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Copyright of Micronanoelectronic Technology is the property of Micronanoelectronic Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Flexible electronics strongly demand the integration of flexible and large‐scale multifunctional oxides. BiFeO3 is one of the most essential multifunctional oxides that could be used in memories, logics, sensors, and actuators. Recently, freestanding single‐crystalline BiFeO3 membranes exhibited superior elasticity and flexibility. However, fabrication and integration of large‐scale freestanding BiFeO3 membranes into flexible electronics remain elusive. In this study, inch‐scale freestanding single‐crystalline BiFeO3 membranes are fabricated with assistance from a water‐soluble sacrificial layer. To transfer flat and crack‐free membranes, all the existing methods are first followed but fail. Then the study introduces a temporary supporting Cu layer on the surface of the as‐grown SiTiO3/Sr3Al2O6/(SrRuO3/)BiFeO3 heterostructure and successfully obtains full and crack‐free 5 mm × 5 mm freestanding membranes on various substrates. The residual strain within the heterostructure releases gradually under the protection of the Cu layer. The freestanding BiFeO3 membranes are relatively uniform among different regions and exhibit good dielectric, ferroelectric, and ferromagnetic properties. Finally, flexible ferroelectric photovoltaic devices are patterned based on those BiFeO3 membranes, and they have open circuit voltage and short circuit current density up to −0.25 ± 0.03 V and 0.82 ± 0.09 µA cm−2, respectively. [ABSTRACT FROM AUTHOR]

Single-crystal silicon carbide has excellent electrical, mechanical, and chemical properties. However, due to its high hardness material properties, achieving high-precision manufacturing of single-crystal silicon carbide with an ultra-smooth surface is difficult. In this work, quantum dots were introduced as a sacrificial layer in polishing for pulsed-ion-beam sputtering of single-crystal SiC. The surface of single-crystal silicon carbide with a quantum-dot sacrificial layer was sputtered using a pulsed-ion beam and compared with the surface of single-crystal silicon carbide sputtered directly. The surface roughness evolution of single-crystal silicon carbide etched using a pulsed ion beam was studied, and the mechanism of sacrificial layer sputtering was analyzed theoretically. The results show that direct sputtering of single-crystal silicon carbide will deteriorate the surface quality. On the contrary, the surface roughness of single-crystal silicon carbide with a quantum-dot sacrificial layer added using pulsed-ion-beam sputtering was effectively suppressed, the surface shape accuracy of the Ø120 mm sample was converged to 7.63 nm RMS, and the roughness was reduced to 0.21 nm RMS. Therefore, the single-crystal silicon carbide with the quantum-dot sacrificial layer added via pulsed-ion-beam sputtering can effectively reduce the micro-morphology roughness phenomenon caused by ion-beam sputtering, and it is expected to realize the manufacture of a high-precision ultra-smooth surface of single-crystal silicon carbide. [ABSTRACT FROM AUTHOR]

Abstract Flexible electronics strongly demand the integration of flexible and large‐scale multifunctional oxides. BiFeO3 is one of the most essential multifunctional oxides that could be used in memories, logics, sensors, and actuators. Recently, freestanding single‐crystalline BiFeO3 membranes exhibited superior elasticity and flexibility. However, fabrication and integration of large‐scale freestanding BiFeO3 membranes into flexible electronics remain elusive. In this study, inch‐scale freestanding single‐crystalline BiFeO3 membranes are fabricated with assistance from a water‐soluble sacrificial layer. To transfer flat and crack‐free membranes, all the existing methods are first followed but fail. Then the study introduces a temporary supporting Cu layer on the surface of the as‐grown SiTiO3/Sr3Al2O6/(SrRuO3/)BiFeO3 heterostructure and successfully obtains full and crack‐free 5 mm × 5 mm freestanding membranes on various substrates. The residual strain within the heterostructure releases gradually under the protection of the Cu layer. The freestanding BiFeO3 membranes are relatively uniform among different regions and exhibit good dielectric, ferroelectric, and ferromagnetic properties. Finally, flexible ferroelectric photovoltaic devices are patterned based on those BiFeO3 membranes, and they have open circuit voltage and short circuit current density up to −0.25 ± 0.03 V and 0.82 ± 0.09 µA cm−2, respectively.

This study investigates the ballistic impact response of two armor steels (Armox Advance and Ramor 500) and a structural wear-resistant steel (Hardox 450) in monolithic, double-layered, and perforated plate configurations. As ammunitions, 7.62 mm NATO Ball, 7.62 × 51 AP (armor piercing), and 12.7 mm APM2 bullets were used in the ballistics tests. The tests were performed per EN 1522/1523 ballistic test standards and at FB6 and FB7 levels. The results showed different perforation behaviors for different plate configurations. All the monolithic plates were perforated with 7.62 mm AP bullets except for Armox Advance. Double-layered plate configurations, on the other hand, showed resistance to penetration. Among those, only the Ramor500 + Ramor 500 double-layered plate configuration was perforated by 7.62 mm AP bullets. All the pre-perforated plate configurations resulted in total protection regardless of ammunition type and plate materials.

Thin and ultrathin carbon films reduce the laser energy required for copper powder fusion in selective laser melting (SLM). The low absorption of infrared (IR) radiation and its excellent thermal conductivity leads to an intricate combination of processing parameters to obtain high-quality printed parts in SLM. Two carbon-based sacrificial thin films were deposited onto copper to facilitate light absorption into the copper substrates. Graphite-like (3.5 µm) and ultra-thin (25 nm) amorphous carbon films were deposited by aerosol spraying and direct current magnetron sputtering, respectively. The melting was analyzed for several IR (1.06 µm) laser powers in order to observe the coating influence on the energy absorption. Scanning electron microscopy showed the topography and cross-section of the thermally affected area, electron backscatter diffraction provided the surface chemical composition of the films, and glow-discharge optical emission spectroscopy (GDOES) allowed the tracking of the in-deep chemical composition of the 3D printed parts using carbon film-covered copper. Ultra-thin films of a few tens of nanometers could reduce fusion energy by about 40%, enhanced by interferences phenomena. Despite the lower energy required, the melting maintained good quality and high wettability when using top carbon coatings. A copper part was SLM printed and associated with 25 nm of carbon deposition between two copper layers. The chemical composition analysis demonstrated that the carbon was intrinsically removed during the fusion process, preserving the high purity of the copper part. [ABSTRACT FROM AUTHOR]

Single-crystal silicon carbide has excellent electrical, mechanical, and chemical properties. However, due to its high hardness material properties, achieving high-precision manufacturing of single-crystal silicon carbide with an ultra-smooth surface is difficult. In this work, quantum dots were introduced as a sacrificial layer in polishing for pulsed-ion-beam sputtering of single-crystal SiC. The surface of single-crystal silicon carbide with a quantum-dot sacrificial layer was sputtered using a pulsed-ion beam and compared with the surface of single-crystal silicon carbide sputtered directly. The surface roughness evolution of single-crystal silicon carbide etched using a pulsed ion beam was studied, and the mechanism of sacrificial layer sputtering was analyzed theoretically. The results show that direct sputtering of single-crystal silicon carbide will deteriorate the surface quality. On the contrary, the surface roughness of single-crystal silicon carbide with a quantum-dot sacrificial layer added using pulsed-ion-beam sputtering was effectively suppressed, the surface shape accuracy of the Ø120 mm sample was converged to 7.63 nm RMS, and the roughness was reduced to 0.21 nm RMS. Therefore, the single-crystal silicon carbide with the quantum-dot sacrificial layer added via pulsed-ion-beam sputtering can effectively reduce the micro-morphology roughness phenomenon caused by ion-beam sputtering, and it is expected to realize the manufacture of a high-precision ultra-smooth surface of single-crystal silicon carbide.

The alluring optoelectronic properties of lead halide perovskites have continued to attract enormous interest from the scientific community. They are among the brightest candidates for future optoelectronic devices. However, making active devices out of single nano/microcrystals of lead halide perovskites has been a major hurdle and this has dulled its position as a future optoelectric material considerably. The notoriety of not withstanding the steps in photolithography is at the core of this problem. Here, a noninvasive sacrificial layer‐assisted photolithography technique is reported to successfully make active nano/microdevices on single nano/microcrystals of water‐soluble lead halide perovskite. The sacrificial layer can easily be removed without altering the photoresist patterns which makes it possible to fabricate complex high‐performance devices on water‐soluble samples. It is believed that this technique can easily integrate with existing technologies and can elevate the research and application in the field of lead halide perovskites and other water‐soluble materials to new heights. [ABSTRACT FROM AUTHOR]

Abstract The alluring optoelectronic properties of lead halide perovskites have continued to attract enormous interest from the scientific community. They are among the brightest candidates for future optoelectronic devices. However, making active devices out of single nano/microcrystals of lead halide perovskites has been a major hurdle and this has dulled its position as a future optoelectric material considerably. The notoriety of not withstanding the steps in photolithography is at the core of this problem. Here, a noninvasive sacrificial layer‐assisted photolithography technique is reported to successfully make active nano/microdevices on single nano/microcrystals of water‐soluble lead halide perovskite. The sacrificial layer can easily be removed without altering the photoresist patterns which makes it possible to fabricate complex high‐performance devices on water‐soluble samples. It is believed that this technique can easily integrate with existing technologies and can elevate the research and application in the field of lead halide perovskites and other water‐soluble materials to new heights.

In this work, we have developed the glass‐based capacitive micromachined ultrasound transducers (G‐CMUTs). The sacrificial layer etching process flow employed for the manufacturing of the G‐CMUTs is reported. Specific G‐CMUTs has significant promise acoustic property with ~130 % bandwidth at ~8.2 MHz. Real time in‐vivo ultrasound imaging capability demonstrates the actual usability of G‐CMUTs technology for medical imaging. [ABSTRACT FROM AUTHOR]

The formation of a stable solid electrolyte interphase (SEI) layer is crucial for enhancing the safety and lifespan of Li metal batteries. Fundamentally, a homogeneous Li + behavior by controlling the chemical reaction at the anode/electrolyte interface is the key to establishing a stable SEI layer. However, due to the highly reactive nature of Li metal anodes (LMAs), controlling the movement of Li + at the anode/electrolyte interface remains challenging. Here, an advanced approach is proposed for coating a sacrificial layer called fluorinated self-assembled monolayer (FSL) on a boehmite-coated polyethylene (BPE) separator to form a stable SEI layer. By leveraging the strong affinity between the fluorine functional group and Li + , the rapid formation of a LiF-rich SEI layer in the cell production and early cycling stage is facilitated. This initial stable SEI formation promotes the subsequent homogeneous Li + flux, thereby improving the LMA stability and yielding an enhanced battery lifespan. Further, the mechanism behind the stable SEI layer generation by controlling the Li + dynamics through the FSL-treated BPE separator is comprehensively verified. Overall, this research offers significant contributions to the energy storage field by addressing challenges associated with LMAs, thus highlighting the importance of interfacial control in achieving a stable SEI layer., (© 2024 The Authors. Small published by Wiley‐VCH GmbH.)

• Hetero-integration of InP on SiO 2 without any adhesives via micro-transfer printing. • Oxygen plasma activation of both source and target enables adhesion and bonding. • Smooth roughness for InP, SiO 2 and uniform step height of InP on SiO 2 is obtained. • Surface analysis shows that additional species are formed on surface after plasma. • Good process window for printing guaranteed at least up to 1 hour after O 2 plasma. Micro-Transfer printing (µTP) is a promising technique for hetero-integration of III-V materials into Si-based photonic platforms. To enhance the print yield by increasing the adhesion between the III-V material and Si or SiO 2 surface, an adhesion promoter like Benzocyclobutene is typically used as interlayer. In this work, we demonstrate µTP of InP based coupons on SiO 2 interlayer without any adhesive interlayer and investigate the mechanism of adhesive free bonding. Source coupons are InP-based coupon stacks on a sacrificial layer that is removed by a chemical wet etch with FeCl 3. For the target we fabricated amorphous-Si waveguides on 8″ wafer encapsulated by a High Density Plasma SiO 2 which was planarized by a chemical mechanical polishing procedure. We used O 2 plasma to activate both source and target to increase adhesion between coupon and substrate. To get a better understanding of the bonding mechanism we applied several surface characterization methods. Root mean square roughness of InP and SiO 2 was measured by atomic force microscopy before and after plasma activation. The step height of the micro-transfer printed source coupon on the target wafer is estimated by optical step profiler. We used Raman peak position mappings of InP to analyze possible strain and contact angle measurements on SiO 2 , before and after plasma activation to observe a change in the hydrophilicity of the surface. X-ray Photoelectron Spectroscopy analysis was used to characterize the surface energy states of P2p, In3d, O1s for InP source and Si2p, O1s for SiO 2 target. Our results demonstrate direct bonding of InP coupons by means of µTP without the need of a strain-compensation layer. In this way, a promising route towards Complementary Metal-Oxide-Semiconductor compatible use of µTP for the hetero-integration of InP is provided. [ABSTRACT FROM AUTHOR]

Thin and ultrathin carbon films reduce the laser energy required for copper powder fusion in selective laser melting (SLM). The low absorption of infrared (IR) radiation and its excellent thermal conductivity leads to an intricate combination of processing parameters to obtain high-quality printed parts in SLM. Two carbon-based sacrificial thin films were deposited onto copper to facilitate light absorption into the copper substrates. Graphite-like (3.5 µm) and ultra-thin (25 nm) amorphous carbon films were deposited by aerosol spraying and direct current magnetron sputtering, respectively. The melting was analyzed for several IR (1.06 µm) laser powers in order to observe the coating influence on the energy absorption. Scanning electron microscopy showed the topography and cross-section of the thermally affected area, electron backscatter diffraction provided the surface chemical composition of the films, and glow-discharge optical emission spectroscopy (GDOES) allowed the tracking of the in-deep chemical composition of the 3D printed parts using carbon film-covered copper. Ultra-thin films of a few tens of nanometers could reduce fusion energy by about 40%, enhanced by interferences phenomena. Despite the lower energy required, the melting maintained good quality and high wettability when using top carbon coatings. A copper part was SLM printed and associated with 25 nm of carbon deposition between two copper layers. The chemical composition analysis demonstrated that the carbon was intrinsically removed during the fusion process, preserving the high purity of the copper part.

Piezoelectric thick films are of real interest for devices such as ceramic Micro-ElectroMechanical Systems (MEMS) because they bridge the gap between thin films and bulk ceramics. The basic design of MEMS includes electrodes, a functional material, and a substrate, and efforts are currently focused on simplified processes. In this respect, screen-printing combined with a sacrificial layer approach is attractive due to its low cost and the wide range of targeted materials. Both the role and the nature of the sacrificial layer, usually a carbon or mineral type, depend on the process and the final device. First, a sacrificial layer method dedicated to screen-printed thick-film ceramic and LTCC MEMS is presented. Second, the recent processing of piezoelectric thick-film ceramic MEMS using spark plasma sintering combined with a protective layer approach is introduced. Whatever the approach, the focus is on the interdependent effects of the microstructure, chemistry, and strain/stress, which need to be controlled to ensure reliable and performant properties of the multilayer electroceramics. Here the goal is to highlight the benefits and the large perspectives of using sacrificial/protective layers, with an emphasis on the pros and cons of such a strategy when targeting a complex piezoelectric MEMS design.

The ability to prepare single crystalline complex oxide freestanding membranes has opened a new playground to access new phases and functionalities not available when they are epitaxially bound to the substrates. The water-soluble Sr 3 Al 2 O 6 (SAO) sacrificial layer approach has proven to be one of the most promising pathways to prepare a wide variety of single crystalline complex oxide membranes, typically by high vacuum deposition techniques. Here, we present solution processing, also named chemical solution deposition (CSD), as a cost-effective alternative deposition technique to prepare freestanding membranes identifying the main processing challenges and how to overcome them. In particular, we compare three different strategies based on interface and cation engineering to prepare CSD (00l)-oriented BiFeO 3 (BFO) membranes. First, BFO is deposited directly on SAO but forms a nanocomposite of Sr-Al-O rich nanoparticles embedded in an epitaxial BFO matrix because the Sr-O bonds react with the solvents of the BFO precursor solution. Second, the incorporation of a pulsed laser deposited La 0.7 Sr 0.3 MnO 3 (LSMO) buffer layer on SAO prior to the BFO deposition prevents the massive interface reaction and subsequent formation of a nanocomposite but migration of cations from the upper layers to SAO occurs, making the sacrificial layer insoluble in water and withholding the membrane release. Finally, in the third scenario, a combination of LSMO with a more robust sacrificial layer composition, SrCa 2 Al 2 O 6 (SC 2 AO), offers an ideal building block to obtain (001)-oriented BFO/LSMO bilayer membranes with a high-quality interface that can be successfully transferred to both flexible and rigid host substrates. Ferroelectric fingerprints are identified in the BFO film prior and after membrane release. These results show the feasibility to use CSD as alternative deposition technique to prepare single crystalline complex oxide membranes widening the range of available phases and functionalities for next-generation electronic devices.

The use of modified lime slurry as a sacrificial layer to protect the original porous substrate has a long tradition in the practice of building and monument conservation in Austria. This paper presents the results of analyses performed on the Natural History Museum Vienna to get more insight into the long-term performance of this conservation method. Stone surfaces on the facade and roof area, covered with an acrylic tempered lime sacrificial layer and subsequently made water-repellent, were tested in situ and in the laboratory. Whilst coatings in the exposed zones were completely vanished in certain areas, the samples from the facade were in a good condition even after nearly twenty years of exposure. Hydrophobic activity could be verified up to a depth of five mm in the porous stone substrates. Despite the general good state of preservation of most surfaces, the existence of highly hydrophobic substrates will definitely restrict the implementation of any future sustainable conservation effort. [ABSTRACT FROM AUTHOR]

The growth of epitaxial complex oxides has been essentially limited to specific substrates that can induce epitaxial growth and stand high temperature thermal treatments. These restrictions hinder the opportunity to manipulate and integrate such materials into new artificial heterostructures including the use of polymeric and silicon substrates and study emergent phenomena for novel applications. To tackle this bottleneck, herein, a facile chemical route to prepare water‐soluble epitaxial Sr3Al2O6 thin films to be used as sacrificial layer for future free‐standing epitaxial complex oxide manipulation is described. Two solution processes are put forward based on metal nitrate and metalorganic precursors to prepare dense, homogeneous and epitaxial Sr3Al2O6 thin films that can be easily etched by milli‐Q water. Moreover, as a proof of concept, a basic heterostructure consisting of Al2O3/Sr3Al2O6 on SrTiO3 is fabricated to subsequently exfoliate the Al2O3 thin film and transfer it to a polymer substrate. This is a robust chemical and low‐cost methodology that could be adopted to prepare a wide variety of thin films to fabricate artificial heterostructures to go beyond the traditional electronic, spintronic, and energy storage and conversion devices. [ABSTRACT FROM AUTHOR]

Freestanding perovskite oxide membranes have drawn great attention recently since they offer exceptional structural tunability and stacking ability, providing new opportunities in fundamental research and potential device applications in silicon-based semiconductor technology. Among different types of sacrificial layers, the (Ca, Sr, Ba) 3 Al 2 O 6 compounds are most widely used since they can be dissolved in water and prepare high-quality perovskite oxide membranes with clean and sharp surfaces and interfaces; However, the typical transfer process takes a long time (up to hours) in obtaining millimeter-size freestanding membranes, let alone realize wafer-scale samples with high yield. Here, a new member of the SrO-Al 2 O 3 family, Sr 4 Al 2 O 7 is introduced, and its high dissolution rate, ≈10 times higher than that of Sr 3 Al 2 O 6 is demonstrated. The high-dissolution-rate of Sr 4 Al 2 O 7 is most likely related to the more discrete Al-O networks and higher concentration of water-soluble Sr-O species in this compound. This work significantly facilitates the preparation of freestanding membranes and sheds light on the integration of multifunctional perovskite oxides in practical electronic devices., (© 2024 Wiley‐VCH GmbH.)

The mechanical actuation of suspended structures in microelectromechanical system (MEMS) switches plays an important role in obtaining an open or short circuit in radio-frequency (RF) transmission lines. These micromachined switches have moving parts which are realized by a sacrificial layer. Several sacrificial materials have been utilized in the fabrication of MEMS structures. The traditional method of using metal such as copper or nickel as a sacrificial layer is difficult due to metal etchant compatibility issues. A photoresist is the best choice for this process. Generally, the HiPR photoresist has been found to be suitable␣for the role of sacrificial layer. However, the HiPR is no longer available in the commercial market. As an alternative to the HiPR, the AZ4620 photoresist can be used. In this paper, a unit process optimization technique is described featuring an AZ4620 photoresist as a sacrificial layer for the microfabrication of a suspended structure. The AZ4620 meets all the requirements for the development of RF MEMS switches. Hence, the recipe and fabrication technique are optimized according to the required thickness. Preliminary measurements of the fabricated switch beam indicate that the required gap has been achieved. This optimized process is compatible with standard MEMS technology. [ABSTRACT FROM AUTHOR]

In order to overcome the simplicity and instability of micron cantilever membrane structure, sacrificial layer technology and multi-layer heterogeneous material composite stacking technology were designated. Based on the research with respect to a multi-layer heterogeneous cantilever beam structure, multi-layer heterogeneous material composite, and sacrificial layer release craft, different characteristics of sacrificial layer material and film preparation craft were analyzed. According to these results, the suitable film preparation craft was generated to reduce the stress between materials and to improve the reliability and percentage of finished products. Our work put multi-layer material composite micro-cantilever beam structure into practice, and accelerated the manufacturing of a micro-acceleration sensor and vibration sensor in the future.

Aiming at the problem of heterogeneity of sealed cavity in silicon microstructure processing technology, the technology of preparing micro-cavity by using porous silicon sacrificial layer is proposed. The effect of current density on the preparation of porous silicon and the effect of porous silicon with different porosity on the formation of micro-cavity in the preparation process of porous silicon were studied. Different process parameters were selected for experiments and the prepared micro-cavities were tested and analyzed. According to the test results, the suitable electrochemical corrosion process parameters were selected to prepare porous silicon, and the micro-cavity was realized by changing the process parameters, which greatly increased the application fields of micro-sensors and micro-actuators. [ABSTRACT FROM AUTHOR]

Copyright of Conservar Património is the property of Associacao Profissional de Conservadores-Restauradores de Portugal and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nowadays, micro-scale piezoelectric devices with high sensitivity are much in demand for transducer technologies. This work suggests a low cost technology consisting of a screen-printing process associated with a sacrificial layer for preparation of microceramic-disks. These printed microdisks are based on a PZT layer sandwiched between two printed electrodes. The printed microdisks can be released from substrates by co-firing, leading to a complete decomposition of the sacrificial layer. The effect of different electrode materials (Au and Ag/Pd) on the releasing behavior is described. Uniform releasing is obtained by Ag/Pd electrodes whereas Au electrodes perform partial sticking on the substrates. Furthermore, the printed microdisks made of different PZT particle sizes are compared in terms of microstructure, electromechanical, and dielectric properties. The dense microdisks obtained from nanometric PZT particles and Ag/Pd electrodes generate high values of effective electromechanical coupling coefficient (45%) and relative permittivity (1200). Therefore, these printed microdisks are considered to be potential candidates for different sensing and actuating applications. [ABSTRACT FROM AUTHOR]

According to the characteristics of earthen sites' erosion and the existing environments of arid and semi-arid zones, this work comes up with the conception of sacrificial layer. Covering the surface of the earthen site with a mud coating layer, similar to the natural materials found at the site, it would provide a protective layer for exogenic forces to destroy, while preserving the earthen site. Experiments were carried out to separately test the shrinkage rate, heat sensitivity, color difference, mechanical properties, vapor permeability, wetting–drying cycle, and rainfall erosion by adding wheat chaff and hemp fibers with different proportions. Experimental results show that wheat chaff and hemp fibers are ideal modified materials for the sacrificial layer with good performance. The optimum proportion of hemp fiber, wheat chaff, and soil was 0.5:1.25:100. The sacrificial layer has broad application prospects to the surfaces of earthen sites in arid and semi-arid zones. [ABSTRACT FROM AUTHOR]

As one of the important technologies in the field of heterogeneous integration, transfer technology has broad application prospects and unique technical advantages. This transfer technology includes the wet chemical etching of a sacrificial layer, such that silicon nano-film devices are released from the donor substrate and can be transferred. However, in the process of wet etching the SiO2 sacrificial layer present underneath the single-crystal silicon nano-film by using the transfer technology, the etching is often incomplete, which seriously affects the efficiency and quality of the transfer and makes the device preparation impossible. This article analyzes the principle of incomplete etching, and compares the four factors that affect the etching process, including the size of Si nano-film on top of the sacrificial layer, the location of the anchor point, the shape of Si nano-film on top of the sacrificial layer, and the thickness of the sacrificial layer. Finally, the etching conditions are obtained to avoid the phenomenon of incomplete etching of the sacrificial layer, so that the transfer technology can be better applied in the field of heterogeneous integration. Additionally, Si MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors) on sapphire substrate were fabricated by using the optimized transfer technology.

Single-crystal silicon carbide has excellent electrical, mechanical, and chemical properties. However, due to its high hardness material properties, achieving high-precision manufacturing of single-crystal silicon carbide with an ultra-smooth surface is difficult. In this work, quantum dots were introduced as a sacrificial layer in polishing for pulsed-ion-beam sputtering of single-crystal SiC. The surface of single-crystal silicon carbide with a quantum-dot sacrificial layer was sputtered using a pulsed-ion beam and compared with the surface of single-crystal silicon carbide sputtered directly. The surface roughness evolution of single-crystal silicon carbide etched using a pulsed ion beam was studied, and the mechanism of sacrificial layer sputtering was analyzed theoretically. The results show that direct sputtering of single-crystal silicon carbide will deteriorate the surface quality. On the contrary, the surface roughness of single-crystal silicon carbide with a quantum-dot sacrificial layer added using pulsed-ion-beam sputtering was effectively suppressed, the surface shape accuracy of the Ø120 mm sample was converged to 7.63 nm RMS, and the roughness was reduced to 0.21 nm RMS. Therefore, the single-crystal silicon carbide with the quantum-dot sacrificial layer added via pulsed-ion-beam sputtering can effectively reduce the micro-morphology roughness phenomenon caused by ion-beam sputtering, and it is expected to realize the manufacture of a high-precision ultra-smooth surface of single-crystal silicon carbide.

Magnetorheological finishing (MRF) is usually used to remove subsurface defects (SSD) of workpieces to improve the laser-induced damage threshold due to its low stress. Although MRF has been widely used to remove surface defects and SSD, the evolution and removal mechanism of surface scratches under MRF have not been fully elucidated. A systematic study is conducted on the scratch removal process and removal ability of MRF. First, an experimental study on the removal of scratches with different depths is carried out, and the effect of the scratch depth on the removal efficiency is analyzed. Second, when the scratches are removed, the processing is performed in two directions: parallel and perpendicular to the scratch. Thereby, the relationship between the scratch removal efficiency (SRE) and the processing direction is analyzed. Finally, based on the scratch removal process and mechanism, an innovative method for efficient scratch removal using a sacrificial layer is proposed. The effectiveness of this method is verified by experiments. This method can significantly improve the SRE of MRF. [ABSTRACT FROM AUTHOR]

This paper proposes a novel electrochemical etching process without the need for a metal mask or photo-resist mask. The selective electrochemical etching using laser-patterned (SEEL) copper layer process consists of three steps: electrodeposition, laser patterning, and electrochemical etching. In the SEEL copper layer process, a deposited copper layer was formed on stainless steel by an electrodeposition process. A patterned copper layer on stainless steel was formed by laser beam irradiation. A patterned copper layer serves as both a sacrificial layer and a protective mask during the electrochemical etching process. The results were observed via scanning electron microscopy and surface profiler measurement. The appropriate conditions for stable SEEL copper layer process were determined. Finally, selective electrochemical etching with various micro patterns on stainless steel was been successfully performed. [ABSTRACT FROM AUTHOR]

Aiming at the problem of poor reliability of beam membrane fabrication in silicon microstructure processing technology, a technique for preparing microbeams using porous silicon sacrificial layer is proposed. The comparison of different porosity, different depths of porous silicon to beam membrane release and the comparison of different beam structures to beam membrane release were studied. The experiment was carried out by selecting different process parameters and testing the prepared beam membrane. According to the test results, the appropriate electrochemical corrosion process parameters were selected to prepare the porous silicon layer with appropriate porosity, large depth, good support effect and fast release speed, which can realize the release of the beam membrane and improve the reliability of the beam membrane. The field of application of microsensors and microactuators has been greatly increased. [ABSTRACT FROM AUTHOR]

This paper presents the fabrication by means of roll-to-roll slot-die coating and characterization of air gap-based cantilever type capacitive acceleration sensors. As the mass of the sensor moves in the opposite direction of the acceleration, a capacitance change occurs. The sensor is designed to have a six layers structure with an air gap. Fabrication of the air gap and cantilever was enabled by coating and removing water-soluble PVA. The bottom electrode, the dielectric layer, and the sacrificial layer were formed using the roll-to-roll slot-die coating technique. The spacer, the top electrode, and the structural layer were formed by spin coating. Several kinds of experiments were conducted for characterization of the fabricated sensor samples. Experimental results show that accelerations of up to 3.6 g can be sensed with an average sensitivity of 0.00856 %/g.

We propose and demonstrate an unconventional method suitable for releasing microelectromechanical systems devices containing an Al layer by wet etching using SiO2 as a sacrificial layer. We used 48% HF solution in combination with 20% oleum to keep the HF solution water-free and thus to prevent attack of the Al layer, achieving an outstanding etch rate of thermally grown SiO2 of ≈1 µm·min−1. We also verified that this etching solution only minimally affected the Al layer, as the chip immersion for ≈9 min increased the Al layer sheet resistance by only ≈7.6%. The proposed etching method was performed in an ordinary fume hood in a polytetrafluorethylene beaker at elevated temperature of ≈70 °C using water bath on a hotplate. It allowed removal of the SiO2 sacrificial layer in the presence of Al without the necessity of handling highly toxic HF gas.