Fabrication of CuO and Cu2O nanoparticles in a thick polyimide film by post heat treatment in a controlled-atmosphere

We investigated the formation of CuO or Cu2O nanoparticles in the thick polyimide films by oxidizing Cu nanoparticles at various temperatures during the post heat-treatment. Cu nanoparticles of 4-5 nm in diameter were initially formed in the polyimide film by the reaction between a Cu film and a polyimide precursor, polyamic acid, and a following thermal curing in a reducing atmosphere. After the subsequent post heat-treatments in oxidizing atmospheres, X-ray diffraction patterns revealed that initial metallic Cu nanoparticles were transformed to Cu2O or CuO nanoparticles depending on the temperature during the post heat-treatment. Cu nanoparticles were oxidized to Cu2O during the post heat-treatment at low temperature while Cu nanoparticles were oxidized to CuO during the post heat-treatment at high temperature. Cross-sectional TEM studies showed that about 4.7 nm sized Cu2O nanoparticles or 4.7-5.2 nm sized CuO nanoparticles were fabricated in a thick polyimide film depending on the post heat-treatment condition. In the optical absorption measurements, the absorption peak from surface plasmon resonance of Cu nanoparticles disappeared during the post heat-treatment in an oxidizing atmosphere.     

ZnO nanowire-based nano-floating gate memory with Pt nanocrystals embedded in Al(2)O(3) gate oxides

The memory characteristics of ZnO nanowire-based nano-floating gate memory (NFGM) with Pt nanocrystals acting as the floating gate nodes were investigated in this work. Pt nanocrystals were embedded between Al(2)O(3) tunneling and control oxide layers deposited on ZnO nanowire channels. For a representative ZnO nanowire-based NFGM with embedded Pt nanocrystals, a threshold voltage shift of 3.8?V was observed in its drain current versus gate voltage (I(DS)-V(GS)) measurements for a double sweep of the gate voltage, revealing that the deep effective potential wells built into the nanocrystals provide our NFGM with a large charge storage capacity. Details of the charge storage effect observed in this memory device are discussed in this paper.     

Memory effects of nonvolatile memory devices with a floating gate fabricated utilizing Ag nanoparticles embedded into a polymethylmethacrylate layer

Nonvolatile memory devices based on a polymethylmethacrylate (PMMA) layer containing Ag nanoparticles were formed by using a spin coating method. High-resolution transmission electron microscopy images showed that Ag nanoparticles were randomly distributed in the PMMA layer. Capacitance-voltage (C-V) curves for the Al/Ag nanoparticles embedded in a PMMA layer/p-Si(100) device at 300 K showed a hysteresis with a large flat-band voltage shift, indicative of the Ag nanoparticles acting as the charge storage in the memory device. The magnitude of the flat-band voltage shift for the memory devices increased with increasing Ag nanoparticle concentration. The operating mechanisms for the writing and the erasing processes for the Al/Ag nanoparticles embedded in a PMMA layer/p-Si(100) device are described on the basis of the C-V results and electronic structures.     

Thin film transistors with Er2O3 gate insulators

Er₂O₃ was used to fabricate thin film transistors (TFTs) using the multiple pumpdown (MPD) method of device fabrication. CdS-Er₂O₃, CdSe-Er₂O₃ and (CdS-CdSe)-Er₂O₃ were used as the semiconductor-insulator combinations. In the “mixed semiconductor” TFT a mixture of CdS and CdSe in the ratio of 1:1 by weight was used. The various transistor parameters are presented. Parameters such as critical donor density, trap density, mobility and crystallite size were calculated using a model proposed by Levinson et al.     

氧化亚铜薄膜的研究进展

氧化亚铜（Cu2O）具有优越的光电性质，是一种具有广泛用途的材料，而且它的制备方法很多。结合最近的研究进展综述了Cu2O薄膜的制备方法与基本性质，分析了Cu2O薄膜研究开发现状，展望了Cu2O薄膜在太阳能电池应用方面的前景。     

Fabrication of copper nanoparticles in a thick polyimide film cured by rapid thermal annealing

We investigated the imidization of a polyimide (PI) and the formation of Cu nanoparticles in a PI film by curinga precursor of PI (polyamic acid (PAA) dissolved in n-methyl-2-pyrrolidinone) in a reducing atmosphere in the rapid thermal annealing (RTA) system. A Cu film was deposited onto the SiO2/Si substrate, and the PAA was spin-coated onto the Cu film. After the PAA reacted with the Cu film, soft-baking was performed to evaporate the solvent. Finally, the PAA was imidized to PI at 450 degrees C by curing in a reducing atmosphere with the RTA. Fourier transform infrared spectroscopy showed that the PAA was successfully imidized by the RTA. X-ray diffraction patterns revealed that Cu nanoparticles formed by RTA curing at 450 degrees C for 5 minutes in a reducing atmosphere, and transmission electron microscopy showed that Cu nanoparticles about 6.5 nm in size were uniformly dispersed in the PI film. Curing by RTA is an attractive method because it takes only a few minutes.     

Behavior of Cu nanoparticles ink under reductive calcination for fabrication of Cu conductive film

Cu nanoparticle ink was prepared from Cu nanoparticles that were coated with a gelatin layer at an average diameter of 46 nm. The Cu nanoparticle ink was applied on the polyimide substrate. Conductive films were fabricated using the Cu nanoparticle ink with a two-step annealing process consisting of oxidative pre-heating at 200 °C under 10 ppm O₂-N₂ mixed gas flow and reductive calcination at 250 °C under 3 vol.% H₂-N₂ mixed gas flow showed a low resistivity of 5 μΩ cm. The hydrolysis of the remaining gelatin layer by H₂O vapor, which was formed during the reduction of the Cu oxide by 3 vol.% H₂-N₂ mixed gas, was suggested. The results suggest the possibility of the removal of the gelatin layer without oxidative pre-heating and simultaneous sintering of Cu nanoparticles in reductive calcination.     

Ion irradiation effects in EuBa2Cu3O y thin film

The effect of He ion irradiation on the pinning potential in EuBa₂Cu₃O _y , thin film was investigated by measuring the temperature dependence of resistivity in magnetic fields. The pinning potential decreased as the ion fluence increased. A slower decrease of pinning potential was observed in higher magnetic field in the fluence region <3.5×10¹⁵ cm^?2.     

TiO2/void/porous Al2O3 shell embedded in polyvinylidene fluoride film for cleaning wastewater

In order to selectively adsorb hydrolyzed polyacryamide (HPAM) and remove oil from oily wastewater, TiO₂/void/porous Al₂O₃ shell particles (TVAs) were designed and prepared though hydrolysis and calcination; subsequently, the TVAs were embedded into polyvinylidene fluoride (PVDF) to prepare composite films (TVAP films). As polymeric supports, TVAP films were employed to immobilize TiO₂ powder. TVAs were characterized using SEM, TEM, FT-IR, BET while TVAP films were characterized by SEM. The results indicate that the particle size of TVAs is mainly distributed between 700 and 800?nm, core-shell structure has been successfully built. The removal rates of TVAP films prepared under the optimum synthesis conditions for oil and HPAM reach 69.70% and 60.20% respectively, performing attractive properties of mass transfer and adsorption. Therefore, TVAP films are desirable as suitable materials to clean oily wastewater.     

Formation and in situ sizing of gamma-Fe2O3 nanoparticles in a microwave flow reactor

Nanocrystalline gamma-Fe2O3 particles were produced in a microwave flow reactor. The reaction of iron pentacarbonyl [Fe(CO)5] with the plasma gases Ar/O2 to form nanosized particles was followed by in situ particle mass spectrometry. The particle mass spectrometer combines a nonintrusive sampling technique with a calibration-free mass determination. The influence of process parameters like microwave power, precursor concentration, and pressure on the particle size was studied. The results reveal a mean particle diameter in the range of 4-5 nm with a slight dependence on the process parameter. The geometric standard deviation of the measured size distribution was always between 1.1 and 1.2.     

Rapid treatment of polyimide film surfaces using high-density microwave plasma for enhancement of Cu layer adhesion

A high-density microwave plasma has been applied to the surface of polyimide (PI) films as a treatment to enhance the adhesion of sputter-deposited copper layers. A very short (∼5 s) exposure to Ar plasma enhanced the contact angle from 72° to ∼14°. X-ray photoelectron spectroscopy and atomic force microprobe measurements showed an increase in hydrophilic radicals (-OH, -CO) and surface roughness, respectively, following the plasma treatment. Peel strength tests of Cu layers deposited on plasma-treated polyimide films showed that the plasma treatment significantly enhanced Cu layer adhesion.     

Self-assembly of silver nanoparticles: Formation of a thin silver film in a polymer matrix

A synthetic route is presented for the preparation of a silver film in presence of UV-radiation. Methoxy polyethylene glycol, a water-soluble polymer, was used as the reducing agent of the silver ions in the presence of an ultraviolet source to produce silver nanoparticles. During solution stirring, a centrifugal force was generated at the center of the solution. At this point on the surface of the solution, the nanoparticles coalesced to form a self-assembly of small subunits that ultimately develops into a film-like network.     

Complete CO oxidation over Cu2O nanoparticles supported on silica gel

We find that nearly monodisperse copper oxide nanoparticles prepared via the thermal decomposition of a Cu(I) precursor exhibit exceptional activity toward CO oxidation in CO/O2/N2 mixtures. Greater than 99.5% conversion of CO to CO2 could be achieved at temperatures less than 250 degrees C for over 12 h. In addition, the phase diagram and pathway for CO oxidation on Cu2O (100) is computed by ab initio methods and found to be in qualitative agreement with the experimental findings.     

An amperometric detector formed of highly dispersed Ni nanoparticles embedded in a graphite-like carbon film electrode for sugar determination

We achieved improved detection limits for sugars by developing a novel thin film containing 0.8% highly dispersed Ni nanoparticles in disordered graphite-like carbon (Ni-NDC) as a detection electrode for high-performance liquid chromatography. The Ni-NDC film was prepared in one step by a simple radio frequency (rf) sputtering method at a temperature below 200 degrees C. We characterized the film by XPS, TEM, and AFM analysis and found that the average Ni nanoparticle size was 3 nm and that the film consisted of a mixture of Ni, NiO, Ni2O3, and Ni(OH)2. We studied the electrochemical detection of sugars using the 0.8% Ni-NDC film electrode. The film electrode had excellent electrocatalytic ability and good stability compared with a Ni-bulk electrode with regard to the electrooxidation of sugars. We employed the Ni-NDC film as an HPLC detection electrode. We achieved a good separation of four sugars (glucose, fructose, sucrose, lactose) at a relatively low constant detection potential (0.40 V vs Ag/AgCl) and a linearity of over 3 orders of magnitude. We obtained improved detection limits for the investigated sugars, namely, 20, 25, 50, and 37 nM for glucose, fructose, sucrose, and lactose, respectively. This is at least 1 order of magnitude lower than the detection limits obtained with a Ni-bulk electrode with the same measurement condition. The Ni-NDC film electrode also showed good reproducibility with a relative standard deviation of 1.75% for 40 consecutive injections of glucose in a flow system.     

Formation of silver nanoparticles by through thin film ablation

Well dispersed Ag nanoparticles have been formed by a process denoted Through Thin Film Ablation. The nanoparticles were deposited on room temperature substrates, had a most probable size of 1 nm, and were not agglomerated. The nanoparticle deposit produced by this process showed no evidence of the larger particles commonly observed from conventional pulsed laser ablation that uses a bulk target. Synthesis of nanoparticles by Through Thin Film Ablation should be possible for any material that can be made as a thin film target and may enable the unique properties of isolated, non-agglomerated nanoparticles to be exploited more fully.