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Injection of precursor molecules into a plasma often results in particle generation or deposition in the source, compromising film quality and plasma operation. We present here a study of ion chemistry and ionic film deposition from hexamethyldisilane (HMDS) using a novel device utilizing vacuum ultraviolet (VUV)‐radiation from a remote atmospheric plasma. Infrared spectroscopy showed that SiO2 ${\text{SiO}}_{2}$‐like films were obtained at the lowest admixture, where impurities are more important and VUV‐photons reach the substrate, while only slightly oxidized films were deposited at high admixtures. Photoionization mainly forms the monomer ion due to collisional stabilization and possibly slow polymerization reactions as found by ion mass spectrometry. The more detailed photochemistry of HMDS‐related ions is discussed based on mass spectra for different admixtures. [ABSTRACT FROM AUTHOR]

Spin coating stands out as the most employed thin-film deposition technique across a variety of scientific fields. Particularly in the past two decades, spin coaters have become increasingly popular due to the emergence of solution-processed semiconductors such as quantum dots and perovskites. However, acquiring commercial spin coaters from reputable suppliers remains a significant financial burden for many laboratories, particularly for smaller research or educational facilities. Prompted by the simple mechanical principles of the device, in this work, we present a 3D-printed analogue that can be printed and assembled in under 10 h and costs less than 5 euros per device. The operating principle is fully mechanical since the rotating motion is induced by gas flow. It does not require any additional components such as DC motors, motor drivers, circuitry or software and thus it can be fully operational off the grid. Additionally, the gas flow generates a purging effect that was found to be rather advantageous for film formation. To prove the effectiveness of this device, we have employed it to fabricate planar thin-film antimony sulfide (Sb2S3) solar cells. The optoelectronic characteristics of solar cells revealed noteworthy improvements, particularly in terms of repeatability, when compared to those fabricated with a commercial spin coater.

Autonomous experiments for material synthesis have been developing with increasing speed. With the expanding search space for accessible materials, the efficient collection of prior knowledge, particularly synthesis conditions, before autonomous experiments is crucial in reducing the number of trials. In this study, we developed a workflow that systematically extracts synthesis conditions from scientific literature. We constructed a knowledge graph to test the simple hypothesis that significant correlations exist between the physical properties and synthesis conditions that appear nearby in a text. The performance of this scheme was demonstrated by extracting the appropriate thin-film synthesis conditions for conductive Nb-doped TiO2. The proposed methodology is expected to accelerate autonomous material synthesis experiments.

Compared to the optimization of a 1D synthesis parameter in materials synthesis, the optimization of multi-dimensional synthesis parameters is challenging for researchers. Bayesian optimization (BO) has shown high performance in optimizing high-dimensional synthesis parameters when appropriate hyperparameters are adopted. However, hyperparameter tuning for the kernel and acquisition functions used in BO is yet to be fully discussed by material researchers. In this study, we simulated materials synthesis under 2D and 3D synthesis conditions using artificial model functions with different process windows to investigate the effects of hyperparameters. The assumed parameters were temperature, oxygen partial pressure, and the sputtering power for thin-film deposition. Our findings indicate that estimating the process window and the range of physical property change based on the experience and knowledge of the materials researcher is crucial for tuning the hyperparameters of the kernel function. The simulations for high-dimensional search spaces case also indicate that the number of trials for optimization of synthesis conditions might reach several hundred or more. Therefore, the dimensionality and range of the search space must be limited based on the number of practical experiments, which is crucial for applying Bayesian optimization to materials synthesis. Our results facilitate fully automated and autonomous materials synthesis using BO and robotics for materials exploration in a high-dimensional search space.

Polyimide is an emerging and very interesting material for substrate and passivation of neural probes. However, the standard curing temperature of polyimide (350 °C) is critical for the microelectrodes and contact pads of the neural probe, due to the thermal oxidation of the metals during the passivation process of the neural probe. Here, the fabrication process of a flexible neural probe, enhanced with a photosensitive and low-temperature cured polyimide, is presented. Annealing tests were performed with metallic films deposited on polyimide, which led to the reduction of the curing temperature to 250 °C, with no significant irregularities in the metallic sample annealed at that temperature and an effective polyimide curing. The use of a lower curing temperature reduces the thermal oxidation of the metals during the polyimide curing process to passivate the neural probe. Additionally, in this fabrication process, the microelectrodes of the neural probe were coated with electrodeposited platinum (Pt), only after the passivation process, and its electrochemical performance was accessed. At 1 kHz, the impedance of the microelectrodes before Pt electrodeposition was approximately 1.2 MΩ, and after Pt electrodeposition, it was approximately 350 kΩ. Pt electrodeposition changed the equivalent circuit of the microelectrodes and reduced their impedance, which will be crucial for future in-vivo tests to acquire the electrical activity of the neurons with the fabricated neural probe. [ABSTRACT FROM AUTHOR]

Open‐air plasma jets are becoming increasingly popular due to easy and affordable large‐scale coating deposition on diverse substrates. However, direct deposition of primary amine groups (NH2), which are attractive as covalent anchor points for molecule grafting, remains challenging. In this study, 3‐aminopropyltrimethoxysilane (APTMS) has been directly polymerized on glass by a plasma jet. Quantification of NH2 showed that APTMS polymerization and NH2 degradation were correlated with Yasuda's parameter and that a compromise between NH2 retention and coating stability is required. Evaporation of APTMS was found to improve surface smoothness and homogeneity but was found to decrease the deposited NH2 concentration, from 3.7 ± 1.3 NH2/nm2 to three times lower. Results showed that deposited NH2 could be used as anchor points for polyethylene glycol chain immobilization. [ABSTRACT FROM AUTHOR]

Recently, thin-film deposition of quantum dot (QDs) to manufacture solar cells and displays have received significant attention due to the lucrative optoelectronic properties of these devices. Unfortunately, (a) the existing macroscopic thin-film deposition models in the literature do not consider the surface-level interactions; (b) the detailed surface-level models do not consider the entire thin-film deposition ensemble; and (c) multiscale modeling studies considering both the scales are not tailored for QD systems. Thus, to address this knowledge gap, in this work, a multiscale thin-film deposition model is developed. First, the droplet distribution and evaporation dynamics during the thin-film deposition of QDs are described using heat and mass balance equations. Second, a microscopic discrete-element method (DEM)-based particle aggregation model that describes the surface-level particle interactions is developed and combined with the macroscopic dynamics. Furthermore, a model predictive controller (MPC) is designed to regulate the film thickness and minimize the film roughness by manipulating key process variables. To design a feasible MPC, a computationally efficient artificial neural network (ANN) model of the thin-film deposition model is constructed, and it is incorporated within the MPC. The closed-loop simulation results showcase the capability of the MPC to achieve the required film thickness and minimize the roughness. • A multiscale model for thin-film deposition of quantum dots (QDs) is developed. • Surface-level particle interactions during the thin-film deposition are modeled. • A neural network-based surrogate model for the thin-film process is constructed. • A model predictive controller (MPC) is formulated to control the film properties. • The MPC drives the process to reach the required film thickness and roughness. [ABSTRACT FROM AUTHOR]

Thin films of ZnWO4, a promising photocatalytic and scintillator material, were deposited for the first time using a reactive dual magnetron sputtering procedure. A ZnO target was operated using an RF signal, and a W target was operated using a DC signal. The power on the ZnO target was changed so that it would match the sputtering rate of the W target operated at 25 W. The effects of the process parameters were characterized using optical spectroscopy, X-ray diffraction, and scanning electron microscopy, including energy dispersive X-ray spectroscopy as well as X-ray photoelectron spectroscopy. It was found that stoichiometric microcrystalline ZnWO4 thin films could be obtained, by operating the ZnO target during the sputtering procedure at a power of 55 W and by post-annealing the resulting thin films for at least 10 h at 600 °C. As FTO coated glass substrates were used, annealing led as well to the incorporation of Na, resulting in n+ doped ZnWO4 thin films.

Pentacene is a well-known conjugated organic molecule with high mobility and a sensitive photo response. It is widely used in electronic devices, such as in organic thin-film transistors (OTFTs), organic light-emitting diodes (OLEDs), photodetectors, and smart sensors. With the development of flexible and wearable electronics, the deposition of good-quality pentacene films in large-scale organic electronics at the industrial level has drawn more research attention. Several methods are used to deposit pentacene thin films. The thermal evaporation technique is the most frequently used method for depositing thin films, as it has low contamination rates and a well-controlled deposition rate. Solution-processable methods such as spin coating, dip coating, and inkjet printing have also been widely studied because they enable large-scale deposition and low-cost fabrication of devices. This review summarizes the deposition principles and control parameters of each deposition method for pentacene and its derivatives. Each method is discussed in terms of experimentation and theory. Based on film quality and device performance, the review also provides a comparison of each method to provide recommendations for specific device applications. [ABSTRACT FROM AUTHOR]

Polyimide is an emerging and very interesting material for substrate and passivation of neural probes. However, the standard curing temperature of polyimide (350 °C) is critical for the microelectrodes and contact pads of the neural probe, due to the thermal oxidation of the metals during the passivation process of the neural probe. Here, the fabrication process of a flexible neural probe, enhanced with a photosensitive and low-temperature cured polyimide, is presented. Annealing tests were performed with metallic films deposited on polyimide, which led to the reduction of the curing temperature to 250 °C, with no significant irregularities in the metallic sample annealed at that temperature and an effective polyimide curing. The use of a lower curing temperature reduces the thermal oxidation of the metals during the polyimide curing process to passivate the neural probe. Additionally, in this fabrication process, the microelectrodes of the neural probe were coated with electrodeposited platinum (Pt), only after the passivation process, and its electrochemical performance was accessed. At 1 kHz, the impedance of the microelectrodes before Pt electrodeposition was approximately 1.2 MΩ, and after Pt electrodeposition, it was approximately 350 kΩ. Pt electrodeposition changed the equivalent circuit of the microelectrodes and reduced their impedance, which will be crucial for future in-vivo tests to acquire the electrical activity of the neurons with the fabricated neural probe.

A thin-film deposition system was developed for the surface coating of X-ray mirrors of up to 1 m in length. With two coating process areas and four sputtering cathodes, various combinations employing a single layer, multilayered, and co-sputtered thin films are possible. Furthermore, it is possible to correct and modify the mirror surface shape by controlling the speed of the substrate stage. In this study, to evaluate the performance of the proposed coating system, the static coating distribution was measured to check the vertical direction. In a 10 mm area, a 0.9% peak-to-valley error and 0.2% root mean square error occurred. A differential deposition test was also performed for the horizontal direction (stage scan direction). In this study, arbitrary shapes were deposited on 100-mm and 400-mm-long mirrors. After removing the measurement error, the deposition error was less than 1 nm (peak-to-valley). The results demonstrate that this system can correct the surface of an X-ray mirror with ultra-high precision. [Display omitted] • System developed for surface coating of X-ray mirrors of up to 1 m long. • Differential deposition by two coating process areas and four sputtering cathodes. • Mirror surface shape corrected and modified by control of substrate stage speed. • The deposition error was less than 1 nm (peak-to-valley). • This system can correct the surface of an X-ray mirror with ultra-high precision. [ABSTRACT FROM AUTHOR]

Pentacene is a well-known conjugated organic molecule with high mobility and a sensitive photo response. It is widely used in electronic devices, such as in organic thin-film transistors (OTFTs), organic light-emitting diodes (OLEDs), photodetectors, and smart sensors. With the development of flexible and wearable electronics, the deposition of good-quality pentacene films in large-scale organic electronics at the industrial level has drawn more research attention. Several methods are used to deposit pentacene thin films. The thermal evaporation technique is the most frequently used method for depositing thin films, as it has low contamination rates and a well-controlled deposition rate. Solution-processable methods such as spin coating, dip coating, and inkjet printing have also been widely studied because they enable large-scale deposition and low-cost fabrication of devices. This review summarizes the deposition principles and control parameters of each deposition method for pentacene and its derivatives. Each method is discussed in terms of experimentation and theory. Based on film quality and device performance, the review also provides a comparison of each method to provide recommendations for specific device applications.

This study presents the design and analysis of energy‐efficient visible light communication‐based downlink and uplink using a thin‐film corner cube retroreflector (TCCR). The uplink establishment from the user device (UD) to base station (BS) is achieved with the retroreflection of the downlink light beams using TCCR in UD. It eliminates the requirement of active optical source in the UD that reduces the power consumption for communication from the battery‐constrained devices. Additionally, the photoelectric effect‐based energy harvesting from lighting sources is also incorporated in the UD. By utilising the thin‐film deposition of photosensitive alkali metals Na, K, Rb, and Cs, light energy has been harvested, and the harvested energy is utilised in the UD for the uplink modulation process. It makes the real self‐sustainable communication towards the battery‐less execution of internet of things (IoT). The proposed system offers the downlink and uplink for the distance of 2.15 m with the data rates of 10 Gbps and 1 kbps, respectively. The maximum harvested energy from the 18 W optical source by using the 100 nm Cs‐TCCR is 104.40 µJ, and it can serve the energy consumption of the uplink modulator to transmit the UD data to the BS. [ABSTRACT FROM AUTHOR]

Abstract Morphology of metal thin layers deposited on polished surfaces of LiNbO 3 crystal with dissimilar electric charges has been studied using various methods of vacuum evaporation. The principal goal of the work is to optimize methods of thin metal coating deposition applied to polar surfaces of LiNbO 3 crystal. The conducted research has demonstrated that Cr deposition on LiNbO 3 crystal faces is characterized by dissimilar polarity results in growth difference conditions of Cr films. The principal role here is played by the sign of the electric charge on the crystal surface along with the type (thermal or magnetron) and conditions observed during sputtering (deposition rate, substrate temperature etc). [ABSTRACT FROM AUTHOR]

This is the first study that described how the interface interactions of graphene oxide (GO) with poly(3-hexylthiophene): 3′H-cyclopropa [8,25] [5,6] fullerene-C60-D5h(6)-3′-butanoic acid 3′-phenyl methyl ester (PCBM) and with poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) are influencing the stability and performance of poly(3-hexylthiophene): poly(3-hexylthiophene) (P3HT) (P3HT:PCBM)-based organic solar cell. The interface functionalization of these carrier-transporting layers was confirmed by XRD pattern, XPS analysis, and Raman spectroscopy. These interfaces chemical bond formation helped to firmly attach the GO layer with PCBM and PEDOT:PSS layers, forming a strong barrier against water molecule absorption and also provided an easy pathway for fast transfer of free carriers between P3HT:PCBM layer and metal electrodes via the backbone of the conjugated GO sheets. Because of these interface interactions, the device fabricated with PCBM/GO composite as an electron transport layer and GO/PEDOT:PSS composite as hole transport layer demonstrated a remarkable improvement in the value of power conversion efficiency (5.34%) and reproducibility with a high degree of control over the environmental stability (600 h). This study is paving a way for a new technique to further improve the stability and PCE for the commercialization of OSCs. [ABSTRACT FROM AUTHOR]

In this paper, we report on the use of molecular level interaction between a composite poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT: PSS) and graphene oxide (GO) hole transport layer (HTL) to improve the long term stability and performance of poly(3-hexylthiophene): poly(3-hexylthiophene): 3′H-cyclopropa [8,25] [5,6] fullerene-C60-D5h(6)-3′-butanoic acid 3′-phenyl methyl ester (P3HT: PCBM)-based bulk heterojunction organic solar cells (OSCs). The device employing this composite HTL demonstrated a maximum power conversion efficiency (PCE) of 4.82% with good reproducibility and retained over 30% of its initial PCE without encapsulation after 15 days under atmospheric conditions. This was a significant improvement compared with devices fabricated with either single GO or PEDOT: PSS HTLs, which retained only 26% and 0% of their initial PCE values of 3.16% and 4.00%, respectively. Hence, we imagine that this air resistant HTL composite will probably contribute significantly to the widespread commercialization of low cost and easily fabricated OSCs. [ABSTRACT FROM AUTHOR]

A brief review of the mathematical methods of thin-film growth simulation and results of their applications is presented. Both full-atomistic and multi-scale approaches that were used in the studies of thin-film deposition are considered. The results of the structural parameter simulation including density profiles, roughness, porosity, point defect concentration, and others are discussed. The application of the quantum level methods to the simulation of the thin-film electronic and optical properties is considered. Special attention is paid to the simulation of the silicon dioxide thin films. [ABSTRACT FROM AUTHOR]

Deposition of nano-composite Mg–F–Si–O films on optical grade silica glass was studied employing RF magnetron co-sputtering from magnesium fluoride (MgF 2 ) and fused silica (SiO 2 ) targets. The aim was to obtain a stable and reliable sputtering process for optical coatings exhibiting a refractive index lower than the one of quartz glass (1.46 at 550 nm) without adding gaseous fluorine to the deposition process. The two magnetrons were installed in a confocal way at 45° off-axis with respect to a static substrate, thus creating a lateral gradient in the thin-film composition. The deposited Mg–F–Si–O coatings were structurally analysed by electron dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The obtained films consist of MgF 2 nanocrystals embedded in a SiO 2 -rich amorphous matrix. Spectroscopic ellipsometry and spectrophotometry measurements showed that they are highly transparent exhibiting a very-low extinction coefficient k and a refractive index n in the desired range between the one of MgF 2 (1.38) and SiO 2 (1.46). Films with n = 1.424 and 1.435 at 550 nm were accomplished with absorption below the detection threshold. [ABSTRACT FROM AUTHOR]

High-performance, Si-based three-dimensional (3D) microbattery systems for powering micro/nanoelectromechanical systems and lab-on-chip smart electronic devices have attracted increasing research attention. These systems are characterized by compatible fabrication and integratibility resulting from the silicon-based technologies used in their production. The use of support substrates, electrodes or current collectors, electrolytes, and even batteries used in 3D layouts has become increasingly important in fabricating microbatteries with high energy, high power density, and wide-ranging applications. In this review, Si-based 3D microbatteries and related fabrication technologies, especially the production of micro-lithium ion batteries, are reviewed and discussed in detail in order to provide guidance for the design and fabrication. [ABSTRACT FROM AUTHOR]

Stainless steel substrates were textured with a checkboard pattern by a NIR laser with different scan pitches and laser powers. The as-textured surfaces were found to be hydrophilic. However, after holding in air for 7–15 days, the surfaces exhibited strong superhydrophobicity with contact angles close to 150° due to a reduction in the oxygen content. Thin-film Ag, Cu, Zn and Al coatings were deposited on the textured surfaces. The as-sputtered Ag and Cu films improved the hydrophobicity of the as-textured surface. However, the as-sputtered Zn and Al coatings increased the hydrophilicity. For all of the coatings, the hydrophobicity improved after aging in air for 7– 15 days. Furthermore, all of the coatings enhanced the corrosion resistance of the textured surface. Overall, the results indicate that laser texturing followed by thin-film metal deposition provides a feasible means of tuning both the wettability and the corrosion resistance of stainless steel surfaces. • The as-textured stainless steel surfaces were found to be hydrophilicby laser modification process. • After holding in air for 7–15 days, the surfaces exhibited strong superhydrophobicity with contact angles close to 150°. • Two processes (texture and metal coating) improved the hydrophobicity of the as-textured surface. • All of the coatings enhanced the corrosion resistance of the textured surface. [ABSTRACT FROM AUTHOR]

In this paper, we introduce a reaction graph-based analysis method to study the mathematical structure and dynamical behavior of thin-film deposition reaction network models. Using this approach, we identify reaction network invariants and determine the chemical significance of these conserved modes for thin-film deposition reaction mechanisms. Furthermore, the species-reaction graphs can be used to distinguish “proper” from problematic reaction networks during the initial stages of reaction kinetic modeling studies. Results are presented in the context of a titania deposition process where the transition from atomic layer deposition to chemical vapor deposition growth modes is observed. [ABSTRACT FROM AUTHOR]

A new process for deposition of a thin-layer coating of Poly(tetrafluoroethylene) (PTFE) on a glass substrate exhibiting superhydrophobicity using supercritical carbon dioxide (sc-CO 2 ) was reported. The process involved placing a PTFE source material and the glass substrate to be coated inside an autoclave in supercritical carbon dioxide (sc-CO 2 ), maintained at 300 °C temperature and 24 MPa, for a time period. The variations in the surface morphology and wetting characteristics of both the coated glass substrate and the PTFE source specimen with increasing time period of the process have been investigated. The morphology of the surfaces was investigated by scanning electron microscopy while the wetting characteristics by contact angle measurement. The surface of the glass substrates was found to be increasingly deposited with minute globulets of PTFE with increasing time of the process. The static water contact angle measured on the coated substrates increased with increasing coating time and the coated substrates showed superhydrophobicity when the coating time exceeds a certain time period. The PTFE source specimen surface became increasingly rough with micron-sized surface swellings and protrusions appearing on the surface with increasing time of the process and showed superhydrophobicity when exposed in the supercritical environment for certain time period. The method may find use in fabricating a thin-layer coating of PTFE for potential microelectronics, microfluidics and sensor applications. [ABSTRACT FROM AUTHOR]

Most thin-film techniques require a multiple vacuum process, and cannot produce high-coverage continuous thin films with the thickness of a few nanometers on rough surfaces. We present a new "paradigm shift" non-vacuum process to deposit high-quality, ultra-thin, single-crystal layers of coalesced sulfide nanoparticles (NPs) with controllable thickness down to a few nanometers, based on thermal decomposition. This provides high-coverage, homogeneous thickness, and large-area deposition over a rough surface, with little material loss or liquid chemical waste, and deposition rates of 10 nm/min. This technique can potentially replace conventional thin-film deposition methods, such as atomic layer deposition (ALD) and chemical bath deposition (CBD) as used by the Cu(In,Ga)Se2 (CIGS) thin-film solar cell industry for decades. We demonstrate 32% improvement of CIGS thin-film solar cell efficiency in comparison to reference devices prepared by conventional CBD deposition method by depositing the ZnS NPs buffer layer using the new process. The new ZnS NPs layer allows reduction of an intrinsic ZnO layer, which can lead to severe shunt leakage in case of a CBD buffer layer. This leads to a 65% relative efficiency increase. [ABSTRACT FROM AUTHOR]

In this work, crystallographic orientation of polycrystalline silicon films on glass formed by continuous wave diode laser crystallization was studied. Most of the grain boundaries were coincidence lattice Σ3 twin boundaries and other types of boundaries such as, Σ6, Σ9, and Σ21 were also frequently observed. The highest photoluminescence signal and mobility were observed for a grain with (100) orientation in the normal direction. X-ray diffraction results showed the highest occupancies between 41 and 70% along the (110) orientation. However, the highest occupancies changed to (100) orientation when a 100 nm thick SiO x capping layer was applied. Suns-Voc measurement and photoluminescence showed that higher solar cell performance is obtained from the cell crystallized with the capping layer, which is suspected from increased occupancies of (100) orientation. [ABSTRACT FROM AUTHOR]

A multiline guided-mode resonance (GMR) filter is applied as a reflector to implement an external cavity laser. We design the resonant element using rigorous numerical methods and fashion an experimental prototype by thin-film deposition, patterning, and etching. A ~100-nm TiO2 grating layer on a ~170-μm-thick glass slab supports thousands of resonant modes. We detect ~10 narrow resonance peaks within a ~10-nm wavelength range centered at the 840-nm wavelength. We apply this multiline GMR device to a gain chip and obtain several simultaneous resonant laser lines that compete for the gain. Precise tuning enables a stable laser line that can be selected from the multiple available resonant lines. [ABSTRACT FROM PUBLISHER]

Carbon and tungsten films were deposited simultaneously from two separate plasmas produced by the thermionic vacuum arc method. Total film thickness, surface roughness, atomic composition, and chemical bonds of atoms at the surface and inside the deposited films were analyzed for different substrate positions of the samples. X-ray photoelectron spectroscopy analyses suggest that tungsten carbide forms predominantly at preferential substrate positions. Variations in the carbon plasma deposition rate were also used to dynamically control the film composition. Larger target–substrate distances result in smoother films but slower composition variations. [ABSTRACT FROM PUBLISHER]

Biometric techniques, such as fingerprint detection, have been widely applied to identify a specific user for security and safety reasons. This work presents an integrated capacitive sensor array for fingerprint detection based on the difference of pressures induced by the ridges and valleys of a finger tip. The 8 × 32 sensing membranes are released by wet etch of the complementary metal oxide semiconductor (CMOS) metal layers and no additional thin-film deposition is required to form the capacitive electrodes. Each membrane contains the CMOS dielectric and metal layers with a total thickness of 3.375 μm. The size of each sensing pixel is 65 × 65 μm3, equivalent to an imaging resolution of 390 dpi. The sensing capacitance and capacitive sensitivity are 12 fF and 1.41 fF/MPa, respectively. The measured spring constant of the membrane is close to the simulated value of 1400 N/m. Part of the fingerprint image is successfully produced by the CMOS sensor array. [ABSTRACT FROM PUBLISHER]

Characteristics of supersonic flow are examined with specific regard to nano-particle thin-film coating. Effects of shockwaves, nozzle geometry, chamber pressure, and substrate location were studied computationally. Shockwaves are minimized to reduce fluctuations in flow properties at the discontinuities across diamond shock structures. Nozzle geometry was adjusted to ensure optimal expansion (i.e., P = P), where shock formation was significantly reduced and flow kinetic energy maximized. When the ambient pressure was reduced from 1 to 0.01316 bar, the nozzle's diverging angle must be increased to yield the optimum condition of minimized adversed effects. Beyond some critical distance, substrate location did not seem to be a sensitive parameter on flow characteristics when P = 0.01316 bar; however, overly close proximity to the nozzle exit caused flow disturbances inside the nozzle, thereby adversely affecting coating gas flow. [ABSTRACT FROM AUTHOR]

We present a novel approach in fast imaging of high-power impulse magnetron sputtering (HiPIMS) discharges in which bandpass optical interference filters are used to isolate the optical emission signal originating from different species populating the plasma. In this paper, we describe the methodology of the proposed diagnostics and discuss its application. In particular, we demonstrate the use of this technique for the time-resolved analysis of HiPIMS discharges operated with a chromium cathode in argon at 4 Pa. Two optical filters were designed and fabricated: (i) one for neutral chromium emission lines (400–540 nm); and (ii) the other one for neutral working gas emission lines and bands (above 750 nm). The introduction of such filters is used to distinguish different phases of the discharge and to reveal numerous plasma effects including background gas excitations during the discharge ignition, gas shock waves, and expansion of metal-rich plasmas. [ABSTRACT FROM PUBLISHER]

Atmospheric-pressure methane-hydrogen micro glow discharges were computationally investigated using a 2-D hybrid model. The plasma model was solved simultaneously witha model for the external circuit. Simulations were conducted for a pin-to-plate electrode configuration with an interelectrode separation of 400 μm. The spatiotemporal evolutions of electrons, species densities, electric field, and electron and gas temperatures were studied. A total of 81 reactions were considered, which included electron-neutral, electron-ion, ion-neutral, and neutralneutral reactions. An 84-step reaction mechanism consisting of 15 surface species and four deposited bulk species was considered. A time-stepping technique was employed to address the time scales of plasma transport (in microseconds) and neutral and fluid transport (in milliseconds) in 2-D simulations with detailed volume and surface chemistry. The simulations indicated H3 + andCH5 + ions to be the most prominent hydrogen and hydrocarbon ions. The gas temperature predictions suggested the discharge to be operating as a nonthermal glow discharge. The effect of discharge current on both plasma and deposition characteristics was studied. The simulations predicted a flat voltage-current characteristic, indicating the discharge to be operating in normal glow mode. The predicted voltage-current characteristic was found to be in favorable agreement with the experimental measurements. With an increase in discharge current, the deposition rate profile expanded in the lateral direction, suggesting that deposition occurred at the cathode spot. [ABSTRACT FROM AUTHOR]

Abstract: Electrospraying (electrohydrodynamic spraying) is a method of liquid atomization by means of electrical forces. In electrospraying, the liquid at the outlet of a nozzle is subjected to an electrical shear stress by maintaining the nozzle at high electric potential. The advantage of electrospraying is that droplets can be extremely small, in special cases down to nanometers, and the charge and size of the droplets can be controlled to some extent by electrical means, i.e., by adjusting the flow rate and voltage applied to the nozzle. Due to its properties, electrospraying is considered as an effective route to nanotechnology. The paper considers the latest achievements in micro- and nano-thin-film production, including self-assembled nanostructures, in solid nano-particle generation, and in the formation of micro- and nanocapsules. [Copyright &y& Elsevier]

This paper reports deposition of silicon at elevated and room temperatures in spatially localized areas of a microchip by plasma-enhanced chemical vapor deposition using microplasmas. The microplasmas are generated by providing dc power to thin-film Ti electrodes patterned on the microchip. Electrode arrangements include configurations in which multiple cathode elements share a single anode. At the operating pressures used, the plasma glow is confined to the region directly over the energized cathodes only, and the deposition is localized to these regions. A silane ambient allows Si to be deposited at 6.7–15.9 nm/min using cathode power densities of 3.65–9.35 W/cm², with the substrate heated to 300 °C. At room temperature, deposition rates up to 4.2 nm/min are realized. Also described is a plasma-coupling technique that permits isolated metal pads to be powered by plasma spreading from a proximate cathode at certain levels of power and pressure. This permits controlled variations of silicon thickness in a subarray of unbiased electrodes, simplifying the powering scheme. [ABSTRACT FROM AUTHOR]

This paper describes the design, fabrication, and testing of electrostatically actuated microshutters used as active shadow masks to pattern evaporated materials. The fabricated microshutters can obstruct a 25-µm-wide aperture at an actuation voltage of 90 V, with a resonant frequency of 4 kHz due to a 400-µm-long actuator. The microshutters integrated with an x-y-z manipulator were used to print patterns of organic material and metal on glass substrates in vacuum with a pixel size of 25 µm. The maximum resolution achievable with this setup is 800 dpi, and we printed active organic light-emitting device arrays of 400 dpi resolution. This printing scheme could enable the patterning of large-area organic optoelectronic devices on diverse substrates. [ABSTRACT FROM AUTHOR]

Abstract: The application of gas cluster ion beam (GCIB) infusion in advanced IC fabrication is described. GCIB processes for surface modifications, additive (junction formation, deposition) and subtractive (etch) processing are discussed. [Copyright &y& Elsevier]

Atomic force microscope analysis, with a resolution of ≲1.1 nm, shows that peak-to-peak surface roughness (Δhp-p) of amorphous silicon films thinner than ≍50 nm on silicon dioxide can be controlled to better than 5 nm. Low-pressure, chemically-vapor-deposited silicon films on silicon dioxide initially show an approximately linear increase in the surface roughness due to growing nuclei as the deposition progresses, followed by a decrease in the surface roughness as growth nuclei coalesce. A simple model based on random nucleation and nuclei growth displays similar trends. Films deposited on rougher substrates show more surface roughness. Surface treatment during the predeposition cleaning process does not significantly affect Δhp-p. As a means of producing smooth surfaces, films thinner than about 20 nm are first deposited more thickly than needed, and then etched back to the desired dimension; the use of a binary HNO3 and HF etching process improves roughness control. Boron-ion implanted and subsequently crystallized 45-nm-thick Si films show significant smoothing with Δhp-p≍2.2 nm. Thin amorphous silicon films deposited by source evaporation are attractive because they can be deposited at room temperature, and have smoother surfaces (Δhp-p≍2.5 nm) than comparable films produced by chemical vapor deposition. [ABSTRACT FROM PUBLISHER]

Using a combination of radio frequency (RF)-compensated and -uncompensated probes, the temporal evolution of the electron density Ne, electron temperature Te and ion impact energy Ei (at an electrically isolated surface) have been determined in the pulsed-plasma polymerisation of acrylic acid. The discharge (excited by 13.56 MHz RF, coupled through an external coil) was operated at a fixed pulse frequency of 500 Hz and pressure of 2.6 Pa, but a variation of powers (5, 20 and 40 W) and duty cycles, (35%, 50% and 75%). The probes were heated prior to measurement to eliminate the formation of insulating deposits on the surface. Experiments have also been performed in pure argon at the same conditions, to act as a comparison. In the acrylic acid afterglow plasma, the electron densities were observed to fall from a maximum of 6×1016 m-3 (in the ‘on’ time) to below 2×1015 m-3 with characteristic decay times of τn∼50 μs, much faster than in argon where τn∼200 μs was found. The density in the ‘on’ time of the pulse was strongly dependent on the discharge power Prf, with a 250% increase in Ne as Prf was increased from 5 to 40 W. As the duty cycle was reduced, the plasma density decreased in the ‘on’ time, giving over a full cycle, lower plasma densities for longer ‘off’ times. Typically, at the start of the ‘on’ time, the electron temperature peaked at values up to 8 eV; however, this decreased is the remainder of the ‘on’ time to about 4 eV. This value was only weakly dependent on the discharge power and duty cycle. During the ‘off’ time, Te fell much more quickly than the density, with characteristic decay times of several 10''s of μs or less. The ion bombarding energy to the floating probe, given by the time-averaged potential drop across the sheath, fell sharply from values up to 65 eV in the ‘on’ time to less than 2 eV in the ‘off’ time, the precise values varying slowly with power and duty. This fall happened with a characteristic time of ∼10 μs (for both acrylic acid and argon), controlled by the drop in Te. The results show that at the higher powers, a significant fraction of the sheath potential drop (up to 25 V) and therefore the ion energy was due to the presence of large RF potential fluctuations in the discharge. These preliminary results show the interesting and highly complex nature of the pulsed-polymerising plasma, particularly the highly modulated ion energies at a boundary or substrate. [Copyright &y& Elsevier]

Abstract: In this paper critical steps in the fabrication process of a microreactor for high-temperature catalytic partial oxidation gas phase reactions are evaluated. The microreactor contains a flow channel etched in silicon, capped with an ultrathin composite membrane consisting of silicon and silicon nitride layers, on which on the topside thin-film heaters and sensors, and on the other side a thin-film catalyst patch are placed. The membrane is designed to have specific heat conductivity and mechanical properties. The paper focuses on three fabrication issues: definition and etching of sub-micron uniform single-crystalline silicon membranes, deposition of well-defined heater structures and temperature sensors on a thin composite membrane, and deposition of well-defined catalytic patches on the same membrane. For the latter two processes novel micromachined shadow masks were developed. Preliminary experiments on the controlled oxidation of hydrogen gas in the explosive regime are discussed, which experiments confirm that heat management in the microreactor is excellent. [Copyright &y& Elsevier]

The performances of metal oxide semiconducting materials used as gas-sensing detectors depend strongly on their structural and morphological properties. The average grain size has been proved to play a prominent role and better sensor performances were found in polycrystalline films where the grain size is few tens of nm or smaller. On the other hand, thermal treatments during thin-film deposition and/or sample postprocessing could lead to a grain coalescence, thus decreasing the conductivity of the sensing film. Avoiding such a phenomenon, still keeping optimized processing conditions, will increase the sensor performances, maintaining the resistivity at acceptable values. In this work, new gas-sensing materials and new thin-film deposition procedures have been investigated. Aiming to preserve the sensitivity, to enhance selectivity and to reduce the drift, thin films of WO3 and CrTiO3 deposited by pulsed-laser ablation (PLA) and of SnO2 deposited by rheotaxial growth and thermal oxidation techniques were comparatively characterized. Three issues were mainly addressed: the variation of the conductivity as a function of RH, the sensitivity toward benzene, CO, acetone, and NO2, and the selectivity. [ABSTRACT FROM PUBLISHER]

Thin-film-deposition techniques used to develop latent fingerprints are continuously maturing. Vacuum metal deposition (VMD) is a commonly used technique in which thin films of gold and zinc are sequentially deposited on a latent fingerprint in a low-pressure chamber. An emerging technique entails the conformal deposition of a columnar thin film (CTF) on a latent fingerprint in a low-pressure chamber. Although specialized apparatus exist for both techniques, we have determined that the VMD technique can be easily implemented in the CTF apparatus. Use of the same apparatus for both of those fingerprint-development techniques can reduce capital costs, process-development time, and provide impetus for field-ready apparatuses. [ABSTRACT FROM AUTHOR]