The first representative of a new class of charge transfer complexes in o-quinone series for organic semiconductors

The first representative of a new class of charge transfer complexes for organic semiconductors was synthesized. The reaction of p-nitroaniline (PNA) with [1,10]-phenanthroline-5,6-dione (PD) results in the formation of a stable molecular charge transfer (CT) complex PNA₃-PD₂ in a ratio of 3:2. The structure of the molecular CT complex PNA₃-PD₂ was established by X-ray diffraction studies. Using the density functional theory method, it is shown that several types of intermolecular interactions are realized in the complex: between the PNA amino group and the nitro group of another PNA molecule, carbonyl groups, and PD nitrogen atoms. Complex PNA₃-PD₂ is stable only in solid form. The diffuse reflectance UV–vis spectrum of PNA₃-PD₂ crystal powder is characterized by the intense weakly structured long-wavelength absorption band up to 650 nm. Quantum chemical calculations of the electronic structure have shown that the complex PNA₃-PD₂ is a straight-band semiconductor with a band gap of 2.11 eV.     

Effects of Y incorporation in TaON gate dielectric on electrical performance of GaAs metal–oxide–semiconductor capacitor

In this study, GaAs metal–oxide–semiconductor (MOS) capacitors using Y‐incorporated TaON as gate dielectric have been investigated. Experimental results show that the sample with a Y/(Y + Ta) atomic ratio of 27.6% exhibits the best device characteristics: high k value (22.9), low interfacestate density (9.0 × 10¹¹ cm^–2 eV^–1), small flatband voltage (1.05 V), small frequency dispersion and low gate leakage current (1.3 × 10^–5A/cm² at V_fb + 1 V). These merits should be attributed to the complementary properties of Y₂O₃ and Ta₂O₅:Y can effectively passivate the large amount of oxygen vacancies in Ta₂O₅, while the positively‐charged oxygen vacancies in Ta₂O₅ are capable of neutralizing the effects of the negative oxide charges in Y₂O₃. This work demonstrates that an appropriate doping of Y content in TaON gate dielectric can effectively improve the electrical performance for GaAs MOS devices.

Capacitance–voltage characteristic of the GaAs MOS capacitor with TaYON gate dielectric (Y content = 27.6%) proposed in this work with the cross sectional structure and dielectric surface morphology as insets.     

Interface formation of Al2O3 on n‐GaN(0001): Photoelectron spectroscopy studies

Al₂O₃ insulator layers were deposited step by step by the physical vapor deposition (PVD) method onto gallium nitride in the wurtzite form, n‐type and (0001)‐oriented. The substrate surface and the early stages of Al₂O₃/n‐GaN(0001) interface formation were characterized in situ under ultra‐high vacuum conditions by X‐ray and ultraviolet photoelectron spectroscopy (XPS, UPS). The electron affinity (EA) of the substrate cleaned by annealing was 3.6 eV. Binding energies of the Al 2p (76.0 eV) and the O 1s (532.9 eV) confirmed the creation of the Al₂O₃ compound in the deposited film for which the EA was 1.6 eV. The Al₂O₃ film was found to be amorphous with a bandgap of 6.9 eV determined from the O 1s loss feature. As a result, the calculated Al₂O₃/n‐GaN(0001) valence band offset (VBO) is ?1.3 eV and the corresponding conduction band offset (CBO) 2.2 eV.     

结晶氮化碳的制备与改性策略

石墨相氮化碳(g-C_3N_4)是最具代表性的二维有机聚合物半导体材料,其具有可见光响应性能、稳定化学结构和优良的生物相容性等优点,在环境和能源领域有非常广阔的应用前景。但是,普通g-C_3N_4材料的热聚合不完全,其体相和表面的缺陷多,因此光生载流子易复合,光催化活性不高。近年来,高活性结晶氮化碳(CCN)的研究得到了国内外学者的广泛关注。本文总结了目前CCN制备及其改性方法:5种代表性制备方法,包括传统熔盐法、预热熔盐法、固态盐法、溶剂法和质子化法;4种代表性CCN的改性方法,包括缺陷引入、形貌控制、单原子修饰和材料复合。文章重点介绍了 CCN制备原理、结构特征与光催化性能。最后,对CCN的制备与改性方法进行了评价,并对其研究方向进行了展望。     

Fe掺杂ZnTe团簇结构和磁性质

本文采用第一性原理密度泛函理论系统的研究了Fe原子单掺杂和双掺杂(ZnTe)12团簇的结构和磁性质。我们考虑了替代掺杂和间隙掺杂。不管是单掺杂还是双掺杂,间隙掺杂团簇都是最稳定结构。团簇磁矩主要来自Fe-3d态的贡献,4s 和4p 态也贡献了一小部分磁矩。由于轨道杂化,相邻的Zn和Te原子上也产生少量自旋。最重要的是,我们指出间隙双掺杂团簇是铁磁耦合,在纳米量子器件有潜在的应用价值。     

Electrical conductivity,optical properties and mechanical stability of 3, 4, 9, 10-perylenetetracarboxylic dianhidride based organic semiconductor

The 3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) doped polymer films were prepared with Polypyrrole (PPy) and Polyvinyl alcohol (PVA) polymers by solution-casting. The change in structure and chemical composition of samples was identified by XRD and FTIR respectively. The UV–visible spectroscopy demonstrates the optical characteristics and band gap properties of sample. The homogeneous morphology of sample for higher wt% of PTCDA was examined by atomic force microscopy (AFM). The differential scanning calorimetry (DSC) results demonstrate the decrease in melting temperature (T_m) and degree of crystallinity (χ_c%) of polymeric organic semiconductor. The mechanical property demonstrates the high tensile strength and improved plasticity nature. Impedance spectroscopy was evaluated to determine the conductivity response of polymeric organic semiconductor. The highest DC conductivity (2.08×10⁻³ S/m) was obtained for 10 wt% of PTCDA at 140 °C. The decrease in activation energy (E_a) represents the non-Debye process and was evaluated from the slope of ln σ_dc vs. 10³/T plot.     

A Combined Experimental and Theoretical Study on the Formation of Ag Filaments on β‐Ag2MoO4 Induced by Electron Irradiation

A combined experimental and theoretical study is presented to understand the novel observed nucleation and early evolution of Ag filaments on β‐Ag₂MoO₄ crystals, driven by an accelerated electron beam from an electronic microscope under high vacuum. The growth process, chemical composition, and the element distribution in these filaments are analyzed in depth at the nanoscale level using field‐emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM) with energy‐dispersive spectroscopy (EDS) characterization. To complement experimental results, chemical stability, structural and electronic aspects have been studied systematically using first‐principles electronic structure theory within a quantum theory of atoms in molecules (QTAIM) framework. The Ag nucleation and formation on β‐Ag₂MoO₄ are a result of structural and electronic changes of the AgO₄ tetrahedral cluster as a constituent building block of β‐Ag₂MoO₄, consistent with Ag metallic formation. The formation of Ag filament transforms the β‐Ag₂MoO₄ semiconductor from n‐ to p‐type concomitant with the appearance of Ag defects.     

丁胺包裹的CdSe量子点敏化的TiO2纳米晶薄膜电子转移机制

利用超快光谱技术系统研究了在丁胺包裹的CdSe量子点敏化的TiO₂纳米晶薄膜起始时刻界面间电子转移动力学。与之前的报道不同,该实验结果表明:CdSe量子点经过表面修饰后,两相电子注入机制--热电子和冷电子注入得以被证实,即:电子能分别从CdSe量子点导带中高的振动能级和导带底转移到TiO₂的导带。该机制详细描绘了电子在纳米界面间转移的图景。进一步研究发现:热电子注入的电子耦合强度(3.6±0.1 meV)比弛豫后的基态电子注入高两个数量级,基于Marcus理论,伴随着0.083 eV的重组能,冷电子注入的耦合强度值为~50 μeV。     

Impact of pressure on transport properties of AlGaN/GaN high electron mobility transistor

The properties of Al_xGa_1−xN/GaN high electron mobility transistor (HEMT) impacted by pressure are characterized quantitatively. The results indicate that the dislocation density increases as the critical thickness decreases with increasing pressure. The two-dimensional electron gas density was found to be linearly changeable with the pressure. A simulation has been completed to verify the influence of electron mobility. The results show that the misfit dislocation scattering induced by the pressure is a major limiting factor for the properties of HEMT.