Aim of this work was, to investigate the preparation of Si NC memories by sputter deposition. The milestones are as follows: - Review of relevant literature. - Development of processes for an ultrathin tunnel-oxide and high quality sputtered SiO2 for use as control-oxide. - Evaluation of methods for the preparation of an oxygen-deficient silicon oxide inter-layer (the precursor of the Si NC layer). - Characterization of deposited films. - Establishment of techniques capable of probing the phase separation of SiOx and the formation of Si NC. - Establishment of annealing conditions compatible with the requirements of current CMOS technology based on experimental results and simulations of Si NC formation. - Preparation Si NC memory capacitors using the developed processes. - Characterization of these devices by suitable techniques. Demonstration of their memory functionality.

The stress development and relaxation of magnetron sputtered copper and amorphous-silicon (a-Si) films at room temperature are studied. Samples were prepared as a function of pressure and deposition power. In-situ stress measurements with the wafer curvature method were made using a helium neon gas laser system with a 10mm beam splitter. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to perform post-growth microstructural and surface analysis. SEM cross-section analysis was used to determine the final film thickness. Phase compositions were studied by X-ray diffraction. The growth rates of copper films decreased with increasing pressure. Copper film stress development followed a non-monotonic compressive, tensile then tensile relaxation curve. In order to investigate further the nature of the stress relaxation, stress curves both after deposition was stopped and after it is restarted were also measured. Correlations between growth rate and pressure were also observed in a-Si sputter deposition. In some contrast to what was observed for Cu deposition, stress measurement during a-Si deposition showed a trend of tensile development and relaxation at all pressures studied. In a new approach to understanding stress relaxation during film growth, an acoustic emission (AE) system is introduced to measure the AE energy during sputter deposition. Evidence shows a certain relation between the strain energy of films calculated using the measured stresses and AE energy recorded during the deposition. AE energy occurs immediately after deposition starts and follows the trend of stress development (increasing hits and energies) and relaxation (decreasing hits and energies). No further signal was detected after deposition, matching the results of stress curve measurements showing that stress magnitude after deposition stays at the same level as before deposition stopped. Results also show a lower AE energy magnitude with increasing deposition pressure.

Aim of this work was, to investigate the preparation of Si NC memories by sputter deposition. The milestones are as follows: - Review of relevant literature. - Development of processes for an ultrathin tunnel-oxide and high quality sputtered SiO2 for use as control-oxide. - Evaluation of methods for the preparation of an oxygen-deficient silicon oxide inter-layer (the precursor of the Si NC layer). - Characterization of deposited films. - Establishment of techniques capable of probing the phase separation of SiOx and the formation of Si NC. - Establishment of annealing conditions compatible with the requirements of current CMOS technology based on experimental results and simulations of Si NC formation. - Preparation Si NC memory capacitors using the developed processes. - Characterization of these devices by suitable techniques. Demonstration of their memory functionality.

The broad theme of the present research investigation is on the preparation and characterization of the ultra thin films. The emerging field of nano science and technology demands the realization of different materials in nanometer dimension and a comprehensive understanding of their novel properties. Especially, the properties of the semiconducting materials in the nano dimensions are quite different from their bulk phase. A phase transition from semimetalic to semiconducting nature occurs at a thickness < 5nm of Sb ultra thin films. These facts emphasize the need for preparing these materials as nano layers and studying their properties as a function their size. Among the various characterization methods available to study the structure and the interfaces, Raman spectroscopy has proved to be a useful technique. In addition to revealing the structural information, Raman spectroscopy can bring out the quantum size effects in the lattice vibrational spectra of lower dimensional solids, stress state of the film in the initial growth stages, chemical nature of materials etc. Raman spectroscopy studies on the quantum structure of Ge and Sb are limited. This is attributed to the two serious limitations of the conventional backscattering of Raman signal. 1. The back scattered Raman signal intensity from the ultra thin layer could be below the detection limit. 2. The lower penetration depth of the lasers could inhibit the information from the buried layers. These limitations could be overcome to a major extent by employing an optical interference technique called IERS. This is basically an anti-reflection structure consisting minimum of three layers. These three layers are essential for achieving the interference conditions. The thicknesses of each layer were calculated using a matrix method. IERS structure consists of 1. A reflecting layer at the bottom of the stack (Platinum or Aluminum) 2. The second layer which is grown above the reflecting layer is a transparent dielectric layer, which introduces the necessary phase shift and hence it is called phase layer.(SiO2 or CeO2) 3. The top ultra thin layer which is to be investigated (Ge or Sb), is grown over the dielectric film and it is the layer which absorbs the most of the incident exciting light and it is called the absorbing layer. In this trilayer structure the thickness of the phase layer and the absorbing layer are adjusted in such a way that the light reflected from the air-ultra thin layer interface and the dielectric-reflector interface are equal in amplitude but opposite in phase. This leads to the destructive interference and a perfect anti-reflection condition is achieved. This enhances the near surface local field and results in the enhanced Raman signal. Regarding the reflection layer, thermally evaporated Al films were used. But the surface studies revealed a large surface roughness of 2.7nm for area of 2 µm×2µm. Also Al is known to react with oxygen and formation of an oxide layer is favored. In an effort to overcome these problems, a platinum layer was chosen instead of Al as a reflecting layer. Dual ion beam sputter deposition was employed to prepare the platinum films and to study the surface property of the films prepared at different secondary ion current density. Thus the process parameters to get the Pt film with the required surface properties were optimized. To prepare the required phase layer, optical thin films of Ceria were used. The optical and structural property of ceria is found to be sensitive to the process parameters. Hence a new deposition technique for preparing the CeO2 thin films was adopted. This technique is called Dual ion beam Sputter Deposition (DIBSD). This technique involves, two ion sources (Kaufman type). One source is used to sputter the target, which is called the primary ion source and the other one is used to assist the growing film, which is called the secondary ion source. Both argon and oxygen were fed into the secondary ion source and oxygen ions in the mixture of the gases (Ar +O2) react with the growing film and the oxygen stoichiometry in the film is maintained. Also the secondary ion bombardment of the growing film helps in the densification and it leads to the increase in the refractive index of the ceria films. The films were found to grow with a preferential orientation along (111) direction. The optical properties of the films were studied by using the transmission spectra of the films from the spectrophotometer. Powder X-Ray diffraction, and Raman spectroscopy, were employed to study the structural properties. Atomic Force Microscopy was used to examine the surface topography and to estimate the surface statistics. A stress free ceria film with a high refractive index of 2.36 at 600nm was prepared for a secondary ion beam current density of 150µA/cm2 and a beam energy of 150 eV. Raman spectra and X-ray diffraction data of these films have revealed the formation of point defects in these films as a function of secondary ion current density. Germanium (Ge) ultra thin layers were prepared by using Ion Beam Sputter Deposition (IBSD) as this technique has a good control over the rate of deposition apart from various other advantages. The Ge ultra thin films were prepared on the multilayer stacks with Al or Pt as a reflecting layer. The germanium films were prepared for the various thicknesses ranging from 1-10 nm. These films were prepared on the multilayer stack of reflecting layer and phase layer. The films were prepared for the different substrate temperatures from 40 °C to 300 °C. The films thus prepared have been analyzed by Interference Enhanced Raman Spectroscopy (IERS) for the structural and quantum size effects, by RBS for the thickness and to study interface diffusion, and Atomic Force Microscopy (AFM) for the analysis of nano structure of the grown films and also for the surface statistics. The thickness of the Ge films was found to be same as that had been calculated from the rate of deposition of the films. The films showed increase in the grain sizes with increase in the thickness of the films. The nanostructure of the films from AFM images confirms this observation. IERS of the films shows the transition from the compressive to stress free nature of the film for the nominal thickness of 1 & 2 nm. The quantum size effects of the films show the asymmetric broadening and peak shift and these observations were studied using the spatial correlation model. The TEM studies on the samples with Pt as a reflecting layer show influence of the underlying layer of CeO2 by the formation Moiré fringes. Antimony (Sb) films were prepared for the different thicknesses (3-10nm) and at different substrate temperatures (40 °C - 200 °C) on the Pt/CeO2 multilayer stacks as the absorbing layer. IERS studies on the films were performed and the results are as follows. Sb films show crystallization with increase in thickness from 3nm to 4nm. The films show amorphous to crystalline transition for the substrate temperature of 200 °C. Quantum size effects on the samples due to the phonon confinement were analyzed by the spatial correlation model. The atomic force microscopic measurements for the nanostructural information on the samples showed that the grain sizes of the films increase with increase in the thickness. Also the surface morphology shows a definite change in the features for the transition of amorphous to crystallization phase. Chapter 1 introduces the importance of Ge and Sb in the present day technologies. The current state of research on these two materials has been discussed. The importance of ceria and Pt films has been highlighted in the context of IERS and for the applications elsewhere. The advantages and disadvantages of ion beam sputter deposition have been described. The importance of Raman spectroscopy as a characterization tool for the nano structures has been shown in this chapter along with an introduction on Raman spectroscopy. Also, the importance of the other complimentary characterization techniques has been discussed. Chapter 2 presents the experimental details used to deposit and characterize the thin films. Details of IBSD and DIBSD processes are given. The characterization pertaining to structural, surface, optical and compositional properties are dealt in detail. Method to compute the optical constants of a transparent film is also given. Chapter 3 presents the properties of reflecting layers. Structural, surface and the compositional (presence of Ar ion) properties of the DIBSD platinum thin films are presented. Chapter 4 presents the optical, structural and surface properties of DIBSD ceria thin films as a function of process parameters. Chapter 5 deals with the growth and Raman analysis of ultra thin Ge films with Al and Pt as reflecting layers. Chapter 6 deals with the growth and Raman analysis of ultra thin Sb films. Chapter 7 gives the summary of the thesis and the future scope of the work.

The effect of compositional modulation on structural and magnetic properties of magnetic heterostructures was explored. The systems under focus were ferromagnetic superlattices Fe81Ni19/Co, metal-insulator multilayers Al2O3/Ni81Fe19, nanoparticles and artificial multilayered pillars. The heterostuctures were grown by magnetron sputtering in a state-of-the-art ultra-high vacuum system. The structural characterization was done by X-ray diffraction and reflectivity, as well as by transmission electron microscopy. Magneto-optical Kerr effect, SQUID and XMCD magnetometry and magnetic force microscopy were used for magnetic characterization. The bilayer thickness, ratio of the constituents and the interface quality influence the magnetic properties (magnetic moments and anisotropy) of metallic heterostructures. In particular, magnetic moments in bcc Fe81Ni19/Co superlattices were found to scale with the interface density thus, implying different magnetic moments at the interfaces as compared to the interior part of the layers. The easy direction of magnetization can be rotated from in-plane to out-of-plane, by increasing the bilayer thicknesses, keeping other parameters unchanged. Consequently, the anisotropy strength is strongly dependent on the repeat distance. Stripe domains appear in the films that possess an out-of-plane magnetization. The average domain period was found to be dependent on the applied in-plane magnetic field and on the total thickness of the films. The structural and magnetic properties of Al2O3/Ni81Fe19 multilayers depend strongly on the individual layers thicknesses. By increasing the amount of the magnetic deposits one can change the obtained film structure, from superparamagnetic nanoparticles to ferromagnetic multilayers. By increasing the oxide layer thickness the magnetic behavior of the nanoparticles can be altered from ferromagnetic, via spin glass like, to a superparamagnetic character.

In this thesis, research on synthesis, structure and characterization of amorphous carbide-based thin films is presented. Crystalline and nanocomposite carbide films can exhibit properties such as high electrical conductivity, high hardness and low friction and wear. These properties are in many cases structure-related, and thus, within this thesis a special focus is put on how the amorphous structure influences the material properties. Thin films within the Zr-Si-C and Cr-C-based systems have been synthesized by magnetron sputtering from elemental targets. For the Zr-Si-C system, completely amorphous films were obtained for silicon contents of 20 at.% or higher. Modeling of these films, as well as experimental results suggest that the films exhibit a network-type structure where the bond types influence the material properties. Higher hardness and resistivity were observed with high amounts of covalent Si-C bonds. Several studies were performed in the Cr-C-based systems. Cr-C films deposited in a wide composition range and with substrate temperatures of up to 500 °C were found to be amorphous nanocomposites, consisting of amorphous chromium carbide (a-CrCx) and amorphous carbon (a-C) phases. The carbon content in the carbidic phase was determined to about 30-35 at.% for most films. The properties of the Cr-C films were very dependent of the amount of a-C phase, and both hardness and electrical resistivity decreased with increasing a-C contents. However, electrochemical analysis showed that Cr-C films deposited at higher substrate temperature and with high carbon content exhibited very high oxidation resistance. In addition, nanocomposite films containing Ag nanoparticles within an amorphous Cr-C matrix were studied in an attempt to improve the tribological properties. No such improvements were observed but the films exhibited a better contact resistance than the corresponding binary Cr-C films. Furthermore, electrochemical analyses showed that Ag nanoparticles on the surface affected the formation of a stable passive film, which would make the Cr-C/Ag films less resilient to oxidation than the pure Cr-C films.

The present research focuses on the coupling of mechanical and electrical properties of materials and culminates in a direct connection between applied strain to thin-films, thin-film electron binding energy, the energy loss via plastic deformation provided by an indentation, and the substrate resistance. The methods used in this research include X-ray photoelectron spectroscopy (XPS), nanoindentation, digital optical microscopy, and sputter coat deposition. It is discovered that there is a shift in electron binding energy on the scale of 0.2 eV to 1.4 eV in gold and palladium thin-films sputtered on polyvinylidene fluoride (PVDF) through the application of strain induced by a convex shape. There is a change in the area beneath the load-displacement curve measured via indentation from 5.55 x 10^-10 J to 4.78 x 10^-10 J when the gold-palladium thin-film sputtered on PVDF is changed from the flat arrangement to the convex arrangement. Furthermore, the strain also changed the electrical resistance of aluminum foil, which indicates that the substrate electrical resistance is affected by the induced strain. The internal resistance of a circuit developed for this research changed from 7.76 ohms for flat samples to 8.03 ohms and 8.33 ohms for flat and convex samples, respectively. It is expected that the research can be used to estimate the strain in nanogears and other devices at small length scales.

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