Ba_xNi_(1–x)La_yFe_(12–y)O_(19)铁氧体的制备与磁性能研究

首先利用溶胶-凝胶法制备了BaxNi1–xFe12O19(x=0.2,0.4,0.6,0.8)样品,通过热重-差示扫描量热仪(TG-DSC)、X射线衍射仪(XRD)和振动试样磁强计(VSM)分析,确定了最佳煅烧温度和最佳Ba-Ni摩尔比。然后利用同样的方法制备了Ba0.6Ni0.4LayFe12–yO19(y=0,0.1,0.3,0.5)样品,利用场发射扫描电镜(FESEM)、XRD和VSM对产物进行表征分析。结果表明Ni2+取代Ba2+,进入其晶格内部,改变了铁氧体的磁性能。La3+的加入改变了铁氧体的矫顽力Hc、饱和磁化强度Ms和剩余磁化强度Mr。当y=0.3时,其Ms和Mr达到最大值,分别为51.0 A.m2/kg和32.3 A·m2/kg。     

Electrosynthesis of organic–inorganic compounds (p–n heterojunction)

An electrochemical deposition procedure by cyclic voltammetry, in an electrolyte solution was adopted for the preparation of thin films of polypyrrole–gallium arsenide composite materials. The properties of the composite layers were studied by cyclic voltammetry, electrochemical impedance spectroscopy and photoelectrochemical measurements. The p- and n-type semiconductor behaviour of the polypyrrole (PPy) and gallium arsenide (GaAs) were studied by photocurrent measurements. It was found that the composite material (PPy–GaAs) had a (p–n) heterojunction behaviour.     

Nina Aleksandrovna Goryunova (1916–1971)

Personalia

Nina Aleksandrovna Goryunova (1916–1971)     

The temperature dependent analysis of Au/TiO2 (rutile)/n-Si (MIS) SBDs using current–voltage–temperature (I–V–T) characteristics

In this study, the main electrical parameters of Au/TiO₂(rutile)/n-Si Schottky barrier diodes (SBDs) were analyzed by using current–voltage–temperature (I–V–T) characteristics in the temperature range 200–380 K. Titanium dioxide (TiO₂) thin film was deposited on a polycrystalline n-type Silicon (Si) substrate using the DC magnetron sputtering system at 200 °C. In order to improve the crystal quality deposited film was annealed at 900 °C in air atmosphere for phase transition from amorphous to rutile phase. The barrier height (Φ_b) and ideality factor (n) were calculated from I–V characteristics. An increase in the value of Φ_b and a decrease in n with increasing temperature were observed. The values of Φ_b and n for Au/TiO₂(rutile)/n-Si SBDs ranged from 0.57 eV and 3.50 (at 200 K) to 0.82 eV and 1.90 (at 380 K), respectively. In addition, series resistance (R_s) and Φ_b values of MIS SBDs were determined by using Cheung's and Norde's functions. Cheung's plots are obtained from the donward concave curvature region in the forward bias semi-logarithmic I–V curves originated from series resistance. Norde's function is easily used to obtain series resistance as a function of temperature due to current counduction mechanism which is dominated by thermionic emission (TE). The obtained results have been compared with each other and experimental results show that R_s values exhibit an unusual behavior that it increases with increasing temperature.     

Halogen adsorption at an As-stabilized β2–GaAs (001)–(2 × 4) surface

Halogen (F, Cl, Br, and I) adsorption at an As-stabilized GaAs (001) surface with the β2–(2 × 4) reconstruction is studied using the plane-wave projected-augmented wave method. The effect of halogens on the structural and electronic characteristics of the semiconductor surface is analyzed. The T₂′ site at the missing row edge is shown to be the energetically most favorable for the adsorption of F, Cl, and Br, whereas I prefers the H₃ site between adjacent arsenic dimers in the third layer from the surface. Ga-halogen bond formation suggests that charge is transferred via the depletion of occupied orbitals of the As-dimer surface atoms, which leads to the weakening of Ga–As bonds in the substrate. The weakening of bonds between substrate-surface atoms due to the interaction of halogens with the surface is estimated.     

Growth,structure, and properties of GaAs-based (GaAs)1–x–y (Ge2) x (ZnSe) y epitaxial films

The possibility of growing the (GaAs)_1–x–y (Ge₂) _x (ZnSe) _y alloy on GaAs substrates by the method of liquid-phase epitaxy from a tin solution–melt is shown. X-ray diffraction shows that the grown film is single-crystal with the (100) orientation and has the sphalerite structure. The crystal-lattice parameter of the film is a _f = 0.56697 nm. The features of the spectral dependence of the photosensitivity are caused by the formation of various complexes of charged components. It is established that the I–V characteristic of such structures is described by the exponential dependence I = I ₀exp(qV/ckT) at low voltages (no higher than 0.4 V) and by the power dependence J ~ V ^α, where the exponent α varies with increasing voltage at high voltages (V > 0.5 V). The results are treated within the framework of the theory of the drift mechanism of current transfer taking into account the possibility of the exchange of free carriers within the recombination complex.     

(Sr_(0.5)Ba_(0.5))_(1.9)Ca_(0.1)NaNb_(5–x)TaxO_(15)陶瓷的介电性能

通过Ta掺杂改性钨青铜陶瓷(Sr0.5Ba0.5)1.9Ca0.1NaNb5–xTaxO15(x=0～0.30),分析了Ta掺杂量对其烧结性能、微观结构及介电性能的影响。陶瓷的烧结温度随x的增大略有提高。当x<0.10时,陶瓷的tC和弛豫性变化不大;当x≥0.10时,tm(1kHz)明显降低,从270℃(x=0)降低至231℃(x=0.30)。且tm随频率增加向高温移动,弛豫性明显增强。认为Ta掺杂引起其性能变化是由于Ta—O键与Nb—O键键能的差异,导致陶瓷氧八面体中心离子位移量以及A位离子有序程度的变化所致。     

Co含量对Ni_(0.9–0.5x)Co_(0.3+1.5x)Mn_(1.8–x)O_4热敏电阻性能的影响

采用传统的固相反应法制备了Ni0.9–0.5xCo0.3+1.5xMn1.8–xO4(Mn和Ni的摩尔比为2:1,x=0~0.7)陶瓷。并且采用XRD和SEM等手段,系统地分析了Co含量对该热敏陶瓷的相结构及显微形貌的影响。结果表明,所研究的陶瓷均为立方晶相,当x≥0.6时出现第二相CoO岩盐相。在–40~125℃的测试范围内,该陶瓷材料表现出明显的NTC特性。随着Co含量的增加,陶瓷的室温电阻率(2 275~914?·cm)及β值(3 718~3 544 K)均逐渐减小,并且出现两个拐点。其导电机理与小极化子的跳跃电导模型相吻合,并且受CoO岩盐相的影响。     

Three-step concept (TSC) in modeling microelectronics reliability (MR): Boltzmann–Arrhenius–Zhurkov (BAZ) probabilistic physics-of-failure equation sandwiched between two statistical models

When encountering a particular reliability problem at the design, fabrication, testing, or an operation stage of a product’s life, and considering the use of predictive modeling to assess the seriousness and the likely consequences of the a detected failure, one has to choose whether a statistical, or a physics-of-failure-based, or a suitable combination of these two major modeling tools should be employed to address the problem of interest and to decide on how to proceed. A three-step concept (TSC) is suggested as a possible way to go in such a situation. The classical statistical Bayes’ formula can be used at the first step in this concept as a technical diagnostics tool. Its objective is to identify, on the probabilistic basis, the faulty (malfunctioning) device(s) from the obtained signals (“symptoms of faults”). The recently suggested physics-of-failure-based Boltzmann–Arrhenius–Zhurkov’s (BAZ) model and particularly the multi-parametric BAZ model can be employed at the second step to assess the remaining useful life (RUL) of the faulty device(s). If the RUL is still long enough, no action might be needed; if it is not, corrective restoration action becomes necessary. In any event, after the first two steps are carried out, the device is put back into operation (testing), provided that the assessed probability of its continuing failure-free operation is found to be satisfactory. If the operational failure nonetheless occurs, the third, technical diagnostics step should be undertaken to update reliability. Statistical beta-distribution, in which the probability of failure is treated as a random variable, is suggested to be used at this step. While various statistical methods and approaches, including Bayes’ formula and beta-distribution, are well known and widely used in numerous applications for many decades, the BAZ model was introduced in the microelectronics reliability (MR) area only several years ago. Its attributes are addressed and discussed therefore in some detail. The suggested concept is illustrated by a numerical example geared to the use of the prognostics-and-health-monitoring (PHM) effort in actual operation, such as, e.g., en-route flight mission.     

高介电(1–x)Ca_(0.7)Nd_(0.2)TiO_(3-x)Ba_(0.4)Sr_(0.6)TiO_3陶瓷微波介电特性

采用固相反应法制备了具有钙钛矿结构的(1–x)Ca_(0.7)Nd_(0.2)TiO_(3-x)Ba_(0.4)Sr_(0.6)TiO_3(0.05≤x≤0.5)陶瓷,并对其烧结行为、相组成、显微结构及微波介电性能进行了研究。结果表明:随着(Ba0.4Sr0.6)2+含量的增加,(1–x)Ca_(0.7)Nd_(0.2)TiO_(3-x)Ba_(0.4)Sr_(0.6)TiO_3(0.05≤x≤0.5)陶瓷的品质因数(Q·f)及谐振频率温度系数(τf)单调递减,而相对介电常数(εr)先升后小幅降低。当x=0.2,且烧结温度为1 450℃时,该介质陶瓷的微波介电性能为:εr=151.3,Q·f=5 900 GHz,τf=399.4×10–6/℃。与CaTiO_3(εr=160,Q·f=6 800 GHz,τf=850×10–6/℃)相比,Q·f和εr略微降低,τf有较大程度的减少,故此陶瓷体系有望替代CaTiO_3成为新一类高介电性微波陶瓷。     

Optical anisotropy in thin films of poly(3,4-ethylenedioxythiophene)–poly(4-styrenesulfonate)

Anisotropic optical constants spectrum of spin-coated thin films of poly(3,4-ethylenedioxythiophene)–poly(4-styrenesulfonate) (PEDOT–PSS) from 200 to 1700 nm were determined using variable-angle spectroscopic ellipsometry and polarized intensity transmission data together with absorption spectroscopy. PEDOT–PSS was found to be very anisotropic, uniaxial with the optic axis parallel to the surface normal. The result is in good agreement with results obtained of chemically polymerized PEDOT layers doped with toluenesulfonate. By adding sorbitol to the PEDOT–PSS dispersion before spin-coating, layers with a higher conductivity were obtained. A detailed study was made of the optical response of these layers in comparison to the PEDOT–PSS prepared from dispersions without sorbitol. The optical anisotropy is important to consider when using PEDOT–PSS in optoelectronic devices, such as polymer light-emitting diodes and photovoltaic devices.     

Simulating Tunneling Electron Transport in the Semiconductor–Crystalline Insulator–Si(111) System

Tunneling carrier transport through a thin insulator (e.g., CaF₂) layer between a Si(111) substrate and a semiconductor gate is theoretically investigated. Along with the conservation of a large transverse wave vector of tunneling particles, the limitation imposed on the availability of states in the gate is taken into account. Due to this limitation, the tunneling currents at low insulator bias are weaker than in an analogous structure with a metal gate electrode. The same feature leads to a change in the shape of the energy distribution of tunneling electrons, both in transport between the substrate and gate conduction bands and during the Si(111) conduction band–gate valence band transfer.     

Analytical V TH and S models for (DMG–GC–stack) surrounding-gate MOSFET

This article presents an analytical model of surface potential, threshold voltage and subthreshold swing for a new structure of surrounding-gate MOSFET by combining dual-material gate, graded channel and gate stack. By comparison with published results, it is shown that the new MOSFET structure can improve the immunity of CMOS-based devices in the nanoscale regime against short-channel effects.     

Formation of Planar Field-Emission Devices Based on Carbon Nanotubes on Co–Nb–N–(O) Alloy

Semiconductors - Integrated field-emission devices and integrated circuits (ICs) based on them are a promising direction in microelectronics, which is associated with the use of low-voltage and...     

(Mg_(1–x)Zn_x)TiO_3系陶瓷微波介电性能的研究

以MgCO3、ZnO和TiO2为原料,用固相反应法制备了(Mg1–xZnx)TiO3(MZT)系陶瓷。研究了ZnO含量对其微观结构和微波介电性能的影响。结果表明:添加适量ZnO,可有效降低烧结温度,拓宽烧结温度范围。当x(ZnO)为30%,烧结温度为1250℃时,MZT陶瓷具有优良微波介电性能,εr为16～18,Q·f为90000GHz,τc为–5.1×10–7℃–1。     

退火温度对La_(1–x)Sr_xCo_(1–y)Fe_yO_3系薄膜NTC阻温特性的影响

利用La_(1–x)Sr_xCo_(1–y)Fe_yO_3(x=0.2,y=0.3)陶瓷靶材,通过真空射频磁控溅射在Al_2O_3基片上制备La_(0.8)Sr_(0.2)Co_(0.7)Fe_(0.3)O_3(LSCF)薄膜,然后在此基础上制备NTC热敏电阻。采用X射线衍射(XRD)分析了材料相的组成,扫描电子显微镜(SEM)分析观察薄膜材料的微观结构,电阻测试仪和四探针仪器测试薄膜的阻温特性,研究不同退火温度对LSCF薄膜室温电阻和材料常数(B值)的影响。结果表明,随着退火温度升高,LSCF薄膜方阻和B值都存在先减小后增大现象,具有显著的NTC阻温特性,其lnR-T~(–1)曲线具有良好的线性度。     

Synthesis of compositionally different multicomponent metal-oxide films (SnO2) x (ZnO)1 − x (x = 1–0.5)

The study is concerned with high-purity SnO₂ and ZnO powders produced from salt solutions of corresponding metals by low-temperature hydrothermal synthesis. Fragments of SnO₂ and ZnO ceramic targets formed as 1 × 8 cm bars are fabricated by dry pressing. The bars are used to form composite targets for ion-beam sputtering and the fabrication of compositionally different (SnO₂) _x (ZnO)_{1 ? x} (x = 1–0.5) films appropriate for the production of gas sensors or transparent electronic devices. The optical and electrical parameters of the films with different compositions are studied.