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Vopsaroiu M.,National Physical Laboratory United Kingdom | Cain M.G.,National Physical Laboratory United Kingdom | Woolliams P.D.,National Physical Laboratory United Kingdom | Weaver P.M.,National Physical Laboratory United Kingdom | And 4 more authors.
Journal of Applied Physics | Year: 2011

The ability to dynamically tune the coercive field of magnetic thin films is a powerful tool for applications, including in magnetic recording disk technologies. Recently, a number of papers have reported the electrical voltage control of the coercive field of various magnetic thin films in multiferroic composites. Theoretically, this is possible in magneto-electric (ME) multiferroics due to the piezoferroelectric component that can be electrically activated to dynamically modify the properties of the magnetic component of the composite via a direct or strain mediated ME coupling. In this paper we fabricated and examined such structures and we determined that the magnetic coercive field reduction is most likely due to a heating effect. We concluded that this effect is probably an artifact that cannot be attributed to a multiferroic coupling. © 2011 American Institute of Physics.

Vopson M.M.,University of Portsmouth | Vopson M.M.,National Physical Laboratory United Kingdom | Lees K.,National Physical Laboratory United Kingdom | Hall M.,National Physical Laboratory United Kingdom | And 4 more authors.
Measurement Science and Technology | Year: 2014

We report the development of a pulsed inductive microwave magnetometer for measurements of ultra-fast magnetization dynamics of soft magnetic thin films. This paper details the instrument construction and the measurement procedure. We show experimentally that our instrument detects nanosecond and sub-nanosecond magnetization precession/relaxation processes, in real time, without the need for data averaging, interpolation or any other post-measurement data processing. This enhanced detection resolution has been achieved by careful design and optimization of the coplanar waveguide, which will be described in detail in this paper. Moreover, we show that, unlike other similar instruments, our apparatus is significantly simplified, reducing the cost as well as the measurement procedure. © 2014 IOP Publishing Ltd.

Li F.M.,University of Cambridge | Waddingham R.,University of Cambridge | Milne W.I.,University of Cambridge | Flewitt A.J.,University of Cambridge | And 4 more authors.
Thin Solid Films | Year: 2011

With the emergence of transparent electronics, there has been considerable advancement in n-type transparent semiconducting oxide (TSO) materials, such as ZnO, InGaZnO, and InSnO. Comparatively, the availability of p-type TSO materials is more scarce and the available materials are less mature. The development of p-type semiconductors is one of the key technologies needed to push transparent electronics and systems to the next frontier, particularly for implementing p-n junctions for solar cells and p-type transistors for complementary logic/circuits applications. Cuprous oxide (Cu2O) is one of the most promising candidates for p-type TSO materials. This paper reports the deposition of Cu2O thin films without substrate heating using a high deposition rate reactive sputtering technique, called high target utilisation sputtering (HiTUS). This technique allows independent control of the remote plasma density and the ion energy, thus providing finer control of the film properties and microstructure as well as reducing film stress. The effect of deposition parameters, including oxygen flow rate, plasma power and target power, on the properties of Cu2O films are reported. It is known from previously published work that the formation of pure Cu2O film is often difficult, due to the more ready formation or co-formation of cupric oxide (CuO). From our investigation, we established two key concurrent criteria needed for attaining Cu2O thin films (as opposed to CuO or mixed phase CuO/Cu2O films). First, the oxygen flow rate must be kept low to avoid over-oxidation of Cu2O to CuO and to ensure a non-oxidised/non-poisoned metallic copper target in the reactive sputtering environment. Secondly, the energy of the sputtered copper species must be kept low as higher reaction energy tends to favour the formation of CuO. The unique design of the HiTUS system enables the provision of a high density of low energy sputtered copper radicals/ions, and when combined with a controlled amount of oxygen, can produce good quality p-type transparent Cu2O films with electrical resistivity ranging from 102 to 104 Ω-cm, hole mobility of 1-10 cm2/V-s, and optical band-gap of 2.0-2.6 eV. These material properties make this low temperature deposited HiTUS Cu 2O film suitable for fabrication of p-type metal oxide thin film transistors. Furthermore, the capability to deposit Cu2O films with low film stress at low temperatures on plastic substrates renders this approach favourable for fabrication of flexible p-n junction solar cells. © 2011 Elsevier B.V. All rights reserved.

Wakeham S.,Plasma Quest Ltd. | Thwaites M.,Plasma Quest Ltd. | Tsakonas C.,Nottingham Trent University | Cranton W.,Nottingham Trent University | And 3 more authors.
Physica Status Solidi (A) Applications and Materials Science | Year: 2010

The temperature sensitive nature of the substrates used in the flexible displays market necessitates a low temperature deposition technique for processing them. ZnS:Mn exhibiting high intensity photoluminescence (PL) and good crystallinity has been deposited onto Si wafers, glass microscope slides and polymeric substrates using a new reactive sputtering technology referred to as HiTUS. This technique enables very high deposition rates and requires no substrate heating. When incorporated as part of a complete EL device, as-deposited ZnS:Mn films are seen to exhibit stable electroluminescence on Si, glass and planarised PET substrate materials. Post annealing of the devices on Si and glass at temperatures of up to 600 °C show that the HiTUS films perform better than equivalent ZnS:Mn films deposited using RF magnetron sputtering.

MacKay P.,Ford Motor Company | Wakeham S.,Plasma Quest Ltd. | Wilde M.,Ford Motor Company | Dutson J.,Plasma Quest Ltd. | Allen J.,AJ Thin Films Consultancy Ltd.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

A new sputter deposition process has been developed based upon remote generation of plasma by a dedicated Plasma Source (PLS). This technique is referred to as high target utilisation sputtering (HiTUS). In contrast to ion beam and magnetron sputtering processes, HiTUS allows fast deposition rates of low stress, high density films from a high percentage (>90%) of the target surface. The process has not previously been applied to thin films for high laser damage threshold applications. The paper will present results of the anti-reflection (AR) coating trials and compare them to two other coating deposition processes - standard e-beam evaporation and hollow cathode ion-assisted e-beam deposition. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

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