Evolution of crystalline structure in SnS thin films prepared by chemical deposition

Crystal structure and morphology undergo significant evolution in thin films of tin(II) sulfide prepared by chemical deposition, over a narrow interval of bath temperature of 20–40 °C, but has not been recognized in previous studies. The chemical bath is constituted using tin(II) chloride, triethanolamine, ammonia(aq.) and thioacetamide. At bath temperature of 20 °C, the deposition rate of the film is 10 nm/h; and at 24 h, a film of thickness 260 nm is obtained. This film is compact and with a predominantly cubic (Cub-) crystalline structure. At 40 °C, the deposition rate is 25 nm/h, and a film of 600 nm in thickness is deposited in 24 h. However, this film has evolved into vertically stacked platelets of orthorhombic (OR-) crystalline structure. The transition from compact-to-platelet morphology as well as from Cub-to-OR-crystalline structure is observed near a deposition temperature, 35 °C. The Cub-SnS has a characteristic high optical band gap, 1.67 eV (direct gap; forbidden transitions) with an electrical conductivity, 10⁻⁷(Ω cm)⁻¹; both properties being un-affected when films are heated at 300 °C in a nitrogen ambient. In OR-SnS, the band gap is 1.1 eV (indirect gap; allowed transitions). The electrical conductivity of such films is notably higher, 10⁻⁴ (Ω cm)⁻¹, which increases further by an order of magnitude when the films have been heated at 300 °C in nitrogen.     

A Self‐Binding,Melt‐Castable,Crystalline Organic Electrolyte for Sodium Ion Conduction

The preparation and characterization of the cocrystalline solid–organic sodium ion electrolyte NaClO₄(DMF)₃ (DMF=dimethylformamide) is described. The crystal structure of NaClO₄(DMF)₃ reveals parallel channels of Na⁺ and ClO₄⁻ ions. Pressed pellets of microcrystalline NaClO₄(DMF)₃ exhibit a conductivity of 3×10⁻⁴ S cm⁻¹ at room temperature with a low activation barrier to conduction of 25 kJ mol⁻¹. SEM revealed thin liquid interfacial contacts between crystalline grains, which promote conductivity. The material melts gradually between 55–65 °C, but does not decompose, and upon cooling, it resolidifies as solid NaClO₄(DMF)₃, permitting melt casting of the electrolyte into thin films and the fabrication of cells in the liquid state and ensuring penetration of the electrolyte between the electrode active particles.     

Proton Conductivities of Graphene Oxide Nanosheets: Single,Multilayer, and Modified Nanosheets

Proton conductivities of layered solid electrolytes can be improved by minimizing strain along the conduction path. It is shown that the conductivities (σ) of multilayer graphene oxide (GO) films (assembled by the drop‐cast method) are larger than those of single‐layer GO (prepared by either the drop‐cast or the Langmuir‐Blodgett (LB) method). At 60 % relative humidity (RH), the σ value increases from 1×10⁻⁶ S cm⁻¹ in single‐layer GO to 1×10⁻⁴ and 4×10⁻⁴ S cm⁻¹ for 60 and 200 nm thick multilayer films, respectively. A sudden decrease in conductivity was observed for with ethylenediamine (EDA) modified GO (enGO), which is due to the blocking of epoxy groups. This experiment confirmed that the epoxide groups are the major contributor to the efficient proton transport. Because of a gradual improvement of the conduction path and an increase in the water content, σ values increase with the thickness of the multilayer films. The reported methods might be applicable to the optimization of the proton conductivity in other layered solid electrolytes.     

Conductive polymers as a new type of thermoelectric material

Thermoelectric properties were investigated for the films of electrically conductive doped polyanilines. The thermoelectric performance, evaluated by thermoelectric figure-of-merit (ZT = T (S² σ) / κ), of various protonic acid-doped polyaniline bulk films was found to depend on the electrical conductivity σ of the film. Thus, the higher the electrical conductivity, the higher the figure-of-merit is, because the thermal conductivity κ of polyaniline films does not depend on the electrical conductivity. Among the conductive bulk films of polyaniline, the highest figure-of-merit (ZT = 1 × 10⁻⁴) was observed for (±)-10-camphorsulfonic acid (CSA)-doped polyaniline in an emeraldine form (σ - 188 S cm⁻¹) at room temperature. The multilayered film, composed of electrically insulating emeraldine base layers and electrically conducting CSA-doped emeraldine salt layers, exhibited 6 times higher ZT at 300 K than that of a bulk film of CAS-doped polyaniline, showing the highest ZT value of 1.1 × 10⁻² at 423 K. Stretching of the CAS-doped polyaniline film also increased the figure-of-merit of doped polyaniline films along the direction of the stretching.     

Electrical and mechanical properties of the zone-drawn polypyrrole films

The zone-drawing method (ZD) was applied to electrochemically synthesized polypyrrole films containing tosylate (PPy/TsO) and the mechanical and electrical properties of the resulting films were investigated. It was found that the electrical conductivity of the zone-drawn film reached 365 S cm⁻¹ in the drawing direction, which was 4.7 times that of the original film. The tensile properties of the zone-drawn film were improved and Young's modulus and strength at break increased to 4.32 GPa and 90.1 MPa from 0.53 GPa and 40.4 MPa of the as-synthesized film, respectively. The dynamic storage modulus (E) increased by the zone-drawing over a whole experimental temperature range and attained 7.0 GPa at room temperature and 4.0 GPa even at 200°C. © 1996 John Wiley & Sons, Inc.     

Effect of post-deposition annealing temperature on RF-sputtered HfO2 thin film for advanced CMOS technology

Structural and electrical properties of HfO₂ gate-dielectric metal-oxide-semiconductor (MOS) capacitors deposited by sputtering are investigated. The HfO₂ high-k thin films have been deposited on p-type <100> silicon wafer using RF-Magnetron sputtering technique. The Ellipsometric, FTIR and AFM characterizations have been done. The thickness of the as deposited film is measured to be 35.38 nm. Post deposition annealing in N₂ ambient is carried out at 350, 550, 750 °C. The chemical bonding and surface morphology of the film is verified using FTIR and AFM respectively. The structural characterization confirmed that the thin film was free of physical defects and root mean square surface roughness decreased as the annealing temperature increased. The smooth surface HfO₂ thin films were used for Al/HfO₂/p-Si MOS structures fabrication. The fabricated Al/HfO₂/p-Si structure had been used for extracting electrical properties such as dielectric constant, EOT, interface trap density and leakage current density through capacitance voltage and current voltage measurements. The interface state density extracted from the G–V measurement using Hill Coleman method. Sample annealed at 750 °C showed the lowest interface trap density (3.48 × 10¹¹ eV⁻¹ cm⁻²), effective oxide charge (1.33 × 10¹² cm⁻²) and low leakage current density (3.39 × 10⁻⁹ A cm⁻²) at 1.5 V.     

Synthesis and characterization of poly(1-benzoylsemicarbazide) and poly(1,3,4-oxadiazole amine) from 2-(p-aminophenyl)-1,3,4-oxadizolin-5-one via ring-opening

A novel thermally stable and semiconducting polyheterocycle, poly(1,3,4-oxadiazole amine), was synthesized from 2-(p-aminophenyl)-1,3,4-oxadiazolin-5-one via ring-opening. The polymer is a new class of ordered alternating copoly(aniline) containing 1,3,4-oxadiazole heterocyclic units. The polymer is highly thermally stable and exhibits no weight loss up to 370°C in air. Its electric conductivity is less than 10⁻¹⁰ S · cm⁻¹ at ambient temperature, but markedly increases to 6,5 · 10⁻⁷ S · cm⁻¹ upon doping with iodine.     

Evaluation of the structural,optical and electrical properties of AZO thin films prepared by chemical bath deposition for optoelectronics

Aluminum doped zinc oxide (AZO) thin films for electrode applications were deposited on glass substrates using chemical bath deposition (CBD) method. The influence of deposition time on the structural, morphological, and opto-electrical properties of AZO films were investigated. Structural studies confirmed that all the deposited films were hexagonal wurtzite structure with polycrystalline nature and exhibited (002) preferential orientation. There is no other impurity phases were detected for different deposition time. Surface morphological images shows the spherically shaped grains are uniformly arranged on to the entire film surface. The EDS spectrum confirms the presence of Zn, O and Al elements in deposited AZO film. The observed optical transmittance is high (87%) in the visible region, and the calculated band gap value is 3.27 eV. In this study, the transmittance value is decreased with increasing deposition time. The room temperature PL spectrum exposed that AZO thin film deposited at (60 min) has good optical quality with less defect density. The minimum electrical resistivity and maximum carrier concentration values were observed as 8.53 × 10⁻³(Ω cm) and 3.53 × 10¹⁸ cm⁻³ for 60 min deposited film, respectively. The obtained figure of merit (ϕ) value 3.05 × 10⁻³(Ω/sq)^{- 1} is suggested for an optoelectronic device.     

Lithium aluminate-doped lithium orthosilicate: Sol-gel ceramics and lithium dynamics

Dense ceramics (Li_4+xSi_1−xAl_xO₄ with 0 ≤ x ≤ 0.3) are obtained by sintering at 700–900°C, without prior calcination, of sol-gel powders prepared by an alkoxide-hydroxide route. In comparison with the pure lithium orthosilicate (3 × 10⁻⁴ S · cm⁻¹ at 350°C), only a slight enhancement of the ionic conductivity is noted for monophase ceramics with Li₄SiO₄-type structure (5 × 10⁻⁴ S · cm⁻¹ at 350°C for x = 0.3). Higher conductivity (2 × 10⁻² S · cm⁻¹ at 350°C) is observed for an heterogeneous material formed of a lithium silicoaluminate phase (x = 0.2) with the Li₄SiO₄-type structure coexisting with lithium hydroxide. In this two-phase material, ac conductivity and ⁷Li spin-lattice relaxation data are consistent with the formation of a new kinetic path, via a thin layer along the interface, which enhances the lithium mobility.     

Effects of gold‐induced crystallization process on the structural and electrical properties of germanium thin films

Gold‐induced (Au‐) crystallization of amorphous germanium (α‐Ge) thin films was investigated by depositing Ge on aluminum‐doped zinc oxide and glass substrates through electron beam evaporation at room temperature. The influence of the postannealing temperatures on the structural properties of the Ge thin films was investigated by employing Raman spectra, X‐ray diffraction, and scanning electron microscopy. The Raman and X‐ray diffraction results indicated that the Au‐induced crystallization of the Ge films yielded crystallization at temperature as low as 300°C for 1 hour. The amount of crystallization fraction and the film quality were improved with increasing the postannealing temperatures. The scanning electron microscopy images show that Au clusters are found on the front surface of the Ge films after the films were annealed at 500°C for 1 hour. This suggests that Au atoms move toward the surface of Ge film during annealing. The effects of annealing temperatures on the electrical conductivity of Ge films were investigated through current‐voltage measurements. The room temperature conductivity was estimated as 0.54 and 0.73 Scm⁻¹ for annealed samples grown on aluminum‐doped zinc oxide and glass substrates, respectively. These findings could be very useful to realize inexpensive Ge‐based electronic and photovoltaic applications.     

Polymeric Semiconductors with a Pre‐Specified Alternation of Conjugated Bonds and Metal Clusters

Summary: In this work the first samples of polymeric semiconductors of a new structure are produced. Their electric conductivity is of the order ∼10⁻² Ohm⁻¹ · cm⁻¹ and it increases with temperature. Their synthesis includes a stage of radiation grafting of a matrix‐type on stretched polyamide films. Conducting molecular circuits in such materials include fragments with conjugated bonds and metal clusters. The alternation of these fragments is determined by the polyamide matrix.

Plot of voltage versus current determined for new polymer semiconducting films where fragments with conjugated bonds alternate with silver clusters.     

Yttrium Doped Copper (II) Oxide Hole Transport Material as Efficient Thin Film Transistor

This work reports development of yttrium doped copper oxide (Y−CuO) as a new hole transport material with supplemented optoelectronic character. The pure and Y-doped CuO thin films are developed through a solid-state method at 200 °C and recognized as high performance p-channel inorganic thin-film transistors (TFTs). CuO is formed by oxidative decomposition of copper acetylacetonate, yielding 100 nm thick and conductive (40.9 S cm⁻¹) compact films with a band gap of 2.47 eV and charge carrier density of ∼1.44×10¹⁹ cm⁻³. Yttrium doping generates denser films, Cu₂Y₂O₅ phase in the lattice, with a wide band gap of 2.63 eV. The electrical conductivity increases nine-fold on 2 % Y addition to CuO, and the carrier density increases to 2.97×10²¹ cm⁻³, the highest reported so far. The TFT devices perform remarkably with high field-effect mobility (μ_sat) of 3.45 cm² V⁻¹ s⁻¹ and 5.3 cm² V⁻¹ s⁻¹, and considerably high current-on/off ratios of 0.11×10⁴ and 9.21×10⁴, for CuO and Y−CuO films, respectively (at −1 V operating voltage). A very small width hysteresis, 0.01 V for CuO and 1.92 V for 1 % Y−CuO, depict good bias stability. Both the devices work in enhancement mode with stable output characteristics for multiple forward sweeps (5 to −60 V) at −1V_g.     

The effect of polyvinyl alcohol (PVA) on the optical,electrical and solid state properties of copper zinc tin sulfide (CZTS) deposited by sensitive spray pyrolysis (SSP)

Recently, the use of CZTS as the basis for other generation of low cost thin films solar cells has stimulated further researches. Its excellent p-type absorber nature, relatively high absorption coefficient and ideal energy band-gap of 1.5eV motivated these efforts. Additionally, CZTS consist of earth-abundant, cheap and non-toxic elements with very low manufacturing cost. Initially, copper indium gallium selenide (CIGS) solar cell device emerged but suffered limitations in further development because of rare indium and gallium in the device structure therefore, CZTS is recently preferred as an alternative to CIGS commercial solar cell absorber layer. In this work, solution mixture of CZTS and PVA was deposited on a substrate at temperature of 150 °C. Sensitive spray pyrolysis was used to grow the thin films where calculated amount of the precursor mixture was allowed to fall and be deposited on a heated substrate to form CZTS/PVA thin films. Subsequently, the thin film samples were annealed at a temperature of 200^oCfor 1 h to achieving pure crystalline thin film formation. SEM, XRD analysis, Optical, Solid State properties and Raman analysis were studied. The XRD analysis showed that the thin films fell into the pure kesterite structure of CZTS. Results show that produced thin films exhibited higher absorption coefficient and optical conductivity than pure CZTS, 10⁶ m^?1 and 10¹⁴(S^?1) against 10⁴cm^?1 and 10¹²(S^?1) respectively. The band-gap is between 1.53eV and 1.73eV. Using a PVA concentration of 0.05 M yielded highest absorbance and optical conductivity with lowest real dielectric constant and transmittance. These improved optical, electrical and solid state properties suitably qualify these thin films as absorber layer material for solar cell applications.     

Oxygen Diffusion into Polymer-Clay Composite Films as a Function of Clay Content and Temperature

Summary: A simple fluorescence technique is proposed for the measurement of the diffusion coefficient of oxygen into polystyrene-clay composite films as a function of clay content and temperature. The composite films were prepared from a mixture of surfactant-free pyrene-labeled polystyrene latexes and modified Na-montmorillonite clay of various compositions at room temperature. Diffusion measurements were performed with films at room temperature for seven different clay contents (0, 5, 10, 20, 30, 50 and 60 wt.%). The diffusion coefficients of oxygen increased from 7.4 × 10⁻¹⁰ to 26.9 × 10⁻¹⁰ cm²s⁻¹ with increasing clay content. On the other hand, diffusion measurements were performed over a temperature range of 25–70 °C for 0, 5 and 20 wt.% clay content films. The calculated diffusion activation energies decreased from 2.44 to 0.44 kcal/mol with increasing clay content. No clay content and temperature effects were observed on quenching rate constant and mutual diffusion coefficient values. The results showed that the diffusion coefficients are strongly dependent on both the temperature and clay content in the film.     

Electrical conductivity of hexacene doped with iodine

Hexacene (HEX) and derivatives such as dihydrohexacene and dihydroxyhexcane quinone were synthesized and thin films of them were prepared by the sublimation method. The structure and conductivity of the films both before and after doping with iodine were studied. The doped HEX film showed the conductivity of 3 × 10^?2 S/cm at room temperature, which was lower than expected since the conductivity of highly ordered pentacene was above 100 Ω^?1 cm^?1. The reason for the low conductivity was considered to be the disorder in molecular alignment since the HEX film showed an amorphous structure. A reversible change in the conductivity of the HEX film was observed in air and in vacuum.     

Hydrogen/oxygen polymer electrolyte membrane fuel cells (PEMFCs) based on alkaline-doped polybenzimidazole (PBI)

When complexed with alkaline such as potassium hydroxide, sodium hydroxide or lithium hydroxide, films (40 μm thick) of polybenzimidazole (PBI) show conductivity in the 5 × 10⁻⁵–10⁻¹ S/cm⁻¹ range, depending on the type of alkali, the time of immersion in the corresponding base bath and the temperature of immersion. It has been shown that PBI has a remarkable capacity to concentrate KOH, even in an alkaline bath of concentration 3 M. The highest conductivity of KOH-doped PBI (9×10⁻² S cm⁻¹) at 25°C obtained in this work is higher than the we had obtained previously as optimum values for H₂SO₄-doped PBI (5 × 10⁻² S cm⁻¹ at 25°C) and H₃PO₄-doped PBI ( 2 × 10⁻³ S cm⁻¹ at 25°C). PEMFCs based on an alkali-doped PBI membrane were demonstrated, and their characteristics exhibited the same performance as those of PEMFCs based on Nafion® 117. Their development is currently under active investigation.     

Preparation of a Star Network PEG-based Gel Polymer Electrolyte and Its Application to Electrochromic Devices

A star network polymer with a pentaerythritol core linking four PEG-block polymeric arms was synthesized, and its corresponding gel polymer electrolyte based on lithium perchlorate and plasticizers EC/PC with the character being colorless and highly transparent has been also prepared. The polymer host was characterized and confirmed to be of a star network and an amorphous structure by FTIR, ^1H NMR and XRD studies. The polymer host hold good mechanical properties for pentaerythritol cross-linking. Maximum ionic conductivity of the prepared polymer electrolyte has reached 8.83 × 10 ^-4 S·cm^-1 at room temperature. Thermogravimetry （TG） of the polymer electrolyte showed that the thermal stability was up to at least 150 ℃. The gel polymer electrolyte was further evaluated in electrochromic devices fabricated by transparent PET-ITO and electrochromically active viologen derivative films, and its excellent performance promised the usage of the gel polymer electrolyte as ionic conductor material in electrochrornic devices.     

Direct fabrication of conductive LB films composed of N-docosylpyridinium-TCNQ

Langmuir-Blodgett (LB) films of N-docosylpyridinium-TCNQ (NDP-TCNQ) were prepared in air. The films deposited at the room temperature showed in-plane conductivity of 4×10-3 S.cm-1 and its absorption spectra in UV and IR regions resembled those for the films composed of mixed-valence TCNQ salts of NDP-(TCNQ)2 rather than for the NDP-TCNQ LB films preparaed under protection of nitrogen. In the case that the films left in a warm environment after each dipping cycle, the absorption in the corresponding region changed. Spectral analysis and XPS study revealed that more TCNQ molecules were produced. The oxidation of TCNQ- in air was considered to be the origin of neutral TCNQ formed.     

Engineered Molecular Chain Ordering in Single‐Walled Carbon Nanotubes/Polyaniline Composite Films for High‐Performance Organic Thermoelectric Materials

Single‐walled carbon nanotubes (SWNTs)/polyaniline (PANI) composite films with enhanced thermoelectric properties were prepared by combining in situ polymerization and solution processing. Conductive atomic force microscopy and X‐ray diffraction measurements confirmed that solution processing and strong π–π interactions between the PANI and SWNTs induced the PANI molecules to form a highly ordered structure. The improved degree of order of the PANI molecular arrangement increased the carrier mobility and thereby enhanced the electrical transport properties of PANI. The maximum in‐plane electrical conductivity and power factor of the SWNTs/PANI composite films reached 1.44×10³ S cm^?1 and 217 μW m^?1 K^?2, respectively, at room temperature. Furthermore, a thermoelectric generator fabricated with the SWNTs/PANI composite films showed good electric generation ability and stability. A high power density of 10.4 μW cm^?2 K^?1 was obtained, which is superior to most reported results obtained in organic thermoelectric modules.     

Magnetic,optical and electrical properties of Mn-doped CuCrO<Subscript>2</Subscript> thin films prepared by chemical solution deposition method

CuCrO₂ and CuCrO₂:Mn thin films were prepared on sapphire substrates by chemical solution deposition method. The effects of the annealing temperatures and Mn concentration on the structural, electrical and optical properties were investigated. The X-ray diffraction measurement was used to confirm the c-axis orientation of CuCrO₂ and CuCrO₂:Mn thin films. The maximum transmittances of the films in the visible region are about 65% with direct band gaps of 3.25 eV. All films showed the p-type conduction and semiconductor behavior. The electrical conductivity decreases rapidly with the increase of Mn content, the maximum of the electrical conductivity of 1.35 × 10⁻² S cm⁻¹ is CuCrO₂ film deposited at 600 °C temperature in 10⁻³ Torr vacuum, which is about four orders of magnitude higher than that of the Mn-doped CuCrO₂ thin film. The energy band of the samples is constructed based on the grain-boundary scattering in order to investigate the conduction mechanism. Moreover, the samples exhibit a clear ferromagnetism, which was likely ascribed to originating from the double-exchange interaction between the Mn³⁺ and Cr³⁺ ions.