Plasma enhancement of current from carbon cathodes for field emission displays

This paper examines the possibility of using a background gas medium to enhance the current available from low threshold carbon cathodes. The field emission current is used to initiate a plasma in the gas medium, and thereby achieve a current multiplication effect. Results on the variation of anode current as a function of electric field and gas pressure are presented. These are compared with model calculations to verify the principles of operation. The influence of ion bombardment on the long term performance thin film carbon cathodes is examined for He and Ar multiplication plasmas. A measure of the influence of current multiplication on display quality is presented by examining light output from two standard low voltage phosphors. Also studied are the influence of doping the carbon with N to lower the threshold voltage for emission as well as the consequent impact on anode current from the plasma.

Thermal plasma synthesis of superparamagnetic iron oxide nanoparticles

Superparamagnetic iron oxide nanoparticles were synthesized by injecting ferrocene vapor and oxygen into an argon/helium DC thermal plasma. Size distributions of particles in the reactor exhaust were measured online using an aerosol extraction probe interfaced to a scanning mobility particle sizer, and particles were collected on transmission electron microscopy (TEM) grids and glass fiber filters for off-line characterization. The morphology, chemical and phase composition of the nanoparticles were characterized using TEM and X-ray diffraction, and the magnetic properties of the particles were analyzed with a vibrating sample magnetometer and a magnetic property measurement system. Aerosol at the reactor exhaust consisted of both single nanocrystals and small agglomerates, with a modal mobility diameter of 8-9 nm. Powder synthesized with optimum oxygen flow rate consisted primarily of magnetite (Fe 3O 4), and had a room-temperature saturation magnetization of 40.15 emu/g, with a coercivity and remanence of 26 Oe and 1.5 emu/g, respectively. © Springer Science+Business Media, LLC 2011.

Room-temperature remote-plasma sputtering of c-axis oriented zinc oxide thin films

Highly c-axis oriented ZnO films have been deposited at room temperature with high rates (∼50 nm·min -1) using an innovative remote plasma sputtering configuration, which allows independent control of the plasma density and the sputtering ion energy. The ZnO films deposited possess excellent crystallographic orientation, high resistivity (>10 9 Ω·m), and exhibit very low surface roughness. The ability to increase the sputtering ion energy without causing unwanted Ar + bombardment onto the substrate has been shown to be crucial for the growth of films with excellent c-axis orientation without the need of substrate heating. In addition, the elimination of the Ar + bombardment has facilitated the growth of films with very low defect density and hence very low intrinsic stress (100 MPa for 3 μm-thick films). This is over an order of magnitude lower than films grown with a standard magnetron sputtering system. © 2012 American Institute of Physics.

Plasma stabilisation of metallic nanoparticles on silicon for the growth of carbon nanotubes

Ammonia (NH 3) plasma pretreatment is used to form and temporarily reduce the mobility of Ni, Co, or Fe nanoparticles on boron-doped mono- and poly-crystalline silicon. X-ray photoemission spectroscopy proves that NH 3 plasma nitrides the Si supports during nanoparticle formation which prevents excessive nanoparticle sintering/diffusion into the bulk of Si during carbon nanotube growth by chemical vapour deposition. The nitridation of Si thus leads to nanotube vertical alignment and the growth of nanotube forests by root growth mechanism. © 2012 American Institute of Physics.

Ion beam, focused ion beam, and plasma discharge machining

Non-conventional methods of machining are used for many engineering applications where the traditional processes fail to be cost-effective. Such processes include Ion Beam Machining (IBM), focused ion beam (FIB) machining and plasma discharge machining. The mechanisms of material removal and associated hardware and software developed for industrial applications of these fascinating electro-physical and chemical machining processes are reviewed together with the latest research findings. © 2009 CIRP.

Hierarchical carbon nanowire microarchitectures made by plasma-assisted pyrolysis of photoresist

We present a new approach for the fabrication and integration of vertically aligned forests of amorphous carbon nanowires (CNWs), using only standard lithography, oxygen plasma treatment, and thermal processing. The simplicity and scalability of this process, as well as the hierarchical organization of CNWs, provides a potential alternative to the use of carbon nanotubes and graphene for applications in microsystems and high surface area materials. The CNWs are highly branched at the nanoscale, and novel hierarchical microstructures with CNWs connected to a solid amorphous core are made by controlling the plasma treatment time. By multilayer processing we demonstrate deterministic joining of CNW micropillars into 3D sensing networks. Finally we show that these networks can be chemically functionalized and used for measurement of DNA binding with increased sensitivity. © 2011 American Chemical Society.

High-density remote plasma sputtering of high-dielectric-constant amorphous hafnium oxide films

Hafnium oxide (HfOx) is a high dielectric constant (k) oxide which has been identified as being suitable for use as the gate dielectric in thin film transistors (TFTs). Amorphous materials are preferred for a gate dielectric, but it has been an ongoing challenge to produce amorphous HfOx while maintaining a high dielectric constant. A technique called high target utilization sputtering (HiTUS) is demonstrated to be capable of depositing high-k amorphous HfOx thin films at room temperature. The plasma is generated in a remote chamber, allowing higher rate deposition of films with minimal ion damage. Compared to a conventional sputtering system, the HiTUS technique allows finer control of the thin film microstructure. Using a conventional reactive rf magnetron sputtering technique, monoclinic nanocrystalline HfOx thin films have been deposited at a rate of ∼1.6nmmin-1 at room temperature, with a resistivity of 1013Ωcm, a breakdown strength of 3.5MVcm-1 and a dielectric constant of ∼18.2. By comparison, using the HiTUS process, amorphous HfOx (x=2.1) thin films which appear to have a cubic-like short-range order have been deposited at a high deposition rate of ∼25nmmin-1 with a high resistivity of 1014Ωcm, a breakdown strength of 3MVcm-1 and a high dielectric constant of ∼30. Two key conditions must be satisfied in the HiTUS system for high-k HfOx to be produced. Firstly, the correct oxygen flow rate is required for a given sputtering rate from the metallic target. Secondly, there must be an absence of energetic oxygen ion bombardment to maintain an amorphous microstructure and a high flux of medium energy species emitted from the metallic sputtering target to induce a cubic-like short range order. This HfOx is very attractive as a dielectric material for large-area electronic applications on flexible substrates. A remote plasma sputtering process (high target utilization sputtering, HiTUS) has been used to deposit amorphous hafnium oxide with a very high dielectric constant (∼30). X-ray diffraction shows that this material has a microstructure in which the atoms have a cubic-like short-range order, whereas radio frequency (rf) magnetron sputtering produced a monoclinic polycrystalline microstructure. This is correlated to the difference in the energetics of remote plasma and rf magnetron sputtering processes. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Deposition of low stress amorphous zinc tin oxide at ambient temperature using a remote plasma sputtering process suitable for delicate substrates

ZnxSnyOz thin films (<100nm thickness), deposited by remote sputtering from a metal target using a confined argon plasma and oxygen gas jet near the sample, were investigated for their material properties. No visible deformation or curl was observed when deposited on plastic. Materials were confirmed to be amorphous and range between 5 and 10 at.% Sn concentration by x-ray diffraction, x-ray photoemission spectroscopy and energydispersive x-ray spectroscopy. Factors affecting the material composition over time are discussed. Depletion of the Sn as the target ages is suspected. © The Electrochemical Society.

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.