Advanced Materials Research Vols. 750-752

Abstract: The films of Mg_xZn_1-xO were prepared on ITO-coated glass substrates by sol-gel method at low temperature. The influence of Mg content x on microstructure and resistive switching behavior in Mg_xZn_1-xO films was systematically investigated. It was found that all Mg_xZn_1-xO samples exhibit a polycrystalline character with a single phase hexagonal wurtzite structure, irrespective of the Mg content x. With the increase of Mg content x, the V_set, V_reset, R_LRS and R_HRS/R_LRS of Mg_xZn_1-xO films increased, but the endure of Mg_xZn_1-xO films switching cycles decreased as the Mg content x is over 0.2 and exhibited a smaller degradation of resistance as the Mg content x is 0.1. The resistance switching mechanism was discussed.

Abstract: Thin films of Zn_1-xMn_xO (x = 0.00, 0.03, 0.07, 0.10) were prepared onto glass substrates by sol-gel spin-coating technique. The structural, morphologic and optical properties of these samples were studied respectively. The XRD patterns show the thin films are all polycrystalline with hexagonal wurtzite structure and no preferred orientation. With the increase of Mn doping, the c-axis lattice constants of the samples shift towards higher values until the doping concentration reaches up to 7%. This indicates that Mn²⁺ substituted for Zn²⁺ of ZnO host. Moreover, the grain size decreases gradually with the increase of Mn doping content. The AFM results indicate surface roughness increases with the increase of Mn doping level. The photoluminescence spectra reveal Mn doping causes a blue shift of the UV peak. The intensity of UV emission peaks increases at the beginning and then decreases with the increase of Mn doping content.

Abstract: Ge2Sb2Te5 thin films and Si doped Ge2Sb2Te5 thin films were deposited by electron beam evaporation method. The crystallization behaviors of the films were investigated by using the in situ resistance measurement. Through in situ resistance measurement, the increases of amorphous stability, crystallization rate and crystalline resistivity after Si doping were observed. The promoted nucleation process and the retardation of crystal growth were found in Si doped samples through the calculation of JMAK equation.

Abstract: GeSbTe (GST) thin films were deposited on Si substrates using electron beam evaporation system and then annealed in nitrogen atmosphere at different temperatures. X-ray diffraction (XRD) and Atomic Force Microscope (AFM) measurements were used to characterize as-deposited and annealed films. Annealing treatment was found to induce changes in microstructure, surface roughness, grain size and so on, indicating that with the increase of annealing temperature, the amorphous state of GST materials change first to face-centered-cubic (fcc) phase state and finally to the stable hexagonal (hex) state. Amorphous Ge₁Sb₂Te₄ film will crystallize under laser irradiation. With increasing irradiation time or irradiation power, the degree of crystallization increases. The Raman spectra of thin film shows three peaks after laser irradiation, the peaks can be attributed to the key vibrations which were caused by crystallization. With the irradiation time increases, the peaks shift.

Abstract: The initial surface reaction mechanisms of atomic layer deposition TiO₂ on H/Si (100 )-2×1 surface using Ti (OCH₃)₄ and H₂O as precursors are investigated by density functional theory. The ALD process is divided into two half-reactions, i.e., Ti (OCH₃)₄ and H₂O half-reactions. The adsorption energy of Ti (OCH₃)₄ on H/Si (100)2×1 surface is only-2.4 kJ/mol. The overall reaction of Ti (OCH₃)₄ is exothermic, which indicates that Ti (OCH₃)₄ half-reactions are favorable on thermodynamic. Howerver, H₂O half-reactions are endothermic and thermodynamically unfavorable.

Abstract: Different parameters are used to characterize the conductivity of copper powder with silver plating. Ethanediamine（C2H8N2） is employed to adjust the pH value of plating solution (solution A), and chelate Cu2+ generated by side reaction, forming sound five-membered ring structure with Cu2+, thus preventing the formation of Cu(NH3)42+ which can avoid adsorption of Cu(NH3)42+ on the surface of copper powder. In this way silver-plated copper powder with conductivity equal to fine silver powder can be obtained, the effects of dosage of C2H8N2 and Tollens' reagent concentration on performance of silver-plated copper powder have also been investigated. The result shows that dosage of C2H8N2 has significant effects on electrical conductivity of silver-plated copper powder. The dosage of C2H8N2 should ensure that pH value of control solution A maintains 9.0~10.0. The concentration of Tollens' reagent should make sure that the generated silver-plated copper powder is most even and continuous and tightness when silver particles in form of heterogeneous nucleation is surrounded on the surface of copper powder, , and the optimum concentration is 0.09mol/L. The conductivity of silver-plated copper powder made by Tollens' reagent with 0.09mol/L concentration is optimal, which is 3.9×10-4Ω•cm,when adjusting the pH value of solution A to 9.5 by C2H8N2 control.

Abstract: A white organic light emitting device (WOLED) with excton confining structure is reported. The blue and red emitting layer consist of 1,4bis (2,2-diphenyl vinyl) benzene (DPVBi) and the bis (1-(phenyl) isoquinoline) iridium (III) acetylanetonate [Ir (piq)₂(acac)] doped into 4,4(-N,N)-dicarbazole-biphenyl (CBP) host, respectively. The devices were made of ITO/ m-MTDATA (40 nm)/ NPB (10 nm) /DPVBi (8 nm)/ Bhen (x nm)/ CBP: Ir (piq)₂(acac) 2% 5nm/ Alq (50 nm )/ LiF (1 nm) / Al (200 nm), by adding excton confining layer, with only a small increase in operating voltage. However, the efficiency of device increases. The electroluminescent (EL) spectra exhibit two peaks at 456 and 628 nm, resulting in white light emission with the Commission Internationale dEclairage (CIE) chromaticity coordinates of (0.222, 0.2402) at 4V to (0.1924, 0.1986) at 13V when x is 8, while the device shows the current efficiency of 4.79 cd/A at 6V, its maximum luminance is 14130 cd/m² at 13V, respectively.

Abstract: Fe₃O₄-coated microsilica composites were synthesized by a novel method. The struction like precursor Fe₃O₄ nanoparticles as the shell and microsillica as the core for the composite has been prepared by chemical reduction method. The Fe₃O₄-coated microsilica composite presents a saturation magnetization value of 38.03 emu/g, which is sufficient to complete magnetic separation. The synthesized magnetic composites are characterized by X-ray diffractometer (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM). The results indicated that Fe₃O₄ nanoparticles successfully coated on microsilica.

Abstract: Radical copolymerization of styrene (St) and maleic anhydride (MA) were typically alternating copolymerization, which generated copolymer styrene-maleic anhydride (SMA). The copolymer was synthesized by solution polymerization method,with benzoyl peroxide (BPO) as initiator and xylene as solvent, and using the yield of copolymer as evaluation criteria, the reaction conditions were researched. The maleic anhydride of molar fraction was 45% in the copolymer measured by chemical titration, combined with the theoretical that the synthesis of styrene-maleic anhydride copolymer was confirmed to be the alternating copolymer. The structure and character of the copolymer was also confirmed by IR. The glass-transition temperature of the alternating copolymer was tested by DSC.

Abstract: The application of the self-cleaning glass to the modern architectures is becoming increasingly wide due to the fact that it is a kind of ecological glass, with environmental protection and outstanding performance. In this paper, the status-quo of the self-cleaning glass, as well as its application and prospect in domestic and abroad are reviewed.