升华法生长AlN体单晶初探

研究了高温升华法(PVT)生长AlN体单晶的技术和材料的性质.使用陶瓷BN坩埚,加热温度约在1900℃左右,生长结果为AlN晶须或致密多晶,难以生长出较大的AlN晶粒.用钨坩埚加热生长温度达到2200℃左右时,在AlN陶瓷片和6H-SiC片上生长了直径22mm的AlN晶体,最大的晶粒尺寸长10mm、直径5mm.利用X射线粉末衍射分析了几种不同AlN样品的结构和组成.讨论了PVT法生长AlN晶体所涉及的化学热力学过程和现象.     

An Analysis of Consumer Preferences among Wireless LAN and Mobile Internet Services

Wireless data communication (WDC) services are increasingly penetrating the market. The two main alternative WDC technologies are wireless LAN and mobile Internet. Services based on these technologies display differences in quality attributes such as terminal device, data transmission speed, pricing scheme and so on. How consumers choose between these two alternatives will be determined by their preferences regarding such quality attributes. In turn, their preferences will affect the evolution of WDC services and related technologies. This study employs a conjoint analysis of consumer valuations of quality attributes of wireless LAN and mobile Internet services. Respondents rate hypothetical service alternatives featuring various combinations of quality attributes. By estimating consumer willingness to pay for the attributes of WDC services, the authors predict the evolution of WDC services and related technologies along various quality dimensions, make a comparison with the results of a previous study, and draw policy implications for national‐and company‐level R&D strategies.     

Complementary Absorbing Star‐Shaped Small Molecules for the Preparation of Ternary Cascade Energy Structures in Organic Photovoltaic Cells

Two anthracene‐based star‐shaped conjugated small molecules, 5′,5″‐(9,10‐bis((4‐hexylphenyl)ethynyl)anthracene‐2,6‐diyl)bis(5‐hexyl‐2,2′‐bithiophene), HBantHBT, and 5′,5″‐(9,10‐bis(phenylethynyl)anthracene‐2,6‐diyl)bis(5‐hexyl‐2,2′‐bithiophene), BantHBT, are used as electron‐cascade donor materials by incorporating them into organic photovoltaic cells prepared using a poly((5,5‐E‐alpha‐((2‐thienyl)methylene)‐2‐thiopheneacetonitrile)‐alt‐2,6‐[(1,5‐didecyloxy)naphthalene])) (PBTADN):[6,6]‐phenyl‐C71‐butyric acid methyl ester (PC₇₁BM) blend. The small molecules penetrate the PBTADN:PC₇₁BM blend layer to yield complementary absorption spectra through appropriate energy level alignment and optimal domain sizes for charge carrier transfer. A high short‐circuit current (J_SC) and fill factor (FF) are obtained using solar cells prepared with the ternary blend. The highest photovoltaic performance of the PBTADN: BantHBT :PC₇₁BM blend solar cells is characterized by a J_SC of 11.0 mA cm^?2, an open circuit voltage (V_OC) of 0.91 V, a FF of 56.4%, and a power conversion efficiency (PCE) of 5.6% under AM1.5G illumination (with a high intensity of 100 mW^?2). The effects of the small molecules on the ternary blend are investigated by comparison with the traditional poly(3‐hexylthiophene) (P3HT):[6,6]‐phenyl‐C61‐butyric acid methyl ester (PC₆₁BM) system.     

Enhanced electromagnetic transmission through a slit surrounded by rectangular grooves

Electromagnetic transmission through a slit surrounded by rectangular grooves in a conducting plane is investigated. An electromagnetic boundary-value problem associated with a slit surrounded by rectangular grooves in a conducting plane is rigorously solved based on the Fourier transform, eigenfunction expansion and mode matching method. The transmission coefficient through the slit is represented in a series. Computation is performed to illustrate the effect of the groove geometry on the transmission behaviours.     

锇在甲酸体系抛光液中化学机械抛光研究

基于金属锇有可能成为大规模集成电路铜互连扩散阻挡层新材料,利用自制的甲酸(HCOOH)体系抛光液对金属锇进行了化学机械抛光研究,利用原子力显微镜(AFM)观察抛光后锇的表面形貌。采用电化学分析方法研究双氧水(H2O2)、HCOOH和苯丙三氮唑(BTA)对样品腐蚀效果的影响。结果表明:当抛光液中仅含H2O2时,金属锇表面腐蚀不明显;而在H2O2-HCOOH体系中,H2O2浓度的增加可使金属锇表面的腐蚀速度明显加快,但不利于金属锇表面钝化膜的形成;缓蚀剂BTA的加入促进了金属锇表面钝化膜的生成,降低了抛光速率,但同时提高了金属锇的表面质量,表面粗糙度Ra由8.0 nm降低到4.2 nm。     

结合空间域与变换域特征提取的盲立体图像质量评价

针对立体图像质量预测准确性不足的问题,该文提出了一种结合空间域和变换域提取质量感知特征的无参考立体图像质量评价模型。在空间域和变换域分别提取输入的左、右视图的自然场景统计特征,并在变换域提取合成独眼图的自然场景统计特征,然后将其输入到支持向量回归(SVR)中,训练从特征域到质量分数域的预测模型,并以此建立SIQA客观质量评价模型。在4个公开的立体图像数据库上与一些主流的立体图像质量评价算法进行对比,以在LIVE 3D Phase I图像库中的性能测试为例,Spearman秩相关系数、皮尔逊线性相关系数和均方根误差分别达到0.967,0.946和5.603,验证了所提算法的有效性。     

Electrically Reconfigurable 3D Spin-Orbitronics

The explosive demands of storage capacity and the von Neumann bottleneck of modern computer architectures trigger many innovations in information technology. Amongst them, nonvolatile spintronics attract considerable attentions for which can embed the computation capability into memory, enable neuromorphic, and probabilistic computing. These exciting progresses typically rely on the manipulation of the relative magnetization orientations of two magnetic layers. By extending to 3D spintronic architectures made of multiple magnetic layers (n), the exponentially increased 2ⁿ magnetic states can provide ample opportunities for implementing novel spintronic functionalities. Here, through building perpendicularly magnetized 3D spin-orbitronic architectures – [Pt/Fe_1−xTb_x/Si₃N₄]_n multilayers, it is demonstrated the electrical programing of 2ⁿ memory states via current-induced spin–orbit torques (SOTs), and the accompanied reconfigurable multifunction in-memory logic features in a single four-terminal Hall device. Further, an electrical readout of these 2ⁿ states, together with the implementation of Boolean logic gates and digital circuitry such as 2–4 and 3–8 decoders, are successfully conducted. More complex logic circuits are also envisioned. The experiments thus substantiate 3D spin-orbitronic structures as a promising platform for exponentially boosting the storage capacity and accommodating in-memory computing that can be important for promoting the emerging 3D nanospintronics.     

High Mobility 3D Dirac Semimetal (Cd3As2) for Ultrafast Photoactive Terahertz Photonics

The Dirac semimetal cadmium arsenide (Cd₃As₂), a 3D electronic analog of graphene, has sparked renewed research interests for its novel topological phases and excellent optoelectronic properties. The gapless nature of its 3D electronic band facilitates strong optical nonlinearity and supports Dirac plasmons that are of particular interest to realize high-performance electronic and photonic devices at terahertz (1 THz = 4.1 meV) frequencies, where the performance of most dynamic materials are limited by the tradeoff between power-efficiency and switching speed. Here, all-optical, low-power, ultrafast broadband modulation of terahertz waves using an ultrathin film (100 nm, λ/3000) of Cd₃As₂ are experimentally demonstrated through active tailoring of the photoconductivity. The measurements reveal the photosensitive metallic behavior of Cd₃As₂ with high terahertz electron mobility of 7200 cm² (Vs)⁻¹. In addition, optical fluence dependent ultrafast charge carrier relaxation (15.5 ps), terahertz mobility, and long momentum scattering time (157 fs) comparable to superconductors that invoke kinetic inductance at terahertz frequencies are demonstrated. These remarkable properties of 3D Dirac topological semimetal envision a new class of power-efficient, high speed, compact, tunable electronic, and photonic devices.     

3D Printed Enzyme-Functionalized Scaffold Facilitates Diabetic Bone Regeneration

Patients with diabetes mellitus (DM) suffer from a high risk of fractures and poor bone healing ability. Surprisingly, no effective therapy is available to treat diabetic bone defect in clinic. Here, a 3D printed enzyme-functionalized scaffold with multiple bioactivities including osteogenesis, angiogenesis, and anti-inflammation in diabetic conditions is proposed. The as-prepared multifunctional scaffold is constituted with alginate, glucose oxidase (GOx), and catalase-assisted biomineralized calcium phosphate nanosheets (CaP@CAT NSs). The GOx inside scaffolds can alleviate the hyperglycemia environment by catalyzing glucose and oxygen into gluconic acid and hydrogen peroxide (H₂O₂). Both the generated H₂O₂ as well as the overproduced H₂O₂ in DM can be scavenged by CaP@CAT NSs, while the initiated hypoxic microenvironment stimulates neovascularization. Moreover, the incorporation of CaP@CAT NSs not only enhance the mechanical property of the scaffolds, but also facilitate bone regeneration by the degraded Ca²⁺ and PO₄³⁻ ions. The remarkable in vitro and in vivo outcomes demonstrate that enzymes functionalized scaffolds can be an effective strategy for enhancing bone tissue regeneration in diabetic conditions, underpinning the potential of multifunctional scaffolds for diabetic bone regeneration.     

A Green Metal–Organic Framework-Cyclodextrin MOF: A Novel Multifunctional Material Based Triboelectric Nanogenerator for Highly Efficient Mechanical Energy Harvesting

The naturally available cyclodextrin has opened up a wide range of research avenues because of its superior characteristics such as being non-toxic, biocompatible, and edible. The cyclodextrin is the green multifunctional material that can add to the triboelectric series and extend its self-powered applications. The ultrasonic synthesized cyclodextrin metal–organic framework (CD-MOF) designed using sodium as a metal ion and cyclodextrin as a ligand for the triboelectric nanogenerator is reported. The various detailed characterizations of the CD-MOFs give an insight into the properties of the synthesized material. The Kelvin probe force microscopy suggests three types of CD-MOFs, exhibiting a positive potential. As per the surface potential, the output of the various CD-MOF based TENG is varied as alpha CD MOF/Teflon > gamma CD-MOF/Teflon > beta CD-MOF/Teflon. The alpha CD MOF/Teflon TENG produces an electrical output of 152 V, 1.2 μA, and 14.3 nC, respectively. The fabricated device output is utilized for powering numerous low-power electronics through a capacitor and bridge rectifier circuit. The multiunit Z-shaped TENG device is attached to various surfaces such as the shoe heel and the backside of the school bag, and the corresponding energy harvesting response is demonstrated.