Structural,electrical and photoluminescence properties of ZnO:Al films grown on MgO(0 0 1) by direct current magnetron sputtering with the oblique target

ZnO:Al films were deposited on MgO(0 0 1) substrates at 300 K and 673 K by direct current magnetron sputtering with the oblique target. The Ar pressure was adjusted to 0.4 Pa and 1.2 Pa, respectively. All the films have a wurtzite structure and a c-axis orientation in the film growth direction. The films deposited at 300 K initially grow with thin columnar grains and subsequently grow with large granular grains on the thin columnar grains. However, the films grown at 673 K consist mainly of dense columnar grains perpendicular to the substrate surface. The ZnO:Al film deposited at 673 K and 0.4 Pa has the lowest resistivity, the highest free electron concentration and Hall's mobility. A temperature dependence of the resistivity within 5–300 K reveals that the films grown at 300 K exhibit a semiconducting behavior and those grown at 673 K show a metal–semiconductor transition. The carrier transport mechanism is Mott's variable range hopping in the temperature range below 90 K for all the films and thermally activated band conduction above 215 K for the films grown at 300 K. Room temperature photoluminescence spectra for wavelengths between 300 nm and 800 nm reveal mainly blue-green emissions centered at 452 nm, 475 nm and 515 nm.     

Characteristics of sputtered Al-doped ZnO films for transparent electrodes of organic thin-film transistor

Aluminum-doped ZnO (AZO) thin-films were deposited with various RF powers at room temperature by radio frequency (RF) magnetron sputtering method. The electrical properties of the AZO film were improved with the increasing RF power. These results can be explained by the improvement of the crystallinity in the AZO film. We fabricated the organic thin-film transistor (OTFT) of the bottom gate structure using pentacene active and poly-4-vinyl phenol gate dielectric layers on the indium tin oxide gate electrode, and estimated the device properties of the OTFTs including drain current-drain voltage (I_D-V_D), drain current-gate voltage (I_D-V_G), threshold voltage (V_T), on/off ratio and field effect mobility. The AZO film that grown at 160 W RF power exhibited low resistivity (1.54 × 10^− 3 Ω·cm), high crystallinity and uniform surface morphology. The pentacene thin-film transistor using the AZO film that's fabricated at 160 W RF power exhibited good device performance such as the mobility of 0.94 cm²/V s and the on/off ratio of ~ 10⁵. Consequently, the performance of the OTFT such as larger field-effect carrier mobility was determined the conductivity of the AZO source/drain (S/D) electrode. AZO films prepared at room temperature by the sputtering method are suitable for the S/D electrodes in the OTFTs.     

CB/PE阻燃抗静电复合材料的制备和性能研究

制备了聚乙烯基炭黑(CB)导电复合材料;并研究了偶联剂、抗静电剂、阻燃剂、增韧剂、碳纤维对CB/聚乙烯(PE)复合材料电性能的影响。其中偶联剂、抗静电剂、阻燃剂、碳纤维对电性能起正作用,能有效降低体系的体积电阻率;新增韧剂在质量分数小于15%之前起正作用,添加量增加则为反作用,不利于炭黑的分散,使材料转变为绝缘体。试验中运用均匀设计的方法对体系配方进行了优化,经过电学、力学和燃烧测试后,筛选得到了综合性能较好的样品。     

基于牺牲阳极法的LiBr改性砂浆性能研究

通过掺入LiBr制备了高活性导电砂浆,研究了LiBr掺量与砂浆电阻率及阳极活性之间的关系。结果表明:LiBr能显著降低砂浆的电阻率,并随掺量增加电阻率降低。当掺量为160 g时,砂浆的电阻率小于100Ω·cm。LiBr的掺入能够活化阳极及促进溶解产物扩散,使阳极具备可持续发出保护电流的能力。     

Effect of film thickness on the surface,structural and electrical properties of InAlN films prepared by reactive co-sputtering

InAlN films of different thicknesses (150 nm, 250 nm, 380 nm, 750 nm and 1050 nm) were grown on Si (111) by means of reactive co-sputtering at 300 °C. Surface morphology results indicated an increase in the grains size and their spacing with increase of the film thickness. The surface of InAlN remained smooth with a slight variation in its RMS roughness from 1.29 nm to 6.62 nm by varying the film thickness. X-ray diffraction patterns exhibited InAlN diffraction peaks with preferred orientation along (002) plane in the thickness range 250 nm to 750 nm, however, the preferred orientation of the film was changed towards (101) plane at 1050 nm. An improvement in the crystallinity of InAlN was observed with increase of the film thickness. Electrical characterization revealed a decrease in the film's resistivity by increasing its thickness to 750 nm, however, the resistivity was found to increase at 1050 nm. The electron concentration indicated an increasing trend whereas changes in the electron mobility were found to be inconsistent with increase of the film thickness.     

Resistivity response to the porosity and permeability of low rank coal

Laojunmiao coal samples from the eastern Junggar basin were studied to understand the relationship between coal resistivity and the physical parameters of coal reservoirs under high temperatures and pressures.Specifically,we analysed the relationship of coal resistivity to porosity and permeability via heating and pressurization experiments.The results indicated that coal resistivity decreases exponentially with increasing pressure.Increasing the temperature decreases the resistivity.The sensitivity of coal resistivity to the confining pressure is worse when the temperature is higher.The resistivity of dry coal samples was linearly related to φ~m.Increasing the temperature decreased the cementation exponent(m).Increasing the confining pressure exponentially decreases the porosity.Decreasing the pressure increases the resistivity and porosity for a constant temperature.Increasing the temperature yields a quadratic relationship between the resistivity and permeability for a constant confining pressure.Based on the Archie formula,we obtained the coupling relationship between coal resistivity and permeability for Laojunmiao coal samples at different temperatures and confining pressures.     

放电等离子体烧结Cu(In0.7Ga0.3)Se2四元合金靶材 的结构和导电性研究

本文选用650℃条件下真空合成的Cu(In0.7Ga0.3)Se2单相合金粉末,通过放电等离子体烧结法制备了CIGS合金靶材,研究了烧结温度、保温时间以及烧结压强等工艺参数对CIGS四元合金靶材的结构与性能的影响,研究表明：烧结温度为500℃以上时,靶材为单一的Cu(In0.7Ga0.3)Se2相,随着烧结温度的升高,靶材的晶粒尺寸增大,致密度和电阻率基本呈线性升高;随着保温时间的延长,靶材晶粒尺寸随之增大,致密度和电阻率也随之升高;随着烧结压强的提高,靶材的致密度增加,而且电阻率得到下降。综上所述,烧结温度为600℃,压强为30MPa,保温时间为5min的工艺条件下,制备靶材的电阻率50Ω?cm,致密度为98%以上。     

Influence of non-ideal circumferential contacts on errors in the measurements of the resistivity of layers using the van der Pauw method

The present work deals with practical consequences of non-point character of circumferential contacts on samples tested using van der Pauw (vdP) method. Apart from the measurement method itself, the fundamental paper of van der Pauw deals also with an estimate of the error due to contact of finite length at the circumference of a circular sample on assumption of equipotential contact region. In general, this is true only in case of vanishing contact resistivity. The present study discusses the consequences of non-fulfilment of this assumption in practice and demonstrates it on real samples made from thin copper foil. The circumferential contact surfaces on these samples are made of the same material and the same thickness as measured sample. It was shown that, in principle, there is no experimental error in the resistivity measurements caused by finite size of contact surfaces. This is a consequence of the trivial fact that the contact surfaces modify only the shape of the sample, which – in the sense of the vdP methodology – can be arbitrary. This conclusion can be further generalised as follows. A non-point contact of lower resistivity than the measured sample results in negative measurement error, whereas the contact of higher resistivity results in positive error. So the magnitude and sign of the error depends not only on the relation between the contact length and sample diameter but also on the relation between the resistivities of the contact and the sample.     

Effects of vacuum sintering temperature on mechanical properties and electric resistance for Cr50–Si50 optical target

Abstract

In this study, two kinds of Cr and Si powders were mixed ingredients in set proportions (Cr/Si?=?50∶50 in weight percentage), and different vacuum sintering temperatures were used to achieve the optimal densification process. The specimens used in this investigation have common microstructures of hardness, XRD, transverse rupture strength and resistivity of the Cr50–Si50 targets. The microstructure shows that the porosity tends to decrease as sintering temperature increases. Conversely, hardness and transverse rupture strength increase as sintering temperature increases. These results agree with the variation in porosity. Additionally, the resistivity tends to decrease with increasing sintering temperature. It should be correlated with the microstructure of Cr50–Si50 targets, increasing the density of CrSi₂ could significantly decrease the resistance. Meanwhile, the resistivity decreases and conductivity increases as the neighbours are closer together, which also results from the decreasing porosity.     

Impact of La3+ substitution on electrical,magnetic, dielectric and optical properties of Ni0.7Cu0.1Zn0.2LaxFe2–xO4 (0 < x < 0.035) system

The oxalate co-precipitation method was used to synthesize the La³⁺ substituted Ni–Cu–Zn (La–NCZ) nanoferrites having chemical composition Ni_0.7Cu_0.1Zn_0.2La_xFe_2–xO₄ (x = 0, 0.015, 0.025 and 0.035). DC resistivity study of nanoferrites shows both the conducting and semiconducting behaviour. The room temperature DC electrical resistivity of Ni–Cu–Zn (NCZ) nanoferrites decreases, whereas Curie temperature increases with increasing La³⁺ content. In the temperature range of 30–170 °C nanoferrites show p-type semiconducting behavior except x = 0.015; thereafter, they show n-type behaviour. The frequency dispersive initial permeability (μ_i) associated with its real and imaginary (μ′ and μ") parts are attributed to the domain wall movement and magnetic spin resonant. The μ_i, μ′ and μ" of La–NCZ nanoferrites are higher than those of pure NCZ nanoferrite. Dielectric constant (ε′), dielectric loss (ε″) and AC resistivity (ρ_AC) of La–NCZ nanoferrites show normal dielectric behaviour. It is found that ε′ of NCZ nanoferrites decreases with the increasing content of La³⁺ ions. The bandgap energy of La–NCZ nanoferrites is achieved in the range 1.36–1.70 eV confirming the semiconducting nature of materials.