The Pd77Cu6Si17 (PCS) thin film metallic glasses (TFMGs) with high glass forming ability and hardness are selected as a hard coating for improving the surface hardness of the AZ31 magnesium alloy. Both micro- and nano-indentation tests are conducted on the specimens with various PCS film thicknesses from 30 to 2000 nm. The apparent hardness and the relative indentation depth (£]) are integrated by a quantitative model. The involved interaction parameters and relative hardness values are extracted from iterative calculations. According to the results, surface hardness can be enhanced greatly by PCS TFMGs in the shallow region, followed by gradual decrease with increasing £] ratio. In addition, the specimens with thinner coating (for example, 200 nm) show greater substrate-film interaction and those with thick coating (for example, 2000 nm) become prone to film cracking. The optimum TFMG coating thickness in this study is estimated to be around 200 nm. Keywords: Magnesium alloys, hardness, sputtering, thin film metallic glass, nanoindentation

This investigation examines a novel means of integrating high-performance ZnO piezoelectric thin films with a flexible stainless steel substrate (SUS304) to fabricate a double-sided piezoelectric transducer. The double-sided piezoelectric transducer is constructed by depositing ZnO piezoelectric thin films on both the front and the back sides of SUS304 substrate. The titanium (Ti) and platinum (Pt) layers were deposited using a dual-gun DC sputtering system between the ZnO piezoelectric thin film and the back side of the SUS304 substrate. Scanning electron microscopy and X-ray diffraction of ZnO piezoelectric films reveal a rigid surface structure and highly c-axis-preferring orientation. To fabricate a transducer with a resonant frequency of about 80 Hz, a cantilever length of 1 cm and a vibration area of 1 cm2 are designed, based on the cantilever vibration theory. The maximum open circuit voltage of the power transducer is approximately 18 V. After rectification and filtering through a 33 nF capacitor, a specific power output of 1.3 £gW/cm2 is obtained from the transducers with a load resistance of 6 M£[.

The purpose of this study is to investigate the effects on DC sputtered thin films after different surface treatments on aluminum targets. Abrasive papers and nonwovens were used to polish the aluminum targets before sputtering. Surface morphology of the aluminum targets before and during sputtering were characterized using surface profiler. In addition, the erosion rate of the aluminum targets was obtained by measuring the changes of the erosion depth with sputtering time at a fixed processing condition. On the other hand, the surface morphology and electrical characteristics of the deposited thin films with respect to different aluminum targets were investigated. We found that surface roughness of the treated aluminum targets is of great importance to the stability of the film quality.

This study is separated into two parts. Firstly, the Ag thin film was deposited on substrates with different average roughness by sputtering to examine the effect of substrate roughness on optical reflection. The results exhibit 10 percent difference of reflectivity within several nanometer changing in average roughness, indicating the reflectivity is easily affected by surface roughness. Secondly, optical reflectivity and electrical resistivity of multi-component AgMgAl alloys, both crystalline and amorphous, were measured. The crystalline alloys exhibit high reflection in infrared region but a steeper drop in visible and ultraviolet regions. By contrast, amorphous alloys show a lower but relatively uniform reflectivity in the visible and infrared regions. In both cases, the reflectivity was observed to scale with the square root of electrical resistivity. The scaling law was explained based on classical reflection theory. The different scaling factors for crystalline and amorphous alloys could be rationalized by the difference in the mean free time of charge carriers. Moreover, the mechanical properties of crystalline and amorphous thin film alloys, including hardness and modulus, were measured by nanoindentation. The hardness of thin film metallic glasses (TFMGs) is obviously higher than crystalline metals, while the modulus of TFMGs is similar to crystalline metals.

This study is using selenization of stacked elemental layers to form Cu(In,Ga)Se2(CIGS). In the process, use Cu/Sb/In/Ga/Se precursor to heat to 550 oC at Se vapor in vacuum chamber. From the result of XRD¡BRaman and EPMA, that show of the precursor do not form to CIGS. After that, The result of using different layers precursor to form CIGS show that only Cu/In/GaSe/Se reach to form CIGS, but it still has second phase. According to the literature¡Athe reason for the formation of CIGS selenide process due to interdiffusion caused the formation of ternary solid phase, the solid phase diffusion reaction could be hampered.And then change to use rapid thermal selenization to form CIGS with two step of heating (hold at 300 oC and 650 oC) at N2 atmosphere. The laminated follow the best results in the selenide process Cu/In/GaSe/Se precursors in Se atmosphere, the (112) preferred orientation is 26.8o-26.9o in the XRD results of the fixed process conditions. EPMA composition analysis and comparison of Ga actual amount will increase with the estimated value of the amount of increase(Estimated value 4atom% actual value 2atom%¡FEstimated value 9.2tom% actual value 10atom%¡AGa/¢»=0.32), but the composition has yet to amend. Then will join Sb on CIGS observed from the SEM results Sb does improve the CIGS thin film flatness as well as to help grain growth in rapid thermal selenization, grain size of about 1 to 3£gm.

The goals of this work were to synthesize high performance perovskite based thin film solid oxide fuel cell (TF-SOFC) cathodes by pulsed laser deposition (PLD), to study the structural, electrical and electrochemical properties of these cathodes and to establish structure-property relations for these cathodes in order to further improve their properties and design new structures. Nanostructured cathode thin films with vertically-aligned nanopores (VANP) were processed using PLD. These VANP structures enhance the oxygen-gas phase diffusivity, thus improve the overall TF-SOFC performance. La0.5Sr0.5CoO3 (LSCO) and La0.4Sr0.6Co0.8Fe0.2O3 (LSCFO) were deposited on various substrates (YSZ, Si and pressed Ce0.9Gd0.1O1.95 (CGO) disks). Microstructures and properties of the nanostructured cathodes were characterized by transmission electron microscope (TEM), high resolution TEM (HRTEM), scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS) measurements. A thin layer of vertically-aligned nanocomposite (VAN) structure was deposited in between the CGO electrolyte and the thin film LSCO cathode layer for TF-SOFCs. The VAN structure consists of the electrolyte and the cathode materials in the composition of (CGO) 0.5 (LSCO) 0.5. The self-assembled VAN nanostructures contain highly ordered alternating vertical columns formed through a one-step thin film deposition using a PLD technique. These VAN structures significantly increase the interface area between the electrolyte and the cathode as well as the area of active triple phase boundary (TPB), thus improving the overall TF-SOFC performance at low temperatures, as low as 400oC, demonstrated by EIS measurements. In addition, the binary VAN interlayer could act as the transition layer that improves the adhesion and relieves the thermal stress and lattice strain between the cathode and the electrolyte. The microstructural properties and growth mechanisms of CGO thin film prepared by PLD technique were investigated. Thin film CGO electrolytes with different grain sizes and crystal structures were prepared on single crystal YSZ substrates under different deposition conditions. The effect of the deposition conditions such as substrate temperature and laser ablation energy on the microstructural properties of these films are examined using XRD, TEM, SEM, and optical microscope. CGO thin film deposited above 500 ºC starts to show epitaxial growth on YSZ substrates. The present study suggests that substrate temperature significantly influences the microstructure of the films especially film grain size.

The objective of this investigation is to measure and analyze surface temperature fluctuations in pool boiling. The surface temperature fluctuations were recorded on silicon surfaces with and without multi-walled carbon nanotubes (MWCNT). Novel Thin Film Thermocouples (TFT) are micro-fabricated on test substrates to measure surface temperatures. A dielectric liquid refrigerant (PF-5060) is used as test fluid. Both nucleate and lm boiling regimes are investigated for the silicon test substrates. Dynamics of nucleate boiling is investigated on the CNT coated substrates. High frequency temperature fluctuation data is analyzed for the presence of determinism using non-linear time series analysis techniques in TISEAN(copyright) software. The impact of subcooling and micro/nano-scale surface texturing using MWCNT coatings on the dynamics of pool boiling is assessed. Dynamic invariants such as correlation dimensions and Lyapunov spectrum are evaluated for the reconstructed attractor. A non-linear noise reduction scheme is employed to reduce the level of noise in the data. Previous investigations in pool boiling chaos, reported in literature were based on temperature measurements underneath the test surface consisting of single or few active nucleation sites. Previous studies have indicated the presence of low-dimensional behavior in nucleate boiling and high-dimensional behavior in CHF and film boiling. Currently, there is no study detailing the effects of multiple nucleation sites, subcooling and surface texturing on pool boiling dynamics. The investigation comprises of four parts: i) in situ micro-machining of Chromelalumel (K-type) TFT, ii) calibration of these sensors, iii) utilizing these sensors in pool boiling experiments iv) analysis of these fluctuations using techniques of nonlinear time series analysis. Ten TFT are fabricated on a rectangular silicon surface within an area of ~ 3.00 cm x 3.00 cm. The sensing junctions of the TFT measure 50 mm in width and 250 nm in depth. Surface temperature fluctuations of the order of i) 0.65-0.93 degrees C are observed near ONB ii) 2.3-6.5 degrees C in FDNB iii) 2.60-5.00 degrees C at CHF and iv) 2.3-3.5 degrees C in film boiling. Investigations show the possible presence of chaotic dynamics near CHF and in film-boiling in saturated and subcooled pool boiling. Fully-developed nucleate boiling (FDNB) is chaotic. No clear assessment of the dynamics could be made in the onset of nucleate boiling (ONB) and partial nucleate boiling (PNB) regimes due to the effects of noise. However, the frequency spectra in these regimes appear to have two independent frequencies and their integral combinations indicating a possible quasiperiodic bifurcation route to chaos. The dimensionality in FDNB, at CHF and in film-boiling is lower in saturated pool boiling as compared to values in corresponding regimes in subcooled pool boiling. Surface temperature fluctuations can damage electronic components and need to be carefully controlled. Understanding the nature of these fluctuations will aid in deciding the modeling approach for surface temperature transients on an electronic chip. Subsequently, the TFT signals can be employed in a suitable feedback control loop to prevent the occurrence of hotspots.

Metal-organic frameworks (MOFs) are hybrid organic-inorganic micro- or mesoporous materials that exhibit regular crystalline lattices with rigid pore structures. Chemical functionalization of the organic linkers in the structures of MOFs affords facile control over pore size and physical properties, making MOFs attractive materials for application in gas-separating membranes. A wealth of reports exist discussing the synthesis of MOF structures, however relatively few reports exist discussing MOF membranes. This disparity owes to challenges associated with fabricating films of hybrid materials, including poor substrate-film interactions, moisture sensitivity, and thermal instability. Since even nanometer scale cracks and defects can affect the performance of a membrane for gas separation, these challenges are particularly acute for MOF membranes. The focus of this work is the development of novel methods for MOF film and membrane fabrication with a view to overcoming these challenges. The MOF film production methods discussed herein include in situ synthesis using ligand-modified or metal-modified supports and rapid thermal deposition (RTD).

The focus of this research is the development of high strength, high conductivity copper films. Pure copper is soft and traditional strengthening mechanisms cause substantial decrease in conductivity. To address the challenge, epitaxial nanotwinned copper films are synthesized on HF etched Si (110) substrates. These films show high hardness (~ 2.8 GPa) due to high density of coherent twin boundaries (CTBs) which effectively block the motion of dislocations similar to grain boundaries (GBs). Resistivity of CTBs is calculated to be an order of magnitude lower than that of GBs. Hence, conductivity of nanotwinned copper is still comparable to that of pure copper. In addition, it is shown that average twin spacing can be controlled by adjusting deposition rate. Analytical studies together with experimental evidence show that nanotwins can improve the strength-to-resistivity ratio significantly in copper. In general, nanocrystalline metals suffer from low ductility. To study plastic deformation via rolling, thick polycrystalline nanotwinned copper foils are sputtered on SiO2 and then peeled off the substrate. Despite the high strength, room temperature rolling experiments show that nanotwinned copper films exhibit stable plastic flow with no shear localization or fracture even at thickness reduction of over 50%. Postdeformation studies of microstructure reveals that the plastic deformation is facilitated by the migration of CTBs normal to the twin boundary plane due to the glide of twinning dislocations in the twin plane. X-ray pole figure measurements show insignificant out of plane rotation as a result of 50% rolling thickness reduction. Thermal stability of nanocrystalline metals is also a concern. Free standing nanotwinned polycrystalline copper films show remarkable thermal stability after annealing at 800 degrees C. The driving force for twin growth is much lower than that for grain coarsening because the energy stored in CTBs is an order of magnitude lower than that of GBs. As a result, the average twin spacing stays below 20 nm after annealing. Such high thermal stability of nanotwins leads to the retention of hardness of 2.2 GPa. Low energy twin boundary may provide a unique way to achieve both high strength and high temperature thermal stability in certain metallic materials.

Thin film solar cells, if film thickness is thinner than the optical absorption length, typically give lower cell performance. For the thinner structure, electric current loss due to light penetration can offset the electric current gain obtained from higher built-in electric field. Light trapping schemes can increase the effective optical absorption length and thus enhance the electric current for thinner solar cells. Here a new light trapping scheme based on light trapping transparent conducting oxide layer (LT-TCO) is proposed to enhance the performance of thin film solar cells. Three different configurations of integrating the LT-TCO layer in solar cells are proposed and evaluated. This research aims to develop the LT-TCO layer with surface texture and good conductivity by pulsed laser deposition (PLD) technique at low temperature. The LT-TCO layer is fabricated by PLD deposition of Al-doped ZnO to achieve multilayer films by tuning of oxygen pressure. The light trapping effect is examined by optical transmittance measurement and the surface texture is characterized by transmission electron microscopy (TEM) technique. The conductivity of LT-TCO layer is measured by resistivity measurement. Thin film CdTe/CdS solar cells are fabricated by PLD technique to develop baseline solar cells for integration of LT-TCO layer. The as-deposited thin film solar cells show relatively low performance and are further processed with various post-deposition treatments to seek efficiency enhancement. The effects of different processes on cell performance are examined by electrical, optical, and microstructure studies. Air annealing of CdS layer and CdCl2 treatment of CdTe layer combined are found to yield the best cell performance. The fabrication issues that limit the cell performance are discussed and future optimizations in fabrication processes are suggested.