Ahmed Al-Haddad

Facile Transferring of Wafer-Scale Ultrathin Alumina Membranes onto Substrates for Nanostructure Patterning

Ordered nanostructure arrays have attracted intensive attention because of their various applications. However, it is still a great challenge to achieve ordered nanostructure patterning over a large area (such as wafer-scale) by a technique that allows high throughput, large pattern area and low equipment costs. Here, through a unique design of the fabrication and transferring processes, we achieve a facile transferring of wafer-scale ultrathin alumina membranes (UTAMs) onto substrates without any twisting, folding, cracking and contamination. The most important in our method is fixing the UTAM onto the wafer-scale substrate before removing the backside Al and alumina barrier layer. It is also demonstrated that the thickness and surface smoothing of UTAMs play crucial roles in this transferring process. By using these perfectly transferred UTAMs as masks, various nanostructure patterning including nanoparticle, nanopore (nanomesh) and nanowire arrays are fabricated on wafer-scale substrates with tunable and uniform dimension. Because there are no requirements for UTAMs, substrates and materials to be deposited, the method presented here shall provide a cost-effective platform for the fabrication of ordered nanostructures on large substrates for various applications in nanotechnology.

The shift of the optical absorption band edge of ZnO/ZnS core/shell nanotube arrays beyond quantum effects

Unlike conventional investigations that focus on the manipulation of optical absorption band edge for a single componential material through quantum confinement effects, in this paper, we study the optical absorption properties of well-ordered ZnO/ZnS core/shell nanotube arrays. Our data point out that the profile of the absorbance spectrum of ZnO/ZnS nanotube arrays is determined by the two components and geometrical parameters of the nanostructure arrays. We find that both of the ZnO and ZnS show a decrease in the optical band gap with the increase in ZnS thickness and the diameter of the nanotube arrays, which is interestingly out of explanation from the material aspect. The subsequent finite-difference-time-domain simulations support such observations and illustrate that the geometrical and periodical parameters could also impact the optical absorption of the core/shell nanostructure arrays, even without concerning the quantum effects.

Highly-Ordered 3D Vertical Resistive Switching Memory Arrays with Ultralow Power Consumption and Ultrahigh Density

Resistive switching random access memories (RRAM) have attracted great scientific and industrial attention for next generation data storage because of their advantages of nonvolatile properties, high density, low power consumption, fast writing/erasing speed, good endurance, and simple and small operation system. Here, by using a template-assisted technique, we demonstrate a three-dimensional highly ordered vertical RRAM device array with density as high as that of the nanopores of the template (10(8)-10(9) cm(-2)), which can also be fabricated in large area. The high crystallinity of the materials, the large contact area and the intimate semiconductor/electrode interface (3 nm interfacial layer) make the ultralow voltage operation (millivolt magnitude) and ultralow power consumption (picowatt) possible. Our procedure for fabrication of the nanodevice arrays in large area can be used for producing many other different materials and such three-dimensional electronic device arrays with the capability to adjust the device densities can be extended to other applications of the next generation nanodevice technology.

Constructing Well-Ordered CdTe/TiO2 Core/Shell Nanowire Arrays for Solar Energy Conversion.

Well-ordered CdTe/TiO2 heteronanostructure arrays are fabricated via a convenient anodic aluminum oxide template-directed approach and applied to photoelectrochemistry and solar energy devices. Both the CdTe and TiO2 present a decent crystalline quality. In comparison to the photoanode with only TiO2 nanotube array, the CdTe/TiO2 heteronanostructure electrodes possess a dramatic performance improvement.