Thin pyrite (FeS2) films prepared by thermal-sulfurating iron films at various temperatures

The structure and morphology of polycrystalline FeS₂ thin films prepared by sulfurating iron films sputtered on glass substrates are reported. The effect of sulfidation temperature on the formation of the FeS₂ thin films has been investigated under 80 kPa sulfur pressure and 20 h annealing time. There is a nearly complete transformation from iron into polycrystalline FeS₂ between 400–600°C sulfidation. Moreover, the film of 400°C sulfidation has approximate FeS₂ stoichiometrical composition and uniform microstructure. With tile increase in sulfidation temperature, the grain size and amount of FeS₂ crystallises increase.     

FeS2/RGO纳米复合材料的制备及热电池放电性能

以氯化亚铁、硫代硫酸钠和氧化石墨烯(GO)为原料, 采用水热法制备FeS₂/还原氧化石墨烯(RGO)纳米复合材料, 并采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、激光粒度分布仪和差热分析仪(DTA)等对FeS₂/RGO复合材料进行了表征。结果表明, 在水热反应过程中加入GO可以防止FeS₂颗粒的团聚, 使FeS₂形成疏松的球状颗粒。采用LiCl-KCl电解质, 在450℃以100mA/cm²电流密度放电时, 截止1.5 V时, FeS₂/RGO比容量为314.9 mAh/g, 较FeS₂高65.6 mAh/g; 采用LiF-LiCl-LiBr电解质, 在500℃以100 mA/cm²电流密度放电, 截止1.5 V时, FeS₂/RGO放电比容量为302.3 mAh/g, 较FeS₂高29.8 mAh/g。与FeS₂相比, 加入石墨烯提高了正极材料的导电性, 单体电池在放电过程中极化电阻相对较小, 使得FeS₂/RGO复合材料表现出较高的放电比容量。     

FeS2@C nanorods embedded in three-dimensional graphene as high-performance anode for sodium-ion batteries

FeS₂ has drawn tremendous attention as electrode material for sodium-ion batteries (SIBs) due to its high theoretical capacity and abundant resources. However, it suffers from severe volume expansion and dull reaction kinetics during the cycling process, leading to poor rate capacity and short cyclability. Herein, a well-designed FeS₂@C/G composite constructed by FeS₂ nanoparticles embedded in porous carbon nanorods (FeS₂@C) and covered by three-dimensional (3D) graphene is reported. FeS₂ nanoparticles can shorten the Na⁺ diffusion distance during the sodiation–desodiation process. Porous carbon nanorods and 3D graphene not only improve conductivity but also provide double protection to alleviate the volume variation of FeS₂ during cycling. Consequently, FeS₂@C/G exhibits excellent cyclability (83.3% capacity retention after 300 cycles at 0.5 A·g⁻¹ with a capacity of 615.1 mA·h·g⁻¹) and high rate capacity (475.1 mA·h·g⁻¹ at 5 A·g⁻¹ after 2000 cycles). The pseudocapacitive process is evaluated and confirmed to significantly contribute to the high rate capacity of FeS₂@C/G.     

Bimetallic sulfide FeS2@SnS2 as high-performance anodes for sodium-ion batteries

A novel hierarchical structure of bimetal sulfide FeS₂@SnS₂ with the 1D/2D heterostructure was developed for high-performance sodium-ion batteries (SIBs). The FeS₂@SnS₂ was synthesized through a hydrothermal reaction and a sulphuration process. The exquisite 1D/2D heterostructure is featured with 2D SnS₂ nanoflakes anchoring on the 1D FeS₂ nanorod. This well-designed FeS₂@SnS₂ provides shortened ion diffusion pathway and adequate surface area, which facilitates the Na⁺ transport and capacitive Na⁺ storage. Besides, the FeS₂@SnS₂ integrates the 1D/2D synthetic structural advantages and synthetic hybrid active material. Consequently, the FeS₂@SnS₂ anode exhibits high initial specific capacity of 765.5 mAh·g⁻¹ at 1 A·g⁻¹ and outstanding reversibility (506.0 mAh·g⁻¹ at 1 A·g⁻¹ after 200 cycles, 262.5 mAh·g⁻¹ at 5 A·g⁻¹ after 1400 cycles). Moreover, the kinetic analysis reveals that the FeS₂@SnS₂ anode displays significant capacitive behavior which boosts the rate capacity.     

Chemical bath deposition of indium sulphide thin films: preparation and characterization

Indium sulphide (In₂S₃) thin films have been successfully deposited on different substrates under varying deposition conditions using chemical bath deposition technique. The deposition mechanism of In₂S₃ thin films from thioacetamide deposition bath has been proposed. Films have been characterized with respect to their crystalline structure, composition, optical and electrical properties by means of X-ray diffraction, TEM, EDAX, optical absorption, TRMC (time resolved microwave conductivity) and RBS. Films on glass substrates were amorphous and on FTO (flourine doped tin oxide coated) glass substrates were polycrystalline ( phase). The optical band gap of In₂S₃ thin film was estimated to be 2.75 eV. The as-deposited films were photoactive as evidenced by TRMC studies. The presence of oxygen in the film was detected by RBS analysis.     

Microstructure, crystallinity, and properties of low-pressure MOCVD-grown europium oxide films

A study of growth, structure, and properties of Eu₂O₃ thin films were carried out. Films were grown at 500–600 °C temperature range on Si(1 0 0) and fused quartz from the complex of Eu(acac)₃·Phen by low pressure metalorganic chemical vapor deposition technique which has been rarely used for Eu₂O₃ deposition. These films were polycrystalline. Depending on growth conditions and substrates employed, these films had also possessed a parasitic phase. This phase can be removed by post-deposition annealing in oxidizing ambient. Morphology of the films was characterized by well-packed spherical mounds. Optical measurements exhibited that the bandgap of pure Eu₂O₃ phase was 4.4 eV. High frequency 1 MHz capacitance–voltage (C–V) measurements showed that the dielectric constant of pure Eu₂O₃ film was about 12. Possible effects of cation and oxygen deficiency and parasitic phase on the optical and electrical properties of Eu₂O₃ films have been briefly discussed.     

二氧化钒-1,4-双(苯并噁唑-2-基)萘复合薄膜及其热致变色和发光性能

二氧化钒(VO₂)是一种较理想的可用于调节室内温度的热致变色智能玻璃材料。然而,VO₂基智能玻璃涂层的应用一直受到其固有的令人不易接受的棕黄色等问题的限制。本文用1, 4-双(苯并噁唑-2-基)萘(KCB)与掺钨二氧化钒纳米颗粒制备了双层结构VO₂-KCB复合薄膜,其中有机荧光分子KCB层吸收太阳光中的紫外线,发出蓝绿色荧光,使复合薄膜在太阳光下呈现浅蓝色或蓝绿色,以改善VO₂薄膜固有的棕黄色。复合薄膜具有9%以上的太阳光调制能力ΔT_sol,可见光透过率T_lum大于73%,且具有较好防紫外性能。这些性能将非常有利于进一步拓展VO₂基智能玻璃涂层的实际应用。      

Excitons in self-organized layered perovskite films prepared by the two-step growth process

Thin films of microcrystalline (C₈H₁₇NH₃)₂PbBr₄ were prepared by a two-step growth process as follows: (1) deposition of PbBr₂ films on substrates and (2) self-organized growth of layered perovskite compounds by exposing the PbBr₂ film to C₈H₁₇NH₃Br vapor in a vacuum chamber. As-synthesized (C₈H₁₇NH₃)₂PbBr₄ films were characterized by using X-ray diffraction, temperature dependence in optical absorption and photoluminescence spectra. (C₈H₁₇NH₃)₂PbBr₄ films created by this synthesis approach were found to microcrystalline form, single phase and highly oriented with a c-axis perpendicular to the substrate surface. (C₈H₁₇NH₃)₂PbBr₄ films showed clear exciton absorption and photoluminescence even at room temperature in the near-ultraviolet region. Exciton binding energy of (C₈H₁₇NH₃)₂PbBr₄ was estimated about 200 meV.     

Field-emission characteristics of chemical vapor deposition-diamond films

Discontinuous and continuous diamond films with different morphologies and qualities were deposited on n²⁺-type Si(100) substrates, using the hot-filament chemical vapor deposition (CVD) technique from CH₄–H₂ gas mixtures. The field-emission characteristics of these diamond films were investigated. The turn-on fields at a 0.01mA/cm² current density were recorded for all the tested CVD-diamond films. It was found that discontinuous diamond films showed a much lower turn-on field (1.2 V/μm) than continuous ones (20 V/μm). The effective working function of continuous diamond films was around 0.1 eV, while that for discontinuous diamond films is about 0.03 eV. O₂ plasma post-deposition sharpening of thick diamond films indicated that the geometrical-field enhancement, caused by the surface topographic changes, has no significant influence on the turn-on field.     

Electronic structure of bulk and (0 0 1) surface layers of pyrite FeS2

The electronic structure of bulk and (0 0 1) surface layers of iron pyrite FeS₂ have been calculated using a modern ab initio pseudo-potential method. For the bulk pyrite the calculated lattice constant, position parameter of sulfur, and band gap are in agreement with experimental values. For the (0 0 1) surface it is found that surface states form a conducting band. The conducting band and the conducting band tail of the bulk conduction manifold overlap and the width of the band gap is not influenced by the surface state. The surface states arise mainly from the iron 3d orbitals in the topmost layer with a smaller contribution from the sulfur 3p states. The relaxation of iron and sulfur atoms is found to be greatest in the top most layer. The surface energy is calculated to be equal to 1.063 J/m².     

Comparative study of crystallization processes in Sb2Te3 films using laser and thermal annealing techniques

Adherent and pin-hole free amorphous Sb₂Te₃ thin films have been obtained by vacuum evaporation at substrate temperatures ≤25 °C. The films have been crystallized by thermal and laser annealing, and the crystallization processes monitored as a function of annealing temperature and laser scan speed. A comparative study of topography reveals disk-shaped crystallized areas in thermal crystallization and dendrite growth in the laser induced process. The crystallized films in both cases contain a single Sb₂Te₃ phase. Activation energy of 2 eV for crystallization, determined using differential scanning calorimetery indicates good room temperature stability of the amorphous states.     

Excimer laser deposition and characteristics of tin oxide thin films

ArF excimer laser assisted chemical vapor deposition of tin oxide thin films on Si was obtained using SnCl₄ and O₂ as precursors. Experimental measurements revealed that the deposition rate increases with incident laser energy density. The composition, structure and ultraviolet-to-visible spectra of the thin films were investigated by means of XPS, SEM, XRD and a UV–Vis techniques. It was shown that SnO₂ and SnOCl₂ coexisted in the thin films, and SnOCl₂ was almost completely converted into SnO₂ after annealing. The SnO₂ thin films deposited at room temperature were amorphous in structure and the grain size of the films became larger after annealing. The transmittance of the SnO₂ thin films is above 90%, the absorption edge is 355 nm and the energy gap is 3.49 eV.     

Cat-CVD-prepared oxygen-rich μc-Si:H for wide-bandgap material

Microcrystalline phase-involved oxygen-rich a-Si:H (hydrogenated amorphous silicon) films have been obtained using catalytic chemical vapor deposition (Cat-CVD) process. Pure SiH₄ (silane), H₂ (hydrogen), and O₂ (oxygen) gases were introduced in the chamber by maintaining a pressure of 0.1 Torr. A tungsten catalyzer was fixed at temperatures of 1750 and 1950 °C for film deposition on glass and crystalline silicon substrates at 200 °C. As revealed from X-ray diffraction spectra, the microcrystalline phase appears for oxygen-rich a-Si:H samples deposited at a catalyzer temperature of 1950 °C. However, this microcrystalline phase tends to disappear for further oxygen incorporation. The oxygen content in the deposited films was corroborated by FTIR analysis revealing SiOSi bonds and typical SiH bonding structures. The optical bandgap of the sample increases from 2.0 to 2.7 eV with oxygen gas flow and oxygen incorporation to the deposited films. In the present thin film deposition conditions, no strong tungsten filament degradation was observed after a number of sample preparations.     

Highly conductive microcrystalline silicon carbide films deposited by the hot wire cell method and its application to amorphous silicon solar cells

Microcrystalline silicon carbide (μc-Si_1−xC_x) films were successfully deposited by the hot wire cell method using a gas mixture of SiH₄, H₂ and C₂H₂. It was confirmed by Fourier transform infrared and X-ray diffraction analyses that the films consisted of μc-Si grains embedded in a-Si_1−xC_x tissue. The p-type μc-Si_1−xC_x films were deposited using B₂H₆ as a doping gas. A dark conductivity of 0.2 S/cm and an activation energy of 0.067 eV were obtained. The p-type μc-Si_1−xC_x was used as a window layer of a-Si solar cells, in which the intrinsic layer was deposited by photo-chemical vapor deposition, and an initial conversion efficiency of 10.2% was obtained.     

简单的溶胶–凝胶法制备致密的铜锌锡硫硒薄膜

采用溶胶–凝胶后硒化法制备了铜锌锡硫硒薄膜, 其薄膜表面平整、无裂纹。通过简化铜锌锡硫前驱体溶胶的制备以及后退火时避免使用硫化氢气体（H₂S）等方法使铜锌锡硫硒薄膜的制备工艺得到简化。选用低毒有机物乙二醇为溶剂,Cu(CH₃COO)₂、Zn(CH₃COO)₂、SnCl₂•2H₂O和硫脲为原料, 制备铜锌锡硫前驱体溶胶。XRD、Raman、EDX和SEM 分析表明制备的铜锌锡硫硒薄膜为锌黄锡矿结构, 所有薄膜均贫铜富锌, 用0.2 g硒粉、硒化20 min得到的铜锌锡硫硒薄膜其结晶较好, 表面晶粒可达1.0 μm左右。透射光谱分析结果表明, 随硒含量的增加, 铜锌锡硫硒薄膜的光学带隙从1.51 eV减小到1.14 eV。     

Preparation of Aluminum Nitride Thin Films by CVD

AlN films were prepared by CVD using aluminum halide (AlCl₃) and aluminum alkyl ((CH₃)3Al) precursors. The appropriate deposition conditions to obtain polycrystalline AlN films using A1C1₃ precursor were found at T_dep = 1173 K, P_tot = 66.6 Pa and N₂/NH₃ = 0.75. It was found that AlN films of different crystallinity can be obtained from (CH₃)₃Al precursor at T_de = 973-1023 K, P_tot = 1.99 kPa, only under a H₂ atmosphere. AlN films can be grown highly oriented in the (210) direction on amorphous quartz substrates depending on their thicknesses. The 0.1 -0.2 μm thick AlN films were transparent and their refractive indexes were about 1.4-1.6.     

Preparation and characterization of chemically deposited PbSnS3 thin films

High-quality and well-reproducible PbSnS₃ thin films have been prepared by a simple and inexpensive chemical-bath deposition method from an aqueous medium, using thioacetamide as a sulphide ion source. X-ray diffraction analysis of the deposited films revealed that the as-deposited films were amorphous, however, an amorphous-to-crystalline phase transition was observed as the result of thermal annealing at 425 K for 1 h. The X-ray structure analysis of the collected powder from the bath annealed at 425 K for 1.5 h revealed an orthorhombic phase.

Analysis of the optical absorption data of crystalline PbSnS₃ films revealed that both direct and indirect optical transitions exist in the photon energy range 1.24–2.48 eV with optical band gaps of 1.68 and 1.42 eV, respectively. However, a forbidden direct optical transition with a band gap value of 1.038 eV dominates at low energy (<1.24 eV). The refractive index changes from 3.38 to 2.16 in the range 500–1300 nm. The high frequency dielectric constant and the carrier concentration to the effective mass ratio calculated from the refractive index analysis were found to be 4.79 and 2.3×10²⁰ cm⁻³, respectively. The temperature dependence of the electrical resistivity of the deposited films follows the semiconductor behaviour with extrinsic and intrinsic conduction. The determined activation energies range are 0.35–0.42 and 0.76–85 eV, respectively.     

Properties of tantalum oxide thin films grown by atomic layer deposition

Thin tantalum oxide films were deposited using atomic layer deposition from TaCl₅ and H₂O at temperatures in the range 80–500 °C. The films deposited at temperatures below 300 °C were predominantly amorphous, whereas those grown at higher temperatures were polycrystalline containing the phases TaO₂ and Ta₂O₅. The oxygen to tantalum mass concentration ratio corresponded to that of TaO₂ at all growth temperatures. The optical band gap was close to 4.2 eV for amorphous films and ranged from 3.9 to 4.5 eV for polycrystalline films. The refractive index measured at λ = 550 nm increased from 1.97 to 2.20 with an increase in growth temperature from 80 to 300 °C. The films deposited at 80 °C showed low absorption with absorption coefficients of less than 100 cm⁻¹ in the visible region.     

Synthesis and characterization of p-type transparent conducting CuAlO2 thin film by DC sputtering

P-type transparent conducting thin films of copper aluminium oxide were prepared by DC sputtering of polycrystalline CuAlO₂ target, which was fabricated by heating a stoichiometric mixture of Cu₂O and Al₂O₃ at 1375 K for 24 h. Thin films of CuAlO₂ were deposited on Si (4 0 0) and glass substrates. The sputtering was performed in Ar+O₂ (40 vol.%) atmosphere and the substrate temperature was 453 K. X-ray diffraction spectra of the films showed the peaks that could be assigned with those of the crystalline CuAlO₂. Fourier transform infrared spectra showed Cu---O, Al---O, O---Cu---O bonding. UV–Vis–NIR spectrophotometric measurement showed high transparency of the films in the visible region. Both direct and indirect band gaps were found to exist and their corresponding estimated values were 3.66 and 2.1 eV, respectively. The room temperature conductivity of the film was fairly high and was of the order of 0.08 S cm⁻¹, while the activation energy was 0.26 eV. Thermoelectric power measurement indicated positive value of Seebeck coefficient and its room temperature value was +128 μV K⁻¹. Positive value of Hall coefficient (R_H=+16.7 cm³ C⁻¹) also confirmed p-type conductivity of the films.     

Indium doped zinc oxide thin films obtained by electrodeposition

Indium doped ZnO thin films were obtained by co-electrodeposition (precursor and dopant) from aqueous solution. XRD analysis showed typical patterns of the hexagonal ZnO structure for both doped and undoped films. No diffraction peaks of any other structure such as In₂O₃ or In(OH)₃ were found. The incorporation of In into the ZnO film was verified by both EDS and XPS measurements. The bandgap energy of the films varied from 3.27 eV to 3.42 eV, increasing with the In concentration in the solution. This dependence was stronger for the less cathodic potentials. The incorporation of In into the film occurs as both, an In donor state in the ZnO grains and as an amorphous In₂O₃ at the grain boundaries.