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Title: EFFECT OF GERMANIUM DOPING ON ERBIUM SENSITIZATION IN THE ERBIUM DOPED SILICON RICH SILICA MATERIAL SYSTEM.
Creator: Ruhge, Forrest, Kik, Pieter, University of Central Florida
Abstract / Description: The continued size reduction in electronic integrated circuits has lead to a demand for on-chip high-bandwidth and low loss communication channels. Optical interconnects are considered an essential addition to the silicon electronics platform. A major challenge in the field of integrated Si photonics is the development of cost effective silicon compatible light sources. This thesis investigates the sensitization of group IV doped silica films emitting at 1.535μm for applications as...
Show moreThe continued size reduction in electronic integrated circuits has lead to a demand for on-chip high-bandwidth and low loss communication channels. Optical interconnects are considered an essential addition to the silicon electronics platform. A major challenge in the field of integrated Si photonics is the development of cost effective silicon compatible light sources. This thesis investigates the sensitization of group IV doped silica films emitting at 1.535μm for applications as silicon compatible light sources. Thin erbium-doped silica films containing excess silicon and germanium were deposited using a multi-gun sputter system. The composition of the deposited materials was verified by Rutherford Backscattering Spectrometry. Samples from each deposition were annealed in a controlled atmosphere tube furnace at temperatures between 500ºC and 1100ºC for 30 minutes. The photoluminescence spectra from the visible to the near-infrared region were acquired while pumping either near or far from the Er3+ absorption lines. Under both excitation conditions all samples annealed at temperatures below 1000ºC show clear emission at 1.535μm from Er3+ ions in the host material. In the current literature this is attributed to exciton mediated excitation of the Er3+. By contrast, in these studies indirect excitation was observed for samples annealed at temperatures well below the onset of nanocrystal nucleation and growth (between 500ºC and 1000ºC), suggesting excitation via small clusters or lattice defects. These findings could have significant implications in the further development of group IV sensitized silicon compatible gain media.
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Date Issued: 2006
Identifier: CFE0001439, ucf:47066
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001439

Title: OPTIMIZATION OF PROCESS PARAMETERS FOR REDUCED THICKNESS CIGSES THIN FILM SOLAR CELLS.
Creator: Pethe, Shirish, Dhere, Neelkanth, University of Central Florida
Abstract / Description: With the advent of the 21st century, one of the serious problems facing mankind is harmful effects of global warming. Add to that the ever increasing cost of fuel and the importance of development of clean energy resources as alternative to fossil fuel has becomes one of the prime and pressing challenges for modern science and technology in the 21st century. Recent studies have shown that energy related sources account for 50% of the total emission of carbon dioxide in the atmosphere. All...
Show moreWith the advent of the 21st century, one of the serious problems facing mankind is harmful effects of global warming. Add to that the ever increasing cost of fuel and the importance of development of clean energy resources as alternative to fossil fuel has becomes one of the prime and pressing challenges for modern science and technology in the 21st century. Recent studies have shown that energy related sources account for 50% of the total emission of carbon dioxide in the atmosphere. All research activities are focused on developing various technologies that are capable of converting sunlight into electricity with high efficiency and can be produced using a cost-effective process. One of such technologies is the CuIn1-xGaxSe2 (CIGS) and its alloys that can be produced using cost-effective techniques and also exhibit high photo-conversion efficiency. The work presented here discusses some of the fundamental issues related to high volume production of CIGS thin film solar cells. Three principal issues that have been addressed in this work are effect of reduction in absorber thickness on device performance, micrononuniformity involved with amount of sodium and its effect on device performance and lastly the effect of working distance on the properties of molybdenum back contact. An effort has been made to understand the effect of absorber thickness on PV parameters and optimize the process parameters accordingly. Very thin (<1 µm) absorber film were prepared by selenization using metallorganic selenium source in a conventional furnace and by RTP using Se vapor. Sulfurization was carried out using H2S gas. Devices with efficiencies reaching 9% were prepared for very thin (<1 µm) CIGS and CIGSeS thin films. It was shown through this work that the absorber thickness reduction of 64% results in the efficiency drop of only 32%. With further optimization of the reaction process of the absorber layer as well as the other layers higher efficiencies can be achieved. The effect of sodium on the device performance is experimentally verified in this work. To the best of our knowledge the detrimental effect of excess sodium has been verified by experimental data and effort has been made to correlate the variation in PV parameter to theoretical models of effect of sodium. It has been a regular practice to deposit thin barrier layer prior to molybdenum deposition to reduce the micrononuniformities caused due to nonuniform out diffusion of sodium from the soda lime glass. However, it was proven in this work that an optimally thick barrier layer is necessary to reduce the out diffusion of sodium to negligible quantities and thus reduce the micrononuniformities. Molybdenum back contact deposition is a bottleneck in high volume manufacturing due to the current state of art where multi layer molybdenum film needs to be deposited to achieve the required properties. In order to understand and solve this problem experiments were carried out. The effect of working distance (distance between the target and the substrate) on film properties was studied and is presented in this work. During the course of this work efforts were taken to carry out a systematic and detailed study of some of the fundamental issues related to CIGS technology and particular for high volume manufacturing of CIGS PV modules and lay a good foundation for further improvement of PV performance of CIGS thin film solar cells prepared by the two step process of selenization and sulfurization of sputtered metallic precursors.
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Date Issued: 2010
Identifier: CFE0003517, ucf:48940
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003517

Title: INVESTIGATIONS ON RF SPUTTER DEPOSITED SICN THIN FILMS FOR MEMS APPLICATIONS.
Creator: Todi, Ravi, Coffey, Kevin, University of Central Florida
Abstract / Description: With the rapid increase in miniaturization of mechanical components, the need for a hard, protective coatings is of great importance. In this study we investigate some of the mechanical, chemical and physical properties of the SiCN thin films. Thin films of amorphous silicon carbide nitride (a-SiCxNy) were deposited in a RF magnetron sputtering system using a powder pressed SiC target. Films with various compositions were deposited on to silicon substrate by changing the N2/Ar gas ratios...
Show moreWith the rapid increase in miniaturization of mechanical components, the need for a hard, protective coatings is of great importance. In this study we investigate some of the mechanical, chemical and physical properties of the SiCN thin films. Thin films of amorphous silicon carbide nitride (a-SiCxNy) were deposited in a RF magnetron sputtering system using a powder pressed SiC target. Films with various compositions were deposited on to silicon substrate by changing the N2/Ar gas ratios during sputtering. Nano-indentation studies were performed to investigate the mechanical properties such as hardness and reduced modulus of the SiCN films. Surface morphology of the films was characterized by using atomic force microscopy (AFM). X-ray photoelectron spectroscopy (XPS) data indicated that the chemical status is highly sensitive to the nitrogen ratios during sputtering. Further, the films were annealed in dry oxygen ambient in the temperature range of 400 – 900°C and characterized using XPS to investigate the chemical composition and oxidation kinetics at each annealing temperature. The surface roughness of these films was studied as a function of annealing temperature and film composition with the help of a "Veeco" optical profilometer. Nano-indentation studies indicated that the hardness and the reduced modulus of the film are sensitive to the N2/Ar ratio of gas flow during sputtering. AFM studies revealed that the films become smoother as the N2/Ar ratio is increased. XPS data indicated the existence of C-N phases in the as-deposited films. The study of oxidation kinetics of RF sputter deposited SiCN thin films, using XPS, suggest that N2 co-sputtering helps to suppress the formation of a surface oxide, by allowing un-bonded Si to bond with N and C inside the vacuum chamber as opposed to bonding with O in atmosphere.
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Date Issued: 2005
Identifier: CFE0000839, ucf:46669
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000839

Title: Optimization of Process Parameters for Faster Deposition of CuIn1-xGaxS2 and CuIn1-xGaxSe2-ySy Thin Film Solar Cells.
Creator: Kaul, Ashwani, Dhere, Neelkanth, Heinrich, Helge, Kar, Aravinda, Chow, Lee, Sundaram, Kalpathy, University of Central Florida
Abstract / Description: Thin film solar cells have the potential to be an important contributor to the world energy demand in the 21st century. Among all the thin film technologies, CuInGaSe2 (CIGS) thin film solar cells have achieved the highest efficiency. However, the high price of photovoltaic (PV) modules has been a major factor impeding their growth for terrestrial applications. Reduction in cost of PV modules can be realized by several ways including choosing scalable processes amenable to large area...
Show moreThin film solar cells have the potential to be an important contributor to the world energy demand in the 21st century. Among all the thin film technologies, CuInGaSe2 (CIGS) thin film solar cells have achieved the highest efficiency. However, the high price of photovoltaic (PV) modules has been a major factor impeding their growth for terrestrial applications. Reduction in cost of PV modules can be realized by several ways including choosing scalable processes amenable to large area deposition, reduction in the materials consumption of active layers, and attaining faster deposition rates suitable for in-line processing. Selenization-sulfurization of sputtered metallic Cu-In-Ga precursors is known to be more amenable to large area deposition. Sputter-deposited molybdenum thin film is commonly employed as a back contact layer for CIGS solar cells. However, there are several difficulties in fabricating an optimum back contact layer. It is known that molybdenum thin films deposited at higher sputtering power and lower gas pressure exhibit better electrical conductivity. However, such films exhibit poor adhesion to the soda-lime glass substrate. On the other hand, films deposited at lower discharge power and higher pressure although exhibit excellent adhesion show lower electrical conductivity. Therefore, a multilayer structure is normally used so as to get best from the two deposition regimes. A multi-pass processing is not desirable in high volume production because it prolongs total production time and correspondingly increases the manufacturing cost. In order to make manufacturing compliant with an in-line deposition, it is justifiable having fewer deposition sequences. Thorough analysis of pressure and power relationship of film properties deposited at various parameters has been carried out. It has been shown that it is possible to achieve a molybdenum back contact of desired properties in a single deposition pass by choosing the optimum deposition parameters. It is also shown that the film deposited in a single pass is actually a composite structure. CIGS solar cells have successfully been completed on the developed single layer back contact with National Renewable Energy Laboratory (NREL) certified device efficiencies (>)11%. The optimization of parameters has been carried out in such a way that the deposition of back contact and metallic precursors can be carried out in identical pressure conditions which is essential for in-line deposition without a need for load-lock. It is know that the presence of sodium plays a very critical role during the growth of CIGS absorber layer and is beneficial for the optimum device performance. The effect of sodium location during the growth of the absorber layer has been studied so as to optimize its quantity and location in order to get devices with improved performance. NREL certified devices with efficiencies (>)12% have been successfully completed.
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Date Issued: 2012
Identifier: CFE0004559, ucf:49261
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004559

Title: CORRELATION BETWEEN PREPARATION PARAMETERS AND PROPERTIES OF MOLYBDENUM BACK CONTACT LAYER FOR CIGS THIN FILM SOLAR CELLS.
Creator: Takahashi, Eigo, Dhere, Neelkanth, University of Central Florida
Abstract / Description: Molybdenum (Mo) thin film back contact layers for thin film CuIn(1-x)GaxSe2 (CIGS) solar cells were deposited onto soda lime glass substrates using a direct current (DC) planar magnetron sputtering deposition technique. Requirements for the Mo thin film as a back contact layer for CIGS solar cells are various. Sheet resistance, contact resistance to the CIGS absorber, optical reflectance, surface morphology, and adhesion to the glass substrate are the most important properties that the Mo...
Show moreMolybdenum (Mo) thin film back contact layers for thin film CuIn(1-x)GaxSe2 (CIGS) solar cells were deposited onto soda lime glass substrates using a direct current (DC) planar magnetron sputtering deposition technique. Requirements for the Mo thin film as a back contact layer for CIGS solar cells are various. Sheet resistance, contact resistance to the CIGS absorber, optical reflectance, surface morphology, and adhesion to the glass substrate are the most important properties that the Mo thin film back contact layer must satisfy. Experiments were carried out under various combinations of sputtering power and working gas pressure, for it is well known that mechanical, morphological, optical, and electrical property of a sputter-deposited Mo thin film are dependent on these process parameters. Various properties of each Mo film were measured and discussed. Sheet resistances were measured using a four-point probe equipment and minimum value of 0.25 Ω/sq was obtained for the 0.6 Ã‚Âµm-thick Mo film. Average surface roughnesses of each Mo film ranged from 15 to 26 ÃƒÂ… were measured by Dektak profilometer which was also employed to measure film thicknesses. Resistivities were calculated from the sheet resistance and film thickness of each film. Minimum resistivity of 11.9 Ã‚ÂµΩ∙cm was obtained with the Mo thin film deposited at 0.1 mTorr and 250 W. A residual stress analysis was conducted with a bending beam technique with very thin glass strips, and maximum tensile stress of 358 MPa was obtained; however, films did not exhibit a compressive stress. Adhesive strengths were examined for all films with a Ã‚Â"Scotch-tapeÃ‚Â" test, and all films showed a good adhesion to the glass substrate. Sputter-deposited Mo thin films are commonly employed as a back contact layer for CIGS and CuInSe2 (CIS)-based solar cells; however, there are several difficulties in fabricating a qualified back contact layer. Generally, Mo thin films deposited at higher sputtering power and lower working gas pressure tend to exhibit lower resistivity; however, such films have a poor adhesion to the glass substrate. On the other hand, films deposited at lower power and higher gas pressure tend to have a higher resistivity, whereas the films exhibit an excellent adhesion to the glass substrate. Therefore, it has been a practice to employ multi-layered Mo thin film back contact layers to achieve the properties of good adhesion to the glass substrate and low resistivity simultaneously. However, multi layer processes have a lower throughput and higher fabricating cost, and requires more elaborated equipment compared to single layer processes, which are not desirable from the industrial point of view. As can be seen, above mentioned process parameters and the corresponding Mo thin film properties are at the two extreme ends of the spectrum. Hence experiments were conducted to find out the mechanisms which influence the properties of Mo thin films by changing the two process parameters of working gas pressure and sputtering power individually. The relationships between process parameters and above mentioned properties were studied and explained. It was found that by selecting the process parameters properly, less resistive, appropriate-surfaced, and highly adhesive single layer Mo thin films for CIGS solar cells can be achieved.
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Date Issued: 2010
Identifier: CFE0003031, ucf:48353
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003031

Title: INVESTIGATION OF REACTIVELY SPUTTERED SILICON CARBON BORON NITRIDE (SICBN) THIN FILMS FOR HIGH TEMPERATURE APPLICATIONS.
Creator: Vijayakumar, Arun, Sundaram, Kalpathy, University of Central Florida
Abstract / Description: The increasing demand for efficient energy systems in the last decade has brought about the development of advanced sensor systems that utilize advance detection methods to help in preventive maintenance of these essential systems. These usually are needed in hard to access environments where conditions are extreme and unfit for human interaction. Thin film based sensors deposited directly on the surfaces exposed to harsh environments can serve as ideal means of measuring the temperature of...
Show moreThe increasing demand for efficient energy systems in the last decade has brought about the development of advanced sensor systems that utilize advance detection methods to help in preventive maintenance of these essential systems. These usually are needed in hard to access environments where conditions are extreme and unfit for human interaction. Thin film based sensors deposited directly on the surfaces exposed to harsh environments can serve as ideal means of measuring the temperature of the component during operation. They provide the basic advantage of proximity to the surface and hence accurate measurement of the surface temperature. The low mass size ratio provides the additional advantage of least interference to system operation. The four elements consisting of Si, C, B, and N can be used to form binary, ternary and quaternary compounds like carbides, nitrides, which are chemically and thermally stable with extreme hardness, thermal conductivity and can be doped n- and p-type. Hence these compounds can be potential candidates for high temperature applications. This research is focused on studying sputtering as a candidate to obtain thin SiCBN films. The deposition and characterization of amorphous thin films of silicon boron carbon nitride (SiCBN) is reported. The SiCBN thin films were deposited in a radio frequency (rf) magnetron sputtering system using reactive co-sputtering of silicon carbide (SiC) and boron nitride (BN) targets. Films of different compositions were deposited by varying the ratios of argon and nitrogen gas in the sputtering ambient. Investigation of the oxidation kinetics of these materials was performed to study high temperature compatibility of the material. Surface characterization of the deposited films was performed using X-ray photoelectron spectroscopy and optical profilometry. Studies reveal that the chemical state of the films is highly sensitive to nitrogen flow ratios during sputtering. Surface analysis shows that smooth and uniform SiCBN films can be produced using this technique. Carbon and nitrogen content in the films seem to be sensitive to annealing temperatures. However depth profile studies reveal certain stoichiometric compositions to be stable after high temperature anneal up to 900ºC. Electrical and optical characteristics are also investigated with interesting results. Finally a metal semiconductor metal structure based optoelectronic device is demonstrated with excellent performance improvement over standard silicon based devices under higher temperature conditions.
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Date Issued: 2007
Identifier: CFE0001914, ucf:47490
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001914

Title: MAGNETIC PROPERTIES OF SPUTTER DEPOSITED FE-BASED AMORPHOUS THIN FILMS FOR RESONATOR APPLICATION.
Creator: China, Chaitali, Coffey, Kevin, University of Central Florida
Abstract / Description: In this study we investigate the magnetic properties of Fe-based amorphous thin films. Fe1-x-y-zBxSiyCz, Fe80-xNixB20, Fe80-xMnxB20, and Fe73-xMnxB27 films were deposited on silicon and glass substrates in a DC and RF magnetron sputtering system. Inductive magnetic measurements were performed to investigate the magnetic properties, including induced anisotropy and magnetostriction, of the as-deposited and annealed films using an M-H Looper. The chemical composition of the films was...
Show moreIn this study we investigate the magnetic properties of Fe-based amorphous thin films. Fe1-x-y-zBxSiyCz, Fe80-xNixB20, Fe80-xMnxB20, and Fe73-xMnxB27 films were deposited on silicon and glass substrates in a DC and RF magnetron sputtering system. Inductive magnetic measurements were performed to investigate the magnetic properties, including induced anisotropy and magnetostriction, of the as-deposited and annealed films using an M-H Looper. The chemical composition of the films was characterized using secondary ion mass spectroscopy (SIMS). The physical thickness of the films was determined by use of a stylus profilometer. The M-H Looper studies indicated that the induced anisotropy (Hk) depends strongly on the nickel concentration as well as on the annealing conditions, specifically the time and temperature of the annealing process. For the same metalloid concentration, the induced anisotropy has a maximum as a function of Ni. For the same nickel concentration and annealing time, it was found that the value of Hk decreases with the increase in annealing temperature. For each composition studied, low temperature long time annealing showed a higher value of Hk compared to high temperature short time annealing. From the magnetostriction values of Fe80-xNixB20 alloys, it was found that the sputter deposited films show similar trend but differ in magnitude when compared with ribbon samples. The magnetostriction of annealed thin films is found to be representative of ribbon samples. A potential composition modification to improve the strength of the field induced anisotropy is the addition of low levels of Mn.
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Date Issued: 2006
Identifier: CFE0001275, ucf:46896
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001275

Title: INVESTIGATION OF REACTIVELY SPUTTERED BORON CARBON NITRIDE THIN FILMS.
Creator: Todi, Vinit, Sundaram, Kalpathy, University of Central Florida
Abstract / Description: Research efforts have been focused in the development of hard and wear resistant coatings over the last few decades. These protective coatings find applications in the industry such as cutting tools, automobile and machine part etc. Various ceramic thin films like TiN, TiAlN, TiC, SiC and diamond-like carbon (DLC) are examples of the films used in above applications. However, increasing technological and industrial demands request thin films with more complicated and advanced properties. For...
Show moreResearch efforts have been focused in the development of hard and wear resistant coatings over the last few decades. These protective coatings find applications in the industry such as cutting tools, automobile and machine part etc. Various ceramic thin films like TiN, TiAlN, TiC, SiC and diamond-like carbon (DLC) are examples of the films used in above applications. However, increasing technological and industrial demands request thin films with more complicated and advanced properties. For this purpose, B-C-N ternary system which is based on carbon, boron and nitrogen which exhibit exceptional properties and attract much attention from mechanical, optical and electronic perspectives. Also, boron carbonitride (BCN) thin films contains interesting phases such as diamond, cubic BN (c-BN), hexagonal boron nitride (h-BN), B4C, [two]-C3N4. Attempts have been made to form a material with semiconducting properties between the semi metallic graphite and the insulating h-BN, or to combine the cubic phases of diamond and c-BN (BC2N heterodiamond) in order to merge the higher hardness of the diamond with the advantages of c-BN, in particular with its better chemical resistance to iron and oxygen at elevated temperatures. New microprocessor CMOS technologies require interlayer dielectric materials with lower dielectric constant than those used in current technologies to meet RC delay goals and to minimize cross-talk. Silicon oxide or fluorinated silicon oxide (SiOF) materials having dielectric constant in the range of 3.6 to 4 have been used for many technology nodes. In order to meet the aggressive RC delay goals, new technologies require dielectric materials with K<3. BCN shows promise as a low dielectric constant material with good mechanical strength suitable to be used in newer CMOS technologies. For optical applications, the deposition of BCN coatings on polymers is a promising method for protecting the polymer surface against wear and scratching. BCN films have high optical transparency and thus can be used as mask substrates for X-ray lithography. Most of the efforts from different researchers were focused to deposit cubic boron nitride and boron carbide films. Several methods of preparing boron carbon nitride films have been reported, such as chemical vapor deposition (CVD), plasma assisted CVD, pulsed laser ablation and ion beam deposition. Very limited studies could be found focusing on the effect of nitrogen incorporation into boron carbide structure by sputtering. In this work, the deposition and characterization of amorphous thin films of boron carbon nitride (BCN) is reported. The BCN thin films were deposited by radio frequency (rf) magnetron sputtering system. The BCN films were deposited by sputtering from a high purity B4C target with the incorporation of nitrogen gas in the sputtering ambient. Films of different compositions were deposited by varying the ratios of argon and nitrogen gas in the sputtering ambient. Investigation of the oxidation kinetics of these materials was performed to study high temperature compatibility of the material. Surface characterization of the deposited films was performed using X-ray photoelectron spectroscopy and optical profilometry. Studies reveal that the chemical state of the films is highly sensitive to nitrogen flow ratios during sputtering. Surface analysis shows that smooth and uniform BCN films can be produced using this technique. Carbon and nitrogen content in the films seem to be sensitive to annealing temperatures. However depth profile studies reveal certain stoichiometric compositions to be stable after high temperature anneal up to 700[degrees]C. Electrical and optical characteristics are also investigated with interesting results. The optical band gap of the films ranged from 2.0 eV - 3.1 eV and increased with N2/Ar gas flow ratio except at the highest ratio. The optical band gap showed an increasing trend when annealed at higher temperatures. The effect of deposition temperature on the optical and chemical compositions of the BCN films was also studied. The band gap increased with the deposition temperature and the films deposited at 500oC had the highest band gap. Dielectric constant was calculated from the Capacitance-Voltage curves obtained for the MOS structures with BCN as the insulating material. Aluminum was used as the top electrode and the substrate was p-type Si. Effect of N2/Ar gas flow ratio and annealing on the values of dielectric constant was studied and the dielectric constant of 2.5 was obtained for the annealed BCN films. This by far is the lowest value of dielectric constant reported for BCN film deposited by sputtering. Lastly, the future research work on the BCN films that will be carried out as a part of the dissertation is proposed.
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Date Issued: 2011
Identifier: CFE0004033, ucf:49181
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004033

Title: CHARACTERIZATION OF ALUMINUM DOPED ZINC OXIDE THIN FILMS FOR PHOTOVOLTAIC APPLICATIONS.
Creator: Shantheyanda, Bojanna, Kalpathy, Sundaram, University of Central Florida
Abstract / Description: Growing demand for clean source of energy in the recent years has increased the manufacture of solar cells for converting sun energy directly into electricity. Research has been carried out around the world to make a cheaper and more efficient solar cell technology by employing new architectural designs and developing new materials to serve as light absorbers and charge carriers. Aluminum doped Zinc Oxide thin film, a Transparent conductive Oxides (TCO) is used as a window material in the...
Show moreGrowing demand for clean source of energy in the recent years has increased the manufacture of solar cells for converting sun energy directly into electricity. Research has been carried out around the world to make a cheaper and more efficient solar cell technology by employing new architectural designs and developing new materials to serve as light absorbers and charge carriers. Aluminum doped Zinc Oxide thin film, a Transparent conductive Oxides (TCO) is used as a window material in the solar cell these days. Its increased stability in the reduced ambient, less expensive and more abundance make it popular among the other TCOÃ‚Â's. It is the aim of this work to obtain a significantly low resistive ZnO:Al thin film with good transparency. Detailed electrical and materials studies is carried out on the film in order to expand knowledge and understanding. RF magnetron sputtering has been carried out at various substrate temperatures using argon, oxygen and hydrogen gases with various ratios to deposit this polycrystalline films on thermally grown SiO2 and glass wafer. The composition of the films has been determined by X-ray Photoelectron Spectroscopy and the identification of phases present have been made using X-ray diffraction experiment. Surface imaging of the film and roughness calculations are carried out using Scanning Electron Microscopy and Atomic Force Microscopy respectively. Determination of resistivity using 4-Probe technique and transparency using UV spectrophotometer were carried out as a part of electrical and optical characterization on the obtained thin film.The deposited thin films were later annealed in vacuum at various high temperatures and the change in material and electrical properties were analyzed.
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Date Issued: 2010
Identifier: CFE0003142, ucf:48623
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003142

Title: STRUCTURAL CHARACTERIZATION OF SPUTTER-DEPOSITED SS304+XAL (X = 0, 4, 7 AND 10 WT.%) COATINGS AND MECHANICALLY MILLED TI, ZR AND HF POWDERS.
Creator: Seelam, Uma Maheswara, Suryanarayana, Challapalli, University of Central Florida
Abstract / Description: Study of the metastable phases obtained by non-equilibrium processing techniques has come a long way during the past five decades. New metastable phases have often given new perspectives to the research on synthesis of novel materials systems. Metastable materials produced by two non-equilibrium processing methods were studied for this dissertation- 304-type austenitic stainless steel (SS304 or Fe-18Cr-8Ni)+aluminum coatings produced by plasma enhanced magnetron sputter-deposition (PEMS) and...
Show moreStudy of the metastable phases obtained by non-equilibrium processing techniques has come a long way during the past five decades. New metastable phases have often given new perspectives to the research on synthesis of novel materials systems. Metastable materials produced by two non-equilibrium processing methods were studied for this dissertation- 304-type austenitic stainless steel (SS304 or Fe-18Cr-8Ni)+aluminum coatings produced by plasma enhanced magnetron sputter-deposition (PEMS) and nanocrystalline Ti, Zr and Hf powders processed by mechanical milling (MM). The objective of the study was to understand the crystallographic and microstructural aspects of these materials. Four SS304+Al coatings with a nominal Al percentages of 0, 4, 7 and 10 wt.% in the coatings were deposited on an SS304 substrate by PEMS using SS304 and Al targets. The as-deposited coatings were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and three-dimensional atom probe microscopy (3DAP). Surface morphology and chemical analysis were studied by SEM. Phase identification was carried out by XRD and TEM. The microstructural features of all the coatings, as observed in the TEM, consisted of columnar grains with the columnar grain width (a measure of grain size) increasing with an increase in the Al content. The coatings had grains with average grain sizes of about 100, 290, 320 and 980 nm, respectively for 0, 4, 7 and 10 wt.% Al. The observed grain structures and increase in grain size were related to substrate temperature during deposition. XRD results indicated that the Al-free coating consisted of the non-equilibrium ferrite and sigma phases. In the 4Al, 7Al and 10Al coatings, equilibrium ferrite and B2 phases were observed but no sigma phase was found. In 10Al coating, we were able to demonstrate experimentally using 3DAP studies that NiAl phase formation is preferred over the FeAl phase at nano scale. During mechanical milling of the hexagonal close packed (HCP) metals Hf, Ti and Zr powders, unknown nanocrystalline phases with face centered cubic (FCC) structure were found. The FCC phases could be either allotropes of the respective metals or impurity stabilized phases. However, upon MM under high purity conditions, it was revealed that the FCC phases were impurity stabilized. The decrease in crystallite size down to nanometer levels, an increase in atomic volume, lattice strain, and possible contamination were the factors responsible for the transformation.
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Date Issued: 2010
Identifier: CFE0003161, ucf:48595
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003161

Title: Deposition and characterization studies of boron carbon nitride (BCN) thin films prepared by dual target sputtering.
Creator: Prakash, Adithya, Sundaram, Kalpathy, Kapoor, Vikram, Yuan, Jiann-Shiun, Jin, Yier, Chow, Louis, University of Central Florida
Abstract / Description: As complementary metal-oxide semiconductor (CMOS) devices shrink to smaller size, the problems related to circuit performance such as critical path signal delay are becoming a pressing issue. These delays are a result of resistance and capacitance product (RC time constant) of the interconnect circuit. A novel material with reduced dielectric constants may compromise both the thermal and mechanical properties that can lead to die cracking during package and other reliability issues. Boron...
Show moreAs complementary metal-oxide semiconductor (CMOS) devices shrink to smaller size, the problems related to circuit performance such as critical path signal delay are becoming a pressing issue. These delays are a result of resistance and capacitance product (RC time constant) of the interconnect circuit. A novel material with reduced dielectric constants may compromise both the thermal and mechanical properties that can lead to die cracking during package and other reliability issues. Boron carbon nitride (BCN) compounds have been expected to combine the excellent properties of boron carbide (B4C), boron nitride (BN) and carbon nitride (C3N4), with their properties adjustable, depending on composition and structure. BCN thin film is a good candidate for being hard, dense, pore-free, low-k dielectric with values in the range of 1.9 to 2.1. Excellent mechanical properties such as adhesion, high hardness and good wear resistance have been reported in the case of sputtered BCN thin films. Problems posed by high hardness materials such as diamonds in high cutting applications and the comparatively lower hardness of c-BN gave rise to the idea of a mixed phase that can overcome these problems with a minimum compromise in its properties. A hybrid between semi-metallic graphite and insulating h-BN may show adjusted semiconductor properties. BCN exhibits the potential to control optical bandgap (band gap engineering) by atomic composition, hence making it a good candidate for electronic and photonic devices. Due to tremendous bandgap engineering capability and refractive index variability in BCN thin film, it is feasible to develop filters and mirrors for use in ultra violet (UV) wavelength region. It is of prime importance to understand process integration challenges like deposition rates, curing, and etching, cleaning and polishing during characterization of low-k films. The sputtering technique provides unique advantages over other techniques such as freedom to choose the substrate material and a uniform deposition over relatively large area. BCN films are prepared by dual target reactive magnetron sputtering from a B4C and BN targets using DC and RF powers respectively. In this work, an investigation of mechanical, optical, chemical, surface and device characterizations is undertaken. These holistic and thorough studies, will provide the insight into the capability of BCN being a hard, chemically inert, low-k, wideband gap material, as a potential leader in semiconductor and optics industry.
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Date Issued: 2016
Identifier: CFE0006378, ucf:51496
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006378

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