Digitized by Kansas State University Libraries

The advent of ferroelectric thin films with strong piezoelectric response has enabled the development of new nano- and micro-electromechanical systems (NEMS/MEMS) capable of large displacements at low voltage levels, aiming to be compatible with complementary metal oxide semiconductor industry. Key to all of these applications is the ability to process ferroelectric materials with maximized electromechanical coupling and to integrate them into the devices. With the continuous drive towards miniaturization of devices for piezoelectric and electronic applications, processing of ultrathin ferroelectric films with maintained large electromechanical coupling is essential to the development of high performance NEMS and MEMS. The piezoelectric response of ferroelectric thin films is profoundly affected by the texture and microstructural characteristics of the material and is severely reduced at sub-micron thickness ranges. For the first time, reproducible synthesis of dense, highly textured and phase-pure PZT thin films was achieved via chemical solution deposition. The consistent processing of ferroelectric thin films resulted in the elimination of the coupling effects of crystallographic anisotropy, porosity and in general microstructural characteristics on the functional properties of the films. This enabled effective study of the key parameters influencing the electromechanical response of the ferroelectric thin films, such as crystallite size (thickness dependence), chemical heterogeneities and substrate clamping. Reproducible synthesis of highly (100)-textured PZT ultrathin films enabled the study of the size effects on the dielectric and piezoelectric response of these films in the thicknesses ranging from 20 up to 260nm. Dielectric and piezoelectric responses of the films monotonically decreased in thinner films. For PZT films at MPB, a critical thickness, ~50nm was observed below which the extrinsic contributions to the dielectric responses of the films are heavily suppressed. After the study and acknowledgment of the severe reduction of the piezoelectric response in ferroelectric ultrathin film, several factors affecting piezoelectric response of ferroelectric films were studied in order to maximize the response especially at low film thickness ranges: chemical homogeneity, residual stresses and substrate clamping as well as using alternative material systems; relaxor ferroelectrics. In particular, a major part of the piezoelectric (and dielectric) response of the PZT has extrinsic sources such as domain or phase boundary motion and vibrations. Special attention was paid throughout this investigation into understanding extrinsic origins in PZT thin films and different approaches was utilized to further activate and enhance their contributions. Focusing on the chemical homogeneity of the ferroelectric films, Different routes were used to process ultrathin films (<200nm) with maintained functional properties. Superior piezoelectric properties - 40% higher piezoelectric response than in conventionally processed films - were achieved in highly (100)-oriented PZT superlattice-like films with controlled compositional gradient centered around MPB composition on Si substrates. Superlattice (SL) or heterolayered ferroelectric thin films consist of alternate layers of ferroelectric materials, or phases, with a compositional gradient normal to the substrate. The dynamic motion of “artificially created” phase boundaries between layer to layer tetragonal and rhombohedral phases participated in the extrinsic contributions to the films’ dielectric and piezoelectric response. This approach led to processing of 200 nm SL films with d33,f values as high as some of the best previously reported data for 1 to 2 µm-thick PZT films. Furthermore, comprehensive processing optimization was carried out on relaxor-ferroelectric PMN-PT thin films. Dense, highly (100)-textured PMN-PT films were synthesized exhibiting the highest d33,f coefficients reported so far in the literature (210pm/V) for corresponding thickness ranges. Control of the microstructural characteristics - texture and density – throughout the whole film thickness was necessary to obtain films with maximized functional properties. To study the effect of substrate clamping on the piezoelectric performance of the films, the Si substrate in PZT and PMN-PT films were back-side etched via dry etching in an inductively coupled plasma reactor. This approach is similar the final state of the films for MEMS applications, where the Si substrate is mostly removed in order to have a free-standing or semi-free standing ferroelectric membrane or cantilever. A giant enhancement in the piezoelectric d33,f coefficient of the substrate-released samples was observed with respect to the films on the virgin substrate. The response increased by at least one order of magnitude from ~75-200 pm/V (for different PZT film thicknesses ranging from 300nm to 1 µm) to ~1500 to 4500 pm/V at reduced Si thickness. Experimental observations in macroscopic dielectric and piezoelectric characterization and microscopic piezo-response force microscopy of the samples indicate larger extrinsic contributions, -possibly with domain dynamic source- to the functional responses of the films in back-side etched samples. A fundamental change in the pattern of the electromechanical activity of the grains between the released and clamped films was observed in the band-excitation piezo-force microscopy investigations; A breakdown of the clustered pattern in the electromechanical activity of the grains in the PZT film. This giant enhancement promises a new pathway for greatly improved electromechanical properties which has a huge potential to enable high performance future device applications.

This thesis defines the term exploitation as it relates to the style of a number of key American film titles that emerged during the 1960s and 1970s, concurrent with the fall of cinema censorship. These productions presented spectacles of convincing corporeality and the adaptation of film techniques which may be labelled ‘realist'. The key films of this thesis will be argued to comprise a cinematic movement that can be labelled exploitation. The first part of this thesis will outline the time period of this study and the methodology used; based upon the historical and comparative writing on the classic Hollywood era of cinema initiated by David Bordwell. Drawing upon Bordwell and other scholars who have engaged with what the Academy recognises as the ‘new film history' (such as Eric Schaefer and his discussion of the classic exploitation film), I will introduce the work of André Bazin and argue that his writing on cinema realism can be attributed and understood as a style of filmmaking. This style is appropriated by exploitation insofar as similar, minimalist representations of modernity were brought to American cinema, albeit presented in generic narratives. The second part of this thesis will look at each of the key exploitation genres in detail: blaxploitation, exploitation-horror and sexploitation. I will engage with previous writing on what may be deemed ‘marginal' cinema and argue that each of the genres discussed in this thesis contain films that approach taboo subject matter with an oppositional approach to their Hollywood ‘other'. This point is especially relevant insofar as exploitation reveals images of physical horror and sexuality that the mainstream hides. In conclusion, this thesis hopes to bring a more contained and studied look at ‘marginal' cinema to the Academy and to give a definition of exploitation that will influence and inspire future studies of the form.

No description available.

This thesis, a two volume study of aspects of those popular cultural forms which increasingly prevail over the home television and video environment (American narrative film in feature and series formats), attempts to identify there a narrative mode of production. The specific problem traced through such a production is that of the outer/inner (visible/invisible) metaphor as it informs the construction of points of 'individualism' in or through the textual surface. This problem is considered in relation both to certain traditional ways of thinking about the American 'imagination' and to specific examples of popular film in the seventies. These considerations are progressively focussed on the question of ideological recognition and on an enlargement of the concept of 'channel' to include those mimetic impulses which maintain a contact between text and reader. Around the theme of an extending 'discourse relation' which establishes certain limits and levels of practice, the thesis considers the relationship of level and metalevel; particularly the idea that an event at one level of description may be 'caused' by an event at another level by virtue of being a 'translation'. The crucial instance relates the spatial positioning of the body, on the screen and in front of it, to 'extrinsic' conditions. Conditions are formulated in terms of a late capitalist transition to unstable postindustrial, at which point the study of narrative systems of signification becomes an exercise in reading structural mediation between popular culture and surrounding socio-economic and historical realities. This shift between significations and communications brings a critical perspective to bear on the dominant ideology thesis and begins to engage with a grounded method of theorising, suggesting that detailed work on textual features of popular culture is not finally discontinuous with the level of description which takes as its object the hypothesised new communication order.

Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Thin films and powders of Ni.Tiï), and CoxTi03 (where x = 0.005 - 0.9) with different stiochiometric ratios were prepared using sol gel techniques. These metal oxides were prepared by spin coating on silicon and titanium substrates followed, by annealing at 400°C and 800°C respectively under a temperature program. A range of films with MxTiOy (where x = 0.005 - 0.9) were prepared and then characterized by optical methods such as Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Rutherford Backscattering Spectroscopy (RBS). X-ray powder diffraction was also used to determine the structural properties of these metal oxides. XRD pattern peaks showed that the powder forms of these metal oxides were well crystallized. Thin films could be amorphous because strong peaks were not present. For nickel titanates preparation, the best trend is at the low concentration of Ni that is 0.3:1 Ni:Ti. It is pure with no impurities of NiO and Ti02. High concentration of Co ranging from 0.7-1:1 Co:Ti forms a C02Ti04 structure with cubic phase. The best route for the CoTi03 preparation is at the low cobalt concentration that is 0.5:1 Co:Ti. Scanning Electron Microscopy (SEM) shows that a film deposited on silicon or a titanium substrate is smooth, uniform and crack-free. It also shows that a cobalt titanate film deposited on a Si substrate is rough, with cracks, whereas on the Ti substrate, it is smooth, uniform and crack-free. AFM studies show that as the concentration of Ni:Ti is reduced and the roughness of the thin film is increased. SEM, FTIR, XRD and RBS suggest that the 0.3:1 and 0.5:1Ni:Ti films with 10nm and 11nm thickness, respectively, iii Stellenbosch University http://scholar.sun.ac.za iv have the same structure. RBS suggests that the 1:1 and 0.5:1 Co:Ti have C0I.39Ti02.29and CoTi04.2 structures with 13nm and 16nm respectively. XRD reveals that NiTi03 and CoTi03 have rhombohedral crystal structure. / AFRIKAANSE OPSOMMING: Dunlagies en poeiers van NixTi03 en CoxTi03 (waar x = 0.005 - 0.9) met verskillende stoigiometriese verhoudings was voorberei deur gebruik te maak van sol gel tegnieke. Hierdie metaaloksiedes was voorberei deur gebruik te maak van "spin coating" op substrate van silikon en titaan gevolg deur konstante verhitting by 'n 400°C en 800°C temperatuur program onderskeidelik. 'n Reeks van lagies met MxTiOy (waar x = 0.005 - 0.9) was voorberei en gekarakteriseer met optiese metodes soos Skandeer Elektron Mikroskopie (SEM), Atoom Interaksie Mikroskopie (AFM) en "Rutherford Backscattering Spectroscopy (RBS)." X-straal Poeier Diffraksie was ook gebruik om die strukturele eienskappe van hierdie metaaloksiedes te bepaal. XRD patroon pieke wys dat die poeier vorms van hierdie metaaloksiedes goed gekristalliseer was. Dunlagies mag ook amorf wees aangesien sterk pieke nie teenwoordig was nie. Vir nikkel titaniete is hierdie die algemene roete vir die NiTi03 voorbereiding. Die beste tendens is by lae konsentrasies van Ni naamlik 0.3:1 Ni:Ti. Dit is suiwer en het geen onsuiwerhede van NiO en Ti02 nie. Hoë konsentrasies van Co vanaf 0.7 - 1:1 Co:Ti vorm 'n Co2Ti04 struktuur met 'n kubiese fase. Die beste roete vir die CoTi03 voorbereiding is by lae kobalt konsentrasie naamlik 0.5 -1:1 Co:Ti. Skandeer Elektron Mikroskopie (SEM) wys dat 'n NiTi03 laag gedeponeer op silikon en titaan substrate gelyk was, eenvorming en sonder krake. Dit wys ook dat die kobalt titaan laag oppervlakte gedeponeer op 'n silikon substraat grof was en het krake getoon. Vir die Ti substraat het dit gewys dat die oppervlaktes gladwas, univormig en sonder krake. AFM studies wys dat as die konsentrasie Ni:Ti verminder word die grofheid van die dunlaag verminder. SEM, FTIR, XRD en RBS dui aan dat die 0.3:1 en 0.5:1 Ni:Ti dunlaag dieselfde struktuur het met 10nm en 11nm dikte onderskeidelik. RBS dui aan dat die 1:1 en 0.5:1 Co:Ti het C01.39Ti02.29en CoTi04.2 strukture onderskeidelik met 13nm en 16nm diktes. XRD toon aan dat NiTi03 en CoTi03 rhombohedrale kristal strukture het.

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

published_or_final_version / abstract / toc / Physics / Master / Master of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy

published_or_final_version / abstract / Physics / Master / Master of Philosophy