Switching mechanisms, electrical characterisation and fabrication of nanoparticle based non-volatile polymer memory devices.

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dc.contributor.author Prime, Dominic Charles
dc.date.accessioned 2010-02-02T10:27:05Z
dc.date.available 2010-02-02T10:27:05Z
dc.date.issued 2010
dc.identifier.uri http://hdl.handle.net/2086/3314
dc.description.abstract Polymer and organic electronic memory devices offer the potential for cheap, simple memories that could compete across the whole spectrum of digital memories, from low cost, low performance applications, up to universal memories capable of replacing all current market leading technologies, such as hard disc drives, random access memories and Flash memories. Polymer memory devices (PMDs) are simple, two terminal metal-insulator-metal (MIM) bistable devices that can exist in two distinct conductivity states, with each state being induced by applying different voltages across the device terminals. Currently there are many unknowns and much ambiguity concerning the working mechanisms behind many of these PMDs, which is impeding their development. This research explores some of these many unanswered questions and presents new experimental data concerning their operation. One prevalent theory for the conductivity change is based on charging and charge trapping of nanoparticles and other species contained in the PMD. The work in this research experimentally shows that gold nanoparticle charging is possible in these devices and in certain cases offers an explanation of the working mechanism. However, experimental evidence presented in this research, shows that in many reported devices the switching mechanism is more likely to be related to electrode effects, or a breakdown mechanism in the polymer layer. Gold nanoparticle charging via electrostatic force microscopy (EFM) was demonstrated, using a novel device structure involving depositing gold nanoparticles between lateral electrodes. This allowed the gold nanoparticles themselves to be imaged, rather than the nanoparticle loaded insulating films, which have previously been investigated. This method offers the advantages of being able to see the charging effects of nanoparticles without any influence from the insulating matrix and also allows charging voltages to be applied via the electrodes, permitting EFM images to capture the charging information in near real-time. Device characteristics of gold nanoparticle based PMDs are presented, and assessed for use under different scenarios. Configurations of memory devices based on metal-insulator-semiconductor (MIS) structures have also been demonstrated. Simple interface circuitry is presented which is capable of performing read, write and erase functions to multiple memory cells on a substrate. Electrical properties of polystyrene thin films in the nanometre thickness range are reported for the first time, with insulator trapped charges found to be present in comparable levels to those in silicon dioxide insulating films. The dielectric breakdown strength of the films was found to be significantly higher than bulk material testing would suggest, with a maximum dielectric strength of 4.7 MV•cm-1 found, compared with the manufacturers bulk value of 0.2 – 0.8 MV•cm-1. Conduction mechanisms in polystyrene were investigated with the dominant conduction mechanism found to be Schottky emission. en
dc.description.sponsorship Engineering and Physical Sciences Research Council (EPSRC) en
dc.description.sponsorship The National Physical laboratory, UK (NPL) en
dc.language.iso en en
dc.publisher De Montfort University en
dc.subject organic electronics en
dc.subject polymer memory device en
dc.subject polystyrene en
dc.subject gold nanoparticles en
dc.subject atomic force microscopy en
dc.subject electrostatic force microscopy en
dc.subject Langmuir Blodgett en
dc.subject trapped charge en
dc.title Switching mechanisms, electrical characterisation and fabrication of nanoparticle based non-volatile polymer memory devices. en
dc.type Thesis or dissertation en
dc.publisher.department Emerging Technologies Research Centre en
dc.publisher.department Faculty of Business and Law. en
dc.type.qualificationlevel Doctoral en
dc.type.qualificationname PhD en

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