Thesis (Ph.D.)--Rochester Institute of Technology, 2007. / Typescript. Includes bibliographical references (leaves 139-145).

Thesis (Ph. D. in Interdisciplinary Materials Sciences)--Vanderbilt University, Dec. 2008. / Title from title screen. Includes bibliographical references.

Thesis (M.S.)--University of Toledo, 2007. / Typescript. "Submitted as partial fulfillment of the requirements for the Masters of Science Degree in Physics." "A thesis entitled"--at head of title. Bibliography: leaves 99-102.

Thesis (Ph. D.)--University of Oregon, 2007. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 95-101). Also available online in ProQuest, free to University of Oregon users.

Thesis (M.Phil.)--Hong Kong University of Science and Technology, 2008. / Includes bibliographical references. Also available in electronic version.

Thesis (Ph. D.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains x, 104 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 97-100).

The goal of the thesis is to make contributions to the development of two new technologies for data storage: perpendicular recording and magneto-optic recording. CoCr and rare earth-transition metal multilayers are the most suitable media for perpendicular recording and magneto-optic recording technologies, respectively. In part A of the thesis, magnetic properties of CoCr thin films produced by dc magnetron sputtering are studied for various deposition conditions. Dielectric constants and extraordinary Hall effect are also studied to provide information complementary to magnetic properties. In part B, new methods are developed for theoretical analysis of the magneto-optics of rare earth-transition metal multilayers, which can be used to optimize the readout of the recording system. Part A For dc magnetron sputtered CoCr films the perpendicular and parallel magnetic coercivities are found to be mainly controlled by the substrate temperature during film growth. Substrate temperatures between 180 and 300 C are necessary to fabricate CoCr thin films for recording media. Films produced in this manner have magnetic anisotropy constants ranging from —1.0 to +0.5 10⁶erg/cc. The magnetic anisotropy has a complicated dependence on a large number of deposition parameters and can be best controlled by the dc sputtering power and the target-to-substrate distance. Based on microstructural analysis film properties are interpreted in terms of the adatom diffusion during film growth. It is found that high adatom mobility and low deposition rate promote positive magnetic anisotropy. The dielectric constants measured by ellipsometry are found to depend on the film thickness because of the change in film morphology during film growth. The effects of asymmetric sputtering are analyzed, and the relationship between the extraordinary Hall effect and the magnetic properties is investigated. Part B The 4x4 matrix method proposed by Lin-Chung and Teitler[P. J. Lin-Chung and S. Teitler, J. Opt. Soc. Am. A 1 703(1984)] is applied to the magneto-optics of the rare earth-transition metal multilayer system. Based on a plane wave model, the above method enables one to calculate the sensitivity of the readout to the layer thicknesses as well as effects of oblique angle of incidence, anisotropy in the nonmagnetic part of the dielectric constants and misalignment of the magnetization. Finally, an improved model is presented to take into account the fact that the reading laser is a strongly focused beam instead of a plane wave. This new model is used to optimize the magneto-optic multilayer system. When the focal spot size of the reading laser beam is less than about three wavelengths, significantly different results are obtained from the focused beam and the plane wave models. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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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.

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.