Film Stress Research Articles

High-Temperature Self-Compensating Absolute Micro-Pressure Sensor and Its Testing Method

In this study, we designed an absolute pressure micro-pressure sensor, with its testing method based on the requirements of high-temperature resistance, self-compensation, and micro-pressure test. The substrate of the sensor is made of raw porcelain through high-temperature sintering, and the functional layer is integrated into the surface of the substrate by silver paste through a screen-printing process. Therefore, the sensor has high temperature resistance. The ceramic base of the sensor is prepared based on the principle of film stress and strain measurement of micro pressure by filling carbon film in raw porcelain layer and using a high-temperature sintering process to obtain an air-tight cavity structure. In the preparation of the functional layer, a unique differential capacitance structure is constructed on the surface of the substrate using the screen-printing process. This hardware temperature self-compensation structure enables the high-precision measurement of the sensor. Finally, the high temperature and absolute pressure micro-pressure sensor are combined with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${C}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}$ </tex-math></inline-formula> conversion circuit to complete the test on the high-temperature-micro pressure composite test platform. The experimental results show the sensor can measure the absolute pressure from 3 to 100 kpa in the temperature range of 23 °C to 300 °C, and the repeatability error of the pressure test is less than 3.3% at 300 °C.

A Study of the Relationship between the Rate of Return Strain of Polytetrafluoroethylene on Time, Mechanical Stress and Dose of Electron Irradiation

The paper is devoted to the study of the influence of factors on the rate of return deformation of polytetrafluoroethylene. The dependence of the rate of return strain (ε'r) on time (t), the dose of electron irradiation (D) and mechanical stress (σ) in thin films of polytetrafluoroethylene has been experimentally investigated. Significant variations of ε'r have been found dependingon on t, D and σ. A decrease in the rate of return deformation during irradiation of the material is associated with the frictional properties between macromolecules and a change in the structure, which leads to a weaker straightening of the polymer and their poor sliding. The resulting curves for both unirradiated and irradiated material are satisfactorily described in the exponential and linear models. For dependencies ε'r on D, these are decreasing functions, and for ε'r on σ, these are increasing functions.

The anisotropic oxidation behavior of Hastelloy X alloy fabricated by laser powder-bed fusion (LPBF) during the cyclic oxidation process

The Hastelloy X alloy manufactured via LPBF has anisotropic oxidation behavior at 900 °C. The vertical cross section (V) specimen has worse oxidation resistance and more severe spalling behavior than the horizontal cross section (H) specimen as its low grain boundary density. During the oxidation process, larger voids was generated at Cr2O3-spinel interface of the V specimen to weaken the adhesive strength of oxidation film, and α-NiMoO4 with high cracking susceptibility only occurred in spinel layer of the V specimen, which broke down under high compressive stress in oxidation film to promote the spalling of oxides.

Active nematic fluid films

Coupling surface deformations with active stresses in two-dimensional nematic liquid crystal films leads to a rich area of investigation, particularly in biological fluid mechanics across multiple scales from tissue mechanics to cell membrane mechanics. In Al-Izzi &amp; Morris (J. Fluid Mech., vol. 957, 2023, A4), the authors derive the complete set of governing equations for such systems. Their results provide an extended theoretical framework with which active nematic fluid films with in-plane flow and out-of-plane deformation can be analysed. To illustrate the potential applications of this framework, a few specific biologically inspired examples are discussed.

Microstructure evolution and mechanical performance of tetrahedral amorphous carbon coatings with dense droplets during annealing

Tetrahedral amorphous carbon (ta-C) coatings with approximately 50% sp3C were deposited onto cemented carbide alloy YG6 and Si wafers via direct vacuum cathode arc (DVCA) evaporation at different substrates temperatures. Coated specimens were annealed in a 5 Pa argon atmosphere. The micromorphology and chemical bonding structure of these coatings with different treatments were characterized using field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). The mechanical performance was tested using a nanoindenter and film stress instrument. The obtained ta-C coatings contained dense droplets of various sizes (“abnormal particles” (An-Ps)). The densities of the An-Ps were controlled by the graphite cathode target arc rather than the substrate temperature, and their ID/IG ratios were close to their counterpart coating matrix. Increasing the substrate temperature was beneficial for increasing the sp2C fraction and the number of aromatic ring sp2C sites. Growth, coalescence, and leveling-diffusion of aggregates in the coating matrix and An-Ps occurred during annealing, which was related to the existing state of the sp2C sites, including the olefinic chain and aromatic ring. The residual stress variation with annealing temperature also depended on the sp2C state. The residual stress in the coating increased during annealing when the number of aromatic ring sp2C sites exceeded a certain critical value.

Application of Cad Systems to Accounting for Mechanical Stresses in the Development of Uncooled Thermal Detectors of the Bolometric Type

A comparative analysis of the characteristics of the main types of bolometers is indicated in the article. The constructive solution of an uncooled thermal detector of the bolometric type, formed using the technology of microelectromechanical systems, is studied. By means of computer simulation in modern computer-aided design systems in microelectronics, a static mechanical analysis was performed to assess the effect of mechanical stresses arising in structural materials during their formation on the magnitude of deformation. It has been established that to ensure the normal functioning of the microbolometer (to reduce the maximum deviation value of the film from the nominal value), it is necessary to reduce the internal mechanical stresses in the NiCr film. For the Si3N4 films, on the contrary, this value should be increased.

Effect of film stress on different electrical properties of PECVD grown SiNx films and its bilayer structures: A study of Si surface passivation strategy

The prevalence of stress during thin film deposition has a substantial influence on the surface passivation of CMOS image sensors (CIS). Our present research thoroughly addresses the effect of film stress on minority carrier lifetime and interface trap density (Dit) of as-deposited and forming gas annealed (FGA, 5% H2, 400 °C for 30 min) SiNx films and their bilayer structures. In this study, plasma-enhanced chemical vapor deposition (PECVD) and atomic layer deposition (ALD) techniques were utilized to synthesize SiNx and SiNx/(top) Al2O3 bilayer structures. After FGA, the minority carrier lifetime and Dit values for 50 nm-SiNx (1607 μs, 7 × 1011 cm−2eV−1), 30 nm-Al2O3 (2670 μs, 7 × 1011 cm−2eV−1), 7 nm-SiNx/30 nm-Al2O3 (1750 μs, 6 × 1011 cm−2eV−1) and 50 nm-SiNx/30 nm-Al2O3 (2300 μs, 34 × 1011 cm−2eV−1) were found. Our statistical analysis indicates that the stress in the SiNx/Al2O3 bilayer structures introduces defects in the films. This affects the carrier lifetime along with Dit values and hence degrades CIS performance. Further, we also performed a stress simulation of SiNx films which corroborated with the overall analysis. We hope that this work facilitates a better understanding of the stress effect on the surface passivation of CIS applications.

Mode mixing performance evaluation and influence of elements on the fiber system behaviour

Abstract This study has clarified various micro electro mechanical system (MEMS) processes performance evaluation based on MEMSolver simulation software. The spin time against final resist thickness for the spin coating of a thin film of photo resist and the oxidation time versus oxide thickness for silicone dioxide growth for &lt;100&gt; silicon in wet oxide are clarified. The diffusion profile for Boron after predeposition and drive in of dopants in silicon and the thickness of silicon dioxide mask for Boron diffusion are demonstrated. The dopant distribution resulting from ion implantation and drive in and the percentage of dose penetrating photo resist mask versus thickness of the mask are reported. The film stress versus the film thickness from wafer bow measurements, aluminum deposition rate against temperature using the electronic beam evaporator and the deposition rate of polysilicon versus silane partial pressure are reported. The etch rate of the thermal oxide against percentage concentration of KOH, the etch rate against the etchant temperature for silicon nitride in hot phosphoric acid, and the etch rate against the etchant temperature for the thermal oxide using buffered hydrofluoric acid (BOE) are outlined.

High-rate deposition of ultra-thick silver film by hollow cathode magnetron sputtering

The deposition of high-performance micro-sized ultra-thick silver films is a critical issue. Hollow cathode magnetron sputtering is one of the promising techniques for depositing ultra-thick silver films. A novel cylindrical “three-dimensional magnetron sputtering” (3-DMS) magnet pack presented here was developed based on a conventional hollow cathode magnet pack to deposit high-performance ultra-thick silver film at a high rate. A stable process condition at the average power of 4 kW is realized by the new cylindrical “3-DMS” magnet pack's 137.5 mm diameter targets and a specially designed cooling well. Comparison of deposition rates with different power supplies and at different average power levels are discussed. The behavior of electrons on the target surface in this magnetic field arrangement is investigated using COMSOL Multiphysics software. The composition, topography, mechanical properties and residual stress of the ultra-thick silver film deposited by different sputtering modes (DCMS, HIPIMS, and Pulsed DCMS) are also discussed.

Perovskite Grain-Boundary Manipulation Using Room-Temperature Dynamic Self-Healing "Ligaments" for Developing Highly Stable Flexible Perovskite Solar Cells with 23.8% Efficiency.

Flexible perovskite solar cells (pero-SCs) are the best candidates to complement traditional silicon SCs in portable power applications. However, their mechanical, operational, and ambient stabilities are still unable to meet the practical demands because of the natural brittleness, residual tensile strain, and high defect density along the perovskite grain boundaries. To overcome these issues, a cross-linkable monomer TA-NI with dynamic covalent disulfide bonds, H-bonds, and ammonium is carefully developed. The cross-linking acts as "ligaments" attached on the perovskite grain boundaries. These "ligaments" consisting of elastomers and 1D perovskites can not only passivate the grain boundaries and enhance moisture resistance but also release the residual tensile strain and mechanical stress in 3D perovskite films. More importantly, the elastomer can repair bending-induced mechanical cracks in the perovskite film because of dynamic self-healing characteristics. The resultant flexible pero-SCs exhibit promising improvements in efficiency, and record values (23.84% and 21.66%) are obtained for 0.062and 1.004cm2 devices; the flexible devices also show overall improved stabilities with T90 >20000bending cycles, operational stability with T90 >1248h, and ambient stability (relative humidity=30%) with T90 >3000h. This strategy paves a new way for the industrial-scale development of high-performance flexible pero-SCs.

Substitutional effect of Mg2+ on structural and magnetic properties of La2MgxNi1‐xMnO6 double‐perovskite thin films

AbstractBy doping different concentrations of Mg2+ at Ni site, the (00l)‐oriented La2MgxNi1‐xMnO6 (abbreviated as LMxNMO, x = 0, 0.1, 0.2, 0.3, 0.4) double‐perovskite thin films were epitaxially grown by pulsed laser deposition. The substitutional effect of Mg2+ on the structural and magnetic properties of the films is comprehensively investigated. It is found that with the increase of Mg‐doping concentration, the in‐plane and out‐of‐plane lattice constants as well as the cell volume of the LMxNMO thin films increase, which could be ascribed to the radius difference between Mg2+ and Ni2+/Ni3+ ions, resulting in the in‐plane compressive stress in LMxNMO films. When the Mg‐doping concentration is small (x ≤ 0.1), the doped Mg2+ tends to substitute Ni3+, which restrains the intensity of antiferromagnetic interaction between Ni3+‐O‐Mn3+, resulting in the reduced the exchange bias field as well as the increased the saturation magnetization. However, when the Mg‐doping concentration increases to x ≥ 0.2, Mg2+ becomes to mainly replace Ni2+ position, which could inhibit the super‐exchange ferromagnetic interaction between Ni2+‐O‐Mn4+ magnetic paths and thus reduce the saturation magnetization. The enhanced magnetic properties can be obtained in the LM0.1NMO double‐perovskite thin film, with a large saturation magnetization of 492.12 emu/cm3 and a high Curie temperature of 262.7 K.

Pressure and folding effects on the buckling of a freestanding compressed thin film.

The combined effects of compressive stress, applied pressure, and edge folding of a freestanding thin film have been theoretically investigated on the buckle morphologies of the structure. In the framework of the Föppl-von Kármán theory of thin plates, the different buckle profiles have been analytically determined, and two buckling regimes have been identified for the film: one regime where the transition from upward to downward buckling is continuous, and one that is discontinuous (snap-through). The critical pressures characterizing the different regimes have then been determined, and an hysteresis cycle has been identified through the study of buckling versus pressure. The case in which the thin film is deposited on a substrate has also been discussed.

Lattice-matched heteroepitaxial preparation of InSb/CdTe on Si (111) substrate by magnetron sputtering

InSb films were deposited on Si (111) substrate using the CdTe buffer layers by magnetron sputtering. The effects of CdTe buffer layers on the crystal structure, morphological optical and electrical properties of InSb films were studied. The study found that the CdTe buffer layer can improve the grain size and reduce the stress of InSb films. Compared with direct growth on Si substrate, the use of the CdTe buffer layer can effectively control the appearance of dislocations at the interface and thus improve the epitaxial quality of InSb films. Furthermore, the surface roughness and carrier mobility of the InSb film depends on the CdTe buffer layer thickness, which is mainly caused by the difference in surface morphology of the buffer layer with different thicknesses. InSb/CdTe structure shows the advantages of lattice-matched heteroepitaxial growth, indicating that CdTe is an effective buffer layer to improve the performance of InSb. The insertion of a buffer layer provides a promising method for the preparation of III-V/II-VI hybrid system on a Si substrate, which can be used for high-performance infrared detectors.

Surface Engineering of Regenerated Cellulose Nanocomposite Films with High Strength, Ultraviolet Resistance, and a Hydrophobic Surface

Regenerated cellulose packaging materials can alleviate the environmental pollution and carbon emissions caused by conventional plastics and other chemicals. They require regenerated cellulose films with good barrier properties, such as strong water resistance. Herein, using an environmentally friendly solvent at room temperature, a straightforward procedure for synthesizing these regenerated cellulose (RC) films, with excellent barrier properties and doping with nano-SiO2, is presented. After the surface silanization modification, the obtained nanocomposite films exhibited a hydrophobic surface (HRC), in which the nano-SiO2 provided a high mechanical strength, whereas octadecyltrichlorosilane (OTS) provided hydrophobic long-chain alkanes. The contents of the nano-SiO2 and the concentrations of the OTS/n-hexane in regenerated cellulose composite films are crucial, as they define its morphological structure, tensile strength, UV-shielding ability, and the other performance of these composite films. When the nano-SiO2 content was 6%, the tensile stress of the composite film (RC6) increased by 41.2%, the maximum tensile stress was 77.22 MPa, and the strain-at-break was 14%. Meanwhile, the HRC films had more superior multifunctional integrations of tensile strength (73.91 MPa), hydrophobicity (HRC WCA = 143.8°), UV resistance (>95%), and oxygen barrier properties (5.41 × 10-11 mL·cm/m2·s·Pa) than the previously reported regenerated cellulose films in packaging materials. Moreover, the modified regenerated cellulose films could biodegrade entirely in soil. These results provide an experimental basis for preparing regenerated-cellulose-based nanocomposite films that exhibit a high performance in packaging applications.

NiAl (0 0 1) terminated surface effect on the growth of the Al thin film

In this work, NiAl alloy material was adopted as a substrate surface to investigate the formation process of Al thin film using molecular dynamics simulation. The NiAl (001) substrate with both Al-terminated and Ni-terminated surface was considered to identify their effect on the growth behavior of Al thin film. The results show that Al atoms follow initially bilayer-like growth mode for both terminated surfaces. At this stage, the film seemed to adopt the fourfold geometry with (001)-orientation. However, upon further deposition, the Al adatoms behavior on the Al-terminated surface becomes different from that on the Ni-terminated surface. The stress analysis along the growth direction indicates that the Al film on the Al-terminated surface has a compressive stress in the bulk film, while on the Ni-terminated surface, the Al film has a tensile stress. These results have a significant effect on the lattice parameter when the Al film exceeds four layers. By using the radial distribution function, we demonstrate that when Al film is deposited on Al-terminated surface, its lattice parameter is changed until 2.85Å, which close to the Al-Al bulk, but on the Ni-terminated surface this value becomes 2.49Å, which is near to the Ni-Ni bulk. These behaviors indicate that Al atoms on (Al or Ni)-terminated are arranged differently. For this, the Al film structure was characterized by common neighbor analysis. It is found that the Al atoms are arranged within the fcc structure for Al-terminated, but for Ni-terminated, the result shows the appearance of the fcc and hcp structures. On the other hand, the surface roughness investigated at 0.1 eV showed that the Al film has a rough surface morphology when deposited on Al-terminated compared to that obtained on Ni-terminated. However, by increasing the incident energy from 0.1 to 2 eV, the surface roughness decreases significantly for both terminated surfaces.

Hot cracking susceptibility prediction from quantitative multi-phase field simulations with grain boundary effects

Hot cracks are notorious defects in casting, welding, and additive manufacturing. Grain boundaries play a key role in hot cracking formation. Still, their effects are often neglected in hot cracking susceptibility predictions, and thus a quantitative picture of hot cracking susceptibility and liquid fracture is still lacking. In this work, we construct a multi-order parameter phase-field model for binary alloy solidification to simulate attractive, neutral, and repulsive grain boundaries in the thin-interface limit. Phase-field simulations of different combinations of grain boundary and bi-crystal growth types are used to obtain solidification path data, which is then used as the input into the Rappaz, Drezet and Gremaud (RDG) model (Rappaz et al., 1999). We study the so-called Λ-shape variation of hot cracking susceptibility as a function of solute concentration, showing that the magnitude of the Λ curve peak shifts to higher values and to lower concentrations as grain boundary energy increases. Meanwhile, the peak magnitude becomes higher and shifts to a higher value and higher concentrations when convergent grain growth is applied. Furthermore, in all cases examined, the corresponding pressure drops predicted for hot cracking exceed the theoretical liquid rupture stress, consistent with experimental observations. These results demonstrate that quantitative phase-field simulations, when coupled with the RDG model, are capable of relatively accurately predicting liquid rapture states relevant to hot cracking since the large disparity between the predicted pressure drop and critical stress of liquid film is eliminated through the consideration of grain boundary effects in the solidification path calculation.

Evolution of microstructure and properties of TiNbCrAlHfN films grown by unipolar and bipolar high-power impulse magnetron co-sputtering: The role of growth temperature and ion bombardment

Growth temperature (Ts) and ion irradiation energy (Ei) are important factors that influence film growth as well as their properties. In this study, we investigate the evolution of crystal structure and residual stress of TiNbCrAlHfN films under various Ts and Ei conditions, where the latter is mainly controlled by tuning the flux of sputtered Hf ions using bipolar high-power impulse magnetron (BP-HiPIMS). The results show that TiNbCrAlHfN films exhibit the typical FCC NaCl-type structure. By increasing Ts from room temperature to 600 °C, the film texture changes from high-surface-energy (111) to low-surface-energy (100) accompanied by a higher crystallinity in the out-of-plane direction and a more disordered growth tilt angle to the surface plane. In addition, compressive stress decreases with increasing Ts, which is ascribed to changes in the film growth both in the early and post-coalescence stages and more tensile thermal stress at elevated Ts. In contrast, a clear texture transition window is seen under various Ei of Hf+ ions, i.e., high-surface-energy planes change to low-surface-energy planes as Ei exceeds ∼110 eV, while low-surface-energy planes gradually transform back to high-surface-energy planes when Ei increases from 210 to 260 eV, indicating renucleation events for Ei > 210 eV. Compressive stress increases with increasing Ei but is still lower than that of a reference series with DC substrate bias UDC = −100 V. The study shows that it is possible to tailor properties of FCC-structured high-entropy nitrides by varying Ts and Ei in a similar fashion to conventional transition metal nitrides using the approach of unipolar and bipolar HiPIMS co-sputtering.

Spatially resolved Raman piezospectroscopy for nondestructive evaluation of residual stress in β-Ga2O3 films

In this paper, the piezospectroscopic effect for β-Ga2O3, i.e. the spectral band shift in response to strain/stress, has been calibrated by the indentation method using spatially resolved Raman spectroscopy for quantitative stress evaluation of Ga2O3 devices, taking advantage of the crack-tip tensile stress field and the spatial probe deconvolution. A series of Vickers indentation prints were introduced on (010) and () Ga2O3 single crystals, and the relationships between observed band shifts and residual stresses were clarified to determine the phonon deformation potentials of the Raman bands. Accordingly, a quantitative analysis of the residual stress field in a Ga2O3 thin film grown on (0001) sapphire by plasma-assisted pulsed laser deposition, which revealed the presence of a gradient of incompletely released stress in the depth direction of the film, is shown as an example.

Insight into the decay mechanism of non-ultra-thin silicon film anode for lithium-ion batteries

Silicon thin-film is one of the most promising silicon anode materials for lithium-ion batteries, with the advantages of high cycle stability and initial coulombic efficiency. The excellent performance of silicon thin-films is due to their ultra-thin thickness (< 200 nm), but this results in their areal capacity too low to be compatible with commercial cathode materials, and only films thicker than 500 nm are practical. However, frequent volume changes in non-ultra-thin silicon films during cycling may cause layer misalignment and separation of the film from substrate. In this paper, silicon films with a thickness of ∼700 nm are prepared by magnetron sputtering on the inhomogeneous surface of a copper foil. The properties of the silicon films and mechanisms involved in the cycling process is investigated by combining experimental means during cycling with calculations of the atomic-scale amorphous lithium-silicon Zintl Phases’ structural volumes before and after cycling. The results show that the volume of silicon doesn't recover after delithiation and there is still significant swelling. The cyclic process causes a superimposed expansion of the volume, but the non-uniform film substrate causes the lateral expansion stresses to offset each other, thereby retaining a relatively stable structure. At the end of 100 cycles, the specific capacity of the silicon film electrode is 1461.5 mAh g −1 (areal capacity 0.242 mAh cm−2), with a capacity retention of 64.35%, and the silicon film thickness becomes 8.5 μm. We believe that by reducing the longitudinal expansion volume or stress of the silicon film, the cycle life of the silicon film can be further optimized.

Structure and mechanical properties of toughening B1 Ta1-xMoxN films with various Mo contents

In this paper, Ta1-xMoxN films with varying Mo contents were deposited by reactive magnetrons sputter in mixed Ar/N2 atmospheres at 350 °C. It's discovered that Ta1-xMoxN films at x = 0.13–0.86 maintains a NaCl type (B1) structure and a strong (200) preferred orientation. Besides, as Mo contents grow, the residual stress of films is attenuated from −3.24 GPa to −1.49 GPa, and the hardness of films first increases and then decreases. Specifically, with a nearly balanced Ta and Mo content (x = 0.57), the Ta1-xMoxN film exhibits higher hardness (39.5 ± 1.2 GPa) and elastic modulus (359.3 ± 8.8 GPa), up by 53.1% and 26.8% compared with TaN, higher fracture toughness, scratch critical load (91.5 N) and elasticity (76.7%). The Ta1-xMoxN film with x = 0.57 obtains lower coefficient of friction (0.417), and higher wear resistance (wear rate: 1.9 × 10−7 mm3/N*m). In addition, the density of states (DOS) in XPS valence band spectra from Ta1-xMoxN films is shifted toward lower binding energy with more Mo contents. Accordingly, the stronger metallic characteristics and the solid solution strengthening effect endow the Ta1-xMoxN films at x = 0.57 with higher hardness and toughness.