Improving Nucleation in the Fabrication of High-Quality 3D Macro-Porous Copper Film through The Surface-Modification of A Polystyrene Colloid-Assembled Template

A new approach is developed to the fabrication of high-quality three-dimensional macro-porous copper films. A highly-ordered macroporous copper film is successfully produced on a polystyrene sphere (PS) template that has been modified by sodium dodecyl sulfate (SDS). It is shown that this procedure can change a hydrophobic surface of PS template into a hydrophilic surface. The present study is devoted to the influence of the electrolyte solution transport on the nucleation process. It is demonstrated that the permeability of the electrolyte solution in the nanochannels of the PS template plays an important role in the chemical electrodeposition of high-quality macroporous copper film. The permeability is drastically enhanced in our experiment through the surface modi. cation of the PS templates. The method could be used to homogeneously produce a large number of nucleations on a substrate, which is a key factor for the fabrication of the high-quality macroporous copper film.

Structure and magnetic properties of CoNiP nanowire arrays embedded in AAO template

Ternary CoNiP nanowire (NW) arrays have been synthesized by electrochemical deposition inside the nanochannels of anodic aluminum oxide (AAO) template. The CoNiP NWs deposited at room temperature present soft magnetic properties, with both parallel and perpendicular coercivities less than 500 Oe. In contrast, as the electrolyte temperature (T-elc) increases from 323 to 343 K, the NWs exhibit hard magnetic properties with coercivities in the range of 1000-2500 Oe. This dramatic increase in coercivities can be attributed to the domain wall pinning that is related to the formation of Ni and Co nanocrystallites and the increase of P content. The parallel coercivity (i.e. the applied field perpendicular to the membrane surface) maximum as high as 2500 Oe with squareness ratio up to 0.8 is achieved at the electrolyte temperature of 328 K. It has been demonstrated that the parallel coercivity of CoNiP NWs can be tuned in a wide range of 200-2500 Oe by controlling the electrolyte temperature, providing an easy way to control magnetic properties and thereby for their integration with magnetic-micro-electromechanical systems (MEMS). (C) 2008 Elsevier B.V. All rights reserved.

Structural and optical properties of Al1-xInxN epilayers on GaN template grown by metalorganic chemical vapor deposition

This paper reports that Al1-xInxN epilayers were grown on GaN template by metalorganic chemical vapor deposition with an In content of 7%-20%. X-ray diffraction results indicate that all these Al1-xInxN epilayers have a relatively low density of threading dislocations. Rutherford backscattering/channeling measurements provide the exact compositional information and show that a gradual variation in composition of the Al1-xInxN epilayer happens along the growth direction. The experimental results of optical reflection clearly show the bandgap energies of Al1-xInxN epilayers. A bowing parameter of 6.5 eV is obtained from the compositional dependence of the energy gap. The cathodoluminescence peak energy of the Al1-xInxN epilayer is much lower than its bandgap, indicating a relatively large Stokes shift in the Al1-xInxN sample.

A study of the degree of relaxation of AlGaN epilayers on GaN template

The strain state of 570nm AlXGa1-xN layers grown on 600nm GaN template by metal organic chemical vapor deposition was studied using Rutherford backscattering (RBS)/channeling and triple-axis X-ray diffraction measurements. The results showed that the degree of relaxation (R) of AlxGa1-xN layers increased almost linearly when x less than or equal to 0.42 and reached to 70% when x = 0.42. Above 0.42, the value of R varied slowly and AI(x)Ga(1-x)N layers almost full relaxed when x = 1 (AIN). In this work the underlying GaN layer was in compressive strain, which resulted in the reduction of lattice misfit between GaN and AlxGa1-xN, and a 570nm AlxGa1-xN layer with the composition of about 0.16 might be grown on GaN coherently from the extrapolation. The different shape of (0004) diffraction peak was discussed to be related to the relaxation. (C) 2004 Elsevier B.V. All rights reserved.

Study on surface morphology of GaN growth by MOCVD on GaN/Si(111) template

The surface morphology of GaN grown by MOCVD on GaN/Si template was studied. Rough morphology and deep pinhole defects on some surface areas of the samples were observed and studied. The formation of rough morphology is possibly related to Ga-Si alloy produced due to poor thermal stability of template at high temperature. The deep pinhole defects generated are deep down to the surface of MBE-grown GaN/Si template. The stress originated from the large thermal expansion coefficient difference between GaN and Si may be related to the formation of the pinhole defects. The surface morphology of the GaN can be improved by optimizing the GaN/Si template and decreasing the growth temperature.

Corrugated surfaces formed on GaAs(331)A substrates: the template for laterally ordered InGaAs nanowires

Morphology evolution of high-index GaAs(331)A surfaces during molecular beam epitaxy (MBE) growth has been investigated in order to achieve regularly distributed step-array templates and fabricate spatially ordered low-dimensional nano-structures. Atomic force microscope (AFM) measurements have shown that the step height and terrace width of GaAs layers increase monotonically with increasing substrate temperature. By using the step arrays formed on GaAs(331)A surfaces as the templates, we have fabricated highly ordered InGaAs nanowires. The improved homogeneity and the increased density of the InGaAs nanowires are attributed to the modulated strain field caused by vertical multi-stacking, as well as the effect of corrugated surface of the template. Photoluminescence (PL) tests confirmed remarkable polarization anisotropy.

Characterization of AlGaN on GaN template grown by MOCVD - art. no. 68410K

AlxGa1-xN layer was grown on sapphire substrate with GaN template by Metal Organic Chemical Vapor Deposition system (MOCVD). High temperature A1N (HT-A1N) interlayer was inserted between AlxGa1-xN layer and GaN template to solve the cracking problem that often appears on AlxGa1-xN surface when directly grown on high temperature GaN template. Optical microscope, scanning electron microscopy (SEM), atomic force microscope (AFM), high resolution x-ray diffraction (HRXRD) and cathodoluminescence (CL) were used for characterization. It was found that the cracking was successfully eliminated. Furthermore, the crystalline quality of AlxGa1-xN layer with HT-A1N interlayer was much improved. Interference fringes were found in the HRXRD images. CL test showed that yellow emission was much reduced for AlGaN layer with HT-A1N interlayer.

High Quality AlGaN Grown on GaN Template with HT-AlN Interlayer

When AlGaN is grown on GaN template, crack networks invariably generate when the thickness of the AlGaN layers over GaN exceeds the critical value. We used thin high temperature deposited AlN layer (HT-AlN) as the interlayer between GaN template and AlGaN epilayer which was very effective in eliminating the cracks in AlGaN epilayer. AlGaN layers with high Al mole fractions were also grown. Characterization showed that the crystalline quality of AlGaN epilayer was fairly good even when the At mole fraction was high.

Corrugated surfaces formed on GaAs (331)a substrates: The template for laterally ordered InGaAs nanowires

Morphology evolution of high-index (331)A surfaces during molecular beam epitaxy (MBE) growth have been investigated in order to uncover their unique physic properties and fabricate spatially ordered low dimensional nanostructures. Atomic Force Microscope (AFM) measurements have shown that the step height and terrace width of GaAs layers increase monotonically with increasing substrate temperature in conventional MBE. However, this situation is reversed in atomic hydrogen-assisted MBE, indicating that step bunching is partly suppressed. We attribute this to the reduced surface migration length of Ga adatoms with atomic hydrogen. By using the step arrays formed on GaAs (331)A surfaces as the templates, we fabricated laterally ordered InGaAs self-aligned nanowires.

Study on surface morphology of GaN growth by MOCVD on GaN/Si(111) template

The surface morphology of GaN grown by MOCVD on GaN/Si template was studied. Rough morphology and deep pinhole defects on some surface areas of the samples were observed and studied. The formation of rough morphology is possibly related to Ga-Si alloy produced due to poor thermal stability of template at high temperature. The deep pinhole defects generated are deep down to the surface of MBE-grown GaN/Si template. The stress originated from the large thermal expansion coefficient difference between GaN and Si may be related to the formation of the pinhole defects. The surface morphology of the GaN can be improved by optimizing the GaN/Si template and decreasing the growth temperature.

Fabrication of Silicon-Based Template-Assisted Nanoelectrode Arrays and Ohmic Contact Properties Investigation

A convenient fabrication technology for large-area, highly-ordered nanoelectrode arrays on silicon substrate has been described here, using porous anodic alumina (PAA) as a template. The ultrathin PAA membranes were anodic oxidized utilizing a two-step anodization method, from Al film evaporated on substrate. The purposes for the use of two-step anodization were, first, improving the regularity of the porous structures, and second reducing the thickness of the membranes to 100 similar to 200 nm we desired. Then the nanoelectrode arrays were obtained by electroless depositing Ni-W alloy into the through pores of PAA membranes, making the alloy isolated by the insulating pore walls and contacting with the silicon substrates at the bottoms of pores. The Ni-W alloy was also electroless deposited at the back surface of silicon to form back electrode. Then ohmic contact properties between silicon and Ni-W alloy were investigated after rapid thermal annealing. Scanning electron microscopy (SEM) observations showed the structure characteristics, and the influence factors of fabrication effect were discussed. The current voltage (I-V) curves revealed the contact properties. After annealing in N-2 at 700 degrees C, good linear property was shown with contact resistance of 33 Omega, which confirmed ohmic contacts between silicon and electrodes. These results presented significant application potential of this technology in nanosize current-injection devices in optoelectronics, microelectronics and bio-medical fields.