EL) thin film device (see figure). The EL spectrum has a series of sharp UV line emissions at 340-380 nm and weaker bands in the blue and red range.

Heterojunction photovoltaic devices were fabricated using single crystal silicon nanowires and the organic semiconductor regioregular poly-(3-hexyl thiophene) (RR-P3HT). N-type nanowires were first grown on an n+ silicon substrate by the vapor-liquid-solid (VLS) method. Devices were then fabricated by filling the gap between the nanowires and a transparent indium tin oxide (ITO) glass electrode with a polymer. For initial devices the gap was filled with P3HT deposited from chlorobenzene solution. Device performance indicates that both silicon and P3HT act as absorbers for photovoltaic response, but that photocurrents were very low due to high series resistance in the cell. A second type of device was fabricated by depositing a thin layer of P3HT on the grown nanowires by dip coating from a dilute solution, and then filling the voids between nanowires and the transparent electrode with the conductive polymer poly-[3,4-(ethylenedioxy)-thiophene]: poly-(styrene sulfonate) (PEDOT:PSS). The relatively high mob...

Silicon nanowires composed of p-n junctions have been grown on 2 × 5 cm glass substrates with a thin layer of indium tin oxide (ITO). These nanowires were grown both directly on ITO utilizing the vapor-solid (VS) method, as well as by vapor-liquid-solid (VLS) method, with a thin layer of gold as a catalyst. Current-voltage analyses show p-n diode characteristics in both cases. When a reverse dc bias was applied, these diodes responded to optical signals incident on the glass surface, showing potential solar-cell application and intriguing possibilities for future optical detection structures. Devices grown via the VS method displayed better electrical properties compared to those produced via the VLS method.

We report here on applying electric fields and dielectric media to achieve controlled alignment of single-crystal nickel silicide nanowires between two electrodes. Depending on the concentration of nanowire suspension and the distribution of electrical field, various configurations of nanowire interconnects, such as single, chained, and branched nanowires were aligned between the electrodes. Several alignment mechanisms, including the induced charge layer on the electrode surface, nanowire dipole-dipole interactions, and an enhanced local electrical field surrounding the aligned nanowires are proposed to explain these novel dielectrophoretic phenomena of one-dimensional nanostructures. This study demonstrates the promising potential of dielectrophoresis for constructing nanoscale interconnects using metallic nanowires as building blocks.

Electrochemical polishing (ECP) of copper (Cu) using solutions of phosphoric acid, sulfuric acid, sodium chloride, ethylene glycol, and hydroxyethylidenediphosphonic acid (HEDP), with or without organic and inorganic additives, has been investigated as an alternative to chemical mechanical polishing (CMP) for integration of low-k dielectrics in microelectronic devices. Copper anodic polarization curves in these solutions were measured. ECP of Cu bulk and thin films in these solutions was evaluated with atomic force microscopy and scanning electron microscopy. It was shown that most of the solutions studied have polarization curves with a limiting current plateau characteristic of ECP. Among them, phosphoric acid, HEDP, and phosphoric acid solutions with ethylene glycol, sodium tripolyphosphate, and Cu oxide as additives produced the best electropolished surfaces (mean roughness: R a

A model has been developed for the rapid melting and resolidification of thin Si films induced by excimer-laser annealing. The key feature of this model is its ability to simulate lateral growth and random nucleation. The first component of the model is a set of rules for phase change. The second component is a set of functions for computing the latent heat and the displacement of the solid–liquid interface resulting from the phase change. The third component is an algorithm that allows for random nucleation based on classical nucleation theory. Consequently, the model enables the prediction of lateral growth length (LGL), as well as the calculation of other critical responses of the quenched film such as solid–liquid interface velocity and undercooling. Thin amorphous Si films with thickness of 30, 50, and 100 nm were annealed under various laser fluences to completely melt the films. The resulting LGL were measured using a scanning electron microscope. Using physical parameters that were consistent with previous studies, the simulated LGL values agree well with the experimental results over a wide range of irradiation conditions. Sensitivity analysis was done to demonstrate the behavior of the model with respect to a select number of model parameters. Our simulations suggest that, for a given fluence, controlling the film’s quenching rate is essential for increasing LGL. To this end, the model is an invaluable tool for evaluating and choosing irradiation strategies for increasing lateral growth in laser-crystallized silicon films.

Thin HfO2 films have been deposited on silicon via atomic layer deposition using anhydrous hafnium nitrate [Hf(NO3)4]. Properties of these films have been investigated using x-ray diffraction, x-ray reflectivity, spectroscopic ellipsometry, atomic force microscopy, x-ray photoelectron spectroscopy, and capacitance versus voltage measurements. Smooth and uniform initiation of film growth has been detected on H-terminated silicon surfaces. As-deposited films were amorphous, oxygen rich, and contained residual NO3 and NO2 moieties from the nitrate precursor. Residual nitrates were desorbed by anneals >400 °C, however, the films remained oxygen rich. Crystallization of thin films (

Properties of copper films produced using atomic layer deposition (ALD) were characterized. Composition, morphology, and electrical properties of these films grown on glass, as well as Ta, TiN, and TaN on silicon wafers were examined. The resistivity of films thicker than about 60 nm was near bulk value. Films were deposited using a two-step ALD process in which copper(II)-1,1,1,5,5,5,-hexafluoroacetylacetonate hydrate and water vapor were introduced in the first step and a reducing agent was introduced in a subsequent step. Five reducing agents were evaluated, with the best results obtained using isopropanol or formalin. The optimum deposition temperature with isopropanol was about 260 °C, whereas it was about 300 °C with formalin. These films were also investigated as seed layers for electrodeposition of thicker Cu layers for possible interconnect applications. Excellent fills in high aspect ratio trenches were demonstrated.

The paper will introduce a simple new method for the synthesis of both hafnium and zirconium nitrate precursors. The intermediate product, dinitrogen pentoxide produced from the extraction of water from fuming nitric acid via phosphorus pentoxide, was condensed with a liquid nitrogen trap into a flask containing either hafnium or zironium tetrachloride. To achieve a high yield, the mixture of fuming nitric acid and phosphorus pentoxide was heated to a certain temperature, from which a large quantity of dinitrogen pentoxide had been generated. In the following steps hafnium or zirconium tetrachloride was refluxed over dinitrogen pentoxide at 30 to 35 °C for about a half-hour. The product was purified by sublimation. Yields above 95% were obtained. The cost for the hafnium nitrate precursor synthesis was estimated. The precursor was not stable at room temperature, and should be stored in refrigerator in sealed vials. No chlorine was detected from both EDS and chemical analysis. The volatility was evaluated ...

Metal chalcogenides based on the C–M–M–C (C = chalcogen, M = metal) structure possess several attractive properties that can be utilized in both electrical and optical devices. We have shown that specular, large area films of γ-InSe and Sb2Se3 can be grown via atomic layer deposition (ALD) at relatively low temperatures. Optical (absorption, Raman), crystalline (X-ray diffraction), and composition (XPS) properties of these films have been measured and compared to those reported for exfoliated films and have been found to be similar. Heterostructures composed of a layer of γ-InSe (intrinsically n-type) followed by a layer of Sb2Se3 (intrinsically p-type) that display diode characteristics were also grown.

Thin (∼10 nm) films comprising of Ta2O5–HfO2, Ta2O5–ZrO2, and ZrO2–HfO2 nanolaminates were deposited and characterized for possible gate dielectric applications. These films were deposited on silicon substrates using atomic layer deposition. The dielectric constants of these films were in 12–14 range and the leakage currents in 2.6×10−8–4.2×10−7 A/cm2 range at 1 MV/cm electric field. It was found that as these films were made thinner, the value of their dielectric constant dropped compared to their bulk values. The dominant leakage current mechanism at low electric fields was determined to be Schottky emission, whereas Poole–Frenkel emission dominated at higher fields.

In this work we have investigated the material properties and electrical performance of polycrystalline silicon films formed by an excimer-laser-anneal (ELA) process in different annealing environments. Particularly, we investigated the ELA process in air, nitrogen, argon, and helium and compared it with the standard ELA process in vacuum. Polysilicon thin-film transistors were fabricated using polysilicon material formed by ELA in different environments. We found that while the performance attributes of polysilicon films annealed in vacuum or inert ambient were quite similar, the performance of polysilicon annealed in air was drastically inferior to all. This result was attributed to the increased oxygen incorporation in the film in the case of the ELA process in air. Oxygen increased the density of both deep states and tail states in the polysilicon bandgap. One mechanism, proposed to account for the deterioration in performance, was the oxygen-induced formation of structural deficiencies in grain boundaries and bulk grain regions and its relation to generation of deep-state and tail-state defects.

A thorough investigation of polysilicon films crystallized from amorphous silicon using a XeCl excimer laser has been completed. Emphasis was placed on the development of large crystals, good uniformity, and low surface roughness, with an eye towards improving throughput. This was accomplished through use of SiO2 barrier layers, multiple passes, and careful consideration of annealing ambient. Thermal modeling was performed to help interpret the observed trends and aid in optimization. By controlling these process parameters, samples were produced with a high degree of uniformity and two-dimensional structural ordering, with grains nearly identical in size and stacked in rows and columns. However, a biproduct of the ordering was the creation of large topographical features at the intersection points of multiple grain boundaries, which lead to surface roughness in the range of 12 nm. By applying more shots to the same area, films with maximum grain sizes on the order of 3 μm and reduced surface roughness (6...

Room temperature electroluminescence has been demonstrated from undoped silicon nanowires that were grown from disilane. Ensembles of nanowires were excited by capacitively coupling them to an ac electric field. The emission peak occurred at about 600 nm from wires of average diameter of about 4 nm. The emission appears to result from band-to-band electron–hole recombination.

Deposition of nickel silicide nanowires has been achieved in the temperature range of 320 to 420 °C by decomposition of silane on nickel surfaces. The substrates consisted of Ni foils and thin Ni films (∼10–100 nm) evaporated on 1-μm-thick layers of SiO2 predeposited on Si wafers. Nanowire growth between two metal pads was achieved with aid of an electric field. It was found that thinner diameter nanowires were produced at low temperatures and that the density of the nanowires was dependent on the reactor pressure. The current–voltage relationship of these nanowires has also been examined.

A technique for depositing high-dielectric-constant metal–oxide thin films is demonstrated that consists of alternating pulses of metal–chloride precursors and Hf(NO3)4 in which Hf(NO3)4 is used as an oxidizing agent as well as a metal source. The use of Hf(NO3)4, rather than a separate oxidizing agent such as H2O, minimizes the potential for oxidation of the Si interface. Unlike HfCl4, a widely used precursor, the high reactivity of Hf(NO3)4 initiates uniform deposition on H-terminated Si beginning with the first pulse. Effective dielectric constants obtained for HfO2 films produced by this method were comparable to HfO2 films deposited using other methods and the leakage current densities were three orders of magnitude less than SiO2 of the same equivalent thickness. Deposition of HfAlOx and HfZrOx ternary oxide films was also examined. The deposition rate for films produced using this method is greater than one monolayer per cycle, indicating a mechanism that is different from standard atomic-layer dep...

Growth of smooth and continuous films of WSe2 has been demonstrated by employing atomic layer deposition (ALD) on 5 cm × 5 cm substrates. The substrates consisted of silicon wafers with a layer of SiO2. The ALD precursors were WCl5 and H2Se. The film properties characterized using Raman spectroscopy and x-ray photoelectron spectroscopy are comparable to those reported for WSe2 films produced by chemical vapor deposition and exfoliation. Carrier mobilities were determined with back-gated transistors. With Pd contacts, median electron and hole mobilities of 531 cm2 V−1 s−1 and 354 cm2 V−1 s−1, respectively, were measured.

An ensemble Monte Carlo simulation of high field transport in ZnS has been developed. The model includes a nonparabolic three valley model of the first conduction band and a single valley in the second conduction band. The density of states for the first conduction band was modeled phenomenologically to resemble the density of states obtained by numerical pseudopotential calculations. This density of states was used only in the calculation of the scattering probabilities and no attempt was made to modify the conductivity effective mass to conform to the band structure at higher energies. The fourth valley in the conduction band is included even though not much is known about the band parameters associated with it. In our first approximation, we treat it as a valley similar to the X valley of the first conduction band, with similar effective mass, deformation potentials, etc. This assumption is not much different from what has been done in previous Monte Carlo treatments. The simulation includes scattering mechanisms associated with acoustic, intervalley and polar optical phonons, as well as ionized impurity scattering and impact ionization. The inclusion of the second conduction band is found to have a significant impact on the energy distribution at fields above 1 MV/cm. The second conduction band is also important because of its effect on the impact ionization rate, which has been calculated. Other results such as drift velocity and average electron energy are presented and are found not to differ much from the results of previous investigations.

A sequential pulsed process is utilized for deposition of nonstoichiometric silicate films without employing an oxidizing agent. The metal precursors were HfCl4, AlCl3, and ZrCl4, as well as Hf(NO3)4 and the silicon source was tris(tert-butoxy)silanol. Unlike atomic layer deposition, the growth per cycle was several monolayers thick, where the enhancement in growth was due to a catalytic reaction. The bulk and electrical properties of these films are similar to those of silicon dioxide. Silicon carbide devices coated with these films show good insulating characteristics.

We report on the electrical properties of HfO2 deposited via atomic layer deposition using Hf(NO3)4 precursor for metal/oxide/semiconductor gate dielectric applications. Thin films, with less than 1% variation in accumulation capacitance over a 150 mm wafer, have been deposited directly on hydrogen-terminated Si wafers. The effective dielectric constant of thin (

We have calculated thermal conductance of graphene nanoribbons (GNRs) and their dependence on the type of ribbon edge termination (zigzag or armchair) and the width of the ribbon, which ranges from 50 Å to 50 μm. Our model incorporates the effect of edge roughness and includes edge roughness correlation functions for both types of termination. The dependence of thermal conductance on the width of the ribbons and relative contribution of different scattering mechanisms are also analyzed by means of the Green’s function approach to the edge scattering. High temperature thermal conductance of the nanoribbons was found to be 0.15 nW/K and 0.18 nW/K (corresponding to thermal conductivity, 4641 and 5266 W/mK, respectively, for 10 μm long GNRs) which is in a good agreement with the experimental results.

We have employed first-principles density-functional calculations to study the electronic characteristics of graphene functionalized by metal-bis-arene and metal-carbonyl molecules. It is shown that functionalization with M-bis-arene (M(C6H6)@gr, M=Ti, V, Cr, Mn, Fe) molecules leads to an opening in the band gap of graphene (up to 0.81eV for the Cr derivative), and functionalization with M-carbonyl (M(CX)3@gr, X=O,N; M= Cr, Mn, Fe, Co) up to one 1eV for M=Cr and X=O, and therefore transforms graphene from a semi-metal to a semiconductor. The band gap induced by attachment of a metal atom topped by a functionalizing group is attributed to modification of π-conjugation and depends on the concentration of functionalizing molecules, metal’s and moiety’s electronic structure. This approach offers a means of tailoring the band structure of graphene and potentially its applications for future electronic devices.

The effect of UV laser radiation on the emission of a ZnS:Tb thin film electroluminescent (EL) device has been investigated. It was found that the EL emission can be enhanced near threshold and attenuated at higher voltages by irradiating the device with UV radiation from an argon ion laser. It is shown that these effects are related to the photogenerated carriers that alter transport and build up of charge and the electric field. Both the charge and the field have been determined in real time to examine the enhancement and attenuation of the EL emission.

Atomic layer deposition has been employed to grow nanowires composed of ZnSe/CdSe superlattices. Growth of the nanowires was initiated using gold nanoparticles and the vapor-liquid-solid mechanism. High-resolution transmission electron microscopy shows that these structures are single crystals and the phase of alternating layers of ZnSe and CdSe is zinc blende. The (111) planes of ZnSe and CdSe are oriented at 60°.

We report electron spin resonance (ESR) observation of interface defects at the HfO2/(111)Si boundary for HfO2 films deposited via atomic layer chemical vapor deposition using Hf(NO3)4 as a precursor. We observe several signals, dominated by one due to a silicon dangling bond at the Si/dielectric interface. This center is somewhat similar to, but not identical to, Si/SiO2 interface silicon dangling bonds. Comparison between ESR and capacitance versus voltage measurements suggests that these dangling bond centers play an important role in HfO2/Si interface traps.

We have employed first-principles density-functional calculations to study the electronic characteristics of covalently functionalized graphene by metal-bis-arene chemistry. It is shown that functionalization with M-bis-arene (M=Ti, V, Cr, Mn, Fe) molecules leads to an opening in the band gap of graphene (up to 0.81eV for the Cr derivative), and as a result, transforms it from a semi-metal to a semiconductor. The band gap induced by attachment of a metal atom topped by a benzene ring is attributed to modification of π-conjugation and depends on the concentration of functionalizing molecules. This approach offers a means of tailoring the band structure of graphene and potentially its applications for future electronic devices.

Five different Nano-materials (NMs) were used for making hybrid conjugates with Protein-A (PrA), a biomolecule that binds specifically with antibodies (Abs). The choice of NMs (Gold, CdS, SrTiO3, Graphene Oxide and Polystyrene) exhibit both inorganic and organic NMs, with a wide range of electrical characteristics i.e., from metal, semiconductor to non conducting dielectric materials. The NMs-PrA conjugates prepared were characterized using UV-visible spectroscopy and fluorescence microscopy before use for biosensor application. These hybrids were than compared for their relative efficacy in enhancing the biosensor signal as recorded using faradaic electrochemical impedance spectroscopy (EIS). A nanogap interdigitated electrodes array (IDEA) sensor was coated with rabbit IgG antibodies and the binding signal from NM-PrA was compared with that of PrA binding alone. The EIS signal was analyzed by fitting the data to a Randles equivalent circuit. Values of two prime circuit elements i.e., charge transfer resistance (R-Ct) and double layer capacitance (C-dl) were determined from the best fit. The difference between the two signals provided the insight into the mechanisms for different NMs and the relative efficiency in signal enhancement.