Thin Film Deposition Process Research Articles

Laser Induced Thermoelectric Voltage Effect of LaNiO<sub>3</sub>/LaAlO<sub>3</sub> Multilayer

LaNiO3 single layer, LaNiO3/LaAlO3 superlattice on vicinal-cut single crystalline LaAlO3 (100) and LSAT (100) substrates were prepared by pulsed laser deposition technique. Single-phased LaNiO3 polycrystal target, which is synthesized by sol-gel method, is employed in the thin film deposition process. The structure and physical properties of both the targets and thin films are analyzed. X-ray diffraction results show LaNiO3 single layer is of c-orientation and textural growth, therefore LaNiO3/LaAlO3 forms not superlattice but multilayer. The ultra-violet LITV (laser induced thermoelectric voltage) effects of the LaNiO3/LaAlO3 mutilayer and LaNiO3 single layer were investigated. A comparison study of the influence of LaNiO3 targets prepared by different sol-gel method on the physical property, and LITV effect of thin films was performed as well.

Enhancing the performance of CZTSSe solar cells with Ge alloying

The ability to alloy Cu2ZnSn(S,Se)4 with Ge provides a unique ability to band-gap engineer the absorber film by controlling the relative cation ratios. In here, a preliminary study on adjusting the Ge to Sn ratio is shown to significantly improve the device performance of CZTSSe thin film solar cells. CZTGeSSe solar cell with total area power conversion efficiency as high as 8.4% has been realized using a nanocrystal-based thin film deposition process. The selenized CZTGeSSe thin film exhibits a bi-layer structure where the thin sintered large-grain layer could be responsible for the poor red-response in external quantum efficiency of the resulting solar cell.

Thin film deposition of diamond using normal paraffins as source of diamond nucleation centers

We propose a process for diamond thin film (DTF) deposition using normal paraffins (nP) as source of diamond nucleation centers. We deposited micro-crystalline diamond thin films (MCDTF) on a Cu substrate using Hot Filament CVD (HFCVD) and Passive Pt/Pd Surface Catalysis (PPt/PdSC) methods. Beeswax and a 1:1 mixture of normal paraffins of the general formula CH3(CH2)nCH3 with n=22 and 26 were tested as nP starting material. The films obtained were characterized by scanning electronic microscopy (SEM), Raman scattering temperature dependent spectroscopy and X-ray diffraction (XRD) methods, all of which confirmed that the deposited material is MCDTF.

RESIDUAL STRESS IN A THIN-FILM MICROOPTOELECTROMECHANICAL (MOEMS) MEMBRANE

Residual stress from the thin film deposition process can have extremely important effects on the functionality and reliability of MOEMS devices. Almost all surface-micromachined thin films are subject to residual stresses. The most common is thermal stress, which accompanies a change in temperature when thin-film is evaporated on substrate and when it cools down to room temperature. This paper presents the surface-micro-machined micromembrane micromachining technology. The principle scheme of the object is presented and working principle of micromembrane is described. Furthermore, using powerful modeling software Comsol Multiphysics comparison of eigenfrequencies of structure with thermal stresses and without it is presented. A possible problem solution will also be included.DOI: http://dx.doi.org/10.5755/j01.mech.18.3.1880

Relation between electrical properties of aerosol-deposited BaTiO3 thin films and their mechanical hardness measured by nano-indentation

To achieve a high capacitance density for embedded decoupling capacitor applications, the aerosol deposition (AD) process was applied as a thin film deposition process. BaTiO3 films were fabricated on Cu substrates by the AD process at room temperature, and the film thickness was reduced to confirm the limit of the critical minimum thickness for dielectric properties. As a result, the BaTiO3 thin films that were less than 1-μm thick showed unstable electric properties owing to their high leakage currents. Therefore, to overcome this problem, the causes of the high leakage currents were investigated. In this study, it was confirmed that by comparing BaTiO3 thin films on Cu substrates with those on stainless steels (SUS) substrates, macroscopic defects and rough interfaces between films and substrates influence the leakage currents. Moreover, based on the deposition mechanism of the AD process, it was considered that the BaTiO3 thin films on Cu substrates with thicknesses of less than 1 μm are formed with chinks and weak particle-to-particle bonding, giving rise to leakage currents. In order to confirm the relation between the above-mentioned surface morphologies and the dielectric behavior, the hardness of BaTiO3 films on Cu and SUS substrates was investigated by nano-indentation. Consequently, we proposed that the chinks and weak particle-to-particle bonding in the BaTiO3 thin films with thicknesses of less than 0.5 μm on Cu substrates could be the main cause of the high leakage currents.

Monte Carlo Simulations Of Elastic Scattering With Applications To Dc And High Power Pulsed Magnetron Sputtering For Ti3SIC2

AbstractWe simulate the particle transport in a thin film deposition process made by PVD (physical vapor deposition) and present several models for projectile and tar-get collisions in order to compute the mean free path and the differential cross section (angular distribution of scattered projectiles) of the scattering process. A detailed description of collision models is of the highest importance in Monte Carlo simulations of high power impulse magnetron sputtering and DC sputtering. We derive an equation for the mean free path for arbitrary interactions (cross sections) that includes the relative velocity between the particles. We apply our results to two major interaction models: hard sphere interaction & screened Coulomb interaction. Both types of interaction separate DC sputtering from HIPIMS.

적층형 초전도 다심 선재 제조

Coated conductors have been developed to increase piece length and critical current for electric power applications. Otherwise, Many efforts were carried out to reduce AC loss of coated conductor for AC applications. Twisting and cabling processes are effective to reduce AC loss but, these processes can not be applied for tape shaped coated conductor. It is inevitable to have thin rectangular shape because coated conductor is fabricated by thin film deposition process on metal substrate. In this study, round shape superconducting wire was first fabricated using coated conductors. First of all, Ag coated conductor was used. coated conductor was slitted to several wires with narrow width below 1mm. 12ea slitted wires were parallel stacked on top of another until making up the square cross-section. The bundle of coated conductors was heat treated to stick on each other by diffusion bonding and then copper plated to make round shape wire. Critical current of round wire was measured 185A at 77K, self field.

Modeling and control of Transparent Conducting Oxide layer surface morphology for improved light trapping

This work first introduces a kinetic Monte–Carlo simulation model for a two species thin film deposition process and demonstrates the use of feedback control, coupled with a suitable actuator design, in manufacturing thin films whose surface morphology has a structure that improves light trapping. This work is relevant in the context of a Transparent Conducting Oxide (TCO) thin film layer manufacturing used in thin film solar cells where it is desirable to produce thin films with precisely tailored surface morphology. Specifically, a two species thin film deposition process involving atom adsorption, surface relaxation and surface migration is initially considered and is modeled using a large-lattice (lattice size=40,000) kinetic Monte–Carlo simulation. Subsequently, thin film surface morphology characteristics like roughness and slope are computed with respect to different characteristic length scales ranging from atomic to the ones corresponding to visible light wavelength and it is found that a patterned actuator design is needed to induce thin film surface roughness and slope at visible light wavelength spatial scales, that lead to desired thin film solar cell performance. Then, an Edwards–Wilkinson type equation is used to model the surface evolution at the visible light wavelength spatial scale and form the basis for the design of a predictive feedback controller whose objective is to manipulate the deposition rate across the spatial domain of the process. The model parameters of the Edwards–Wilkinson equation are estimated from kinetic Monte–Carlo simulations and their dependence on the deposition rate is used in the formulation of the predictive controller to predict the influence of the control action on the surface roughness and slope throughout the thin film growth process. Analytical solutions of the expected surface roughness and surface slope at the visible light wavelength spatial scale are obtained by solving the Edwards–Wilkinson equation and are used in the predictive controller formulation and in the control action calculation. The controller is applied to the large-lattice kinetic Monte–Carlo simulation. Simulation results demonstrate that the proposed controller and patterned actuator design successfully regulate aggregate surface roughness and slope to set-point values at the end of the deposition.

Duplex Hard Coatings with Aditional Ion Implantation

In this paper, we present the results of a study of TiN thin films which are deposited by a Physical Vapour Deposition (PVD) and Ion Beam Assisted Deposition (IBAD). In the present investigation the subsequent ion implantation was provided with N2+ ions. The ion implantation was applied to enhance the mechanical properties of surface. The thin film deposition process exerts a number of effects such as crystallographic orientation, morphology, topography, densification of the films.. A variety of analytic techniques were used for characterization, such as scratch test, calo test, Scanning electron microscopy (SEM), Atomic Force Microscope (AFM), X-ray diffraction (XRD) and Energy Dispersive X-ray analysis (EDAX).

Low temperature plasma deposition of silicon thin films: From amorphous to crystalline

We report on the epitaxial growth of crystalline silicon films on (100) oriented crystalline silicon substrates by standard plasma enhanced chemical vapor deposition at 175°C. Such unexpected epitaxial growth is discussed in the context of deposition processes of silicon thin films, based on silicon radicals and nanocrystals. Our results are supported by previous studies on plasma synthesis of silicon nanocrystals and point toward silicon nanocrystals being the most plausible building blocks for such epitaxial growth. The results lay the basis of a new approach for the obtaining of crystalline silicon thin films and open the path for transferring those epitaxial layers from c-Si wafers to low cost foreign substrates.

Atomic Layer Deposition of Thin Inorganic Coatings onto Renewable Packaging Materials

Biopolymers play still a relatively minor role in the packaging material markets. For this to grow further there are problems to be solved, such as inadequate barrier properties and moisture sensitivity. Atomic layer deposition (ALD) is one potential solution. Atomic layer deposition is a layer-by-layer thin film deposition process based on self-limiting gas-solid reactions. It is well suited for producing pinhole free barrier coatings uniform in thickness at relatively mild process conditions. The purpose of this presentation is to summarize our recent work done concerning atomic layer deposition of thin aluminum oxide layers onto biopolymers.

The characteristics of transparent conducting Al-doped zinc oxide thin films deposited on polymer substrates

Al-doped zinc oxide (AZO) transparent, conductive thin films were deposited on inexpensive polyethylene terephthalate substrates, using radio frequency (rf) magnetron sputtering, with an AZO ceramic target (the Al2O3 content is approximately 2 wt%). This paper presents an effective method for the optimization of the parameters for the deposition process for AZO thin films with multiple performance characteristics, using the Taguchi method, combined with grey relational analysis. Using the Taguchi quality design concept, an L9 orthogonal array was chosen for the experiments. The effects of various process parameters (rf power, substrate-to-target distance, substrate temperature and deposition time) on the electrical, structural, morphological and optical properties of AZO films were investigated. In the confirmation runs, using grey relational analysis, the electrical resistivity of the AZO films was found to have decreased from 5.0 × 10−3 to 1.6 × 10−3 Ω-cm and the optical transmittance was found to have increased from 74.39 to 79.40%. The results demonstrate that the Taguchi method combined with grey relational analysis is an economical way to obtain the multiple performance characteristics of AZO films with the fewest experimental data. Additionally, by applying an Al buffer layer, of thickness 10 nm, the results show that the electrical resistivity was 3.1 × 10−4 Ω-cm and the average optical transmittance, in the visible part of the spectrum, was approximately 79.12%.

A Supersonic Plasma Jet Source for Controlled and Efficient Thin Film Deposition

A novel plasma source suitable for controllable nanostructured thin film deposition processes is proposed. It exploits the separation of the process in two distinct phases. First precursor dissociation and radical formation is performed in a dense oxidizing plasma. Then nucleation and aggregation of molecular clusters occur during the expansion into vacuum of a supersonic jet. This allows a superior control of cluster size and energy in the process of film growth. Characterization of the plasma state and source performances in precursor dissociation have been investigated. The performances of this new Plasma Assisted Supersonic Jet Deposition technique were demonstrated using organic compounds of titanium to obtain TiO2 thin nanostructured films.

Modification of surface properties of bell metal by radiofrequency plasma polymerization

Radiofrequency (RF) plasma polymerization is a convenient thin film deposition process as it facilitates the synthesis of polymer films with stable physico-chemical properties suitable for various applications in microelectronic, optical, and biomedical fields. The unique properties of these plasma polymerized films as compared to the conventional ones are strongly related to the proper adjustment of the external plasma discharge parameters and selection of suitable monomer. It is also important to study the fundamental chemistry of RF plasma polymerization process, so that one can successfully correlate the internal features of the discharge with the film properties and explore their possible technological applications. The possibility of using styrene-based plasma polymer (SPP) films on bell metal as protective coatings is explored in this work. Depositions of the films are carried out in RF Ar/styrene discharge at working pressure of 1.2 × 10−1 mbar and at the RF power range of 20 to 110 W. Optical emission spectroscopy (OES) is used to study the active species generated during plasma polymerization, while Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) are used to analyze the internal chemical structures of the films. The protective performances of the SPP films are attempted to correlate with the results obtained from OES, FT-IR, and XPS analyses.

Aluminum induced formation of SiGe alloy in Ge/Si/Al thin film structure

In this work, a study of aluminum induced crystallization (AIC) of thin film germanium/silicon/aluminum (Ge/Si/Al) structure on oxidized silicon is presented. The Ge/Si/Al trilayer structure was prepared in three consecutive thin film deposition processes. The AIC was performed in nitrogen at 500°C within time duration between 1 and 9h. The progress of crystallization was monitored by optical microscopy, Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS). It was found that in Ge/Si/Al structure the AIC can lead to formation of SiGe alloy at temperature of 500°C. This presents an alternative low-temperature formation method of SiGe which is suitable for integration with the conventional Si technology in electronic device fabrication.

Nitrogen Introduction in pp‐HMDSO Thin Films Deposited by Atmospheric Pressure Dielectric Barrier Discharge: An XPS Study

AbstractWe report on the change of chemistry involved by molecular nitrogen in the deposition process of pp‐HMDSO thin films with an AP‐DBD, using HMDSO as chemical precursor. By modifying the composition of the main gas from pure argon to pure nitrogen, thin films composition varied from SiOC:H to SiOCN:H. A small amount of nitrogen favours polymer chain propagation, by consuming species responsible for chain termination and playing a role in propagation phase. Higher nitrogen content leads to more cross‐linked coatings. The use of optical emission spectroscopy together with FT‐IR and XPS is shown to be relevant to study such processes.magnified image

An Investigation of CdZnTe Thin Films for Photovoltaics

Thin film solar cells are widely investigated for terrestrial and space photovoltaic and offer a variety of choices in terms of the device design and fabrication. A variety of substrates, such as flexible or rigid, metal or insulator, can be used for deposition of different layers using different techniques, including physical vapor deposition (PVD), chemical vapor deposition, electrochemical deposition, plasma-based, hybrid, etc. For large-area devices required for realistic applications, thin-film device fabrication becomes complex and requires proper control over the entire process sequence. Detailed investigation of thin-film deposition processes can help in achieving high-efficiency devices over large areas for different solar cells. PVD techniques were extensively used to deposit thin film by using a few targets simultaneously. In this study, single target CdZnTe is used for deposition on glass. Two hundred nm thin films were fabricated. Structural and optical properties of CdZnTe thin films are investigated.

Influence of the oxygen partial pressure and post-deposition annealing on the structure and optical properties of ZnO films grown by dc magnetron sputtering at room temperature

A systematic study for the optimization of the deposition process of ZnO thin films grown by dc magnetron sputtering at room temperature was carried out using different oxygen partial pressures and deposition times. We have established a correlation between the oxygen partial pressure, the chemical composition and the crystalline structure of the films.Stoichiometric and highly oriented ZnO thin films along the (0 0 2) crystal plane with very good optical performance were obtained for a relative oxygen gas flow of 20% in the gas mixture. Higher O2 concentrations resulted in non-stoichiometric ZnO with an excess of oxygen, which exhibited a lower degree of crystallinity and slightly higher band-gap energy.X-ray absorption near edge structure (XANES) analysis indicated that this excess of oxygen was incorporated in molecular form inducing a reduction in the crystallinity of the material. Post-deposition annealing treatments up to 500 °C significantly improved their crystallinity as confirmed by x-ray diffraction and XANES. Therefore, it has been found that it is possible to grow ZnO at room temperature with high crystal quality and good optical response by controlling the growth conditions.

Simulation and control of aggregate surface morphology in a two-stage thin film deposition process for improved light trapping

This work focuses on the development of a model predictive control algorithm to simultaneously regulate the aggregate surface slope and roughness of a thin film growth process to optimize thin film light reflectance and transmittance. Specifically, a two-stage thin film deposition process, which involves two microscopic processes: an adsorption process and a migration process, is modeled based on a one-dimensional solid-on-solid square lattice. The first stage of this process utilizes a uniform deposition rate profile to control the thickness of the thin film and the second stage of the process utilizes a spatially distributed deposition rate profile to control the surface morphology of the thin film. Kinetic Monte Carlo (kMC) methods are used to simulate this two-stage thin film deposition process. To characterize the surface morphology and to evaluate the light trapping efficiency of the thin film, aggregate surface roughness and slope corresponding to length scale of visible light are introduced as the root-mean squares of the aggregate surface height profile and aggregate surface slope profile. An Edwards–Wilkinson (EW)-type equation with appropriately computed parameters is used to describe the dynamics of the surface height profile and predict the evolution of the aggregate root-mean-square (RMS) roughness and aggregate RMS slope. A model predictive control algorithm is then developed on the basis of the EW equation model to regulate the aggregate RMS slope and the aggregate RMS roughness at desired levels. Closed-loop simulation results demonstrate the effectiveness of the proposed model predictive control algorithm in successfully regulating the aggregate RMS slope and the aggregate RMS roughness at desired levels that optimize thin film light reflectance and transmittance.

Dynamics and control of aggregate thin film surface morphology for improved light trapping: Implementation on a large-lattice kinetic Monte Carlo model

This work demonstrates the use of feedback control, coupled with a suitable actuator design, in manufacturing thin films whose surface morphology is characterized by a desired visible light reflectance/transmittance level. The problem is particularly important in the context of thin film manufacturing for thin film solar cells where it is desirable to produce thin films with precisely tailored light trapping characteristics. Initially, a thin film deposition process involving atom adsorption and surface migration is considered and is modeled using a large-lattice (lattice size=40,000) kinetic Monte Carlo simulation. Subsequently, thin film surface morphology characteristics like roughness and slope are computed with respect to different characteristic length scales ranging from atomic to the ones corresponding to visible light wavelength and it is found that a patterned actuator design is needed to induce thin film surface roughness and slope at visible light wavelength spatial scales, which lead to desired thin film reflectance and transmittance levels. Then, an Edwards–Wilkinson-type equation (a second-order stochastic partial differential equation) is used to model the surface evolution at the visible light wavelength spatial scale and form the basis for the design of a feedback controller whose objective is to manipulate the deposition rate across the spatial domain of the process. The model parameters of the Edwards–Wilkinson equation are estimated from kinetic Monte Carlo simulations and their dependence on the deposition rate is used in the formulation of the predictive controller to predict the influence of the control action on the surface roughness and slope throughout the thin film growth process. Analytical solutions of the expected surface roughness and surface slope at the visible light wavelength spatial scale are obtained by solving the Edwards–Wilkinson equation and are used in the control action calculation. The cost function of the controller involves penalties on both surface roughness and slope from set-point values as well as constraints on the magnitude and rate of change of the control action. The controller is applied to the large-lattice kinetic Monte Carlo simulation. Simulation results demonstrate that the proposed controller and patterned actuator design successfully regulate aggregate surface roughness and slope to set-point values at the end of the deposition that yield desired levels of thin film reflectance and transmittance.