In this study, the characteristics of Nickel-doped LPD-TiO2 films on silicon substrate were investigated. In our experiment, we do some measurement about physical, chemical and electrical properties for undoped and Nickel-doped LPD-TiO2 films and discussed with them. The TiO2 film thickness was characterized by field emission scanning electron microscopy ( FE-SEM ), structure was characterized by X-ray diffraction (XRD), chemical properties was characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and electrical properties was characterized by leakage current: current-voltage (B1500A) and dielectric constant: capacitance-voltage (4980A). For the electrical property improvements, we investigated the Ni-doped LPD-TiO2 films by the post-anneal treatments in nitrogen, oxygen and nitrous oxide ambient. For nickel doping, the nickel chloride was used as the doping solution and the electrical characteristics were improved. After thermal annealing in nitrous oxide at 700 oC, the dielectric constant of polycrystalline titanium oxide film is 29 and can be improved to 94 with nickel doping.

An uniform titanium oxide film was grown on indium tin oxide/glass substrate with the aqueous solutions of ammonium hexafluoro-titanate and boric acid. The as-deposition titanium oxide film shows good electrochromic property because of fluorine passivation on defects and dangling bonds. The transmittance of as-grown titanium oxide on indium tin oxide/glass with a thickness of 270 nm is about 85% at the wavelength of 550 nm. By 50 times electrochromic cycling test, the transparency ratio of TiO2 film is kept at 45% between fully colored state and fully bleached state at the wavelength of 550 nm. Under ultraviolet illumination, the growth of titanium oxide film grown is enhanced. The root mean squared value of surface roughness is improved from 3.723 to 0.523 nm. Higher fluorine concentration from (NH4)2TiF6 passivate defects and dangling bonds of titanium oxide during the growth. After 50 times electrochromic cycling test, the transparency ratio UV-TiO2 is improved from 37.5% to 42.4% at the wavelength of 550 nm. The electrical characteristics of nickel-doped titanium oxide films on p-type (100) silicon substrate by liquid phase deposition were investigated. For nickel doping, the nickel chloride was used as the doping solution and the electrical characteristics were improved. After thermal annealing in nitrous oxide at 700 oC, the dielectric constant of polycrystalline titanium oxide film is 29 and can be improved to 94 with nickel doping. Uniform nickel oxide film was grown on a conducting glass substrate with the aqueous solution of saturated NiF2¡E4H2O solution and H3BO3. The quality of NiO is improved after thermal annealing at 300 oC in air from the decrease of oxygen vacancy and better F ion passivation on defects and dangling bonds. The transmittance of as-deposited NiO/ITO/glass with a thickness of 100 nm is about 78% and improved to 88% after annealing at the wavelength of 550 nm. By the electrochromic cycling test 50 times on annealed NiO film, the transparency ratio is kept at 48% between fully colored state and fully bleached state at the wavelength of 550 nm. By the memory time test, the annealed LPD-NiO film has shorter memory time. The growth of nickel oxide film grown on indium-tin oxide/glass substrate by liquid phase deposition is enhanced under ultraviolet photo-irradiation was studied. a-Ni(OH)2 dominates the composition of as-grown NiO film. After thermal treatment at 300 oC,a-Ni(OH)2 is transformed into NiO. For thermally treated NiO under ultraviolet photo-irradiation, the recrystallization and the colored and bleached transmittance after 50 times electrochromic test were improved. Both improvements come from fluorine passivation. Transparent and conductive thin films consisting of p-type nickel oxide (NiO) semiconductors were prepared by liquid phase deposition. A resistivity of 8 x 10-1 -cm was obtained for NiO films prepared at liquid phase deposition. The transmittance of NiO is almost 70 % in the 550 nm wavelength was obtained for a 384.3 nm thick NiO film.

Study of rare-earth manganites has been a very active research area in the last few years in condensed matter physics. This is due to the interesting phenomena such as (1) colossal magneto resistance (2) charge, orbital and spin ordering and (3) phase separation exhibited by these materials as a function of doping, pressure and temperature [1-3]. There is a lot of experimental data available in literature on different doped manganites, but no satisfactory and complete theoretical understanding is available yet. Though different theoretical models proposed are able to explain certain individual physical properties, a unified theory is missing which can comprehensively explain the full phase diagram. The study of such complex systems requires a probe that is sensitive to various interactions observed in manganites such as spin-spin interactions, spin-lattice interactions, spin-orbit interactions, crystal field interactions and the magnetic environment of the spins. Electron paramagnetic resonance (EPR) being sensitive to these interactions is an ideal probe for investigating these strongly correlated systems. A number of EPR studies have been reported in the paramagnetic phase of manganites, throwing light on the complex spin dynamics present in the manganites [4-10]. There are a few reports in the ferromagnetic state of manganites [11-12]. In recent years, a few studies reporting the observation of phase separation using EPR have also been published [13-15]. Charge ordering phase is the other interesting phase, which is not understood from EPR point of view [16-19]. Recently there are a few reports on suppression of CO phase by reducing the particle size from micro to nano range [20-22]. In this thesis we present the results of Electron Magnetic Resonance (EMR) (EPR in the paramagnetic phase and FMR: ferromagnetic resonance in the ferromagnetic phase) studies supported by magnetization and magneto-transport studies of the following : (1) various magnetic phases in the two electron doped manganite Ca1-xCexMnO3 (CCMO) (2) Charge ordered phase vs. ferromagnetic metallic phase as a function of Cr and Ni doping at the Mn site of Nd0.5Ca0.5MnO3 (NCMO) and comparison between the effect of the two dopants, and (3) a study of nano-sized particles (with different particle size) of Cr doped NCMO. Chapter 1 of the thesis consists of a brief introduction to the general features of manganites describing various phenomena and the interactions underlying them. Further we have written a detailed overview of EPR studies in manganites describing the current level of understanding in the area. In this chapter we have also described the experimental methodology and the analysis procedure adopted in this work. Chapter 2 reports the magnetization, transport and electron paramagnetic resonance studies (EPR) on two electron-doped manganites Ca1-xCexMnO3 (0.075 ≤ x ≤ 0.20). The various compositions of CCMO were prepared by solid-state synthesis and characterized by different techniques like XRD, SEM, EDX, and ICPAES. Our magnetization and transport results are consitent with the earlier reports [23-25]. For compositions x ≥ 0.13, all the EPR parameters viz. intensity, linewidth and the resonance field show signatures of a CO phase and at low temperature coexistence of two magnetic phases. x = 0.1 composition shows the most interesting results. Though the EPR intensity and resonance field indicate the presence of a CO phase, the EPR linewidth shows behaviour of a spin-disordered phase which we attribute to a possible spin-liquid phase [26]. The linewidth for x = 0.11 composition shows a combination of a CO and a spin-disorderd phase. For low composition x = 0.075, we observe a weak ferromagnetic phase and later on at low temperatures an antiferromagnetic phase. We do not observe the CO phase for this composition. In chapter 3, we present the magnetization, magnetotransport and EMR studies on Cr doped NCMO (0.0 ≤ x ≤ 0.10) [27]. The samples were prepared by solid-state synthesis and characterized by various techniques like XRD, SEM, EDX, and ICPAES. The magnetization studies show that the Cr doping induces ferromagnetic phase at low temperatures. With the increase of Cr doping the magnetization increases at the expense of the CO phase and for higher doping CO phase disappears completely. The Cr doping induces insulator-metal transition and with increase of Cr doping the metallic phase increases. The doped samples show high CMR, almost 100%, near the TC. The EMR studies in the paramagnetic phase indicate a CO phase for low Cr doping and the presence of short-range dynamical CO-OO correlations for higher Cr doping, which were not observed in magnetization studies. We observe two EPR signals at low temperatures for the Cr doped samples. For 3% doping, the two signals appear well above TC whereas for higher doping (5%, 10%) the two signals were observed in the FM phase. We rule out the possibility of the two-signal behaviour arising from the coexistence of two magnetic phases. For higher doping, the presence of two signals in FM phase can be attributed to magnetic anisotropy. With increase of Cr doping, magnetic anisotropy decreases which is also supported by reduction of magnetic anisotropy in magnetization measurements. But it cannot explain the observation of two signals above TC in the 3% doped sample. In chapter 4, we present the magnetization, magnetotransport and EMR studies on Ni doped NCMO (0.0 ≤ x ≤ 0.10). The samples were prepared by solid-state synthesis and characterized by various techniques like XRD, SEM, EDX, and ICPAES. The magnetization studies show that the Ni doping induces ferromagnetic phase at low temperatures. With the increase of Ni doping, though the CO phase is suppressed, the FMM phase also weakens which is different from the behaviour observed in Cr doped NCMO. The Ni doping induces insulator-metal transition and with increase of Ni doping, the metallic phase weakens. The magnetic anisotropy increases with increase of Ni doping as obtained from magnetization measurements and the EMR data also corroborates the same fact. The EMR studies in the paramagnetic phase indicate a CO phase for low Ni doping and the presence of short-range dynamical CO-OO correlations for higher Ni doping, which were not observed in magnetization studies. We observe two signals in the FM phase, which again can be attributed to the magnetic anisotropy. In chapter 5, we present EMR studies on nano-particles of Cr doped NCMO for x = 0.03. We have prepared nano-particles of three different sizes by the sol-get route. The samples were characterized by various techniques like XRD, SEM, EDX, and ICPAES. The particle sizes are 50, 100, 200 nm. We also compare the results of nano samples with the bulk samples. The ac susceptibility measurements show that the FM phase increases with the reduction of particle size. The EMR measurements show that the magnetic anisotropy decreases with decrease of particle size. The EMR linewidth in the paramagnetic phase increases with the decrease of particle size. The EMR intensity also increases with the reduction of particle size consitent with the magnetization results. The EMR results show that the reduction of particle size is one more way of inducing FM phase more effectively. Also the CO phase gets suppressed with the reduction of particle size. The two-signal feature is observed for all the particles. For nano-sized particles, the two signals appear in FM phase whereas in bulk sample they appeared well above TC. For 50 nm sized particles, the two signals appear well below 40 K. Thus we conclude that with decrease of particle size, the magnetic anisotropy decreases. The thesis concludes with a brief writeup summarizing the results and indicating possible future directions of research in the area.

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