Materials Science Forum Vol. 848

Abstract: With the development of semiconductor technology, the size of complementary metal oxide semiconductor (CMOS) devices has been scaled down to nanoscale dimensions. The technology of copper interconnection is the mainstream technology, so the request of the copper target is more and more rigor. This article analyzes the impact factors on the copper alloy target capability, including oxidation and strength. The aim of this investigation is to set up a bridge between the vendors of copper targets and the foundries of integrated circuit (IC) chip, and the base for the next generation copper targets.

Abstract: Organic/inorganic stacks were deposited on flexible polycarbonate substrate using inductively coupled plasma chemical vapor deposition (ICP-PECVD) for permeation barrier application. The effects of deposition temperature, RF power, gas flow ratio, deposition pressure on film properties of surface roughness, water vapor transmission rate (WVRT) were investigated. Energy dispersive spectrum (EDS), atomic force microscopy (AFM) and transmission electron microscopy (TEM) were used to characterize the film characteristics of the stack layers. It was found that the surface roughness Ra was as low as is 0.25 nm. The WVRT values of the optimum barriers structures were 10^-2g/m² day (1 pair of stacks) and 4.8 x 10^-5g/m² day (4 pair of stacks). This result indicated that the permeation barrier films prepared by ICP-PECVD could be a promising candidate for flexible electronic applications.

Abstract: CH₃NH₃PbI₃ thin film was deposited by a dual-source evaporation system under high vacuum (∼10⁻⁴ Pa). The crystallographic phase was analyzed by X-ray diffraction and confirmed as the perovskite structure. The optical properties of the thin film have been investigated in the spectral range 300-1800 nm. The analysis of the absorption coefficient () reveals direct allowed transition with corresponding energy 1.58 eV. The surface morphology of the film was characterized by atomic force microscopy (AFM). The observed features exhibited by CH₃NH₃PbI₃ give a vital chance to explore its application for various optoelectronic devices. To see its other potential utility, Al/CH₃NH₃PbI₃ /ITO Schottky diodes were fabricated. Based on the analyzing the I-V measurement for the Al/CH₃NH₃PbI₃/ ITO device, the basic device parameters such as barrier height and ideality factor were determined. At the low-voltage region, the current conduction in the device is ohmic type. The charge transport phenomenon appears to be space charge limited current (SCLC) at higher-voltage regions.

Abstract: Two kinds of commercial LED phosphors (green phosphor LuAG:Ce³⁺ and red phosphor CaAlSiN₃:Eu²⁺) with polymethyl methacrylate (PMMA) powders were mixed to prepare film phosphors with tunable emission peak in photoluminescence spectrum by flat vulcanizing machine under the temperature of 170 ^oC and pressure of 2 MPa. The physical phase, surface morphology, transmittance, luminescence spectra of samples were characterized by means of X-ray diffraction (XRD), Environmental scanning electron microscopy (ESEM), Ultraviolet-Visible (UV-Vis) spectrophotometry and Fluorescence spectrometer. The results show that the film phosphors phase was consistent with raw phosphors, phosphor particles were uniformly distributed, and fluorescence spectra with different proportions of phosphors in different position can be adjusted. Tested by HSP 3000 spectrum analyzer, the white LEDs fabricated by blue chip and composite film phosphor containing 5 wt% green phosphor and 1.5 wt.% red phosphor, which refers to the remote excitation technique, possessed color coordinate of (0.3715, 0.3280) and color rendering index (CRI) of 87 when it was driven at power of 36 V/140 mA, reaching the international advanced level.

Abstract: In order to solve the problem that low thermal conductivity of the plastics for the heat of LED, SiC/Phenolic resin for the heat of LED were fabricated combining powder metallurgy. The effects of particles diameters, content and adding nanoparticles on thermal conductivity of the fabricated composites were investigated, the mechanical properties were also characterized. The experimental results showed that the materials were obtained, and the insulation performance of the fabricated SiC/Phenolic resin was higher than the industry standard one, the thermal conductivity reached 4.1W/(m·k)^-1. And the bending strength of the fabricated composites was up to 68.11MPa. The problem of low thermal conductivity of the material is expected to be solved. In addition, it is meaningful for improving LED life.

Abstract: Ni-doped Ge-Te (Ni-GT) material was proposed and investigated for phase change random access memory (PCRAM) applications. With Ni addition, the crystallization temperature, data retention ability and crystallization speed were obviously improved. The surface roughness of crystalline Ni-GT films was decreased by Ni incorporation. Moreover, temperature dependent transmission electron microscopy (TEM) was applied to investigate the phase change behavior of Ni-GT films. All the experimental results demonstrated that Ni-GT material has potential for high-speed PCRAM applications in high temperature environment.

Abstract: CdSe cores with larger radius were prepared by means of two-steps injection of the Cd precursor. Efforts were made to avoid the Ostwald ripening process during the quantum dots grown up. The prepared CdSe cores showed zinc-blende structure with size exceeded over 7 nm. The emission efficiency of prepared quantum dots were 15%, while it increased drastically up to 43% after the formation of ZnCdS shells on the CdSe cores. Morphologies and structures of the quantum dots were characterized by HR-TEM and XRD diffraction. The obtained quantum dots with emission wavelengths more than 660 nm were expected to find their applications in bio-imaging and plant illuminations.

Abstract: Gallium-doped zinc oxide (GZO) thin films were fabricated by radio frequency (RF) magnetron sputtering on glass and silicon substrate at room temperature. The fabrication process, structure, optical properties, and electrical properties of the thin films with different powers (50 W, 70W, and 100 W) were studied to obtain more knowledge about the semiconductor performance. X-ray diffraction (XRD) analysis indicated that the GZO films were polycrystalline and preferred c axis orientation. The average transmittance decreased form 93% to 84% in the visible range, and all the optical band gap was about 3.05 eV when the power increased from 50W to 100W. Simultaneously, the GZO thin film transistors (TFTs) with excellent transfer characteristic prove that GZO thin film is a potential semiconductor material candidate which can be used for the active layer in thin film transistors fabrication.

Abstract: P-type transparent conducting SnO thin films were directly fabricated using RF magnetron sputtering. The electronic properties of the SnO thin films were enhanced by Na ion implantation and annealing at 200°C. The growth and implantation conditions were systemically investigated. The electronic properties, optical properties, microstructure and surface morphologies of the films were characterized. It was observed that the structure of the Na-doped SnO films was crucial to improving their p-type conductivity.

Abstract: Lanthanum orthophosphate (LaPO₄) is a useful host for doping rare earth ions with high quantum efficiencies. In the present investigation the monoclinic LaPO₄ and LaPO₄:Sm³⁺ were synthesized via hydrothermal route. SEM, XRD, FTIR and Raman spectroscopy as well as the luminescence spectroscopy were utilized to character the samples of the Sm³⁺-doped LaPO₄. The results indicated that the lattice parameters decreased linearly with Sm³⁺ concentration, and general linear hypsochromic shifts regarding Sm³⁺ concentration were observed in infrared spectroscopic wavenumbers and Raman band positions. The emission spectra showed that Sm³⁺ ions were in more non-centrosymmetric environment when Sm³⁺ concentration increased.