Low temperature fabrication of Ni–P metallic patterns on ITO substrates utilizing inkjet printing

A low temperature process to fabricate high resolution metallic lines on indium tin oxide (ITO) substrates using inkjet printing and subsequent electroless plating is described in this study. In this method, a thermo-sensitive (styrene-co-NIPAAm)/Pd (St-co-NIPAAm/Pd) nanoparticle-based ink was printed onto ITO substrates to create patterned catalytic sites, where nickel is subsequently deposited by electroless plating to form metal lines with desired width and conductivity. The inkjet printing variables such as droplet spacing and printing voltage, as well as the Ni electroless deposition variables such as deposition time and temperature were systematically investigated to obtain the optimum parameters. The adhesion of the deposited Ni–P coating to the ITO substrate was evaluated by a scotch tape test method. Optical microscope observation shows that a continuous pattern was formed with a printing voltage of 37 V and a droplet spacing of 50 μm. The irritating coffee ring effect was significantly suppressed by raising the substrate temperature to 50 °C and increasing the electroless plating temperature to 75 °C. High-resolution conductive metal lines can be easily and successfully fabricated using our method, which shows good potential for preparing the metallic lines as front or back electrodes in solar cells.     

Arsenic vapor pressure dependence of surface morphology and silicon doping in molecular beam epitaxial grown GaAs (n11)A (n=1–4) substrates

Surface morphology of undoped AlGaAs/GaAs asymmetric double quantum wells (ADQWs) and Si-doped single epitaxial GaAs layers were studied by atomic force microscopy. Samples were prepared on GaAs(n11)A (n=1–4) substrates in molecular beam epitaxy at different As pressures and the same substrate temperature and Ga flux. The surfaces of (n11)A ADQWs change from rough to smooth and featureless with increasing As pressures, while that of (100) sample shows an inverse change according to the atomic force microscopy results. Triangular pyramidal facets were observed at lower As pressure for (111)A and (211)A orientations. The interface roughness of ADQWs was improved at higher As pressure showing by a transmission electron microscope observation. The conduction type of (n11)A (n<=4) was p-type for lower As pressure and n-type for higher As pressure.     

Molecular beam epitaxy of ZnxBe1−xSe: Influence of the substrate nature and epilayer properties

We have studied the heteroepitaxial growth of Zn_xBe_1−xSe onto Si, GaAs and GaP substrates. By comparing the growth on these different substrates, we showed that lattice-matching is not a sufficient condition to achieve a good epitaxy. Then we have investigated by low-temperature photoluminescence and reflectivity spectroscopies a series of Zn_xBe_1−xSe alloys with Be content up to 70%. This allowed us to locate the direct-to-indirect band-gap cross over at x=0.46. We found a bowing parameter b=0.97 eV for the direct band-gap in the whole composition range. Finally, Zn_0.59Be_0.41Se and Zn_0.55Be_0.45Se alloys lattice-matched, respectively, to GaP and Si substrates are direct band-gap semiconductors which exhibit band-gap at 3.72 eV and 3.85 eV.     

Evaluation of compositional intermixing at interfaces in Si(Ge)/Si1−x Gex heteroepitaxial structures grown by molecular beam epitaxy with combined sources of Si and GeH4

The main causes of the diffusion spreading of a solid-solution composition near the boundaries of the Si transport channel in a Si/Si_1?x Ge_x heterostructure grown by molecular-beam epitaxy combined with solid (Si) and gaseous (GeH₄) sources are considered. For the grown structures, the contributions from various mechanisms involved in forming the profile of the metallurgical boundary of the layer are compared and the effect of channel boundary spreading on the mobility of a two-dimensional electron gas in the channel is evaluated.     

Influence of the surface roughness of the bottom electrode on the resistive-switching characteristics of Al/Al2O3/Al and Al/Al2O3/W structures fabricated on glass at 300 °C

Resistive-switching devices based on Metal–Insulator–Metal (MIM) structures have shown promising memory performance characteristics while enabling higher density of integration. Usually, these MIM devices are fabricated using different processing conditions including high temperature thermal treatments that could lead to undesirable chemical reactions in the insulator material and at its interface with the metals involved. In this work, we compare the electrical characteristics of MIM devices (fabricated on glass at 300 °C) that use aluminum or tungsten as bottom electrode (BE) in order to study the influence of a highly reactive (aluminum) or inert (tungsten) metal electrode on the memory characteristics. We found that the switching characteristics of Al₂O₃ (from a high-resistance state HRS to a low-resistance state LRS and vice versa), are highly dependent on the surface roughness of the BE, the thickness of Al₂O₃ and the current compliance (CC) which limits the electron density flowing through both top/bottom electrodes.     

The electrical and optical properties of InAs irradiated with electrons (∼2 MeV): The energy structure of intrinsic point defects

The results of experimental studies of the electrical and optical properties of n-and p-InAs crystals irradiated with electrons at an energy of ～2 MeV and doses as high as D = 1 × 10¹⁹ cm^?2 are reported. Specific features of the annealing (at temperatures as high as 800°C) of radiation defects are also reported. The electronic structure of nonrelaxed V_As, V_In, As_In, In_As defects is calculated. A relation between the electrical properties and the Fermi level position in irradiated InAs on the one hand and the electronic structure of the intrinsic defects and special features of the energy-band spectrum of InAs on the other hand is discussed.     

Structural and optical properties of ZrB2 and HfxZr1−xB2 films grown by vicinal surface epitaxy on Si(1 1 1) substrates

ZrB₂ and Hf_xZr_1?xB₂ films were grown on 4° miscut Si(1 1 1) substrates by chemical vapor deposition of gaseous Hf(BH₄)₄ and Zr(BH₄)₄. The films display superior structural and optical properties when compared with ZrB₂ films grown on on-axis Si(1 1 1). The observed improvements include an optically featureless surface with rms roughness of ～2.5–3.5 nm, a ～50% reduction in the amount of residual strain, and a ～50% lower resistivity. These properties should promote the use of diboride films as buffer layers for nitride semiconductor epitaxy on large-area Si substrates.     

Contiki IEEE 802.15.4 MAC Layer Protocols: Implementation and Evaluation of Node’s Throughput and Power Consumption

Wireless Personal Communications - Internet of Multimedia Things (IoMT), a special subset of Internet of Things (IoT), is a novel paradigm which is progressively increasing and gaining in...     

Local lifetime control by light ion irradiation: impact on blocking capability of power P–i–N diode

The impact of local lifetime control by ¹H⁺ and ⁴He²⁺ irradiation on blocking characteristics of power P–i–N diodes was studied in the dose range up to 5×10¹² cm⁻². Energies and doses for both types of projectiles were chosen in a way to create a comparable damage in three qualitatively different regions close to the anode junction. Blocking capabilities of irradiated diodes were measured, compared and simulated. The results show that there is no difference between hydrogen and helium irradiation if the damage is located inside the anode area. When the damage peak is placed into the N-base side of the anode junction and the dose of protons exceeds 10¹²  cm⁻², blocking capability of the diode drastically decreases while it stays at the same level for analogous irradiation by helium ions.     

Research for Optimizing Band-Edge Characteristics of the LC Elliptic Filter About Low Voltage–Power Line’s High-Speed Communication in the Coal Mine: LC Elliptic Filter About Low Voltage PLC in the Coal Mine

Wireless Personal Communications - Because the environment is bad in the coal mine, it is difficult to establish an effective information sharing network. Low voltage–power line has many...     

Evaluation of the conversion efficiency of thin-film single-junction (a-Si:H) and tandem (μc-Si:H + a-Si:H) solar cells by analysis of the experimental dark and load current-voltage (I–V) characteristics

The aim of the study is to apply a method commonly used to determine the efficiency of multi-junction nanoheterostructure III?CV solar cells by analysis of the dark current-voltage (I?CV) characteristics to such an unconventional semiconducting material as amorphous silicon. a-Si:H and a-Si:H/??c-Si:H p-i-n structures without a light-scattering sublayer or an antireflection coating are studied. The results of measurements of the dark I?CV characteristics demonstrate that the voltage dependence of the current has several exponential portions. The conversion efficiency of solar cells (SCs) is calculated for each portion of the dark I?CV characteristic. This yields a dependence of the potential SC efficiency on the generation current density or on the photon flux. The observed agreement between the data derived from the experimental characteristics and results of calculations can be considered satisfactory and acceptable, thus the method suggested for measurement and analysis of dark I?CV characteristics and tested earlier on SCs based on crystalline III?CV compounds acquires a universal nature. The analysis of the characteristics of p-i-n amorphous silicon structures and the calculation of potential efficiencies, based on this analysis, extend the authors?? understanding of this class of devices and make it possible to improve the technology and photoconversion efficiency of SCs of this kind.     

Sol–Gel Grown SnO<Subscript>2</Subscript> Nanoparticles: Evaluation of Structure,Morphology, and Raman Spectra

Tin oxide (SnO₂) nanoparticles (TONPs) were prepared using sol–gel method under different growth conditions. The influence of calcination temperature (450°C and 600°C) and molecular weight of polyethylene glycol (PEG 300 and PEG 4000) on the nanocrystallinity, surface morphology, and Raman spectra of as-prepared TONPs were evaluated. Variation of calcination temperature and dopant (sulfosuccinic acid, SA) was found to affect considerably the structure, surface morphology, and Raman activities of the TONPs. The size of TONPs estimated using Scherrer equation was discerned to be in the range of 15–32 nm. The observed intensity enhancement in the Raman vibrational modes at lower calcination temperature was attributed to the enlargement of TONPs size. The absorption of molecules at the TONPs surface led to a quenching in the A ₂ g and Eu Raman peaks. Raman peaks centered around 673 cm^?1, 799 cm^?1, 640 cm^?1 , and 432 cm^?1 corresponding to A1g, B2g, A1g, and Eg modes, respectively have manifested highest peaks intensity. Furthermore, the enhancement of the Eg mode due to the addition of SA dopant was ascribed to the Jahn–Teller distortion mechanism.     

Degradation of micromorphous thin-film silicon (α-Si/μ<Emphasis Type="Italic">c</Emphasis>-Si) solar modules: Evaluation of seasonal efficiency based on the data of monitoring

A method for assessing the efficiency of α-Si/μc-Si solar modules is developed; the method is based on monitoring current and voltage at the point of highest voltage and on measuring the temperature at the surface of the module. The technique for assessment of the parameters of the α-Si/μc-Si modules in the course of their operation after initial degradation of the module is described; the results of parameter evaluation are compared with the values measured in the laboratory. The error in evaluating parameters was no larger than 3%; this error amounted to 0.36% in the case of estimating the parameters under standard conditions and maximal power of the module. This method can be used for evaluating a module’s efficiency and for short-term prediction (day, week) of the power generated by a solar power plant under conditions of operation using standard tools for monitoring.     

Vacuum production of OTFTs by vapour jet deposition of dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) on a lauryl acrylate functionalised dielectric surface

Roll-to-roll (R2R) production of organic transistors and circuits require patterned deposition of organic layers at high deposition rate. Here we demonstrate a vapour-jet process for the rapid deposition of the organic semiconductor dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT). The deposition rate achieved, equivalent to ∼200 nm/s onto a stationary substrate, was several orders of magnitude faster than ordinary thermal evaporation. Nevertheless, transistor yield was 100% with an average mobility of 0.4 cm²/V in a single pass deposition onto a substrate moving at 0.15 m/min. We also demonstrate a vacuum, high rate R2R-compatible process for surface-functionalising a gate dielectric layer with lauryl acrylate which enabled an all-vacuum route to the fabrication of a five-stage ring oscillator.     

First-principles of wurtzite ZnO (0001) and (000ī) surface structures

The surface structures of wurtzite ZnO (0001) and (000^-1) surfaces are investigated by using a first-principles calculation of plane wave ultra-soft pseudo-potential technology based on density functional theory (DFT). The calculated results reveal that the surface energy of ZnO–Zn is bigger than that of ZnO–O, and the ZnO–Zn surface is more unstable and active. These two surfaces are apt to relax inward, but the contractions of the ZnO–Zn surface are smaller than the ZnO–O surface. Due to the dispersed Zn4s states and the states of stronger hybridization between the Zn and O atoms, the ZnO–Zn surface shows n-type conduction, while the O2p dangling-bond bands in the upper part of the valence cause the ZnO–O surface to have p-type conduction. The above results are broadly consistent with the experimental results.