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This work discusses microLED arrays as light sources for implementing optical sectioning structured illumination microscopy (OS‐SIM) and targeted illumination (TI) for neural imaging applications. We demonstrated a microstripe array to generate patterned light for OS‐SIM and an individually addressable 20 × 20 microLED array as a light source for implementing TI in a widefield imaging setup. [ABSTRACT FROM AUTHOR]

Electrowetting-based adaptive optics are of great interest for applications ranging from confocal microscopy to LIDAR, but the impact of low-frequency mechanical vibration on these devices remains to be studied. We present a simple theoretical model for predicting the resonance modes induced on the liquid interface in conjunction with a numerical simulation. We experimentally confirm the resonance frequencies by contact angle modulation. They are found to be in excellent agreement with the roots of the zero-order Bessel functions of the first kind. Next, we experimentally verify that external axial vibration of an electrowetting lens filled with density mismatched liquids (Δ ρ = 250 kg/m3) will exhibit observable Bessel modes on the liquid–liquid interface. An electrowetting lens filled with density matched liquids (Δ ρ = 4 kg/m3) is robust to external axial vibration and is shown to be useful in mitigating the effect of vibrations in an optical system. [ABSTRACT FROM AUTHOR]

We demonstrate a method that permits wavefront aberration correction using an array of electrowetting prisms. A fixed high fill factor microlens array followed by a lower fill factor adaptive electrowetting prism array is used to correct wavefront aberration. The design and simulation of such aberration correction mechanism is described. Our results show significant improvement to the Strehl ratio by using our aberration correction scheme which results in diffraction limited performance. Compactness and effectiveness of our design can be implemented in many applications that require aberration correction, such as microscopy and consumer electronics. [ABSTRACT FROM AUTHOR]

The thermal atomic layer etching (ALE) of VO2 was demonstrated using sequential exposures of BCl3 and SF4. The VO2 etch rate measured by quartz crystal microbalance investigations at 250 °C was 2.3 Å/cycle. The mass losses during individual BCl3 and SF4 reactions were nearly self-limiting versus BCl3 and SF4 exposures. The VO2 etch rates were also dependent on temperature and varied from 0.05 Å/cycle at 150 °C to 2.3 Å/cycle at 250 °C. Fourier transform infrared (FTIR) spectroscopy studies observed VO2 etching by monitoring the decrease in absorbance from V—O stretching vibrations in the VO2 film. The FTIR spectra during the initial BCl3 exposures on the VO2 film observed the growth of absorbance from B—O stretching vibrations from B2O3 and the concurrent loss of V=O vibrational features. These changes were consistent with BCl3 converting VO2 to B2O3. The FTIR difference spectra during subsequent SF4 and BCl3 reactions also observed the growth and loss of absorbance features that were attributed to F3V=O and V—F stretching vibrations, respectively. These changes indicate that SF4 fluorinates VO2 to form a VOF3 surface layer and then BCl3 undergoes ligand-exchange with VOF3 to volatilize the VOF3 surface layer as VOCl3. There was also evidence for conversion of VO2 to B2O3 during BCl3 exposures and then removal of B2O3 by SF4 exposures. In addition, quadrupole mass spectrometry (QMS) measurements observed that the SF4 exposures produced ion intensities for SOxFyClz products in oxidation states greater than 4+. These SOxFyClz products indicate that SF4 is being oxidized and acting as a deoxyfluorination reactant. Concurrently, the QMS analysis also monitored ion intensity for S8+, S7+, S6+, S5+, and S4+. These S8 electron impact ionization products argue that SF4 oxidation occurs concurrently with SF4 reduction. The QMS also observed ion intensities corresponding to VCl4+ and VOCl3+. The presence of VOCl3+ indicates that the oxidation state of vanadium has increased to 5+ in some of the volatile etch products. The QMS also detected trichloroboroxin (B3O3Cl3) during BCl3 exposures. B3O3Cl3 is a known etch product of B2O3 during BCl3 exposures. BCl3 can convert VO2 to B2O3 and then proceed to etch the converted B2O3. Thermal VO2 ALE using BCl3 and SF4 reveals the rich complexity of surface etching reactions that can proceed by multiple pathways including conversion, ligand-exchange, and oxidation state changes. [ABSTRACT FROM AUTHOR]

Direct monitoring techniques of fouling in membrane-based filtration processes can be implemented as part of an effort to reduce the negative effects of membrane fouling. In particular, monitoring techniques with chemical characterization capability are crucial for the formulation of effective fouling prevention and mitigation strategies. In the present work, Raman spectroscopy was applied as an in-situ monitoring technique for calcium carbonate scaling on commercial reverse osmosis membranes. The bench-scale Raman monitoring system allowed for a qualitative chemical assay of the scaled membrane surface at sequential downstream and upstream axial positions. The time evolution of the downstream and upstream calcium carbonate Raman signal was evaluated with respect to computed values of local concentration at the membrane surface, revealing a statistically significant dependence (p < 0.001). The real-time Raman data were bolstered by results of post-mortem analysis (scanning electron microscopy, gravimetric measurements, and laser interferometry). The employed technique was capable of detecting crystals with characteristic lengths <50 μm. Preliminary evidence of polymorph detection was also presented with recommendations for improvements in the technique. [ABSTRACT FROM AUTHOR]

Because of the low dimensional power of its force scaling law, surface tension is appropriate for carrying out reshaping and assembly in the microstructure size domain. This paper reviews work on surface tension powered self-assembly of microstructures. The existing theoretical approaches for rotational assembly are unified. The demonstrated fabrication processes are compared. Mechanisms for accurately determining the assembled shape are discussed, and the limits on accuracy and structural distortion are considered. Applications in optics, electronics and mechanics are described. More complex operations (including the combination of self-assembly and self-organization) are also reviewed. [926] Index Terms--Capillary force, mieroelectromechanical systems (MEMS), microsystems, microoptoelectromechanical systems (MOEMS), self-assembly, surface tension.

-Ultrathin Al2O3 atomic layer deposition (ALD) films with low pinhole density were fabricated using a deposit and etchback approach. This strategy was able to avoid the pinholes that originated during nonuniform nucleation of Al2O3 ALD films. In this method, an Al2O3 ALD film was deposited to a thickness greater than the desired thickness to reduce the number of pinholes and form a more continuous Al2O3 ALD film. Subsequently, the Al2O3 ALD film was etched back to a smaller thickness using thermal Al2O3 atomic layer etching (ALE). The number of pinholes in the resulting Al2O3 ALD film was measured by the percentage yield of metal-insulator-metal (MIM) capacitors based on an Ag/Al2O3/Al structure that did not have an electrical short. The device yield was improved using the deposition and etchback approach. For example, using device areas of 0.01 mm2, Al2O3 ALD films that were grown to 5 nm in the MIM capacitor gave a yield of 30%–40%. In contrast, Al2O3 ALD films that were grown to 24 nm and then etched back to 5 nm to form the MIM capacitor provided a yield of 65%–75%. This increase in yield of approximately 100% indicates that the deposit and etchback approach can improve the yield of MIM devices based on ultrathin Al2O3 ALD films. Although this method has been previously suggested to improve the quality of ultrathin films, this report is believed to be the first demonstrated application of using the deposit and etchback approach for device fabrication. Additional experiments revealed that a portion of the yield improvement can be attributed to the fluorination of the Al2O3 ALD films that produced a volume expansion when forming AlF3. This expansion may produce a compressive stress that helps to close the pinholes. The dielectric constant was also measured for Al2O3 ALD films versus Al2O3 film thickness. The dielectric constant was the same for as-deposited Al2O3 ALD films and Al2O3 ALD films that were first grown to 24 nm and then etched back to smaller thicknesses. This agreement indicates that the dielectric constant can be understood in terms of a series capacitor model and that Al2O3 ALE does not affect the electrical properties of the Al2O3 films. [ABSTRACT FROM AUTHOR]

Gallium nitride nanowires (NWs) grown on silicon-on-insulator wafers by means of selective area epitaxy are directly integrated into scanning probe cantilever fabrication. These cantilevers with NW probe tips are coated with tungsten by atomic layer deposition to take measurements on gold embedded in silicon to test the RF response of the cantilever to changes in the material properties. The sensitivity of the cantilever RF capacitance measurement was tested on a microcapacitor reference sample with 0.7 – 7.1 $\mu {m}^{2}$ microcapacitors on 10 $nm$ SiO2 steps. These probes have an estimated noise-limited sensitivity of 12.5 $aF$ , demonstrating the first RF cantilever with a selectively grown NW probe tip. [2021-0240] [ABSTRACT FROM AUTHOR]