The Raman optothermal technique has been the most successful method for measurement of thermal conductivity of two dimensional (2D) materials, and was used to measure the thin films for the first time in this work. In this technique, a laser is focused at the center of a thin film and used to measure the peak position of a Raman-active mode. As the laser power is increased, the sample is heated which enables red-shift Raman mode due to thermal softening. Another comparison experiment is conducted by placing the samples on a heating platform and monitor the change of Raman-active mode peak position shift. Combining these two sections of experiments provide us the thermal modeling can then be used to extract the thermal conductivity from the measured shift rate. We have used a refined version of the optothermal Raman technique to study thermal conductivity of thin films of Bi 2 Te 3 and Sb 2 Te 3 , at extreme temperatures and mechanical strains. It is the first thermal measurement on these two materials by Raman optothermal technique. This work also addresses several important issues in the measurement of thermal conductivity of thin films using Raman spectroscopy.

The variation of their crystallinity, in other words, the order of atom arrangement of grain boundaries in electroplated gold thin films was investigated by changing their manufacturing conditions. Then, the effect of the crystallinity on both their mechanical and electrical properties was measured by using nano-indentation test and electromigration test. The crystallinity of the gold thin films was varied by changing the under-layer material used for electroplating. Also, the micro texture of gold thin films was evaluated by EBSD (Electron Back-Scatter Diffraction) and XRD (X-Ray Diffraction). It was clarified that the crystallinity of the electroplated gold thin films changed drastically depending on the crystallinity of the under-layer materials and electroplating conditions such as current density and temperature. This variation of the crystallinity should have caused wide variation of mechanical properties of the films. In addition, their mechanical properties such as Young’s modulus and hardness showed wide variation by about 3 times comparing with those of bulk gold. Similarly, the EM resistance of the electroplated gold bumps varied drastically depending on the ratio of porous grain boundaries and their crystallinity. Both the ratio and crystallinity also varied depending on the crystallinity of the under layer and electroplating conditions. The effective lifetime of the gold bumps was successfully predicted by considering both the crystallinity and residual stress of fine gold bumps. The lifetime varied more than 10 times as a strong function of the crystallinity of grain boundaries in the fine bumps. Therefore, it is very important to control the crystallinity of the under-layer for electroplating in order to control the distribution of the mechanical properties and reliability of the electroplated gold thin films.

Nanotechnology fabrication has become a popular field in the development of advanced and cutting-edge technologies. Deposition processes are industrialized to achieve nano-thin films with absolute control over the film thickness, conformal and uniform film growth over complex structures, and minimal to no defects or pinholes. Atomic layer deposition (ALD) has revealed itself as a possible candidate to achieve these requirements. However, the in-depth understanding of the physical and chemical formation of the thin film is still unfamiliar to reactor designers, engineers and scientists. For the purposes of this study, the interest involves the mechanistic factors of geometry influences, fluid flow, and mass transportation on the heterogeneous chemical reaction process. Through an industrial ALD process recipe, the transitional and recirculation phenomena observed in the Atomic Layer Deposition (ALD) thin film process are seen to exert a significant influence on the effective formation and growth of the thin film on the substrate. Topological fluid dynamics are used to analyze the two-dimensional numerical simulations of the backward-facing step (BFS) phenomena and the recirculation flow patterns typically found within a horizontal ALD reactor. Focus is placed on investigating the saddle points in the resulting vortex shedding, eddy distortion and recirculation due to the BFS phenomena. The topological analysis is conducted for symmetrical step heights of 7.5mm and 10 mm respectively. Findings revealed close similarities to experimental studies.

The objective of this study is to investigate the effect of film thickness on the bandgap of oxygen (O 2 )-doped titanium nitride (TiN) thin films. To accomplish this, high-quality two-dimensional O 2 -doped TiN films have been prepared on single-crystal sapphire substrates using a pulsed laser deposition method. The film thicknesses were varied from 3 to 100 nm by varying the number of laser pulses, while other deposition parameters are kept constant. X-ray diffraction (XRD) patterns have shown that the films grow in (111) orientation on the sapphire substrate. The increase in the intensity of the XRD (111) peak also demonstrates a better orientational alignment of the TiN films with substrate as the film thickness increases. The x-ray rocking curve has been used to measure the full width half maxima (FWHM) for each film. The FWHM values has been found to vary from 0.07 to 0.2° as the film thickness decreases. This is taken to indicate that the grain size decreases with a decrease in film thickness. Ultraviolet visible spectroscopy measurements in the wavelength range (200–800 nm) have been performed as well, which indicates an increase in the bandgap of O 2 -doped TiN films with a decrease in film thickness. The decrease in the film thickness leads to a blue shift of the peak in the ultraviolet-visible absorption (UV-A) region; this blueshift is accompanied by an increase in the bandgap of O 2 -doped TiN from 3.2 to 3.8 eV. The change in the bandgap due to a change in film thickness has been explained using the quantum confinement effect.

Titanium alloys have found application in many sectors and are regarded as one of the most valuable materials of the 21 st century. Although titanium alloys have many promising properties, the tribo-corrosion properties still happen to be a limiting factor. In this research study, radio frequency (RF) magnetron sputtering was used to deposit refractory ceramic (TiC) thin films coatings on the surface of titanium alloys in order to enhance and improve the wear and corrosion resistance properties. Different combinations of the sputtering process parameters were used for the deposition process. The varied sputtering process parameters were RF Power, sputtering time, and temperature. The macroscratch, microscratch (adhesion test) and, corrosion properties of the coatings were investigated using the pin on-disk wear test, micro-scratch tribometer, and electrochemical potentiostat, respectively. The results show improvement in the wear and corrosion properties of the coated samples. The results also revealed the influence of the sputtering process parameters on the evolving wear and corrosion properties of the coated samples. Scanning electron microscope (SEM) was used to capture the wear scar and analyses the failure mode of the coatings.

Uranium and thorium oxides have critical roles as fuels in existing nuclear power plants, as well as in proposed reactor concepts. The thermal conductivity of these materials determines their ability to transfer heat from the reactor core to the surrounding coolant. Additionally, these actinide compounds are of interest in condensed matter physics because of the 5f orbitals and unique electron interaction, coupling, and scattering events that can occur. Because of the radioactivity of thorium and uranium, thin film measurements of actinide materials are used to limit the amount of operator exposure, but standard thermal characterization methods are not well suited for thin films. This paper presents the process of depositing thin film UO x and ThO x samples of nm-μm thicknesses and the results of thermal property measurements. Thin films were deposited on silicon and glass substrates via dc-magnetron sputtering using an argon/oxygen mixture as the working gas. The thermal properties of the films were measured by the Thermal Conductivity Microscope (TCM). This uses one laser to generate thermal waves and a second laser to measure the magnitude and phases of the thermal waves to obtain the conductivity of materials. The results of the research show that the UO x film properties are lower than bulk values and that the role of the substrate has a considerable effect on determining the measured properties. Future work aims at improving the deposition process. Epitaxial film growth is planned. Additional understanding of thermal property measurements is targeted.

In this study, micro-scale strain sensors were embedded in a silicon chip to measure the variation of the local stress distribution around thin film interconnections used for 3D semiconductor modules. Piezoresistive effect of single crystal silicon was applied to the sensors. The stress sensitivity at room temperature was 1.3 MPa/Ω. Even though the stress sensitivity varied as a strong function of temperature, it was confirmed that this sensor can measure the stress distribution quantitatively in the temperature range from room temperature to 80°C at most. And the variation of the residual stress in electroplated copper thin films during heat treatment was investigated from the viewpoint of the change of stress amplitude during a thermal cycle. From the obtained results, it was confirmed that the recrystallization occurred when the films were annealed at only 200°C, and the change of the micro textue of the films caused the change of their residual stress. Therefore, it is very important to control the micro texture during electroplating for assuring long term reliability of interconnections.

This study develops a new experimental system to investigate surface buckling patterns that emerge due to the biaxial compression of elastomeric bilayer spherical shell. The sample used in this study is a thick PDMS (polydimethylsiloxane) substrate and a thin PDMS film. In order to induce biaxial strain to the surface of PDMS substrate, air pressured device like bulge test is first developed. This system enables a flat PDMS plate to isotropically expand and become a hemisphere due to air pressure. In other words, the surface of PDMS substrate is stretched and subjected to biaxial loading. Subsequently, a thin PDMS film is covered on the hemisphere substrate. By releasing the air pressure, the pre-stretch in the substrate is released gradually and the outer film is subjected to biaxial compression. During the biaxial compression, various film buckling patterns are observed. It is found that the surface buckling patterns are wrinkle formation that is associated with film delamination. This formation pattern is dependent on the surface strain distribution, i.e. radial strain and circumferential strain. In order to control the pattern of buckling-delamination, we systematically changed the material parameters, such as the film thickness, Young’s modulus, interfacial fracture toughness, etc. Our experiment is capable in reproducing various wrinkle patterns with film delamination on an elastomeric bilayer spherical shell.

The present study aims at studying the characteristics of thermocapillary migration with varying levels of lateral restraints. A temperature gradient is created by heating and cooling either side of the substrate. When a droplet is placed near hot side it spreads as thin film and migrates towards the cold side. The advancing end assumes the shape of a parabolic rim while the receding end stays as a thin film. It is observed that the droplet decelerates to attain a steady state velocity and undergoes slight acceleration near the cold end of the substrate. The observed velocity trend follows the temperature gradient on the substrate. The velocity increases with the droplet volume and substrate temperature gradient. The liquid viscosity is observed to have a diminishing effect on migration velocity. The effect of lateral spread confinement is studied by performing experimental trails on substrates with different widths. It is found that reducing the substrate width increases the migration velocity due to increased footprint resulting in larger thermocapillary force. The results observed in the present study highlights the importance of thermocapillary flows in many academic and industrial applications.

Analytical solutions of thin film dampers are useful for determining critical speeds and stability of rotor systems. Most thin film dampers in use are of short axial length, and closed-form solutions to the Reynolds equations exist for estimating pressure, forces, and damping for these types of dampers. This article compares the fluid film forces and damping estimated by the short film bearing model form of the Reynolds equations to the calculated forces and damping of a transient computational fluid dynamic simulation. For this comparison, the fluid was assumed to be incompressible, laminar, and isoviscous. The fluid film forces and damping are calculated from integrating the pressure distribution over the surface of the damper due to small amplitude motions about a steady state static off-center circular orbit. In this case, no cavitation is assumed, and the journal has no angular velocity, so direct stiffness cannot be calculated from the closed-form solution. Radial clearance, journal length, and journal eccentricity have a significant effect on fluid force and damping within a thin film damper. Fluid density does not affect fluid force or damping substantially, while fluid viscosity does. Both the closed-form solutions and computational fluid dynamics simulation compare well with each other and reflect these trends.

The need to test for the durability and capability of a coating before being subjected to service is highly important for engineering applications. Ultra-low indentation of nano-hardness and nano-scratch are valuable methods of measuring durability and near-surface mechanical properties of thin films. AISI 304 stainless steel was coated with Repellix superhydrophobic coating using chemical vapor deposition (CVD) and atomic layer deposition (ALD) techniques at constant processing parameters. The deposited films were characterized through nanoindentation, nanoscratch, and water contact angle to establish the effect of coating technique on the mechanical properties of the thin films. The results established that the ALD deposition technique has better hardness but less wear resistance when compared to the sample produced using the CVD method. ALD also showed to have a lower contact angle in comparison with a coating deposited by CVD. Overall, it is expected that the substrate coated by CVD would outperform samples produced via ALD as regards to typical applications where good wear and corrosion resistance are required.

This paper investigates the purge flow rate in a reactor scale simulation of an Atomic Layer Deposition (ALD) process. A three-dimensional numerical analysis approach was implemented in the ALD process to fabricate thin films of aluminium oxide (Al 2 O 3 ). Despite the abundance of literature on the specific use of, and increase in deposited material through the process of ALD, limited studies exist on the physical and chemical processes that occur during the growth of ALD. Previous literature has indicated that purging has presented a major challenge in the effective deposition rate of the ALD process. The precise purge flow rate has also been greatly contended. The importance of the purge sequence within the ALD process cannot be overemphasized. The term purge sequence refers to the essential property that defines the ALD advanced nano-fabrication technique in producing ultra-thin film. Therefore, this study focused on the purge flow rate effects of the ALD process. The reactants employed in the simulation process were trimethyl-aluminium (TMA) and ozone (O 3 ) as the metal and oxidant precursors, respectively, and inert argon as the purge gas. Numerical simulations were carried out at a stable operating pressure of 1 torr, with a substrate temperature of 200°C, and three purge flow rates of 20, 10 and 5 sccm, respectively. An extended ozone exposure is crucial to in providing an adequately oxidized substrate. It is discovered that the 5 sccm flow rate shows, superior mass fractions, unity surface coverage and a time extensive surface deposition rate. The 20 sccm, 10 sccm and 5 sccm purge flow rate growth obtained a 0.58, 0.92, and 1.6 Å/cycle, respectively. The findings revealed close similarities to experimental behaviours and recorded growth.

The thin film solar cells (TFSCs) are becoming more widely implemented due to their light weight, lower cost, and flexibility when compared to the conventional monocrystalline silicon wafer solar cells. Common materials used in the TFSCs today are amorphous silicon (a-Si) and microcrystalline silicon due to their abundance. However, these materials suffer from decreased absorption efficiency especially in the infrared range due to the sub-micron thickness of the absorber. Cadmium Telluride/Cadmium Sulfide (CdTe/CdS) is a promising candidate for TFSC material due to the near ideal, direct band gap of the CdTe, which allows it to be implemented without suffering greatly from decreased absorption efficiency. Nano-texturing is a widely researched and implemented way to increase the absorption of TFSCs. In this project, the wave optical analyses for the wavelength range of 300–1100 nm were executed using ANSYS High Frequency Structural Simulator (HFSS) to study the interaction of the geometric parameters of the nano-structures in CdS/CdTe TFSCs. A 3X3 factorial design of experiments was implemented to investigate 3 different levels of the height (H), diameter (D), and period (Pd) for a conical shaped nano-texture pattern and to study their effect on the absorption and the short circuit current (J sc ). A total of 27 different combinations were investigated. It was found that the model with H = 1000 nm, D = 1000 nm, and P/D = 1 had the highest J sc of 26.66 mA/cm 2 , a 29.14 % increase from the planar control cell. In addition, it was noted that when the P/D ratio is 1, an increase in both height and diameter will increase J sc . Finally, when the height was 200 nm, an increase in the diameter has little to no effect on J sc . These findings are important to TFSCs manufactures to better design the nano-texturing implemented in TFSCs.

This review focuses on modern energy attributes and to identify alternative energy source and technology that satisfy energy trilemma requirements. The results and findings of the study show that photovoltaic (PV) solar cells technologies have the potentials of satisfying the global energy quest if deployed more. This study x-rays the different PV cells technologies in terms of generation chronology, power conversion efficiencies (PCE), (EPBT), present status and outlook. This study harmonises many photovoltaic performance indexes from review as follow: PV module power conversion efficiencies (PCE) of solar cells: lab -mono-Si (26.7%), multi-Si (22.3%), CIGS (21.7%), for and CdTe (21.0%); commercial - mono-Si (17%), CdTe (16.0%); energy payback time (EPBT) in Europe, 1–1.5 years and 1.5–3.5 years for thin film and crystalline silicon PV systems, respectively, 3 months and 8 months for perovskite (PSC) and CdTe solar cells respectively. The price of PV has drastically declined from $76/W in 1997 to $0.3/W in 2015. By 2050 and 2100, PV solar technology is expected to provide 20% and over 60% of the world’s energy supply, respectively. This will account for 50% CO2 emissions reduction globally. The projections depend on further improvement on the performance indexes and lifetime, series resistance, and optical properties. CdTe technology performs better than other technologies at elevated temperature, hence, recommended for tropical regions.

In the present work, the deformation behavior in metallic film subjected to ultra-short laser heating is investigated. Static thermo-elastic behavior is predicted for 100 nm thin film of either single layer or multiple layers. The temperature distribution is estimated from dual-phase lag non-Fourier heat conduction model. The maximum temperature after single pulse is achieved 730 K. The temperature profile for this pulse laser is used to compute elastic stress and distortion field following the minimization of potential energy of the system. In the present work, the simulation has been proposed by developing 3D finite element based coupled thermo-elastic model using dual phase lag effect. The experimental basis of transient temperature distribution in ultra-short pulse laser is extremely difficult or nearly impossible, the model results have been validated with literature reported thermal results. Since the temperature distribution due to pulse laser source varies with time, the stress analysis is performed in incremental mode. Hence, a sequentially coupled thermo-mechanical model is developed that is synchronized between thermal and mechanical analysis in each time steps of transient problem. The maximum equivalent stress is achieved 0.3 GPa. Numerical results show that the predicted thermal stress may exceeds the tensile strength of the material and may lead to crack or damage the thin film.

Various brittle fractures have been found to occur at grain boundaries in polycrystalline materials. In thin film interconnections used for semiconductor devices, open failures caused by electro- and strain-induced migrations have been found to be dominated by porous random grain boundaries that consist of a lot of defects. Therefore, it is very important to explicate the dominant factors of the strength of a grain boundary in polycrystalline materials for assuring the safe and reliable operation of various products. In this study, both electron back-scatter diffraction (EBSD) analysis and a micro tensile test in a scanning electron microscope was applied to copper thin film which is used for interconnection of semiconductor devices in order to clarify the relationship between the strength and the crystallinity of a grain and a grain boundary quantitatively. Image quality (IQ) value obtained from the EBSD analysis, which indicates the average sharpness of the diffraction pattern (Kikuchi pattern) was applied to the crystallinity analysis. This IQ value indicates the total density of defects such as vacancies, dislocations, impurities, and local strain, in other words, the order of atom arrangement in the observed area in nano-scale. In the micro tensile test system, stress-strain curves of a single crystal specimen and a bicrystal specimen was measured quantitatively. Both transgranular and intergranular fracture modes were observed in the tested specimens with different IQ values. Based to the results of these experiments, it was found that there is the critical IQ value at which the fracture mode of the bicrystal specimen changes from brittle intergranular fracture at a grain boundary to ductile transgranular fracture in a grain. The strength of a grain boundary increases monotonically with IQ value because of the increase in the total number of rigid atomic bonding. On the other hand, the strength of a grain decreases monotonically with the increase of IQ value because the increase in the order of atom arrangement accelerates the movement of dislocations. Finally, it was clarified that the strength of a grain boundary and a grain changes drastically as a strong function of their crystallinity.

Electroplated gold thin films have been used for micro bumps in flip chip packing structures. However, it has been reported that physical properties and micro texture of the electroplated thin films vary drastically comparing with those of conventional bulk material, depending on their electroplating process. In addition, since one bump is going to consist of a few grains or a single grain due to the miniaturization of the 3D structures, it shows strong anisotropic mechanical properties because a face-centered cubic crystal essentially has strong anisotropy of physical properties. Therefore, there should be the wide distribution of characteristics of the micro bumps depending on their micro structure and the variation of the crystallinity of grains and grain boundaries enlarges the width of the distributions of various properties. Particularly, it was found that the long-term reliability of micro bumps and interconnections is degraded drastically by porous grain boundaries with a lot of defects because of the acceleration of atomic diffusion along the porous grain boundaries under the application of high current density (electromigration) and high mechanical stress (stress-induced migration). In this study, the effect of crystallinity, in other words, the order of atom arrangement of grain boundaries in electroplated gold thin films on the EM resistance was investigated experimentally. The crystallinity of the gold thin films was varied drastically by changing the under-layer material used for electroplating; such as Cr (30 nm) / Pt (50 nm)/ Au (200 nm) and Ti (50 nm) / Au (100 nm). The mechanical properties of the electroplated gold thin films were measured by using a nano-indentation test. Also, the micro textures such as crystallinity and crystallographic orientation of gold thin films were investigated by EBSD (Electron Back-Scatter Diffraction) and XRD (X-Ray Diffraction). It was clarified that the crystallinity of the electroplated gold thin films changed drastically depending on the crystallinity of the under-layer materials and heat treatment conditions after electroplating. This variation of the crystallinity should have caused the wide variation of mechanical properties of the electroplated gold films. Therefore, it is very important to control the crystallinity of the under layer used for electroplating in order to control the mechanical properties and reliability of the electroplated gold thin films.

In this study, the tribological behavior of the Trihexyl tetradecylphosphonium-bis(2,4,4-trimethylpentyl)phosphinate [THTDP][Phos] ionic liquid with and without single-wall carbon nanotubes (SWCNT) dispersion as a thin boundary layer was intended for investigation. However, the surface heat treatment process was not sufficient to form a thin film on the sample surfaces. Thus, in each test condition, the lubricating agents were used as external (liquid) lubricants. Specifically, [THTDP][Phos] and ([THTDP][Phos]+0.1 wt.% SWCNT) boundary film layers were applied on 6061-T6 aluminum alloy disk samples and tested under sliding contact with 1.5 mm diameter 420C stainless steel balls using a ball-on-flat linearly reciprocating tribometer. A commercially available Mobil Super 10W-40 engine oil (MS10W40) was also tested and used as this investigation’s datum. The tribological behavior of [THTDP][Phos] and ([THTDP][Phos]+SWCNT) boundary film layers was analyzed via wear volume calculations from optical microscopy measurements, as well as by observation of the transient coefficient of friction (COF) obtained through strain gauge measurements made directly from the reciprocating member of the tribometer. Results indicate the potential for reduction of wear volume and coefficient of friction in the IL lubricated steel-on-aluminum sliding contact through (SWCNT) dispersion in the ionic liquid. Wear results are based on measurements obtained using optical microscopy (OM). Results discussed display improved tribological performance for both [THTDP][Phos] and ([THTDP][Phos]+SWCNT) over baseline MS10W40 oil lubricant for both roughness values tested for the steel-on-aluminum contact. No measurable improvements were observed between [THTDP][Phos] and ([THTDP][Phos]+SWCNT) tests.

Air bearing is future main supporting way of high-speed machinery such as turbocharger, micro gas-turbine engine. Foil bearing is a new type of air bearing which is lubricated by the thin-film air with its self-adapting elastic foil structure. It has many significant advantages such as non-pollution, longer working life, higher reliability, and lower friction loss. Different from foil journal bearing, in present the study of foil thrust bearing is extremely insufficient, especially about how to accurately predict the pressure distribution and efficiently improve the bearing capacity. The pressure distribution prediction of foil thrust bearing air film directly impacts the bearing stiffness and damping design, and then influences bearing capacity. The Reynolds equation commonly used to do such estimation is not accurate enough since the influence of temperature on air property parameters is ignored. The inaccurate prediction leads a catastrophic reduction to the bearing performance. In order to solve this problem, we propose a model to accurately predict the pressure distribution and capacity of foil thrust bearing using CFD method, as well estimating the relationship between air film clearance thickness, rotation speed, environment temperature and the capacity. Firstly, we simulate the pressure distribution of air film and then evaluate the simulation result by constrained experiments. We also correct the simulation by using modified air parameters obtained from experiment. The experimental results indicate our corrected simulation model is accurate with error less than 4%. Secondly, we compare simulation and experiment pressure results under different conditions. The model accuracy sensitivity varies within 10% under different rotation speed, air film clearance thickness and environment temperature. Finally, we use corrected model to analyze capacity impact parameters. We find the capacity of bearing increases with the decreasing of average air film clearance thickness under fixed speed of the thrust disc. The smaller clearance thickness is, the more influence its variation has on the bearing capacity. Meanwhile, the capacity of the bearing decreases with the reducing thrust disc speed under constant clearance thickness, and it decreases more obviously in the lower speed. The capacity reaches its largest under 200 °C and it falls with the increases or decreases of environment temperature. The model in this paper provides important theoretical foundation when designing the stiffness, damping and temperature control of each bearing area.

Intense pulsed light sintering (IPL) of nanoparticles on rigid or flexible substrates enables rapid fabrication of thin films and patterns over large areas. In IPL, visible light from a high energy xenon lamp is absorbed by the nanoparticles for rapid sintering of metallic and non-metallic nanoparticles. This plasmonic optical absorption during the process for metal nanoparticles has been shown to depend on individual nanoparticle size. However, but there is little understanding of how this absorption depends on nanoparticle size distribution during IPL. This work incorporates a fully three-dimensional packing model along with an electromagnetic model of plasmonic absorption in silver nanoparticles to bridge this gap. It is shown that smaller standard deviation in a unimodal distribution and smaller size ratios in a bimodal distribution demonstrate relatively higher optical absorption in IPL.