Effect of Mg doping on optical and electrical properties of SnO2 thin films: An experiment and first-principles study

Transparent Mg-doped p-type conductive SnO₂ thin films were fabricated on quartz substrates by sol–gel method. Effect of Mg doping on structural, morphological, optical, and electrical properties of SnO₂ films were investigated. A single phase of tetragonal rutile structure was observed in Mg-doped SnO₂ films. The optical bandgap energy of the Mg-doped SnO₂ films showed a systematical redshift with respect to the undoped SnO₂ film, and the resistivity significantly increased with the increase of Mg concentration. A conduction type transform from n to p was also observed. The strong ultraviolet and comparatively weak blue/green emissions were observed in room temperature photoluminescence, suggesting the dipole-forbidden rule of bulk SnO₂ is broken in Mg-doped SnO₂ films. These results were supported by first-principles electronic structure calculations.     

Growth and electrical properties of high-Curie point rhombohedral Mn-Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 thin films

High-quality ternary relaxor ferroelectric (100)-oriented Mn-doped 0.36Pb(In_1/2Nb_1/2)O₃-0.36Pb(Mg_1/3Nb_2/3)O₃-0.28PbTiO₃ (Mn-PIMNT) thin films were grown on SrRuO₃-buffered SrTiO₃ single-crystal substrate in a wide deposition temperature range of 550-620°C using the pulsed laser deposition method. The phase structure, ferroelectric, dielectric, piezoelectric properties, and nanoscale domain evolution were studied. Under the deposition temperature of 620°C, the ferroelectric hysteresis loops and current-voltage curves showed that the film owned significantly enhanced remnant ferroelectric polarization of 34.5 μC/cm² and low leakage current density of 2.7 × 10⁻¹⁰ A/cm². Moreover fingerprint-type nanosized domain patterns with polydomain structures and well-defined macroscopic piezoelectric properties with a high normalized strain constant of 40 pm/V was obtained. Under in situ DC electric field, the domain evolution was investigated and 180° domain reversal was observed through piezoelectric force microscope. These global electrical properties make the current Mn-PIMNT thin films very promising in piezoelectric MEMS applications.     

Preparation and characterization of heteroepitaxial Zn2SnO4 single crystalline films prepared on MgO (100) substrates

Zinc stannate (Zn₂SnO₄) films were deposited on MgO (100) substrates by pulsed laser deposition, and Zn₂SnO₄ monocrystalline films were obtained by postannealing process. The structures, surface morphologies, and optical properties of the Zn₂SnO₄ films annealed at different temperatures were investigated in detail. Crystal structure analyses showed that the film annealed at 800°C was single crystal Zn₂SnO₄ with an inverse-spinel structure. The heteroepitaxial mechanism was further clarified by a schematic diagram, and the epitaxial relationships between the film and substrate were Zn₂SnO₄ (400) || MgO (200) with Zn₂SnO₄ [001] || MgO [001]. The obtained Zn₂SnO₄ films exhibited excellent transparency. The optical band gap of the 800°C-annealed Zn₂SnO₄ film was about 3.97 eV. The extinction coefficients and refractive indexes of the Zn₂SnO₄ films annealed at different temperatures as a function of wavelength were analyzed in detail.     

Microstructure,optical and electrical properties of sputtered HfTiO high-k gate dielectric thin films

The microstructure, optical and electrical properties of HfTiO high-k gate dielectric thin films deposited on Si substrate and quartz substrate by RF magnetron sputtering have been investigated. Based on analysis from x-ray diffraction (XRD) measurements, it has been found that the as-deposited HfTiO films remain amorphous regardless of the working gas pressure. Meanwhile, combined with characterization of ultraviolet-visible spectroscopy (UV–vis) and spectroscopy ellipsometry (SE), the deposition rate, band gap and optical properties of sputtered HfTiO gate dielectrics were determined. Besides, by means of the characteristic curves of high frequency capacitance–voltage (C–V) and leakage current density–voltage (J–V), the electrical parameters, such as permittivity, total positive charge density, border trap charge density, and leakage current density, have been obtained. The leakage current mechanisms are also discussed. The energy band gap of 3.70 eV, leakage current density of 1.39×10⁻⁵ A/cm² at bias voltage of 2 V, and total positive charge density and border trap charge density of 9.16×10¹¹ cm⁻² and 1.3×10¹¹ cm⁻², respectively render HfTiO thin films deposited at 0.6 Pa, potential high-k gate dielectrics in future CMOS devices.     

正八面体锡酸锌的水热合成

用醋酸锌和亚锡酸钠作为原料,锌锡物质的量比为2∶1,反应体系中有矿化剂氢氧化钠存在,用水热合成方法,在180~220 ℃水热反应10~48 h,成功制备出正八面体纯锡酸锌晶体。用X射线衍射（XRD）、扫描电镜 （SEM）对产物进行了表征。研究了介质的酸碱性、原料配比、反应温度、反应时间等因素对产物合成的影响。     

Modified electrical properties of chemical solution deposited epitaxial BiFeO3 thin films by Mn substitution

The effect of Mn substitution on microstructure and electrical properties of epitaxial BiFeO₃ (BFO) thin films grown by an all-solution approach was investigated. Raman analysis reveals that the Mn atoms substitution at Fe sites can result in Jahn-Teller distortion and thus lead to the weakness of long-range ferroelectric order. In addition, the break-down characteristics of BFO thin films are improved with the increase of Mn atoms content, although the leakage current is gradually increased. Meanwhile, the grain size, the dielectric constant and loss are also increased with the increase of Mn content. The P-E hysteresis loops and PUND results demonstrate that the intrinsic ferroelectric polarization is effectively improved with Mn atoms substitution as the grain size increased and Mn atoms play a role of nucleation sites. However, the ferroelectric properties are deteriorated with the excess substituted Mn content due to the higher leakage current.     

固体酸SO4^2-/SnO2催化合成DOP的研究

采用自制的固体酸SO4^2-/SnO2为催化剂合成DOP，分别考察了催化剂用量、醇酐比、反应时间等对合成DOP的影响。实验表明，在DOP的合成中最佳的合成条件是：采用14g的SO4^2-/SnO2催化剂／mol（苯酐），醇酐比为2.35：1，反应时间为3．5h，其酯化率可达91％以上。SO4^2-/SnO2作为该反应的催化剂具有催化活性高、寿命长、可多次重复使用、产物易纯化分离、且产品色泽浅等优点，可望代替传统浓硫酸作催化剂应用于DOP的合成。     

二氧化锡薄膜的制备和应用研究进展

介绍了近年来二氧化锡薄膜的制备方法和在功能材料中的应用。探讨了各种方法的特点,提出了今后二氧化锡薄膜的发展趋势和应用前景。     

Effect of substrate temperature on microstructure and optical properties of nanocrystalline alumina thin films

Aluminum oxide (Al₂O₃) thin films were deposited on silicon (100) and quartz substrates by pulsed laser deposition (PLD) at an optimized oxygen partial pressure of 3.0×10^?3 mbar in the substrate temperatures range 300–973 K. The films were characterized by X-ray diffraction, transmission electron microscopy, atomic force microscopy, spectroscopic ellipsometry, UV–visible spectroscopy and nanoindentation. The X-ray diffraction studies showed that the films deposited at low substrate temperatures (300–673 K) were amorphous Al₂O₃, whereas those deposited at higher temperatures (≥773 K) were polycrystalline cubic γ-Al₂O₃. The transmission electron microscopy studies of the film prepared at 673 K, showed diffuse ring pattern indicating the amorphous nature of Al₂O₃. The surface morphology of the films was examined by atomic force microscopy showing dense and uniform nanostructures with increased surface roughness from 0.3 to 2.3 nm with increasing substrate temperature. The optical studies were carried out by ellipsometry in the energy range 1.5–5.5 eV and revealed that the refractive index increased from 1.69 to 1.75 (λ=632.8 nm) with increasing substrate temperature. The UV–visible spectroscopy analysis indicated higher transmittance (>80%) for all the films. Nanoindentation studies revealed the hardness values of 20.8 and 24.7 GPa for the films prepared at 300 K and 973 K respectively.     

Effect of substrate temperature on structural and electrical properties of BaZr0.2Ti0.8O3 lead-free thin films by pulsed laser deposition

Barium zirconate titanate (BaZr_0.2Ti_0.8O₃, BZT) 250 nm thick thin films were fabricated by pulsed laser deposition and the influence of the substrate temperature on their preferred orientation, microstructure, morphology and dielectric properties was investigated. Dielectric measurements indicated the (1 1 0)-oriented BZT thin films deposited at 750 °C to show good dielectric properties with high dielectric constant (~500 at 100 kHz), low loss tangent (<0.01 at 100 kHz), and superior tunability (>70% at 400 kV/cm), while the largest figure of merit was 78.8. The possible microstructural background responsible for the high dielectric constant and tenability is discussed. In addition, thin films deposited at 750 °C with device quality factor of 8738 and dielectric nonlinearity coefficient of 1.66×10⁻¹⁰ J/C⁴m⁵ were demonstrated.     

Structural,optical and morphological evolution of Ga2O3/Al2O3 (0001) films grown at various temperatures by pulsed laser deposition

This study systematically investigated the structural, optical, and morphological evolution of Gallium oxide (Ga₂O₃) films deposited at different substrate temperatures on Al₂O₃(0001) using pulsed laser deposition (PLD). The thickness of the Ga₂O₃ films was standardized in order to eliminate its effect on the film properties. The effect of substrate temperature from room temperature to 600 °C on the film's transmittance, crystalline structure, chemical composition and surface morphology, was explored. The plasma species generated during the deposition of the PLD process were monitored and analyzed employing in situ optical emission spectroscopy. The deposition rate of the films decreased with increasing substrate temperature. X-ray photoelectron spectroscopy was used to detect both Ga³⁺ and Ga ⁺ oxidation states in all prepared films, which indicated substoichiometric Ga₂O₃ films deficient in oxygen. The percentage of non-lattice oxygen decreased with increasing substrate temperature. At optimal condition, mono-crystaline β-Ga₂O₃ was produced with a high visible and near-infrared transmittance, large grain size and smooth surface, which is suitable for the application in high-performance power electric devices and photoelectronic devices.     

Fabrication and electrical properties of Bi2-xSbxTe3 ternary nanopillars array films

Highly oriented Bi_2-xSb_xTe₃ (x?=?0, 0.7, 1.1, 1.5, 2) ternary nanocrystalline films were fabricated using vacuum thermal evaporation method. Microstructures and morphologies indicate that Bi_2-xSb_xTe₃ films have pure rhombohedral phase with well-ordered nanopillars array. Bi, Sb and Te atoms uniformly distributed throughtout films with no precipitation. Electrical conductivity of Bi_2-xSb_xTe₃ films transforms from n-type to p-type when x?>?1.1. Metal-insulator transition was observed due to the incorporation of Sb in Bi₂Te₃. Bi_2-xSb_xTe₃ film with x?=?1.5 exhibits optimized electrical properties with maximum electrical conductivity σ of 2.95?×?10⁵ S?m^?1 at T?=?300?K, which is approximately ten times higher than that of the undoped Bi₂Te₃ film, and three times higher than previous report for Bi_0.5Sb_1.5Te₃ films and bulk materials. The maximum power factor PF of Bi_0.5Sb_1.5Te₃ nanopillars array film is about 3.83?μW?cm^?1 K^?2 at T?=?475?K. Highly oriented (Bi,Sb)₂Te₃ nanocrystalline films with tuned electronic transport properties have potentials in thermoelectric devices.     

ZnO负载SnO2复合材料的制备及其气敏性能

以五水四氯化锡（SnCl₄·5H₂O）和乙酸锌[Zn （AC）₂·2H₂O]为原料,氢氧化钠（NaOH）为沉淀剂,采用简单的水热法,使二氧化锡（SnO₂）纳米颗粒锚定在蚕蛹状氧化锌（ZnO）表面,一步成功合成了二氧化锡/氧化锌（SnO₂/ZnO）复合材料。采用X射线衍射仪（XRD）、透射电镜（TEM）、高分辨透射电镜（HRTEM）和氮气吸附脱附仪（BET）对材料的结构和形貌进行了表征,研究并讨论了温度、乙醇浓度等因素对SnO₂、ZnO及SnO₂/ZnO复合材料气敏性能的影响。结果表明,所得样品为SnO₂纳米颗粒与蚕蛹状ZnO的复合物,SnO₂纳米颗粒较均匀地负载在ZnO表面。SnO₂/ZnO复合材料气敏元件在最佳工作温度为240℃时,对200μL/L乙醇的灵敏度达到39.68,与SnO₂（24.53）及ZnO （17.8）相比,气敏性能得到了很大的提高。     

Influence of growth temperature on the microstructure and electrical transport properties of epitaxial NiCo2O4 thin films

In the work reported here, NiCo₂O₄ films were grown epitaxially on LaAlO₃ (111) substrates at temperatures between room temperature and 700?°C. The effects of the substrate temperature (T_sub) on the structural, electrical and magnetic properties and on the Hall effect of the film were investigated. T_sub has a great influence on the cation disorder. High T_sub makes substitution of Ni (Oh) for Co (Td) easier, and changes the relative Ni³⁺/Co³⁺ concentration. The film grown at 400?°C had a relatively larger concentration of Ni³⁺, which lowers the resistivity and enhances the ferrimagnetism of the NiCo₂O₄ film. In addition, a sign change in the Hall coefficient from negative to positive was observed with increasing measurement temperature for each of the samples grown at different substrate temperatures.     

Dispersive optical constants and electrical properties of nanocrystalline CuInS2 thin films prepared by chemical spray pyrolysis

Nanocrystalline CuInS₂ thin films were deposited on borosilicate glass substrates via chemical spray pyrolysis method. The structural, morphological, optical, and electrical properties were studied as a function of increasing annealing temperature from 250 to 350 ̊C. XRD analysis showed mixed phases at lower temperatures with the preferred orientation shifting towards the (112) chalcopyrite CuInS₂ plane at higher substrate temperature. The crystallite size increased slightly between 13 and 18 nm with increase in annealing temperature. The optical band gap was determined on basis of Tauc extrapolation method and the Wemple–Di-Domenico single oscillator model. Possible structural and quantum confinement effect may have resulted in relatively larger band gaps of 1.67–2.04 eV, relative to the bulk value of 1.5 eV. The presence of Cu_xS in the as-deposited and wurtzite peaks after annealing at 350 ^̊C play a role in influencing the optical and electrical properties of CuInS₂ thin films.     

Growth and optical properties of large-scale MoS2 films with different thickness

The synthesis of large-scale molybdenum disulfide (MoS₂) with high quality is highly desirable for the promising applications in flexible optoelectronic devices. Here, we report a feasible one-step chemical vapor deposition (CVD) synthesis of continuous MoS₂ films with different layer-number via adjusting the growth temperature in the range of 740–800 °C. Influences of the annealing treatments at diverse temperature ranging from 300 to 500 °C on Raman and PL spectra of the monolayer MoS₂ film grown at 780 °C are reported. PL characterization shows that the PL emission of film annealed at 400 °C exhibits highest intensity with a blue-shift in comparison to that of the pristine film grown at 780 °C. The PL fluctuation of the MoS₂ film annealed at 400 °C is mainly originated from the high crystalline quality and strain-release. This study sheds a light on growth and performance optimization of the large-area two-dimensional transition metal dichalcogenides films.     

碳量子点修饰g-C3N4/SnO2复合材料光催化性能

以四氯化锡五水合物、乙二醇和氨水为原料,在微波辅助水热条件下快速合成氧化锡纳米颗粒,以尿素 为前体在马弗炉中退火得到g-C₃N₄,使用柠檬酸和乙二胺为原料水热合成碳量子点。室温下,将碳量子点/ g-C₃N₄/SnO₂在通风橱中进行搅拌得到碳量子点负载的氮化碳/氧化锡复合材料。通过透射电子显微镜（TEM）、 X射线衍射（XRD）、氮气吸附-解吸等温线（BET）、紫外-可见分光光度计（UV-vis）、电子自旋（顺磁）共振波谱仪（ESR）对复合材料的形貌、结构特征、吸光度和光催化过程中的活性物质等进行表征和分析,并通过在紫外光下降解罗丹明B（RhB）测试样品的光催化性能。试验结果表明,紫外-可见分光光谱吸收边缘的红移说明碳量子点负载后能提高复合材料在可见光区域的响应,光催化试验表明碳量子点负载能提高g-C₃N₄/SnO₂复合材料的光催化性能,当碳量子点负载量为7%时复合材料的降解效率最高,在3h内对RhB的降解效率为97%。此外,微波辅助水热法能在短时间内大量合成氧化锡纳米颗粒,且氧化锡纳米颗粒具有较小的晶粒尺寸（8.5nm）,可以高效制备并应用于环保领域。     

Effect of Ni doping on the structural,electrical, and optical properties of transparent CuCrO2 films grown using pulsed laser deposition

In this study, the structural, electrical, and optical properties of CuCr_1?xNi_xO₂ epitaxial films (x?=?0, 0.01, 0.03, 0.05), which exhibited p-type properties, were investigated. The (001)-oriented epitaxial films were deposited on c-plane α-Al₂O₃ substrates using pulsed laser deposition at a growth temperature of 700?°C and oxygen pressure of 10 mTorr. The optical energy band gap of the CuCr_0.95Ni_0.05O₂ film was determined to be 3.22?eV. The hole carrier concentration of the CuCrO₂ film increased from 5.1?×?10¹⁴ to 2.2?×?10¹⁷ cm^?3 upon doping with 5?at% Ni. Based on Hall measurement and X-ray photoelectron spectroscopy results, it was suggested that the substituted Ni²⁺ dopants at Cr³⁺ sites formed an acceptor level without any charge compensation with Cu²⁺ and/or Cr⁴⁺.     

Dielectric and ferroelectric properties of multilayer BaTiO3/NiFe2O4 thin films prepared by solution deposition technique

In this work different lead-free multilayered structures, composed of perovskite BaTiO₃ and spinel NiFe₂O₄ thin layers, were obtained by solution deposition method. Structural characterization of the sintered thin films confirmed the well-defined layered structure with overall thickness from 160 to 600 nm, crystalline nature of perovskite BaTiO₃ and spinel NiFe₂O₄ phases without secondary phases (after sintering below 900 °C) and grains on nanometer scale. Dielectric properties of the multiferroic multilayer BaTiO₃/NiFe₂O₄ thin films were analyzed in temperature and frequency range from 30 °C to 200 °C and 100 Hz to 1 MHz, respectively. In comparison to the pure BaTiO₃ films, the introduction of ferrite layer reduces dielectric response and increases low frequency permittivity dispersion of the multilayer thin films. The multilayer samples have shown relatively low dielectric loss with stronger contribution of conductivity at higher temperatures, and characteristic broad peak representing “relaxation” of the interface charge accumulation.