Effect of the Substrate Nature on the CdPbS Film Composition and Mechanical Stresses at the “Film–Substrate” Interface

Semiconductors - The role of substrates of different natures on the phase composition, morphology, and mechanical stresses at the “film–substrate” interface during the chemical...     

High-Quality Nickel Ferrite Synthesized by a Modified Sol–Gel Technique Applied as Microstrip Patch Antenna Substrate

Journal of Electronic Materials - This paper presents the production of nickel ferrite powder synthesized by a sol–gel technique modified by ionic coordination reaction. Morphological powder...     

Growth of GaN on Magnesium Aluminate Substrate by LP-MOVPE

Epitaxial GaN films have recently attracted much attention due to their optoelectronic applications in the blue/ultraviolet region and for their high temperature stability.High-brightness blue and green light emitting diodes(LEDs) have already been made commer-ciallyava...     

Effect of a Nanodimensional Polyethylenimine Layer on Current–Voltage Characteristics of Hybrid Structures Based on Single-Crystal Silicon

In this paper the study of the tunneling current–voltage (I–V) characteristics of silicon surfaces with n- and p-type conductivity as a function of roughness in the presence of an adsorbed insulating layer of polyethylenimine (PEI) is presented. A new approach is proposed for analysis of the tunnel current–voltage characteristics of a metal–insulator–semiconductor structure based on the combination of two models (Simmons and Schottky). Such joint analysis demonstrates the effect of surface states and evaluates changes in the band bending and electron affinity after the deposition of the polyelectrolyte layer on the semiconductor surface. As a result, we are able to differentiate between the equilibrium tunnel barrier (qφ ₀) and the barrier height (qφ _B). It is shown that the deposition of the polymer leads to an increase of the equilibrium tunnel barrier by more than 250 meV, irrespective of the roughness and the conductivity type of the silicon substrate. The PEI deposition also leads to changes in the barrier height (less than 25 meV) that are smaller than the equilibrium tunnel barrier changes, indicating pinning of the Fermi level by the electron surface states that are energetically close to it. These surface states can trap charge carriers, a process leading to the formation of a depletion region and band bending on the semiconductor surface. Moreover, the change in the barrier height qΔφ _B depends on the conductivity type of the semiconductor, being positive for n-type and negative for p-type, in contrast to qΔφ ₀, which is positive for all substrates. The change is explained by capture of electrons preferably from the semiconductor space-charge region in the presence of a cationic polyelectrolyte, e.g., PEI.     

Electron–Electron and Electron–Phonon Interactions in Graphene on a Semiconductor Substrate: Simple Estimations

The problem of epitaxial graphene formed on a semiconductor substrate is considered in the context of the extended Hubbard and Holstein–Hubbard models for electron–electron and electron–phonon interactions. The Haldane–Anderson model is chosen for the density of states of the substrate. Three regions of the phase diagram, specifically, spin- and charge-density waves and a spin- and charge-homogeneous paramagnetic state are considered. For a number of special cases used as examples, the similarities and differences of the electron states of graphene on semiconductor and metal substrates are demonstrated. It is shown that the main difference arises, if the Dirac point of graphene lies within the band gap of the semiconductor. Numerical estimations are performed for a SiC substrate.     

Effect of Annealing on the Surface Morphology and Current–Voltage Characterization of a CZO Structure Prepared by RF Magnetron Sputtering

Semiconductors - In this study, we investigated the Cu-doped ZnO (CZO) structure. This structure was deposited on the Si and glass substrates using the RF magnetron sputtering technique....     

Substrate temperature effects on the structural and photoelectric properties of ZnS：In films

Indium doped ZnS （ZnS：In） films were prepared on glass substrate using thermal evaporation technol- ogy. It was found that the structural, optical and electrical properties of ZnS：ln films strongly depend on the substrate temperature （Ts）. By X-ray diffraction （XRD）, atomic force microscopy （AFM）, transmittance spectroscopy, and electric performance measurements, the effect of Ts on ZnS：In film is studied in detail. It reveals that Ts has impor- tant effect on ZnS grain size, crystallinity, lattice disorder, etc., which further leads to the obvious influence on its optical and electrical performance. Under the optimized Ts, the performance, especially the conductivity, achieved in this work is far higher than that reported for other n-type ZnS films.     

Dielectric and Optical Properties of CdS–Polymer Nanocomposites Prepared by the Successive Ionic Layer Adsorption and Reaction (SILAR) Method

The successive ionic layer adsorption and reaction (SILAR) method has been used to grow epitaxial CdS–polymer nanostructures as thin films with different surface morphology and particle size. The main purpose of the study was to investigate the dielectric properties and a.c. electrical conductivity (σ _a.c.), by a.c. impedance spectroscopy between 1 kHz and 1 MHz, at room temperature, of CdS–polymer nanocomposites produced by use of 2, 6, and 10 cycles of SILAR. The surface morphology and optical absorption of the samples were characterized by scanning electron microscopy (SEM) and UV–visible spectroscopy, respectively. Determination of the energy gaps of CdS–polymer nanocomposites prepared by use of different numbers of cycles of SILAR reveals that the band gap decreases with increasing number of cycles (J. Cryst. Growth 305, 175–180, 2007). This behavior is because of the growth of nanoparticles in the matrix materials, and can be explained by changes in the amount of confinement as a consequence of particle size variation. SEM images also confirm that different numbers of cycles lead to different morphology. Frequency-dependent dielectric properties and a.c. electrical conductivity of the samples prepared by use of different numbers of cycles of SILAR were investigated, and comparative studies on some electrophysical properties of the samples are reported. Experimental results show that values of the dielectric constant (ε′), dielectric loss (ε″), dielectric loss tangent (tanδ), the real (M′) and imaginary (M″) parts of electric modulus, and σ _a.c. are highly dependent on the frequency and the number of cycles. It can be concluded that changing the frequency and the number of cycles substantially alters both the dielectric properties and a.c. electrical conductivity of the samples.     

In Situ Synthesis of Titanium Nickel Intermetallic Compounds Layer and TiN Coating By Laser Cladding

1 Introduction Laser cladding technology has been widely used in ma- terial processing and tool repairing because it causes little distortion and leads to high quality coatings [1]. Since the appearance ofhigh power diode lasers, the laser cladding is more efficient, economical and flexible[2￣5]. Titanium nickel alloys have excellent properties such as low density, high strength, and high chemical stability, which have promoted their applications in the aerospace, chemical, petrochemical and …     

Layout Design and Optimization of RF Spiral Inductors on Silicon Substrate

使用三维电磁场模拟的方法对相同硅衬底结构下不同布图结构的螺旋电感进行了模拟和分析.通过改变电感匝数、电感金属的宽度和间隔以及电感的内径,模拟和分析了电感性能的变化.给出了引起电感性能变化的原因.结果表明优化电感的几何参数可以有效地改善电感性能.得出了一些实用的设计原则,可有效地指导射频集成电路中集成电感的设计.     

Effect of Heat Treatment on the Thermoelectric Properties of Bismuth–Antimony–Telluride Prepared by Mechanical Deformation and Mechanical Alloying

In this work, p-type 20%Bi₂Te₃–80%Sb₂Te₃ bulk thermoelectric (TE) materials were prepared by mechanical deformation (MD) of pre-melted ingot and by mechanical alloying (MA) of elemental Bi, Sb, and Te granules followed by cold-pressing. The dependence on annealing time of changes of microstructure and TE properties of the prepared samples, including Seebeck coefficient, electrical resistivity, thermal conductivity, and figure-of-merit, was investigated. For both samples, saturation of the Seebeck coefficient and electrical resistivity were observed after annealing for 1 h at 380°C. It is suggested that energy stored in samples prepared by both MA and MD facilitated their recrystallization within short annealing times. The 20%Bi₂Te₃–80%Sb₂Te₃ sample prepared by MA followed by heat treatment had higher a Seebeck coefficient and electrical resistivity than specimens fabricated by MD. Maximum figures-of-merit of 3.00 × 10^?3/K and 2.85 × 10^?3/K were achieved for samples prepared by MA and MD, respectively.     

Enhancement of Spin–Orbit Interaction by Bandgap Engineering in InAs-Based Heterostructures

We investigated Rashba spin–orbit interaction in various InAs-based heterostructures to evaluate the relative significance of the electric field in the quantum wells (QWs) and at the interfaces. Test structures were designed in such a way that the peak of the electron wave function was located on the abrupt band discontinuity at the front end of the main channel, whereas a control sample had no band discontinuity in the middle of the QW. The Rashba coefficient obtained for the test structures was almost double that of the control sample. Significant contribution of the electric field at the band discontinuity was verified by k · p calculation. Bandgap engineering was shown to be effective for obtaining an increased Rashba coefficient.     

Influence of air gaps on the thermal–electrical–mechanical behavior of a copper metallization

Shrinking the IC dimensions the dielectric insulation between metal interconnects has become one of the major limits on increasing circuit speed. A lot of possible new low-k materials failed to meet specifications: too leaky, too soft, too unstable, and too expensive. Due to this air gaps beside the metallization are one solution. The reliability of ULSI multilevel copper metallizations under electro- and stress migration stress test conditions is investigated here with finite element analysis. A determination of the electrical and mechanical stress in a 3D copper metallization model based on the 45 nm technology node is carried out and the impact of a variation of the applied current density as well as geometrical parameters on the thermal–electrical and mechanical behavior is investigated. For a determination of the reliability the mass flux and mass flux divergence are separately calculated by a user routine. The influence of air gaps on single via structures and structures with a chain of four vias on the thermal–electrical–mechanical behavior is determined.     

Simulation and analysis of performance on the Compass™ enhanced by GEO and IGSO

Positioning accuracy of the Global Navigation Satellite System (GNSS) can be analyzed by Positioning Dilution Of Precision (PDOP). In order to enhance the navigating performance of Asia and the Pacific areas, this paper analyzes the next generation Beidou™ navigation satellite system (Compass™) enhanced by Geostationary Earth Orbit (GEO) and Inclining GeoSynchronized Orbit (IGSO). As global navigation satellite system, Compass™ must be robust enough to avoid system layoff, when some nodes are not available. So, the Compass™ enhanced by GEO and IGSO constellation is proposed and analyzed its PDOP proformance, this paper shows some exciting results of performance of Compass™ enhanced by GEO and IGSO. From the simulation results, we can found that: when more than fifteen satellites are invalid, the enhanced system could be operating normally.     

Effect of Substrate Nitridation on Properties of Thick GaN Film Grown by Hydride Vapour Phase Epitaxy

Thick GaN films were grown on the sapphire substrate by hydride vapour phase epitaxy. The properties of GaN films were found to be significantly influenced by the duration of exposing the sapphire substrate to ammonia prior to the GaN growth initiation. The crystalline quality of GaN films revealed by high resolution X-ray diffraction were strongly dependent on the nitridation time, which determined substrate surface topography. The different nitridation schemes strongly affected the morphology of GaN overlayers resulting in the blue shift of the main excitonic peak in photoluminescence spectra at room temperature.     

The influence of a voltage ramp on the measurement of I–V characteristics of a solar cell

For convenience and efficiency the voltage applied to a Si solar cell is often fairly rapidly driven from zero to the open circuit value typically at a constant rate of 1 V per millisecond. During this time the values of the current are determined as a function of the instantaneous voltage thus producing an I–V characteristic. It is shown here that the customary expressions for the current as a function of cell parameters remain still valid provided that the diffusion length in the expression for the dark current is changed from its steady state value L to the effective diffusion length L_i given by

$\text{L}{}_1\text{= L}\text{1+}\text{q}\text{V}\text{?}\text{kT}{}^{\mathrm{\tau }}\text{,}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$

where V is the ramp rate considered constant and τ is the lifetime of minority carriers. This result is true to a very good approximation provided that low level injection prevails.     

Excitation and Propagation of Sommerfeld–Zenneck Surface Waves on a Conducting Strip in the Centimeter-Wave Band

The paper presents the results of experimental studies and the analysis of the surface electromagnetic wave propagation along metal conducting strips in the centimeter-wave band, which is convenient for simulation of open waveguides for the optical and terahertz bands of electromagnetic radiation.     

An Integrated Luminescent Information Encryption–Decryption and Anticounterfeiting Chip Based on Laser Induced Graphene

Visual optical information encryption–decryption and anti-counterfeiting (IEDAC) technology play a vital role in the field of information security. Recent luminescent information encryption technologies face the disadvantages of depending on external large-scale stimulus decryption equipment, inability to read out repeatedly, and information leakage, impeding the practical applications of luminescence encryption. Here, an integrated luminescent IEDAC chip is proposed, which provides a convenient approach to store and decipher pre-patterned luminescence information based on laser engraved template and film heater. The luminescent encryption chip contains a double-layer structure made up of long persistent phosphors based on SrCaGa₄O₈ host and a laser induced graphene heater, which makes it possible to decrypt information on a single chip. This design enables dual-mode (photoluminescence/long persistent luminescence), dual-color (blue/yellow-green), and multi-level IEDAC function, providing a novel insight and integrated strategy for implementing advanced IEDAC technologies.     

Time effect of annealing on phase transformations of Cu–Al–Cr nano-ferrites prepared by a co-precipitation method

Amounts of the as-prepared CuAl_0.6Cr_0.2Fe_1.2O₄ nanoparticles by the co-precipitation method have been annealed for different time t for each amount at 800 °C. The samples were characterized using XRD, IR and Mössbauer spectroscopy. The structure of the nanoparticles was transformed from cubic-to-tetragonal-to-cubic with the increase in t. This transformation was assigned to the Jahn–Teller effect (JTE) of Cu²⁺ ions. The transformation process from cubic to tetragonal occurred at annealing time 12 h, whereas the transformation from tetragonal-to-cubic occurred at t≥16 h. The crystallite size, lattice parameters, IR band positions and intensities, force constants, threshold frequency, Debye temperature and stiffness constant were affected by JTE and showed dependence on t. The Mössbauer spectra and parameters confirmed the transformation process by JTE and showed dependence on t. This study confirmed that the increase of annealing time can leads to moving the metallic ions between the crystal sublattices against their site preference and increasing the inversion of cation distributions.