UV photoconductivity characteristics of ZnO nanowire field effect transistor treated by proton irradiation

We investigated the UV photoconductivity characteristics of ZnO nanowire field effect transistors (FETs) irradiated by proton beams. After proton beam irradiation (using a beam energy of 10 MeV and a fluence of 10 12 cm -2), the drain current and carrier density in the ZnO nanowire FETs decreased, and the threshold voltage shifted to the positive gate bias direction due to the creation of interface traps at the SiO 2/ZnO nanowire interface by the proton beam. The interface traps produced a higher surface barrier potential and a larger depletion region at the ZnO nanowire surface, affecting the photoconductivity and its decay time. The UV photoconductivity of the proton-irradiated ZnO nanowire FETs was higher and more prolonged than that of the pristine ZnO nanowire FETs. The results extend our understanding of the UV photoconductivity characteristics of ZnO nanowire devices and other materials when irradiated with highly energetic particles. © 2012 Elsevier B.V. All rights reserved.

The development of a scanning strategy for the manufacture of porous biomaterials by selective laser melting.

Porous structures are used in orthopaedics to promote biological fixation between metal implant and host bone. In order to achieve rapid and high volumes of bone ingrowth the structures must be manufactured from a biocompatible material and possess high interconnected porosities, pore sizes between 100 and 700 microm and mechanical strengths that withstand the anticipated biomechanical loads. The challenge is to develop a manufacturing process that can cost effectively produce structures that meet these requirements. The research presented in this paper describes the development of a 'beam overlap' technique for manufacturing porous structures in commercially pure titanium using the Selective Laser Melting (SLM) rapid manufacturing technique. A candidate bone ingrowth structure (71% porosity, 440 microm mean pore diameter and 70 MPa compression strength) was produced and used to manufacture a final shape orthopaedic component. These results suggest that SLM beam overlap is a promising technique for manufacturing final shape functional bone ingrowth materials.

UV durable colour pigment doped SmA liquid crystal composites for outdoor trans-reflective bi-stable displays

High brightness trans-reflective bi-stable displays based on smectic A (SmA) liquid crystals (LCs) can have nearly perfect transparency in the clear state and very high reflection in the scattered state. Because the LC material in use is stable under UV radiation, this kind of displays can stand for strong day-light and therefore be ideal for outdoor applications from e-books to public signage and advertisement. However, the colour application has been limited because the traditional colourants in use are conventional dyes which are lack of UV stability and that their colours are easily photo bleached. Here we present a colour SmA display demonstrator using pigments as colourant. Mixing pigments with SmA LCs and maintain the desirable optical switching performance is not straightforward. We show here how it can be done, including how to obtain fine sized pigment nano-particles, the effects of particle size and size distribution on the display performance. Our optimized pigments/SmA compositions can be driven by a low frequency waveform (∼101Hz) to a scattered state to exhibit colour while by a high frequency waveform (∼103Hz) to a cleared state showing no colour. Finally, we will present its excellent UV life-time (at least >7.2 years) in comparison with that of dye composition (∼2.4 years). The complex interaction of pigment nano-particles with LC molecules and the resulting effects on the LC electro-optical performances are still to be fully understood. We hope this work will not only demonstrate a new and practical approach for outdoor reflective colour displays but also provide a new material system for fundamental liquid crystal colloid research work. © 2012 SPIE.

Band gap opening of graphene after UV/ozone and oxygen plasma treatments

Graphene grown by Chemical Vapor Deposition (CVD) on nickel subsrate is oxidized by means of oxygen plasma and UV/Ozone treatments to introduce bandgap opening in graphene. The degree of band gap opening is proportional to the degree of oxidation on the graphene. This result is analyzed and confirmed by Scanning Tunnelling Microscopy/Spectroscopy and Raman spectroscopy measurements. Compared to conventional wet-oxidation methods, oxygen plasma and UV/Ozone treatments do not require harsh chemicals to perform, allow faster oxidation rates, and enable site-specific oxidation. These features make oxygen plasma and UV/Ozone treatments ideal candidates to be implemented in high-throughput fabrication of graphene-based microelectronics. © 2011 Materials Research Society.