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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.

This thesis contains four parts. In the first part, we investigate the post treatment of low-temperature-deposited high dielectric constant (high-k) thin films to enhance their properties. The high-pressure oxygen (O2 and O2+UV light) is employed to improve the properties of low-temperature-deposited metal oxide dielectric films and interfacial layer. In this study, 13nm HfO2 thin films are deposited by sputtering method at room temperature. Then, the oxygen treatments with a high-pressure of 1500 psi at 150 ¢J are performed to replace the conventional high temperature annealing. According to the XPS analyses, integration area of the absorption peaks of O-Hf and O-Hf-Si bonding energies apparently raise and the quantity of oxygen in deposited thin films also increases from XPS measurement. In addition, the leakage current density of standard HfO2 film after O2 and O2+UV light treatments can be improved from 3.12¡Ñ10-6 A/cm2 to 6.27¡Ñ10-7 and 1.3¡Ñ10-8 A/cm2 at |Vg| = 3 V. The leakage current density is significantly suppressed and the current transport mechanism is transformed from trap-assisted tunneling to Schottky-Richardson emission due to the passivation of traps inside HfO2 film and interfacial layer. The proposed treatment is applicable for the future flexible electronics. In the second part of this thesis, we study the memory characteristics of CoSi2 nanocrystals with SiO2 or Al2O3/HfO2 multiple layer tunnel oxide. Due to the property of high-k, it can provide thicker physics thickness than thermal oxide (SiO2) under identical equivalent oxide thickness (EOT) and enhances the reliability without reducing the programming speed. By engineering the different dielectric constant materials and the energy band structure, the performance of nonvolatile memory can be improved. The device that employs HfO2/Al2O3/HfO2 as tunnel oxide exhibits better memory window and carrier injection efficiency than the device employing thermal oxide. Furthermore, the device employs Al2O3/HfO2/Al2O3 as tunnel oxide present the better retention characteristics than the device employs HfO2/Al2O3/HfO2 as tunnel oxide. The corresponding mechanisms were also discussed. For the advanced nonvolatile application, high-k material - hafnium oxide was applied on the resistance switching nonvolatile memory device as resistive switching layer with TiN/Ti/HfO2/TiN structure in the third part of this thesis. By using a thin Ti layer as the reactive buffer layer into the anode side, the proposed device exhibits superior bistable characteristics. Since the Ti can easily absorb oxygen atoms from buried HfO2, the TiN/Ti bi-layer can greatly improve the resistive switching characteristics. The mechanism of the proposed device is dominated by the redox reaction between the Hf and HfOX. In addition, the proposed device has multi-bit storage ability to enhance the storage density. From the temperature-dependent measurements, the low ambient temperatures would cause the formation and rupture of the conduction path with discordant quality and quantity during every switching cycle, which give rise to a wide distribution of the HRS and LRS resistance and instability of resistive switching properties. In the fourth part of this thesis, we investigate the characteristics of an advanced Cu-induced resistance switching non-volatile memory with Pt/Cu/SiON/TiN/SiO2/Si structure. By inserting a Cu ultra thin film between the SiON layer and Pt top electrode, the device exhibits bipolar resistive switching characteristics after a forming process at 13.6 V. However, the forming and resistive switching process can not be observed in the device if the Cu thin film is omitted. Additionally, we employ a two-step forming process to reduce the forming voltage to 7.5 V. During the forming process, the bias-induced Cu could form a filament-like stretched electrode, but the ¡§set¡¨ and ¡§forming¡¨ voltage of the proposed device take place on different polarity. Therefore, we suppose a bipolar switching mechanism, and our device is dominated by the formation and rupture of the oxygen vacancies in a conduction path between the Cu filament and TiN button electrode. The device also demonstrates stable resistance states during 105 cycling bias pulse operations and acceptable retention characteristics after an endurance test at 85¢J. The I-V switching curves are analyzed to realize the carrier transport mechanisms in different bias regions and resistance states. Additionally, the effective thickness of the resistance switching layers (deff) for the samples with different SiON thickness is also extracted from the related mechanism and demonstrated that the deff is independent with the initial SiON thickness. The corresponding mechanisms and the deff verify the bipolar switching is dominated by the formation and rupture of the oxygen vacancies in conduction path between Cu filament and TiN bottom electrode.

Driven by ever growing demands of miniaturization, increased functionality, high performance and low cost for microelectronic products and packaging, embedded passives will be one of the key emerging techniques for realizing the system integration which offer various advantages over traditional discrete components. Novel materials for embedded capacitor applications are in great demand, for which a high dielectric constant (k), low dielectric loss and process compatibility with printed circuit boards are the most important prerequisites. To date, no available material satisfies all these prerequisites and research is needed to develop materials for embedded capacitor applications. Conductive filler/polymer composites are likely candidate material because they show a dramatic increase in their dielectric constant close to the percolation threshold. One of the major hurdles for this type of high-k composites is the high dielectric loss inherent in these systems. In this research, material and process innovations were explored to design and develop conductive filler/polymer nanocomposites based on nanoparticles with controlled parameters to fulfill the balance between sufficiently high-k and low dielectric loss, which satisfied the requirements for embedded decoupling capacitor applications. This work involved the synthesis of the metal nanoparticles with different parameters including size, size distribution, aggregation and surface properties, and an investigation on how these varied parameters impact the dielectric properties of the high-k nanocomposites incorporated with these metal nanoparticles. The dielectric behaviors of the nanocomposites were studied systematically over a range of frequencies to determine the dependence of dielectric constant, dielectric loss tangent and dielectric strength on these parameters.

Doctor of Philosophy / Department of Chemical Engineering / James H. Edgar / Gallium nitride is a promising semiconductor for fabricating field effect transistors for power electronics because of its unique physical properties of wide energy band gap, high electron saturation velocity, high breakdown field and high thermal conductivity. However, these devices are extremely sensitive to the gate leakage current which reduces the breakdown voltage and the power-added efficiency and increases the noise figures. To solve this problem, employing a gate dielectric is crucial to the fabrication of metal insulator semiconductor high electron mobility transistors (MISHEMTs), to reduce the leakage current and increase the magnitude of voltage swings possible. For this device to be successful, imperfections at the oxide-semiconductor interface must be suppressed to maintain the high electron mobility of the device. This research explored multiple high dielectric constant gate oxides (Al[subscript]2O[subscript]3, TiO[subscript]2, and Ga[subscript]2O[subscript]3), deposited on different crystalline orientations and polarities of GaN by atomic layer deposition (ALD) to form metal oxide semiconductor capacitors, including effects of pretreatment on N-polar GaN, ALD TiO[subscript]2/Al[subscript]2O[subscript]3 nano-laminate on thermal oxidized Ga-polar GaN and ALD Al[subscript]2O[subscript]3 on [Italic]c- and [Italic]m-plane GaN Surface pretreatments were shown to greatly alter the morphology of reactive N-polar GaN which is detrimental to the electrical properties. 14 nm thick ALD Al[subscript]2O[subscript]3 films were directly deposited on N-polar GaN without thermal or chemical pretreatments which yield a smooth surface (RMS=0.23 nm), low leakage current (2.09 x 10[superscript]-[superscript]8 A/cm[superscript]2) and good Al[subscript]2O[subscript]3/GaN interface quality, as indicated by the low electron trap density (2.47 x 10[superscript]10 cm[superscript]-[superscript]2eV[superscript]-[superscript]1). In the nano-laminate study, a high dielectric constant of 12.5 was achieved by integrating a TiO[subscript]2/Al[subscript]2O[subscript]3/Ga[subscript]2O[subscript]3 oxide stack layer, while maintaining a low interface trap density and low leakage current. There was a strong correlation between the surface morphology and electrical properties of the device discovered from comparing the ALD Al[subscript]2O[subscript]3 on [Italic]c- and [Italic]m-plane GaN, namely smooth surface lead to small hysteresis. These results indicate the promising potential of incorporation gate dielectric for future GaN devices.

High dielectric constant materials are of technological importance as they lead to the miniaturization of the electronic devices. In this context, the observation of anomalously high dielectric constant (>104) in the body-centered cubic perovskite-related (Space group Im3) material Calcium Copper Titanate ((CaCu3Ti4O12)(CCTO)) over wide frequency (100 Hz – 1MHz at RT) and temperature (100 – 600 K at 1 kHz ) ranges has attracted a great deal of attention. However, high dielectric constant in CCTO is not well understood yet, though internal barrier layer capacitor (IBLC) mechanism is widely been accepted. Therefore, the present work has been focused on the preparation and characterization of CCTO ceramic and to have an insight into the origin of high dielectric constant. Influence of calcination temperature, processing conditions, microstructure (and hence grain size), composition, doping etc on the electrical characteristics of CCTO ceramics were investigated. Electrical properties were found to be strongly dependent on these parameters. The dielectric constant in CCTO was observed to be reduced considerably on substituting La+3 on Ca+2 site. The formation temperature of CCTO was lowered substantially (when compared to conventional solid-state reaction route) by adopting molten-salt synthesis. The dielectric loss in CCTO was reduced by incorporating glassy phases at the grain boundary. Potential candidates for the practical applications such as charge storage devices, capacitors etc, with dielectric constant as high as 700 at 300 K was accomplished in a three-phase percolative composite fabricated by incorporating Aluminium particle into CCTO-epoxy composite. Polycrystalline CCTO thin films with dielectric constant as high as ~ 5000 (1 kHz and 400 K) were fabricated on Pt(111)/Ti/SiO2/Si substrates using radio frequency magnetron sputtering. Effect of sintering conditions on the microstructural, ferroelectric and varistor properties of CCTO and LCTO ceramics belonging to the high and low dielectric constant members of ACu3M4O12 family of oxides were investigated in detail and are compared. Ferroelectric-like hysteresis loop (P vs E) and weak pyroelectricity were observed in CCTO and plausible mechanisms for this unusual phenomenon have been proposed.

High dielectric constant materials are of technological importance as they lead to the miniaturization of the electronic devices. For instance, in the case of memory devices based on capacitive components, such as static and dynamic random access memories, the dielectric constant will ultimately decide the level of miniaturization. In this context, the observation of anomalously high dielectric constant (>10) in the double perovskite Sr2SbMnO6 (SSM) over wide frequency (100 Hz1 MHz) and (190373 K) temperature range has attracted a great deal of attention. However, unfortunately their dielectric losses were also high which limit their use for possible capacitor and related applications. The dielectric loss however was known to decrease with decreasing crystallite size in electroceramics. Therefore, the present work has been focused on the synthesis of nanocrystalline SSM powders by moltensalt route. The characterization of the ceramics fabricated from these powders for their microstructural and dielectric properties. A cubic phase of SSM powder was obtained by calcining the as synthesized powders at 900°C/10h by using sulphate flux. The crystallite size was ~ 60 nm. The activation energy associated with the particle growth was found to be 95 ± 5 kJmol-1 . The ceramic sintered at 1075°C/16h exhibited high dielectric constant (>10at 1 kHz) with low loss (0.72 at 1 kHz) at room temperature. The results are interpreted in terms of a twolayer model with conducting grains partitioned from each other by poorly conducting grain boundaries. Using this model, we attributed the two electrical responses in impedance and modulus formalisms to the grain and grain boundary effects, respectively, while the detected Debyelike relaxation and large dielectric constant were explained in terms of MaxwellWagner relaxation.

No description available.

Abstract The purpose of this task is to synthesize a dielectric substrate material through a sintering process, which can be used for non-invasive physiological sensor development. Low loss, high dielectric constant ceramic material is used. Sintering process is employed to ensure stable structure and homogeneous dielectric properties of the substrate. Samples were prepared with TiO2 and in combination with CuO and Al2O3. All samples were measured and validated in 500 MHz to 20 GHz frequency range. Characterization measurements were performed with a Vector Network Analyzer, FieldFox N9918A, and connected to Keysight, open ended coaxial probe and performance probe. Reflection based measurement method was used due to its simplicity, speed and requirement of wideband data. The dielectric measurement results of developed samples show non-frequency dispersive behaviour, high dielectric constant and data was also selected at 2.45 GHz in aligned to the industrial, scientific and medical band. The resulting measurements show the highest dielectric constant of 16.6 at 2.45 GHz with a very low loss behaviour. / Målet är att syntetisera ett material, genom sintringsprocess, som kan användas som ett dielektriskt substrat för utveckling av sensorer. Det dielektriska materialet har keramisk materialstruktur och innehar högt dielektricitetskonstant med låga dielektriska materialförluster. Denna uppgift kräver att dielektriska materialet ska vara stabilt och inneha isotropiska egenskaper efter att genomgått sintringsprocess. Proverna förberedes med TiO2 och även i kombination med TiO2 tillsammans med CuO och Al2O3. Proverna mäts i frekvensområdet 500 MHz till 20 GHz. Mätningarna utförs med Vector Network Analyzer, FieldFox N9918A från Keysight. Resultat som visas och jämförs i arbetet är tagna vid 2.45 GHz eftersom det används och är standardiserat för medicinskt frekvensband. Högsta uppmätta dielektricitetskonstant har värdet av 16,6. Resultaten visar även låga förluster i dielektrikumet.