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At least 1,189 records · Page 66
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Large Area Transfer of Bismuth‐Based Layered Oxide Thin Films Using a Flexible Polymer Transfer Method

Magnetic and ferroelectric oxide thin films have long been studied for their applications in electronics, optics, and sensors. The properties of these oxide thin films are highly dependent on the film growth quality and conditions. To maximize the film quality, epitaxial oxide thin films are frequently grown on single-crystal oxide substrates such as strontium titanate (SrTiO 3 ) and lanthanum aluminate (LaAlO 3 ) to satisfy lattice matching and minimize defect formation. However, these single-crystal oxide substrates cannot readily be used in practical applications due to their high cost, limited availability, and small wafer sizes. One leading solution to this challenge is film transfer. In this demonstration, a material from a new class of multiferroic oxides is selected, namely bismuth-based layered oxides, for the transfer. A water-soluble sacrificial layer of Sr 3 Al 2 O 6 is inserted between the oxide substrate and the film, enabling the release of the film from the original substrate onto a polymer support layer. The films are transferred onto new substrates of silicon and lithium niobate (LiNbO 3 ) and the polymer layer is removed. These substrates allow for the future design of electronic and optical devices as well as sensors using this new group of multiferroic layered oxide films.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Control of deviatoric stress in the diamond anvil cell through thermal expansion mismatch stress in thin films

Elastic and plastic properties of materials and phase transitions at extreme conditions vary with both hydrostatic pressure and deviatoric stress. To generate and measure controlled deviatoric stress at pressures beyond those accessible with large volume differential and rotational presses and optical access for spectroscopy, experiments tested the combination of diamond anvil cell and thin film technology. Thin films of polycrystalline Cr-doped Al 2 O 3 ruby were prepared using pulsed laser deposition on single-crystal substrates of either Al 2 O 3 sapphire or yttria-stabilized cubic zirconia for contrasting initial film stress, and loaded in diamond anvil cells for confining stress. The piezospectroscopic response of the ruby films demonstrates consistently higher deviatoric stress in the film on zirconia relative to the film on the control sapphire, and an increase in deviatoric stress with applied load. Complementary synchrotron X-ray diffraction of the zirconia substrate confirmed that no pressure-induced phase transitions impacted the stress state of the ruby film, but differences in compressibility of film and substrate result in changes in film stress analogous to thermal expansion mismatch. Furthermore, this technique may be applied to evaluate elastic and plastic response of thin films of a variety of materials under extreme stress.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Mechanical, Barrier and Antioxidant Properties of Chitosan Films Incorporating Cinnamaldehyde

Chitosan films (CF) [1 and 2% w/v] alone and with cinnamaldehyde (CNE) [0.25, 0.5 and 1% v/v] were prepared using an emulsion method, and the obtained films were characterized in terms of water vapor permeability (WVP), water solubility and optical, mechanical and antioxidant properties. The incorporation of CNE at 1% (v/v) significantly decreased the water solubility of the film by approximately 4% for the 1 and 2% CF films, whereas the WVP increased (2.5–3.5 times). The incorporation of CNE (0.25 and 0.5%) into 2% CF significantly increased the tensile strength (TS) (62 and 34%, respectively) and the percent elongation (%E) values, 26, 30 and 52% for CF that contained 0.25, 0.5 and 1% CNE, respectively. The largest value of the elasticity modulus (EM) was observed for 2% CF with 0.25% CNE. All films exhibited a yellow appearance (b*), but the CNE content had a marked impact on the coloration of the films. The CNE recoveries of the CF films (1 and 2%) with 1% of CNE were high (43 and 67%). The antioxidant activities indicated that the incorporation of 1% CNE into CF films (1 and 2%) increased the antioxidant activity. The protective effects of the films with and without CNE on erythrocytes were very strong (36–72% hemolysis inhibition). These results suggest there are potential applications for CF-CNE films as active packaging for the preservation of food products.

36 MATERIALS SCIENCE↗
DOE OSTI2019

A Simple Approach for the Synthesis of Cellulose Nanofiber Reinforced Chitosan/PVP Bio Nanocomposite Film for Packaging

The development of chitosan-based food packaging film has been increasing due to its wider availability, biodegradability, low-cost, and renewability. The purpose of this study was to develop cellulose nanofibers (CNFs) reinforced Chitosan/PVP(CHP) green bio nanocomposite film by solvent casting method with enhanced barrier and mechanical property. CNFs of dimension 9–11 nm and 100–200 nm were extracted from jute fibers by directly treating it with HNO{sub 3}–NaNO{sub 2} mixture. Bio nanocomposite films were synthesized with various concentrations of CNFs and evaluated using SEM, TGA/DTG and XRD to analyze the morphology, thermal behavior and crystallinity of bio nanocomposite films. SEM analysis revealed the uniform dispersion of CNFs in CHP matrix. Thermal stability of prepared bio nanocomposite films was improved with the loading of 5 wt% of cellulose nanofibers. ATR(FT-IR) spectra shows physical interaction between all the components of bio nanocomposite film. The bio nanocomposite films were also characterized for physical property like thickness, mechanical testing and barrier properties. The addition of CNFs significantly enhanced the mechanical property of bio nanocomposite films. Furthermore, water and oxygen transmission rate of bio nanocomposite film decreased with the increase in CNFs concentration. Overall the performed studies confirmed, the use of CNFs in polymer matrix makes it possible to produce a flexible, transparent, thermally stable bio nanocomposite film with enhanced mechanical and barrier properties for food packaging applications.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Effect of Yb Substitution on Microstructure and Superconducting Properties of Y{sub 1−x}Yb{sub x}Ba{sub 2}Cu{sub 3}O{sub 7−δ} Films

The purpose of this study was to improve the critical current density (J{sub c}) of YBa{sub 2}Cu{sub 3}O{sub 7−δ} (YBCO) superconducting films at high magnetic fields. Thin Y{sub 1−x}Yb{sub x}Ba{sub 2}Cu{sub 3}O{sub 7−δ} (Y{sub 1−x}Yb{sub x}BCO) superconducting films on LaAlO{sub 3} substrates were prepared by modified low-fluorine metal organic deposition method (LF-MOD) in order to investigate the effect of Yb substitution on the microstructure and superconducting properties of a YBCO-coated conductor. In this study, single-phased, c-axial-aligned Y{sub 1−x}Yb{sub x}BCO films were obtained. Yb doping had a little effect on the critical temperature (T{sub c}) and transition width (ΔT) values of Y{sub 1−x}Yb{sub x}BCO films. An abnormal phenomenon was observed that the J{sub c} of Y{sub 1−x}Yb{sub x}BCO films at low field was smaller than that of the pure YBCO film, but the J{sub c} of Y{sub 1−x}Yb{sub x}BCO films at high field was much greater than that of the undoped YBCO film. Compared to pure YBCO film, the J{sub c} values of Y{sub 0.75}Yb{sub 0.25}BCO and Y{sub 0.25}Yb{sub 0.75}BCO films were enhanced by a factor of 8 at 8 T, 65 K, which meant that chemical substitution of Yb into the Y site could improve flux pinning significantly under the high magnetic field in Y{sub 1−x}Yb{sub x}BCO coated conductors.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Thickness-Dependent Thermal Oxidation of Ni into NiO Thin Films

We report thickness-dependent thermal oxidation in Ni (t = 10–300 nm) thin films exposed to air annealing and the resulting vibrational, magnetic and electrical properties of Ni films deposited directly on thermally oxidized Si substrate using magnetron sputtering technique at ambient temperature. As-deposited Ni films exhibit face-centred cubic structure with fine crystals and large lattice constant (a{sub Ni}) at lower t (< 50 nm). With increasing t, a{sub Ni} decreases and approaches to bulk value. With increasing T{sub A}, a{sub Ni} not only decreases to bulk Ni due to improved crystallization but also reduces below bulk Ni for t > 50 due to formation of NiO. The relative fraction of Ni and NiO in annealed films up to 400 {sup ∘}C strongly depends on t. Annealing Ni films at 500 {sup ∘}C results into complete oxidation of Ni into granular-type NiO. X-ray reflectivity studies reveal that oxidation process occurs from surface of the films converting Ni into NiO possibly through layer by layer process, which is subtle to t. Raman spectra show that intensity ratio between one-phonon longitudinal optical (LO) and two-phonon LO bands decreases and intensity of two-magnon band increases with increasing t for films annealed at particular T{sub A}. This confirms the growth of NiO not only with increasing T{sub A}, but also with t. As-deposited films exhibit ferromagnetism at room temperature. The presence of Ni and NiO in annealed films implies coexistence of ferromagnetic and antiferromagnetic interactions, leading to tunable exchange bias (H{sub E}), whose magnitude strongly depends on the ratio between Ni and NiO. Electrical resistance (R) of the as-deposited Ni films decreases with increasing t and follows the Namba’s model. Upon annealing, R increases largely due to oxidation of Ni. The observed results are explained on the basis of thickness dependent thermal oxidation process with increasing T{sub A}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Study on mechanically alloyed tin telluride screen-printed films for optoelectronic device applications

Narrow band gap semiconductor tin telluride (SnTe) was synthesized by mechanical alloying and its film was deposited on glass substrates by the economically and commercially feasible screen-printing technique. Deposition of the film was followed by sintering. Different analytical techniques were utilized to study the structure, surface morphology, elemental, optical and electrical characteristics of the film. X-ray diffraction analysis confirms that the film is polycrystalline in nature and exhibits rock salt type structure with preferred orientation of grains along (200) direction. EDAX spectrum confirms the presence of Sn and Te elements in the film. SEM image shows that the film exhibits uniform surface. The energy band gap of the film was determined by reflection spectra. The film is found to have a direct band gap of 0.37 eV. The dark electrical conductivity and activation energy of the film were measured in temperature range 300–380 K. Hall Effect measurement indicates that the film has p-type electrical conductivity.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Study of the Electrical and Diffusion Barrier Properties in Ultrathin Carbon Film-Coated Copper Microwires for Interconnects

Four specimen patterns with the microstructure of a microcopper wire are deposited on the Si-wafer substrate plus thermal oxide (SiO{sub 2}) film as the top layer. Each pattern was prepared to have two kinds of specimens, including with and without ultrathin carbon film between the copper wire and the top layer (SiO{sub 2}). The effect of carbon film on electrical properties is evaluated via the measurements of the I (current)–V (voltage) curve, sheet electrical resistance, current leakage, and its ratio and effective permittivity. A rapid thermal annealing (RTA) technique is provided as an economic and efficient method to grow the ultrathin carbon film rapidly as the interlayer. Appropriate choices of 900 °C and 3 min as the annealing temperature and time can produce ultrathin carbon film with nearly 100% coverage of the copper surface. The sheet resistance of specimen demonstrates the behavior exactly opposite to that of the carbon film coverage of wire surface. The combined effect of elevating the voltage and annealing temperature of the specimen with carbon film on the current leakage is much lower than that arising in the specimen without carbon film, so long as the carbon films operating at that temperature (between 350 and 500 °C) are still sustainable. The differences in current leakage and effective permittivity between these two kinds of specimen are significantly increased by raising the temperature. The intensity (IC) of copper diffusions into the SiO{sub 2} layer in the specimens with the carbon film demonstrates behavior similar to that of current leakage (CL). The IC and CL values for the temperatures ≦ 350 °C are much lower than those obtained at 500 °C.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Tribological behavior of N-doped ZnO thin films by metal organic chemical vapor deposition under lubricated contacts

N-doped ZnO thin films were deposited on 304L stainless steel through the pyrolysis of zinc acetate and ammonium acetate in different ratios at a temperature of 420 degrees C using metal organic chemical vapor deposition. Compositional and structural analyzes of the films were performed by using Rutherford backscattering spectroscopy and X-ray diffraction. The frictional behavior of the thin films and 304L stainless steel substrate was evaluated using a ball-on-flat configuration with reciprocating sliding under marginally lubricated and fully flooded conditions. Al alloy (2017) was used as ball counterface, while basestock synthetic polyalfaolefin oil (PAO10) without additives was used as lubricant. The flat and ball counterface surfaces were examined to assess the wear dimension and failure mechanism. Under marginally lubricated condition, N-doped ZnO thin films provided significant reduction in friction, whereas the films have minimal or no effect in friction under fully flooded condition. N-doped ZnO thin films showed a significant effect in protecting the ball counterface as wear volume was reduced compared with that of the substrate under the marginally lubricated condition. Under the fully flooded condition, with the exception of one of the films, the wear volume of the N-doped ZnO thin films ball reduced compared with that of the substrate. In all the ball counterfaces for N-doped ZnO thin films under both conditions, wear occurred through abrasive mechanism of various degrees or mild polishing. Thus, superfluous lubrication of N-doped ZnO thin films is not necessary to reduce friction and wear.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Oxygen and relative humidity monitoring with films tailored for enhanced photoluminescence

In this study, approaches to generate porous or doped sensing films, which significantly enhance the photoluminescence (PL) of oxygen optical sensors, and thus improve the signal-to-noise (S/N) ratio, are presented. Tailored films, which enable monitoring the relative humidity (RH) as well, are also presented. Effective porous structures, in which the O 2 -sensitive dye Pt octaethylporphyrin (PtOEP) or the Pd analog PdOEP was embedded, were realized by first generating blend films of polyethylene glycol (PEG) with polystyrene (PS) or with ethyl cellulose (EC), and then immersing the dried films in water to remove the water-soluble PEG. This approach creates pores (voids) in the sensing films. The dielectric contrast between the films’ constituents and the voids increases photon scattering, which in turn increases the optical path of the excitation light within the film, and hence light absorption by the dye, and its PL. Optimized sensing films with a PEG:PS ratio of 1:4 (PEG’s molecular weight M w ~8000) led to ~4.4× enhancement in the PL (in comparison to PS films). Lower M w ~200 PEG with a PEG:EC ratio of 1:1 led to a PL enhancement of ~4.7×. Film-dependent PL enhancements were observed at all oxygen concentrations. The strong PL enhancement enables (i) using lower dye (luminophore) concentrations, (ii) reducing power consumption and enhancing the sensor’s operational lifetime when using organic light emitting diodes (OLEDs) as excitation sources, (iii) improving performance when using compact photodetectors with no internal gain, and (iv) reliably extending the dynamic range.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Investigation of fuel film formation and soot emissions in a GDI engine during cold-start with Split-injection strategies

This study investigates the impact of fuel-film formation on engine-out soot emissions in a gasoline direct injection (GDI) engine under cold-start conditions. Split-injection strategies were applied by varying the number of injections, injection duration, and total fuel quantity to affect wall wetting and control the average in-cylinder equivalence ratio. A combined experimental and numerical approach was employed to analyze fuel-film deposition, combustion efficiency, and engine-out soot and unburnt hydrocarbons (UHC) emissions. In particular, fuel film distribution estimated by means of non-reacting, 3-D, computational fluid dynamics (CFD) simulations, together with experimentally measured soot data, were used to investigate fuel film formation and its role in soot generation. In the experiments, a skip-fired engine control strategy was applied to mimic the transient nature of engine cold-start operation. The results indicate that, under the same total number of injections, increasing the average in-cylinder equivalence ratio through longer injection durations improves combustion stability, as indicated by the decrease of the coefficient of variation of IMEP n (Net Indicated Mean Effective Pressure) from 6.0 % to 0.6 %. However, this strategy leads to higher soot emissions, which increased by nearly an order of magnitude, primarily due to enhanced wall-film formation. In contrast, increasing the number of injections while maintaining a constant equivalence ratio significantly impacts fuel-film deposition and, consequently, soot emissions, with a fivefold reduction of the measured engine-out soot, decreasing from 3.5 mg to 0.7 mg. A soot-film correlation was developed and achieved a high coefficient of determination (r 2 = 0.95) and was further extended to account for spark timing effects. These findings confirm the effectiveness of split-injection for avoiding wall film formation and soot emissions, and the critical role of fuel film in soot generation, supporting the hypothesis that pool fires play a crucial role in contributing to soot formation under these cold-start conditions. In conclusion, the study also indicates the value of a predictive soot-film correlation for developing cold-start emission control strategies.

Engine Cold-start↗
DOE OSTI2020

Thermal stability of oxidized ultrathin Li films on TZM for plasma facing components

For improved understanding of the behavior of Li plasma facing components (PFCs) in the presence of oxygen impurities, we report on the thermal stability of ultrathin (up to 1.0 nm) LiO x films on a titanium-zirconium-molybdenum (TZM) alloy substrate over the temperature range of 310–1400 K. LiO x films were prepared by either post-oxidation of Li films or Li films deposited on an oxygen-precovered TZM surface. Thermal stability of these films was studied using a combination of temperature programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and low-energy ion scattering (LEIS). For post-oxidized Li films, TPD showed that no Li desorption occurred until temperatures above 620 K, and then Li desorbed from the surface via at least three desorption peaks. The O 1s XPS spectra on the post-oxidized films at 310 K indicate the formation of lithium oxide (Li2O) and peroxide/hydroxide (Li 2 O 2 /LiOH). The peroxide/hydroxide converts to oxide after heating to 680 K with no desorption of Li or O 2 , and then this film decomposes to liberate Li into the gas phase while leaving oxygen at the TZM surface. Heating the LiO x films to 1070 K led to a solid-state reaction with surface Mo atoms of the substrate to form a condensed binary lithium molybdenum oxide (LixMoOy) phase, which upon further heating decomposed to liberate gas phase binary lithium molybdenum oxide species. Li deposition on an oxygen-precovered TZM surface formed a complex, highly stable, oxygen rich, Li-O-Mo interfacial oxide. Li desorption from multilayer Li films on oxygen-precovered TZM surfaces occurred in a metallic Li multilayer peak and three other oxide-derived peaks. These results support the improved thermal stability of oxidized lithium as compared to metallic Li and have implications for Mo impurity transport into the plasma at high temperatures.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Electrochemical properties of Li[Li{sub 0.2}Mn{sub 0.54}Co{sub 0.13}Ni{sub 0.13}]O{sub 2} cathode thin film by RF sputtering for all-solid-state lithium battery

The Li[Li{sub 0.2}Mn{sub 0.56}Ni{sub 0.13}Co{sub 0.13}]O{sub 2} thin films were prepared by radio frequency magnetron sputtering on Pt/Ti/SiO{sub 2}/Si substrate with target contained a 5% excess of lithium precursor. Thin films were deposited under various deposition conditions such as working pressure, gas ratio of Ar and O{sub 2}, and the temperature of in-situ annealing treatment. The thin films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The electrochemical property was estimated by a WBC3000 cycler with Li|Li[Li{sub 0.2}Mn{sub 0.54}Ni{sub 0.13}Co{sub 0.13}]O{sub 2} half-type cell at 1C charge/discharge rate. The (0 0 3) and (1 0 4) diffraction peaks which represent layered {alpha}-NaFeO{sub 2} type structure (space group R-3m) were observed. Optimal magnetron sputtering conditions were detected. The 500 Degree-Sign C annealed thin film after deposited at 10 m Torr in Ar:O{sub 2}=3:1 shows a high discharge capacity of around 62 {mu}Ah/cm{sup 2} {mu}m with a high cyclic retention. - Graphical abstract: The Li[Li{sub 0.2}Mn{sub 0.56}Ni{sub 0.13}Co{sub 0.13}]O{sub 2} films is suitable for Lithium thin film battery. The film exhibits great discharge capacity (62 {mu}Ah/cm{sup 2} {mu}m) up to 200 cycles. Highlights: Black-Right-Pointing-Pointer High capacity thin films were deposited by RF magnetron sputtering. Black-Right-Pointing-Pointer Sputtering conditions were optimized by structural and electrochemical analysis. Black-Right-Pointing-Pointer Li[Li{sub 0.2}Mn{sub 0.56}Ni{sub 0.13}Co{sub 0.13}]O{sub 2} thin film shows a high capacity, 62 {mu}Ah/cm{sup 2} {mu}m. Black-Right-Pointing-Pointer The thin film shows an excellent cycling stability up to 200 cycles.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Investigations of the crystallization mechanism of CrSb and CrSb{sub 2} multilayered films using in-situ X-ray diffraction and in-situ X-ray reflectometry

Chromium and antimony multilayered films with variable elemental layer thickness were deposited on (1 0 0)-Si substrate cooled with liquid nitrogen. The stoichiometry of the films was adjusted to Cr:Sb=1:1 and 1:2. The thickness of Cr-Sb repeating units of these multifilms was varied between 11.4 and 102.5 A. Satellite maxima in the X-ray reflectivity curves observed for films in the as-deposited state demonstrate an alternating stacking of the evaporated elements. The reactivity of the superlattice reactants was investigated with temperature dependent in-situ X-ray diffractometry and X-ray reflectometry. The crystallization temperature of CrSb depends on the double-layer thickness and is about 90 Degree-Sign C for a Cr:Sb ratio of 1:1 and double-layer thickness of 53.7 A where nucleation and crystal formation occurs at the element interfaces, while for a thin double-layer thickness (11.4 A) first interdiffusion of the elements occurs before crystallization starts, i.e., an amorphous intermediate is formed prior to crystallization of CrSb. A decomposition reaction into CrSb{sub 2} occurs at about 230 Degree-Sign C, and up to about 575 Degree-Sign C, CrSb, CrSb{sub 2} and amorphous Cr coexist. For the ratio Cr:Sb=1:2 and a thin double-layer thickness prior to crystallization of CrSb{sub 2} nano-sized crystallites with a composition near CrSb{sub 2} nucleate and grow. These crystallites are then successively transformed in long-range ordered crystals exhibiting a pronounced preferred orientation. For films with a thicker repeat unit first formation of CrSb is observed which then reacts with elemental Sb yielding crystalline CrSb{sub 2}. An activation energy for interdiffusion of Cr and Sb of about 1.8 eV is estimated for a film with Cr:Sb=1:1 exhibiting a double-layer thickness of about 53.7 A and an energy for crystal growth of about 1.1 eV. For the film with the thinner double-layer thickness of 11.4 A a lower value of the activation energy for interdiffusion is obtained. For CrSb{sub 2} the energy for crystal growth is about 3.0 eV being significantly larger than for CrSb. Specific resistivity and Hall coefficient measurements were performed for crystalline CrSb and CrSb{sub 2} films. The temperature-dependent resistivity measurement exhibits a metallic behavior for CrSb and semi-conducting properties for CrSb{sub 2}. - Graphical abstract: The compound CrSb{sub 2} crystallizes from the amorphous state via intermediate formation of CrSb. Highlights: Black-Right-Pointing-Pointer CrSb and CrSb{sub 2} crystallize at very low temperatures in multilayered films. Black-Right-Pointing-Pointer Film thickness determines crystallization at interfaces or from amorphous intermediate. Black-Right-Pointing-Pointer Prior to crystallization of CrSb{sub 2}, highly textured CrSb crystallizes first. Black-Right-Pointing-Pointer Depending on the film thickness CrSb{sub 2} exhibits different preferred orientations.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Bismuth(III) dialkyldithiophosphates: Facile single source precursors for the preparation of bismuth sulfide nanorods and bismuth phosphate thin films

Two different phase pure materials (Bi{sub 2}S{sub 3} and Bi{sub 2}P{sub 4}O{sub 13}) have been prepared under different conditions using the same single source precursors. Solvothermal decomposition of the complexes, Bi(S{sub 2}P(OR){sub 2}){sub 3} [where, R=Methyl (Me) (1), Ethyl (Et) (2), n-Propyl (Pr{sup n}) (3) and iso-Propyl (Pr{sup i}) (4)] in ethylene glycol gave orthorhombic bismuth sulfide nanorods, whereas aerosol assisted chemical vapor deposition (AACVD) of the same precursors deposited monoclinic bismuth tetraphosphate (Bi{sub 2}P{sub 4}O{sub 13}) thin films on glass substrates. Surface study of the thin films using SEM illustrated the formation of variety of nanoscale morphologies (spherical-, wire-, pendent-, doughnut- and flower-like) at different temperatures. AFM studies were carried out to evaluate quality of the films in terms of uniformity and roughness. Thin films of average roughness as low as 1.4 nm were deposited using these precursors. Photoluminescence studies of Bi{sub 2}P{sub 4}O{sub 13} thin films were also carried out. - Graphical abstract: Solvothermal decomposition of bismuth(III) dialkyldithiophosphates in ethylene glycol gave Bi{sub 2}S{sub 3} nanoparticles, whereas aerosol assisted chemical vapor deposition of these single source precursors deposited Bi{sub 2}P{sub 4}O{sub 13} thin films. Display Omitted - Highlights: • Preparation of phase pure orthorhombic Bi{sub 2}S{sub 3} nanorods and monoclinic Bi{sub 2}P{sub 4}O{sub 13} thin films. • Use of single source precursors for deposition of bismuth phosphate thin films. • Use of solvothermal decomposition and AACVD methods. • Morphology controlled synthesis of Bi{sub 2}P{sub 4}O{sub 13} thin films. • Bi{sub 2}S{sub 3} nanorods and Bi{sub 2}P{sub 4}O{sub 13} thin films using same single source precursors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Homoepitaxy of ZnO and MgZnO Films at 90 °C

The aqueous synthesis of uniform single crystalline homoepitaxial zinc oxide, ZnO, and magnesium zinc oxide, Mg{sub x}Zn{sub 1−x}O, films under very low temperature conditions at T=90 °C and ambient pressure has been explored. A maximum Mg content of 1 mol% was recorded by energy dispersive spectroscopy. The growth on the polar (0 0 0 1) and (0 0 0 1¯) faces resulted in films that are strongly different in their structural and optical quality as evidenced by high-resolution X-ray diffraction, secondary electron microscopy, and photoluminescence. This is a result of the chemistry and temperature of the solution dictating the stability range of growth-governing metastable species. The use of trisodium citrate, Na{sub 3}C{sub 6}H{sub 5}O{sub 7}, yielded coalesced, mirror-like homoepitaxial films whereas adding magnesium nitrate hexahydrate, Mg(NO{sub 3}){sub 2}·6H{sub 2}O, favors the growth of films with pronounced faceting. - Graphical abstract: Homoepitaxial ZnO films grown from aqueous solution below boiling point of water on a ZnO substrate with off-orientation reveal parallel grooves that are characterized by (1 0 1{sup ¯} 1) facets. Adding trisodium citrate yields closed, single-crystalline ZnO films, which can further be functionalized. Alloying with MgO yields MgZnO films with low Mg content only. - Highlights: • A simple method to synthesize uniform single crystalline homoepitaxial ZnO and MgZnO films. • ZnO growth on (0 0 0 1) and (0 0 0 1{sup ¯}) face resulted in films that are strongly different in their structural and optical quality. • Single crystalline MgZnO film was fabricated under mild conditions (90 °C and ambient pressure). • Mg incorporation of nearly 1 mol% was obtained while maintaining single phase wurtzite structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Aqueous phase deposition of dense tin oxide films with nano-structured surfaces

Dense tin oxide films were successfully fabricated in an aqueous solution. The pH of the solutions was controlled to pH 1.3 by addition of HCl. Precise control of solution condition and crystal growth allowed us to obtain dense tin oxide films. Concave–convex surface of fluorine-doped tin oxide (FTO) substrates was entirely-covered with the continuous films. The films were about 65 nm in thickness and had nano-structured surfaces. Morphology of the films was strikingly different from our previous reported nano-sheet assembled structures. The films were not removed from the substrates by strong water flow or air blow to show strong adhesion strength. The aqueous solution process can be applied to surface coating of various materials such as nano/micro-structured surfaces, particles, fibers, polymers, metals or biomaterials. - Graphical abstract: Dense tin oxide films of 65 nm were successfully fabricated in an aqueous solution. They had nano-structured surfaces. Concave-convex substrates were entirely-covered with the continuous films. - Highlights: • Dense tin oxide films of 65 nm were successfully fabricated in an aqueous solution. • They had nano-structured surfaces. • Concave–convex substrates were entirely-covered with the continuous films.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Fabrication of graphene/polyaniline composite multilayer films by electrostatic layer-by-layer assembly

A novel graphene/polyaniline composite multilayer film was fabricated by electrostatic interactions induced layer-by-layer self-assembly technique, using water dispersible and negatively charged chemically converted graphene (CCG) and positively charged polyaniline (PANI) as building blocks. CCG was achieved through partly reduced graphene oxide, which remained carboxyl group on its surface. The remaining carboxyl groups not only retain the dispersibility of CCG, but also allow the growth of the multilayer films via electrostatic interactions between graphene and PANI. The structure and morphology of the obtained CCG/PANI multilayer film are characterized by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, Ultraviolet–visible absorption spectrum (UV–vis), scanning electron microscopy (SEM), Raman spectroscopy and X-Ray Diffraction (XRD). The electrochemical properties of the resulting film are studied using cyclic voltammetry (CV), which showed that the resulting CCG/PANI multilayer film kept electroactivity in neutral solution and showed outstanding cyclic stability up to 100 cycles. Furthermore, the composite film exhibited good electrocatalytic ability toward ascorbic acid (AA) with a linear response from 1×10{sup −4} to 1.2×10{sup −3} M with the detect limit of 5×10{sup −6} M. This study provides a facile and effective strategy to fabricate graphene/PANI nanocomposite film with good electrochemical property, which may find potential applications in electronic devices such as electrochemical sensor. - Graphical abstract: A novel graphene/polyaniline (CCG/PANI) film was prepared by layer-by-layer assembly. - Highlights: • A novel graphene/polyaniline (CCG/PANI) film was prepared by layer-by-layer assembly. • The water dispersible and negatively charged graphene (CCG) was used as building block. • CCG was achieved through partly reduced graphene oxide with carboxyl group on its surface. • CCG/PANI film kept electroactivity in neutral solution and showed good stability. • Good electrocatalytic ability toward ascorbic acid was also demonstrated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗