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Frequency-domain probe beam deflection (FD-PBD) is an experimental technique for measuring thermal properties that combines heating by a modulated pump laser and measurement of the temperature field via thermoelastic displacement of the sample surface. In the conventional implementation of FD-PBD, the data are mostly sensitive to the in-plane thermal diffusivity. We describe an extension of FD-PBD that introduces sensitivity to through-plane thermal conductance by immersing the sample in a dielectric liquid and measuring the beam deflection created by the temperature field of the liquid. We demonstrate the accuracy of the method by measuring (1) the thermal conductivity of a 310 nm thick thermally grown oxide on Si, (2) the thermal boundary conductance of bonded interface between a 3C-SiC film and a single crystal diamond substrate, and (3) the thermal conductivities of several bulk materials. We map the thermal boundary conductance of a 3C-SiC/diamond interface with a precision of 1% using a lock-in time constant of 3 ms and dwell time of 15 ms. The spatial resolution and maximum probing depth are proportional to the radius of the focused laser beams and can be varied over the range of 1–20 μm and 4–80 μm, respectively, by varying the 1/e2 intensity radius of the focused laser beams from 2 to 40 μm. FD-PBD with liquid immersion thus enables fast mapping of spatial variations in thermal boundary conductance of deeply buried interfaces. [ABSTRACT FROM AUTHOR]

In fiber spinning of photopolymers, surface tension limits the diameter of the fiber that can be produced due to the Rayleigh–Plateau instability. Submerging a pre-fiber jet in a miscible environment liberates the system from capillary effects, thus allowing the jet to be stretched into thin threads without instability. In this work, we systematically investigated a spinning method using miscible liquids, called jet-assisted wet spinning (JAWS), where stretching is achieved by a nearby submerged liquid jet. The diameter of the pre-fiber jet is a function of its flow rate and position relative to the assisting submerged liquid jet. A particular case where the main jet is modeled as the Landau–Squire jet is used to demonstrate the tracer-like thinning behavior of the pre-fiber jet. Experiments show that buoyancy has a significant impact on the pre-fiber jet diameter because of its influence on the entrainment trajectory. Overall, our results demonstrate the potential for the parallelization of JAWS for high-throughput fiber production. [ABSTRACT FROM AUTHOR]

Hexagonal boron nitride (hBN) has brought widespread attention as a host material of various quantum emitters due to its two-dimensional nature and wide bandgap. Among the versatile quantum emitters in hBN, the negatively charged boron vacancy ( V B − ) stands out for its high contrast of optically detected magnetic resonance signal and the ability of spin control. Here, we report a method to implement 8.6-fold photoluminescence enhancement of V B − by using a solid immersion lens (SIL). We further combined an Au waveguide, Ag nanoparticles, and SIL to achieve an 18.6-fold photoluminescence overall enhancement of V B − . Our work provides a portable method to enhance the collection and emission efficiency of V B − , which is helpful for its practical applications in quantum technologies such as quantum sensing and quantum information. [ABSTRACT FROM AUTHOR]

We report on ten-stage interband cascade light-emitting diodes (ICLEDs) using an InAs/GaAsSb superlattices active region with a peak emission wavelength of 4.9 μm at the temperature of 80 K. The ICLED devices integrated with an immersion lens achieve a wall-plug quantum efficiency of 6.6% and an emittance of 1.9 W/cm2 under 80 K and 7.7 A/cm2, which is seven times larger than the basic device without the immersion lens. We present a detailed analysis of the recombination rates and their relationship with the quantum efficiency. The Shockley–Read–Hall and Auger recombination rates were measured using carrier-density dependent time-resolved photoluminescence spectra. The band structure of InAs/GaAsSb superlattices is calculated to study their relationship with the Auger recombination rates. [ABSTRACT FROM AUTHOR]

Non-wetting solids have been extensively studied for about 20 years due to the spectacular mobility they provide to water drops. However, they have other noteworthy properties: For instance, such materials immersed in water entrain a plastron of air, a phenomenon exploited by many creatures to hunt or breathe underwater. We measure the thickness of this plastron and model the results by modifying the Landau–Levich–Derjaguin theory established for a plate drawn out of a wetting liquid. [ABSTRACT FROM AUTHOR]

Grayscale lithography allows the creation of micrometer-scale features with spatially controlled height in a process that is fully compatible with standard lithography. Here, solid immersion lenses are demonstrated in silicon carbide using a fabrication protocol combining grayscale lithography and hard-mask techniques to allow nearly hemispherical lenses of 5 μ m radius to be etched into the substrate. Lens performance was benchmarked by studying the enhancement obtained in the optical collection efficiency for single quantum emitters hosted in silicon carbide. Enhancement by a factor of 4.4 ± 1.0 was measured for emitters not registered to the center of the lens, consistent with devices fabricated through other methods. The grayscale hard-mask technique is highly reproducible, scalable, and compatible with CMOS technology, and device aspect ratios can be tuned after resist patterning by controlling the chemistry of the subsequent dry etch. These results provide a reproducible, low-cost, high-throughput and industrially relevant alternative to focused ion beam milling for the creation of high-aspect-ratio, rounded microstructures for quantum technology, and microphotonic applications. [ABSTRACT FROM AUTHOR]

Optical components based on metasurfaces (metalenses) offer an alternative methodology for microlens arrays. In particular, metalens arrays have the potential of being monolithically integrated with infrared focal plane arrays (IR FPAs) to increase the operating temperature and sensitivity of the latter. In this work, we demonstrate a type of transmissive metalens that focuses the incident light (λ = 3–5 μm) on the detector plane after propagating through the substrate, i.e., solid-immersion type of focusing. The metalens is fabricated by etching the backside of the detector substrate material (GaSb here), making this approach compatible with the architecture of back-illuminated FPAs. In addition, our designs work for all incident polarizations. We fabricate a 10 × 10 metalens array that proves the scalability of this approach for FPAs. In the future, these solid-immersion metalenses arrays will be monolithically integrated with IR FPAs. [ABSTRACT FROM AUTHOR]

Acoustic waves have been widely applied in communications, medical treatment, military, and other aspects. In this Letter, we explore acoustic imaging properties of three-dimensional Maxwell's fish-eye lens (3D-MFEL) with elevated refractive index profile, the analytical and numerical results show that a 3D-MFEL based on solid immersion mechanism can achieve super-resolution imaging without chromatic aberration. In addition, introducing vortex waves into the 3D-MFEL, we further explore the super-resolution imaging properties in reconstructing vortex waves. The valid combination of 3D-MFEL and solid immersion mechanism provides a meaningful way for super-resolution imaging, which also paves a way forward for future designing and manufacturing in acoustic super-imaging systems. [ABSTRACT FROM AUTHOR]

Among wide-bandgap compound semiconductors, gallium nitride is the most widely available material due to its prevalence in the solid state lighting and high-speed/high-power electronics industries. It is now known that GaN is one of only a handful of materials to host color centers that emit quantum light at room temperature. In this paper, we report on a bright color center in a semi-polar gallium nitride substrate emitting at room temperature in the near-infrared. We show that a hemispherical solid immersion lens, near index matched to the semiconductor, can be used to enhance the photon collection efficiency by a factor of 4.3 ± 0.1 while improving the lateral resolution by a factor equal to the refractive index of the lens. [ABSTRACT FROM AUTHOR]

Unique effects of terahertz (THz)-wave–matter interaction push rapid progress in THz optoelectronics aimed at bridging the problematic THz gap. However, majority of modern methods of THz spectroscopy and imaging are still hampered by low spatial resolution. Common lens/mirror-based THz optics fails to overcome the Abbe barrier and usually provides resolution larger than a free-space wavelength λ (i.e., hundreds of micrometers or even few millimeters). To mitigate this difficulty, supperresolution THz imaging modalities were introduced recently, among which we particularly underline different methods of THz scanning-probe near-field microscopy. They not only rely on strong light confinement on sub-wavelength probes and provide resolution down to ∼ 10 − 1 – 10 − 3 λ but also suffer from small energy efficiency or presume an interplay among imaging resolution, signal-to-noise ratio, and performance. In this paper, we consider reflection-mode THz solid immersion (SI) microscopy that offers some compromise between the high imaging resolution of 0.15 λ and high energy efficiency, which is due to the absence of any subwavelength probe in an optical scheme. Recent achievements, challenging problems, and prospects of SI microscopy are overviewed with an emphasis on resolving the inverse problem and applications in THz biophotonics. [ABSTRACT FROM AUTHOR]

We have developed a method of terahertz (THz) solid immersion (SI) microscopy for continuous-wave reflection-mode imaging of soft biological tissues with a sub-wavelength spatial resolution. In order to achieve strong reduction in the dimensions of the THz beam caustic, an electromagnetic wave is focused into the evanescent field volume behind a medium with a high refractive index. We have experimentally demonstrated a 0.15λ-resolution of the proposed imaging modality at λ = 500 μm, which is beyond the Abbe diffraction limit and represents a considerable improvement over the previously-reported arrangements of SI imaging setups. The proposed technique does not involve any sub-wavelength near-field probes and diaphragms, thus, avoiding the THz beam attenuation due to such elements. We have applied the developed method for THz imaging of various soft tissues: a plant leaf blade, cell spheroids, and tissues of the breast ex vivo. Our THz images clearly reveal sub-wavelength features in tissues, therefore, promising applications of THz SI microscopy in biology and medicine. [ABSTRACT FROM AUTHOR]

The integration of single quantum dots (QDs) into a planar Fabry–Pérot microcavity has been established as a direct and viable approach to vertically steer photons emitted from the quantum emitters, resulting in a strong increase in the source brightness, which becomes particularly evident when a lens with a low numerical aperture is used. However, the spectral bandwidth of QD–microcavity structures is limited and determined by their intrinsic quality factor; these structures are, thus, not ideal for the extraction of entangled photon pairs or for studies of exciton dynamics. We have found that, when a deterministic low-index solid immersion lens is placed on top of the QD in a QD–microcavity structure, the structure exhibits an enhancement in the bandwidth to 27 nm and a source brightness of 23%. The solid immersion lens is deterministically fabricated via two-photon absorption and can be remade several times without perturbing the QD, ensuring that the QD's intrinsic properties are preserved and ensuring its long-term reliability. [ABSTRACT FROM AUTHOR]

Modulating the thermal emission of a material in the infrared (IR) range can be essential for various practical applications such as smart textiles, camouflage, and anti-counterfeiting. Although many different materials or structures have been proposed, the complex manufacturing processes are still hindering their widespread use. Herein, a facile femtosecond laser processing technology and a drop-coating method are introduced to form a patternable low emissivity film. Laser-treated polyimide films resulted in superhydrophilic structured surfaces that are uniformly coated with silver-nanowires (AgNWs) in aqueous solutions for low emissivity surfaces. Furthermore, the emissivity of the samples is as low as ∼0.2 without deterioration over 800 bending-releasing cycles. The as-prepared films also display good thermal camouflage properties, namely, the films reduced the thermal radiation temperature of an object by 35.8 °C when the object temperature was ∼69.1 °C. Additionally, this IR camouflage effect of the AgNWs coated samples shows excellent stability even in harsh environments such as immersion in water, acid, alkali, and salt solution and applied voltage. We also show that information encryption was possible by adjusting the amount of AgNWs. The design of this programmable patterned low emissivity film indicates an idea for the thermal camouflage and anti-counterfeiting technology, which can carry more abundant application scenario and disguise them more complex and sophisticated. [ABSTRACT FROM AUTHOR]

We report on the design of a single element planar solid immersion lens which is theoretically capable of confining light to a focal spot with full width half maximum of 0.29 λ (154 nm at λ = 532 nm) and achieving an effective numerical aperture of 1.732. Devices are fabricated and initial optical characterization is performed using a far-field imaging technique providing a lower bound on the numerical aperture of 0.7. Experimental results compare well with two dimensional finite element method simulations. Devices can be mass produced using ultraviolet lithography and produce focal volumes lower than expensive microscope objectives. [ABSTRACT FROM AUTHOR]

4H–silicon carbide (SiC) shows the capability of hosting a large number of promising emitters for quantum technology. However, due to its high refractive index, the collection of photoluminescence emission is compromised for further applications. Here, we demonstrate a scalable approach of manufacturing solid-immersion lenses (SILs) on 4H–SiC. The procedure results in SILs with high effective NA. The fluorescence collection efficiency of single quantum emitters under the SILs shows 3.4 times enhancement confirmed by confocal microscopy of individual V 2 . [ABSTRACT FROM AUTHOR]

We present an experimental and theoretical study of the immersing properties of a micron-sized solid immersion lens (μ-SIL) and evaluate its capabilities of functioning as a near-field probe. It was found that the μ-SIL reduces an impinging focused spot by a factor of approximately its refractive index, similarly to a macroscopic solid immersion lens. This reduced immersed spot is used to investigate the visibility of a periodic grating structure. Results show an improvement in the visibility by approximately 30% when compared to confocal microscopy, demonstrating the potential application of these tiny micro-lenses as a near-field probe in scanning microscopy and other high-resolution optical systems. [ABSTRACT FROM AUTHOR]

The refractive index of homogenous particle population can be determined by the so-called immersion liquid method. The idea is to find a known liquid whose refractive index matches the index of the particles. We report on a method that simultaneously obtains the refractive index of particles and that of the immersion liquid. It is based on a system using internal light reflection and Fresnel’s theory. The method includes a series of straightforward reflection measurements and a fitting procedure. The validity of the method was tested with CaF2 particles. The method has applications within scientific studies of microparticles and nanoparticles or micro-organism in suspensions. It can be also be utilized in industry for the detection of the refractive index of products involving particles for the purpose of improvement of product quality. [ABSTRACT FROM AUTHOR]

Solid-state single-photon emitters are key components for integrated quantum photonic devices. However, they can suffer from poor extraction efficiencies, caused by the large refractive index contrast between the bulk material they are embedded in and air: this results in a small fraction (that can be as low as ∼0.1%) of the emitted photons reaching free-space collection optics. To overcome this issue, we present a device that combines a metallic nano-ring, positioned on the sample surface and centered around the emitter, and an epoxy-based super-solid immersion lens, deposited above the ring devices. We show that the combined broadband lensing effect of the nano-ring and the super-solid immersion lens significantly increases the extraction of light emitted by single InAs/GaAs quantum dots into free space: we observe cumulative enhancements that allow us to estimate photon fluxes on the first collecting lens approaching 1 × 106 counts per second, from a single quantum dot in bulk. The combined broad-band enhancement in the extraction of light can be implemented with any kind of classical and quantum solid-state emitter and opens the path to the realisation of scalable bright devices. The same approach can also be implemented to improve the absorption of light, for instance, for small-area broadband photo-detectors. [ABSTRACT FROM AUTHOR]

ZnMgO thin films deposited on (100) Si substrates by RF sputtering were annealed at 800, 900, and 1000°C after phosphorus plasma immersion ion implantation. X-ray diffraction spectra confirmed the presence of (1010) and (1013) peaks for all the samples. However, in case of the annealed samples, the (0002) peak was also observed. Scanning electron microscopy images revealed the variation in surface morphology caused by phosphorus implantation. Implanted and non-implanted samples were compared to examine the effects of phosphorus implantation on the optical properties of ZnMgO. Optical characteristics were investigated by low-temperature (15 K) photoluminescence experiments. Inelastic exciton-exciton scattering and localized, and delocalized excitonic peaks appeared at 3.377, 3.42, and 3.45 eV, respectively, revealing the excitonic effect resulting from phosphorus implantation. This result is important because inelastic exciton-exciton scattering leads to nonlinear emission, which can improve the performance of many optoelectronic devices. [ABSTRACT FROM AUTHOR]

In this paper, a technique for reflection mode immersion 2D laser-ultrasound tomography of solid objects with piecewise linear 2D surface profiles is presented. Pulsed laser radiation was used for generation of short ultrasonic probe pulses, providing high spatial resolution. A piezofilm sensor array was used for detection of the waves reflected by the surface and internal inhomogeneities of the object. The original ultrasonic image reconstruction algorithm accounting for refraction of acoustic waves at the liquid-solid interface provided longitudinal resolution better than 100 μm in the polymethyl methacrylate sample object. [ABSTRACT FROM AUTHOR]

We demonstrate the enhancement of immersion nonlinear ultrasonic testing (NLUT) by exploiting superlattices (SLs). NLUT can detect sub-wavelength micro-structural changes in solids by measuring the fundamental and second harmonic frequencies. The amplitude of second harmonic frequency increases with the presence of defects or other heterogeneities. The immersion NLUT is beneficial as water provides a consistent coupling condition; however, water generates high nonlinearity that can mask the weak non-linearity originated from the micro-structural features in solids. In this research, SLs are proposed to remove the non-linearity arisen from water and experimental instruments. The SLs made of a periodic arrangement of composite layers can provide a band gap to restrict the propagation of a specific range of frequencies between transmitter and receiver. The periodic arrangement of solid-fluid layers is numerically designed and experimentally adapted to the immersion NLUT. Our results imply that the periodic array of 100 μm thick glass and 100 μm thick water layers provides a band gap that blocks 4.5MHz (the second harmonic frequency), while this periodic structure passes 2.25MHz (the first harmonic frequency). The improvement in the sensitivity of the NLUT is demonstrated through detecting the micro-structural changes associated with plastic deformation in aluminum 1100 specimens. It is revealed that the proposed methodology enhances the damage detection sensitivity of immersion NLUT by an order of magnitude as compared to the current practice. [ABSTRACT FROM AUTHOR]

We have developed a method of solid immersion THz imaging—a non-contact technique employing the THz beam focused into evanescent-field volume and allowing strong reduction in the dimensions of THz caustic. We have combined numerical simulations and experimental studies to demonstrate a sub-wavelength 0.35λ0-resolution of the solid immersion THz imaging system compared to 0.85λ0-resolution of a standard imaging system, employing only an aspherical singlet. We have discussed the prospective of using the developed technique in various branches of THz science and technology, namely, for THz measurements of solid-state materials featuring sub-wavelength variations of physical properties, for highly accurate mapping of healthy and pathological tissues in THz medical diagnosis, for detection of sub-wavelength defects in THz non-destructive sensing, and for enhancement of THz nonlinear effects. [ABSTRACT FROM AUTHOR]

We demonstrate the trapping of beads in water with a microfabricated Fresnel zone plate. Beads are loaded onto the microfabricated optical traps using conventional optical tweezers and fluorescence microscopy is used to track bead position. Analysis of the bead position as a function of time is used to determine trapping stiffness. We present experiments showing the three-dimensional trapping of 2 μm diameter beads with trapping stiffnesses that are comparable to conventional optical tweezers when the zone plate efficiency is taken into account. [ABSTRACT FROM AUTHOR]

1700-nm window has been demonstrated to be a promising excitation window for deep-tissue multiphoton microscopy (MPM). Long working-distance water immersion objective lenses are typically used for deep-tissue imaging. However, absorption due to immersion water at 1700 nm is still high and leads to dramatic decrease in signals. In this paper, we demonstrate measurement of absorption spectrum of deuterium oxide (D2O) from 1200 nm to 2600 nm, covering the three low water-absorption windows potentially applicable for deep-tissue imaging (1300 nm, 1700 nm, and 2200 nm). We apply this measured result to signal enhancement in MPM at the 1700-nm window. Compared with water immersion, D2O immersion enhances signal levels in second-harmonic generation imaging, 3-photon fluorescence imaging, and third-harmonic generation imaging by 8.1, 24.8, and 24.7 times with 1662-nm excitation, in good agreement with theoretical calculation based on our absorption measurement. This suggests D2O a promising immersion medium for deep-tissue imaging. [ABSTRACT FROM AUTHOR]

Plasmonic lithography has been used in nanofabrication because of its utility beyond the diffraction limit. The resolution of plasmonic lithography depends on the nano-gap between the nanoaperture and the photoresist surface--changing the gap distance can modulate the line-width of the pattern. In this letter, we demonstrate solid-immersion lens based active non-contact plasmonic lithography, applying a range of gap conditions to modulate the line-width of the pattern. Using a solid-immersion lens-based near-field control system, the nano-gap between the exit surface of the nanoaperture and the media can be actively modulated and maintained to within a few nanometers. The line-widths of the recorded patterns using 15- and 5-nm gaps were 47 and 19.5 nm, respectively, which matched closely the calculated full-width at half-maximum. From these results, we conclude that changing the nano-gap within a solid-immersion lens-based plasmonic head results in varying line-width patterns. [ABSTRACT FROM AUTHOR]

Microsphere-assisted imaging is an extraordinary simple technology that can obtain optical superresolution under white-light illumination. Here, we introduce a method to improve the resolution of a microsphere lens by increasing its numerical aperture. In our proposed structure, BaTiO3 glass (BTG) microsphere lenses are semi-immersed in a S1805 layer with a refractive index of 1.65, and then, the semi-immersed microspheres are fully embedded in an elastomer with an index of 1.4. We experimentally demonstrate that this structure, in combination with a conventional optical microscope, can clearly resolve a two-dimensional 200-nm-diameter hexagonally close-packed (hcp) silica microsphere array. On the contrary, the widely used structure where BTG microsphere lenses are fully immersed in a liquid or elastomer cannot even resolve a 250-nm-diameter hcp silica microsphere array. The improvement in resolution through the proposed structure is due to an increase in the effective numerical aperture by semi-immersing BTG microsphere lenses in a high-refractiveindex S1805 layer. Our results will inform on the design of microsphere-based high-resolution imaging systems. [ABSTRACT FROM AUTHOR]

Solvent immersion imprint lithography (SIIL) was used to directly nanostructure conjugated polymer films. The technique was used to create light-emitting diffractive optical elements and organic semiconductor lasers. Gratings with lateral features as small as 70 nm and depths of ~25 nm were achieved in poly(9,9-dioctylfluorenyl-2,7-diyl). The angular emission from the patterned films was studied, comparing measurement to theoretical predictions. Organic distributed feedback lasers fabricated with SIIL exhibited thresholds for lasing of ~40 kW/cm², similar to those made with established nanoimprint processes. The results show that SIIL is a quick, convenient and practical technique for nanopatterning of polymer photonic devices. [ABSTRACT FROM AUTHOR]

We demonstrate a series of advantages of microsphere-assisted imaging over confocal and solid immersion lens microscopies including intrinsic flexibility, better resolution, higher magnification, and longer working distances. We discerned minimal feature sizes of ~50-60 nm in nanoplasmonic arrays at the illumination wavelength λ=405 nm. It is demonstrated that liquid-immersed, high-index (n~1.9-2.1) spheres provide a superior image quality compared to that obtained by spheres with the same index contrast in an air environment. We estimate that using transparent microspheres at deep UV wavelengths of ~200 nm might make possible imaging of various nanostructures with extraordinary high ~30 nm resolution. [ABSTRACT FROM AUTHOR]

Plasma Immersion Ion Implantation (PIII) is a promising alternative to beam line implantation to produce a single layer of nanocrystals (NCs) in the gate insulator of metal-oxide semiconductor devices. We report herein the fabrication of two-dimensional Si-NCs arrays in thin SiO2 films using PIII and rapid thermal annealing. The effect of plasma and implantation conditions on the structural properties of the NC layers is examined by transmission electron microscopy. A fine tuning of the NCs characteristics is possible by optimizing the oxide thickness, implantation energy, and dose. Electrical characterization revealed that the PIII-produced-Si NC structures are appealing for nonvolatile memories. [ABSTRACT FROM AUTHOR]

This letter reported that a dielectric elastomer actuator (3M VHB), which is immersed in a liquid dielectric bath, is enhanced tremendously in dielectric strength up to 800 MV/m, as compared to 450 MV/m for the actuator operated in air. The bath consists of silicone oil (Dow Corning Fluid 200 50cSt), which is 6.5 times more thermally conductive than air, and it is found able to maintain the actuator at a stable temperature. As a result, the oil-immersed dielectric elastomer actuator is prevented from local thermal runaway, which causes loss of electrical insulation, and consequently avoids the damage by electromechanical instability. [ABSTRACT FROM AUTHOR]

Phosphorus doping of 4H SiC is performed by KrF excimer laser irradiation of 4H SiC immersed in phosphoric acid. Phosphorus is incorporated to a depth of a few tens of nanometers at a concentration of over 1020/cm3 without generating significant crystal defects. Formation of a pn junction diode with an ideality factor of 1.06 is demonstrated. [ABSTRACT FROM AUTHOR]

We show here a technique of soft lithography to microfabricate efficient solid immersion lenses (SIL) out of rubber elastomers. The light collection efficiency of a lens system is described by its numerical aperture (NA), and is critical for applications as epifluorescence microscopy [B. Herman, Fluorescence Microscopy (BIOS Scientific, Oxford/Springer, United Kingdom, 1998). While most simple lens systems have numerical apertures less than 1, the lenses described here have NA=1.25. Better performance can be engineered though the use of compound designs; we used this principle to make compound solid immersion lenses (NA=1.32). An important application of these lenses will be as integrated optics for microfluidic devices. We incorporated them into a handheld rubber microscope for microfluidic flow cytometry and imaged single E. Coli cells by fluorescence. [ABSTRACT FROM AUTHOR]

A method to control the ion current in direct-current plasma-immersion ion implantation (PIII) is reported for low-pressure magnetized inductively coupled plasma. The ion current can be conveniently adjusted by applying bias voltage to the conducting grid that separates plasma formation and implantation (ion acceleration) zones without the need to alter the rf input power, gas flux, or other operating conditions. The ion current that diminishes with an increase in grid bias in magnetized plasmas can be varied from 48 to 1 mA by increasing the grid voltage from 0 to 70 V at 250 kV sample bias and 0.5 mTorr hydrogen pressure. High implantation voltage and monoenergetic immersion implantation can now be achieved by controlling the ion current without varying the macroscopic plasma parameters. The experimental results and interpretation of the effects are presented in this letter. This technique is very attractive for PIII of planar samples that require on-the-fly adjustment of the implantation current at high implantation voltage but low substrate temperature. In some applications such as hydrogen PIII-ion cut, it may obviate the need for complicated sample cooling devices that must work at high voltage. [ABSTRACT FROM AUTHOR]

The sheath thickness in plasma immersion ion implantation has been investigated in the presence of a transverse magnetic field. It has been found that the steady-state sheath thickness increases with increasing magnetic field strength. This result is in line with a simplified model of the sheath in which the steady-state sheath thickness is determined by the plasma density and ion velocity at the sheath edge. These results suggest that a magnetic field may be used to control the high-voltage sheath in plasma immersion ion implantation. [ABSTRACT FROM AUTHOR]

By inducing two-photon absorption within the active layer of a proprietary silicon test chip, we demonstrate here solid-immersion-lens-enhanced nonlinear frequency-variation mapping of a 500-MHz ring oscillator circuit at 1560 nm. This work compares the performance of conventional single-photon linear methodologies against advanced two-photon alternatives and reports a maximum laser-induced change in the oscillator stage-delay of approximately 1 ps, and a signal injection resolution of 260 nm. [ABSTRACT FROM AUTHOR]

A permanent annular magnet positioned at the grounded anode alters the discharge characteristics in enhanced glow discharge plasma immersion ion implantation (EGD-PIII). The nonuniform magnetic field increases the electron path length and confines electron motion due to the magnetic mirror effect and electron-neutral collisions thus occur more frequently. The plasma potential and ion density measured by a Langmuir probe corroborate that ionization is improved near the grounded anode. This hybrid magnetic field EGD-PIII method is suitable for implantation of gases with low ionization rates. [ABSTRACT FROM AUTHOR]

The efficiency of photon collection from optically active defect centers in bulk diamond is greatly reduced by refraction at the diamond-air interface. We report on the fabrication and measurement of a geometrical solution to the problem; integrated solid immersion lenses (SILs) etched directly into the surface of diamond. An increase of a factor of 10 was observed in the saturated count-rate from a single negatively charged nitrogen-vacancy (NV-) within a 5 μm diameter SIL compared with NV-'s under a planar surface in the same crystal. Such a system is potentially scalable and easily adaptable to other defect centers in bulk diamond. [ABSTRACT FROM AUTHOR]

The optical band gap and activation energy of polypropylene (PP) induced by an Ar plasma immersion ion implantation technique were studied in detail. It was revealed that the structural alternation with an increase in polymer chain cross-linking in the ion beam affected layer enhanced the optical properties of PP. The optical band gap, calculated from the transmittance spectra, decreased from 3.44 to 2.85 eV with the Ar plasma ion energy from 10 to 50 keV. The activation energy, determined from the band tail of the transmittance spectra, decreased while the electrical conductivity increased with the Ar plasma ion energy. [ABSTRACT FROM AUTHOR]

The implantation energy and retained dose uniformity in enhanced glow discharge plasma immersion ion implantation (EGD-PIII) is investigated numerically and experimentally. Depth profiles obtained from different samples processed by EGD-PIII and traditional PIII are compared. The retained doses under different pulse widths are calculated by integrating the area under the depth profiles. Our results indicate that the improvement in the impact energy and retained dose uniformity by this technique is remarkable. [ABSTRACT FROM AUTHOR]

In enhanced glow discharge plasma immersion ion implantation that involves a small-pointed anode and large area tabular cathode, the high negative substrate bias acts as the plasma producer and supplies the implantation voltage. An electric field is created to focus the electrons and the electron-focusing field in turn enhances the glow discharge process. The sheath physics is theoretically investigated using numerical simulation based on the multiple-grid particle-in-cell code. Electron focusing is corroborated and the plasma sheath has enough expansion when t=40 μs so that a uniform distribution of the incident ion fluence is attained. [ABSTRACT FROM AUTHOR]

We report on the synthesis of SiGe layers on silicon by gas immersion laser doping. GeCl4 molecules are adsorbed on the surface and further incorporated into the Si top layer by a pulsed laser induced melt/regrowth process. Structural and chemical characterizations of the SiGe layers have been performed by using complementarily Rutherford backscattering spectrometry and x-ray Diffraction which indicate that Ge incorporation in the Si matrix results in a fully strained SiGe layer with gradual Ge concentrations reaching up to 18.5% near the surface. [ABSTRACT FROM AUTHOR]

Surface modification of ZnO nanocombs was performed through a Ti plasma immersion ion implantation (PIII) with low bias voltages ranging from 0 to 5 kV to quench surface-originated exciton emission. The ion energy dependent surface modification on ZnO was investigated using transmission electron microscopy and temperature-dependent photoluminescence (PL). The surface exciton (SX) was clearly identified for the as-grown sample at 4.5 K, and complete quenching was observed for sample treated with 5 kV PIII due to surface state passivation. The SX related surface states were located within 5 nm in depth from the surface corresponding to the implantation depth of 5 kV PIII. Room-temperature PL enhancement of these surface-modified ZnO nanocombs was observed and discussed. The results show that PIII can become a viable technique for nanostructure surface passivation. [ABSTRACT FROM AUTHOR]

The collapse of the ion sheath in front of a dielectric substrate during argon plasma immersion ion implantation is investigated using a Langmuir probe. The probe signals during the buildup and collapse of the ion sheath are recorded from a lime glass substrate with a magnesium metal plate placed on top. The collapsing speed of the ion sheath is shown to strongly depend on the secondary electron emission coefficient of the substrate. The authors’ results show that it is possible to derive secondary electron emission coefficients from insulating materials based on the probe signals. [ABSTRACT FROM AUTHOR]

Plasma immersion ion nitridation is used to produce thin HfO2 films with improved thermal and electrical properties. The film composition is investigated by examining the chemical shifts of the Hf 4f, Si 2p, and N 1s core-level spectra using x-ray photoelectron spectroscopy. The improved thermal stability and interfacial microstructure are further confirmed by high-resolution cross-sectional transmission electron microscopy. Electrical studies show an equivalent oxide thickness of about 1.25 nm, a negligible hysteresis of about 5 mV, and a low fixed charge density. [ABSTRACT FROM AUTHOR]

The application of hemispherical solid immersion lenses (SILs) is an approach to increasing the spatial resolution attainable with infrared (IR) microscopy. A hemispherical SIL forms an image for which the effective numerical aperture and magnification are increased by a factor of the SIL material index of refraction. A microscope designed for exploration of IR SIL imaging based on a hemispherical ZnSe SIL, an InSb focal plane array detector, and a broadband IR laser source is described. The imaging characteristics of this system are reported, including the spatial resolution improvement achieved in the imaging of organic test samples. [ABSTRACT FROM AUTHOR]

A solid immersion lens (SIL) is applied with Raman spectroscopy to selectively analyze strained silicon thin films. The SIL was fabricated using a high index optical fiber, n=1.9. The fabrication allows for integration with an atomic force microscope (AFM) for repeated approach and feedback of the SIL to the surface. The evanescent field emanating from the SIL was investigated using near-field optical microscopy and the decay length was ∼150 nm. This was then combined with a Raman spectrometer coupled to an online AFM having a completely free optical axis permitting optical investigations of opaque samples such as strained silicon. [ABSTRACT FROM AUTHOR]

Rectifying undoped and nitrogen-doped ZnO/p-Si heterojunctions were fabricated by plasma immersion ion implantation and deposition. The undoped and nitrogen-doped ZnO films were n type (n∼1019 cm-3) and highly resistive (resistivity ∼105 Ω cm), respectively. While forward biasing the undoped-ZnO/p-Si, the current follows Ohmic behavior if the applied bias Vforward is larger than ∼0.4 V. However, for the nitrogen-doped-ZnO/p-Si sample, the current is Ohmic for Vforward<1.0 V and then transits to J∼V2 for Vforward>2.5 V. The transport properties of the undoped-ZnO/p-Si and the N-doped-ZnO/p-Si diodes were explained in terms of the Anderson model and the space charge limited current model, respectively. [ABSTRACT FROM AUTHOR]

Polymerase chain reaction (PCR) is performed in the thermal convection created by a micro immersion heater. Instead of repetitive heating and cooling, the temperature gradient induces thermal convection which drives the reaction liquid between hot and cold parts of the chamber. The convection triggers DNA amplification as the DNA melts into two single strands in the hot region and replicates with the use of proteins into twice the amount in the cold region. The constant heater is simply dipped into the reaction solution. Compared to previous experiments, we demonstrate that convective PCR is possible in a robotically accessible open vessel. Our approach compares well with fast PCR cyclers and replicates DNA 500 000 fold within 20 minutes. We reduce the necessary components for PCR to cheap, single-use components and therefore increasing the prospects of bringing PCR to point of care applications—even in third world countries. [ABSTRACT FROM AUTHOR]

A near-field planar solid immersion mirror (PSIM) has been developed and applied to the writing and reading of marks in a phase-change material. Light focusing of a PSIM is realized by a two-dimensional parabolic reflective surface integrated in a planar waveguide. Using a PSIM fabricated out of a waveguide consisting of a 100 nm Ta2O5 core layer and a SiO2 cladding layer on an Al2O3–TiC substrate, we have recorded marks with dimensions of λ/4. [ABSTRACT FROM AUTHOR]

The ion flux on the wafer surface during plasma immersion ion implantation is investigated by three-dimensional simulations and experiments. Due to the finite size of the wafer and its stage, the evolving sheath acts as a lens that focuses the positive ions to distinct regions on the wafer surface. Depending on the sheath profile, two focusing effects are identified. Discrete focusing involves ions entering the sheath from its frontal side and leads to the formation of a passive surface near the wafer edge, while the modal focusing affects ions entering the sheath from the lateral side of the stage and are eventually directed to the wafer center. [ABSTRACT FROM AUTHOR]