Showing papers on "Silicon nitride published in 2018"

Excellent corrosion protection performance of epoxy composite coatings filled with silane functionalized silicon nitride

Abstract: Silicon nitride was firstly used as anticorrosive pigment in organic coatings. An effective strategy by combining inorganic fillers and organosilanes was used to enhance the dispersibility of silicon nitride in epoxy resin. The formed nanocomposites were applied to protect Q235 carbon steel from corrosion. The anticorrosive performance of modified silicon nitride with silane (KH-570) was investigated by electrochemical impedance spectroscopy (EIS), water absorption and pull-off adhesion methods. With the increase of immersion time, the corrosion resistance as well as adhesion strength of epoxy resin coating and unmodified silicon nitride coating decreased significantly. However, for the modified silicon nitride coating, the corrosion resistance and adhesion strength still maintained 5.7×1010 Ω cm2 and 7.6 MPa after 2400-h and 1200-h immersion, respectively. The excellent corrosion resistance performance could be attributed to the chemical interactions between KH-570 functional groups and silicon nitride powders, which mainly came from the easy formation of Si-O-Si bonds. Furthermore, the modified silicon nitride coating formed a strong barrier to corrosive electrolyte due to the hydrophobic of modified silicon nitride powder and increased bonds.

Nanophotonic Pockels modulators on a silicon nitride platform

Abstract: Silicon nitride (SiN) is emerging as a competitive platform for CMOS-compatible integrated photonics. However, active devices such as modulators are scarce and still lack in performance. Ideally, such a modulator should have a high bandwidth, good modulation efficiency, low loss, and cover a wide wavelength range. Here, we demonstrate the first electro-optic modulators based on ferroelectric lead zirconate titanate (PZT) films on SiN, in both the O-band and C-band. Bias-free operation, bandwidths beyond 33 GHz and data rates of 40 Gbps are shown, as well as low propagation losses (α ≈ 1 dB cm−1). A half-wave voltage-length product of 3.2 V cm is measured. Simulations indicate that further improvement is possible. This approach offers a much-anticipated route towards high-performance phase modulators on SiN. Active devices such as modulators made of silicon nitride still lack performance. Here, the authors demonstrate electro-optic modulators based on ferroelectric lead zirconate titanate films on silicon nitride, in both the O- and the C-band with a modulation bandwidth beyond 33 GHz and with data rates of 40 Gbps.

Photonic Damascene Process for Low-Loss, High-Confinement Silicon Nitride Waveguides

Abstract: We report on fabrication of high-confinement and low loss silicon nitride ( $\text{Si}_{3}\text{N}_{4}$ ) waveguides using the photonic Damascene process. This process scheme represents a novel fabrication approach enabling reliable, wafer-scale fabrication of high-confinement optical waveguides. A reflow step of the silica preform reduces sidewall scattering to values not attainable with conventional etching, and reduces losses and backscattering significantly, resulting in a waveguide attenuation of 5.5 dB/m. We discuss the critical aspects of the process in detail and demonstrate the fabrication of high stress $\text{Si}_{3}\text{N}_{4}$ waveguides with unprecedentedly large dimensions ( $\text{1.75}\,\mu \text{m} \times \text{1.425}\,\mu \text{m}$ ) providing high-confinement at midinfrared wavelengths. A device characterization strategy allowing for systematic extraction of statistically relevant loss values is discussed and reveals the effects of the sidewall smoothing.

Efficient and Stable CsPbBr3 Quantum-Dot Powders Passivated and Encapsulated with a Mixed Silicon Nitride and Silicon Oxide Inorganic Polymer Matrix.

Abstract: Despite the excellent optical features of fully inorganic cesium lead halide (CsPbX3) perovskite quantum dots (PeQDs), their unstable nature has limited their use in various optoelectronic devices. To mitigate the instability issues of PeQDs, we demonstrate the roles of dual-silicon nitride and silicon oxide ligands of the polysilazane (PSZ) inorganic polymer to passivate the surface defects and form a barrier layer coated onto green CsPbBr3 QDs to maintain the high photoluminescence quantum yield (PLQY) and improve the environmental stability. The mixed SiNx/SiNxOy/SiOy passivated and encapsulated CsPbBr3/PSZ core/shell composite can be prepared by a simple hydrolysis reaction involving the addition of adding PSZ as a precursor and a slight amount of water into a colloidal CsPbBr3 QD solution. The degree of the moisture-induced hydrolysis reaction of PSZ can affect the compositional ratio of SiNx, SiNxOy, and SiOy liganded to the surfaces of the CsPbBr3 QDs to optimize the PLQY and the stability of CsPbB...

Photonic chip for laser stabilization to an atomic vapor with 10 −11 instability

Abstract: Devices based on spectroscopy of atomic vapors can measure physical quantities such as magnetic fields, RF electric fields, time and length, and rotation and have applications in a broad range of fields including communications, medicine, and navigation. We present a type of photonic device that interfaces single-mode silicon nitride optical waveguides with warm atomic vapors, enabling precision spectroscopy in an extremely compact (<1 cm3) package. We perform precision spectroscopy of rubidium confined in a micro-machined, 27 mm3 volume, vapor cell using a collimated free-space 120 μm diameter laser beam derived directly from a single-mode silicon nitride waveguide. With this optical-fiber integrated photonic spectrometer, we demonstrate an optical frequency reference at 780 nm with a stability of 10−11 from 1 to 104 s. This device harnesses the benefits of both photonic integration and precision spectroscopy for the next generation of quantum sensors and devices based on atomic vapors.

Nonlinear optics on silicon-rich nitride—a high nonlinear figure of merit CMOS platform [Invited]

Abstract: CMOS platforms with a high nonlinear figure of merit are highly sought after for high photonic quantum efficiencies, enabling functionalities not possible from purely linear effects and ease of integration with CMOS electronics. Silicon-based platforms have been prolific amongst the suite of advanced nonlinear optical signal processes demonstrated to date. These include crystalline silicon, amorphous silicon, Hydex glass, and stoichiometric silicon nitride. Residing between stoichiometric silicon nitride and amorphous silicon in composition, silicon-rich nitride films of various formulations have emerged recently as promising nonlinear platforms for high nonlinear figure of merit nonlinear optics. Silicon-rich nitride films are compositionally engineered to create bandgaps that are sufficiently large to eliminate two-photon absorption at telecommunications wavelengths while enabling much larger nonlinear waveguide parameters (5x–500x) than those in stoichiometric silicon nitride. This paper reviews recent developments in the field of nonlinear optics using silicon-rich nitride platforms, as well as the outlook and future opportunities in this burgeoning field.

Surface modulation of silicon nitride ceramics for orthopaedic applications

Abstract: IntroductionSilicon nitride (Si3N4) is a ceramic material presently implanted during spine surgery. It has a fortunate combination of material properties such as high strength and fracture toughnes...

Integrated High-Q Crystalline AlN Microresonators for Broadband Kerr and Raman Frequency Combs

Abstract: Development of planar-integrated microresonators with high quality factors (Q’s) is crucial for nonlinear photonics in a robust chip. Compared with silicon and silicon nitride, aluminum nitride (AlN) features intrinsic quadratic and cubic susceptibilities as well as an enormous band gap (∼6.2 eV), making it ideal for nonlinear optical interactions. However, sputtered polycrystalline AlN is susceptible to scattering and defect-related absorption losses, thereby inducing limited Q-factors. Here, we demonstrate single-crystalline AlN epitaxially grown on sapphire as a novel nonlinear platform for broadband chip-scale frequency comb generation. We fabricate an AlN-on-sapphire microring with a high loaded Q-factor of 1.1 × 106 and achieve a pure broadband Kerr comb with observable spectral lines ranging from ∼145 to 275 THz and a low parametric threshold of ∼25 mW. As crystalline AlN exhibits strong Raman gain, we further investigate the influence of stimulated Raman scattering (SRS) on four-wave mixing (FWM) ...

Carrier-Induced Degradation in Multicrystalline Silicon: Dependence on the Silicon Nitride Passivation Layer and Hydrogen Released During Firing

Abstract: Carrier-induced degradation (CID) of multicrystalline silicon (mc-Si) solar cells has been receiving significant attention; however, despite this increasing interest, the defect (or defects) responsible for this degradation has not been determined yet. Previous studies have shown that the surface passivation layer and the firing temperature have a significant impact on the rate and extent of this degradation. In this paper, we further study this impact through an investigation of the CID behavior of the mc-Si wafers passivated with six different silicon nitride layers, each fired at four different peak temperatures. At low firing temperatures, no significant difference in the CID was identified between the samples with different passivation layers; however, a large range of degradation extents was observed at higher firing temperatures. Using Fourier transform infrared spectroscopy, a correlation was found between the degradation extent and the amount of hydrogen released from the dielectric during firing. We verified that no degradation of the surface passivation quality occurred, indicating that the degradation is primarily associated with a bulk defect.

Achieving Ultralow Wear with Stable Nanocrystalline Metals.

Abstract: Recent work suggests that thermally stable nanocrystallinity in metals is achievable in several binary alloys by modifying grain boundary energies via solute segregation. The remarkable thermal stability of these alloys has been demonstrated in recent reports, with many alloys exhibiting negligible grain growth during prolonged exposure to near-melting temperatures. Pt-Au, a proposed stable alloy consisting of two noble metals, is shown to exhibit extraordinary resistance to wear. Ultralow wear rates, less than a monolayer of material removed per sliding pass, are measured for Pt-Au thin films at a maximum Hertz contact stress of up to 1.1 GPa. This is the first instance of an all-metallic material exhibiting a specific wear rate on the order of 10-9 mm3 N-1 m-1 , comparable to diamond-like carbon (DLC) and sapphire. Remarkably, the wear rate of sapphire and silicon nitride probes used in wear experiments are either higher or comparable to that of the Pt-Au alloy, despite the substantially higher hardness of the ceramic probe materials. High-resolution microscopy shows negligible surface microstructural evolution in the wear tracks after 100k sliding passes. Mitigation of fatigue-driven delamination enables a transition to wear by atomic attrition, a regime previously limited to highly wear-resistant materials such as DLC.

Annealing-free Si3N4 frequency combs for monolithic integration with Si photonics

Abstract: Silicon-nitride-on-insulator (SiNOI) is an attractive platform for optical frequency comb generation in the telecommunication band because of the low two-photon absorption and free carrier induced nonlinear loss when compared with crystalline silicon. However, high-temperature annealing that has been used so far for demonstrating Si3N4-based frequency combs made co-integration with silicon-based optoelectronics elusive, thus reducing dramatically its effective complementary metal oxide semiconductor (CMOS) compatibility. We report here on the fabrication and testing of annealing-free SiNOI nonlinear photonic circuits. In particular, we have developed a process to fabricate low-loss, annealing-free, and crack-free Si3N4 740-nm-thick films for Kerr-based nonlinear photonics featuring a full process compatibility with front-end silicon photonics. Experimental evidence shows that micro-resonators using such annealing-free silicon nitride films are capable of generating a frequency comb spanning 1300–2100 nm via optical parametrical oscillation based on four-wave mixing. This work constitutes a decisive step toward time-stable power-efficient Kerr-based broadband sources featuring full process compatibility with Si photonic integrated circuits on CMOS lines.

Encapsulated Silicon Nitride Nanobeam Cavity for Hybrid Nanophotonics

Abstract: Most existing implementations of silicon nitride photonic crystal cavities rely on suspended membranes due to their low refractive index. Such floating membranes are not mechanically robust, making them suboptimal for developing a hybrid optoelectronic platform where new materials, such as layered 2D materials, are transferred onto prefabricated optical cavities. To address this issue, we design and fabricate a silicon nitride nanobeam resonator where the silicon nitride membrane is encapsulated by material with a refractive index of ∼1.5, such as silicon dioxide or PMMA. The theoretically calculated quality factor of the cavities can be as large as 105, with a mode-volume of ∼2.5(λ/n)3. We fabricated the cavity and measured the transmission spectrum with the highest quality factor reaching 7000. We also successfully transferred monolayer tungsten diselenide on the encapsulated silicon nitride nanobeam and demonstrated coupling of the cavity with both the monolayer exciton and the defect emissions.

Broadband transparent and CMOS-compatible flat optics with silicon nitride metasurfaces [Invited]

Abstract: Metasurface optics is a promising candidate for realizing the next generation of miniaturized optical components. Unlike refractive optics, these devices modify light over a wavelength-scale thickness, changing the phase, amplitude, and polarization. This review details recent developments and state-of-the-art metasurfaces realized using silicon nitride. We emphasize this material as to date it has the lowest refractive index with which metasurfaces have been experimentally demonstrated. The wide band gap of silicon nitride enables reduced absorption over a broad wavelength range relative to its higher index counterparts, providing a CMOS-compatible platform for producing a variety of high efficiency metasurface elements and systems.

Efficient third-harmonic generation in composite aluminum nitride/silicon nitride microrings

Abstract: Aluminum nitride and silicon nitride have recently emerged as important nonlinear optical materials in integrated photonics for their quadratic and cubic optical nonlinearity, respectively. A composite aluminum nitride and silicon nitride waveguide structure, if realized, will simultaneously allow highly efficient second- and third-harmonic generation on the same chip platform and therefore assists 2f-3f self-referenced frequency combs. On-chip third-harmonic generation, being a higher-order nonlinear optics effect, is more demanding than second-harmonic generation due to the large frequency difference between the fundamental- and third-harmonic frequencies, which implies a large change of refractive indices and more stringent requirements on phase matching. In this work we demonstrate high-efficiency third-harmonic generation in a high-Q composite aluminum nitride/silicon nitride ring cavity. By carefully engineering the microring resonator geometry of the bilayer structure to optimize the quality factor, mode volume, and modal overlap of the optical fields, we report a maximum conversion efficiency of 180% W−2, corresponding to an absolute conversion efficiency of 0.16%. This composite photonic chip design provides a solution for efficient frequency conversion over a large wavelength span, broadband comb generation, and self-referenced frequency combs.

Area-Selective Atomic Layer Deposition of TiN, TiO2, and HfO2 on Silicon Nitride with inhibition on Amorphous Carbon

Abstract: The demand for transistors and memory devices with smaller feature sizes and increasingly complex architectures furthers the need for advanced thin film patterning techniques. A prepatterned, sacrificial layer can be used as a template for bottom-up fill of new materials which would otherwise be difficult to pattern using traditional top-down lithographic methods. This work investigates initial growth of TiN, TiO2, and HfO2 thin films during thermal atomic layer deposition (ALD) onto a high density, amorphous carbon (aC) sacrificial layer. ALD of TiN by TiCl4/NH3 at 390 °C, TiO2 by Ti(OCH3)4/H2O at 250 °C, and HfO2 by HfCl4/H2O at 300 °C on as-deposited aC films resulted in uninhibited, continuous thin film growth. We find that carbon surface reduction and passivation using a H2 plasma resulted in delayed film coalescence for TiN, TiO2, and HfO2 on the aC. After 200 TiN cycles on H2 plasma-treated aC, Rutherford backscattering spectrometry shows Ti levels below the detection limit (8 × 1013 at/cm2), where...

Characterization of Hybrid InP-TriPleX Photonic Integrated Tunable Lasers Based on Silicon Nitride (Si 3 N 4 /SiO 2 ) Microring Resonators for Optical Coherent System

Abstract: We demonstrate detailed characterization results of a hybrid InP-TriPleX photonic integrated tunable laser based on silicon nitride microring resonators. A tuning range of 50 nm across the C-band, side-mode suppression ratio (SMSR) >50 dB, high output power (∼10 dBm), linewidth of <80 kHz across the whole tuning range, and μs switching speed are achieved. The delayed self-heterodyne (DSH) method is used for the linewidth measurement, the lowest linewidth can be achieve is ∼35 kHz. The FM noise spectrum is also measured to show the 1/f noise and white noise characterization. Furthermore, the device demonstrates performance comparable with commercial external cavity lasers in 64-QAM coherent system.

High-efficiency hybrid amorphous silicon grating couplers for sub-micron-sized lithium niobate waveguides

Abstract: We demonstrate hybrid amorphous silicon uniform grating couplers for efficient coupling between the standard single-mode fiber and sub-micron lithium niobate waveguides. The grating couplers exhibit coupling efficiency of −3.06 dB and 1-dB bandwidth of 55 nm. The amorphous silicon grating couplers can also provide a universal building block applicable to other photonic platforms such as silicon nitride waveguides, whose moderate refractive index values prevent high efficiency grating couplers to be fabricated in the native waveguide.

Silicon-Based Optical Mirror Coatings for Ultrahigh Precision Metrology and Sensing.

Abstract: Thermal noise of highly reflective mirror coatings is a major limit to the sensitivity of many precision laser experiments with strict requirements such as low optical absorption. Here, we investigate amorphous silicon and silicon nitride as an alternative to the currently used combination of coating materials, silica, and tantala. We demonstrate an improvement by a factor of $\ensuremath{\approx}55$ with respect to the lowest so far reported optical absorption of amorphous silicon at near-infrared wavelengths. This reduction was achieved via a combination of heat treatment, final operation at low temperature, and a wavelength of $2\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$ instead of the more commonly used 1550 nm. Our silicon-based coating offers a factor of 12 thermal noise reduction compared to the performance possible with silica and tantala at 20 K. In gravitational-wave detectors, a noise reduction by a factor of 12 corresponds to an increase in the average detection rate by three orders of magnitude ($\ensuremath{\approx}{12}^{3}$).

Nonlinear silicon nitride waveguides based on a PECVD deposition platform.

Abstract: In this work, we present a nonlinear silicon nitride waveguide. These waveguide are fabricated by readily available PECVD, conventional contact UV-lithography and high-temperature annealing techniques, thus dramatically reducing the processing complexity and cost. By patterning the waveguide structures firstly and then carrying out a high-temperature annealing process, not only sufficient waveguide thickness can be achieved, which gives more freedom to waveguide dispersion control, but also the material absorption loss in the waveguides be greatly reduced. The linear optical loss of the fabricated waveguide with a cross-section of 2.0 × 0.58 µm2 was measured to be as low as 0.58 dB/cm. The same loss level is demonstrated over a broad wavelength range from 1500 nm to 1630 nm. Moreover, the nonlinear refractive index of the waveguide was determined to be ~6.94 × 10−19 m2/W, indicating that comparable nonlinear performance with their LPCVD counterparts is expected. These silicon nitride waveguides based on a PECVD deposition platform can be useful for the development of more complicated on-chip nonlinear optical devices or circuits.

Characteristic Study of Silicon Nitride Films Deposited by LPCVD and PECVD

Abstract: This paper analyzes and compares the characteristics of silicon nitride films deposited by low pressure chemical vapor deposition (LPCVD) and plasma enhanced chemical vapor deposition (PECVD), with special attention to the hydrogenation and chemical composition of silicon nitride films. Three different LPCVD processes at various DCS and NH3 gas flow rates and deposition temperatures, together with PECVD using SiH4 and NH3 and ICP CVD using SiH4 and N2, were compared. The silicon nitride film deposition rate decreases with an increasing NH3/DCS ratio in LPCVD, which also leads to an increase in the refractive index and a decrease in the residual stress in the film. There is nearly no hydrogen incorporated in the LPCVD films, which differs from PECVD and ICP CVD that show significant Si-H and N-H bonds. The chemical composition of silicon nitride films is mostly Si-rich, except for the LPCVD process at high NH3/DCS ratio with near stoichiometric chemistry.

Counter-rotating cavity solitons in a silicon nitride microresonator.

Abstract: We demonstrate the generation of counter-rotating cavity solitons in a silicon nitride microresonator using a fixed, single-frequency laser. We demonstrate a dual three-soliton state with a difference in the repetition rates of the soliton trains that can be tuned by varying the ratio of pump powers in the two directions. Such a system enables a highly compact, tunable dual comb source that can be used for applications such as spectroscopy and distance ranging.

Effect of Stress and Temperature on the Optical Properties of Silicon Nitride Membranes at 1,550 nm

Abstract: Future gravitational-wave detectors operated at cryogenic temperatures are expected to be limited by thermal noise of the highly reflective mirror coatings. Silicon nitride is an interesting material for such coatings as it shows very low mechanical loss, a property related to low thermal noise, which is known to further decrease under stress. Low optical absorption is also required to maintain the low mirror temperature. Here, we investigate the effect of stress on the optical properties at 1,550 nm of silicon nitride membranes attached to a silicon frame. Our approach includes the measurement of the thermal expansion coefficient and the thermal conductivity of the membranes. The membrane and frame temperatures are varied, and translated into a change in stress using finite element modeling. The resulting product of the optical absorption and thermo-optic coefficient (dn/dT) is measured using photothermal common-path interferometry.

Plasma enhanced atomic layer deposition (PEALD) of SiN using silicon-hydrohalide precursors

Abstract: Methods for forming silicon nitride films are provided. In some embodiments, silicon nitride can be deposited by atomic layer deposition (ALD), such as plasma enhanced ALD. One or more silicon nitride deposition cycle comprise a sequential plasma pretreatment phase in which the substrate is sequentially exposed to a hydrogen plasma and then to a nitrogen plasma in the absence of hydrogen plasma, and a deposition phase in which the substrate is exposed to a silicon precursor. In some embodiments a silicon hydrohalide precursors is used for depositing the silicon nitride. The silicon nitride films may have a high side-wall conformality and in some embodiments the silicon nitride film may be thicker at the bottom of the sidewall than at the top of the sidewall in a trench structure. In gap fill processes, the silicon nitride deposition processes can reduce or eliminate voids and seams.

Deuterated silicon nitride photonic devices for broadband optical frequency comb generation.

Abstract: We report and characterize low-temperature, plasma-deposited deuterated silicon nitride films for nonlinear integrated photonics. With a peak processing temperature less than 300°C, it is back-end compatible with complementary metal-oxide semiconductor substrates. We achieve microresonators with a quality factor of up to 1.6×106 at 1552 nm and >1.2×106 throughout λ=1510–1600 nm, without annealing or stress management (film thickness of 920 nm). We then demonstrate the immediate utility of this platform in nonlinear photonics by generating a 1 THz free-spectral-range, 900 nm bandwidth modulation-instability microresonator Kerr comb and octave-spanning, supercontinuum-broadened spectra.

Silicon nitride-on-silicon bi-layer grating couplers designed by a global optimization method.

Abstract: Silicon nitride-on-silicon bi-layer grating couplers were designed for the O-band using an optimization-based procedure that accounted for design rules and fabricated on a 200 mm wafer. The designs were sufficiently robust to fabrication variations to function well across the wafer. A peak fiber-to-chip coupling efficiency to standard single mode fiber of -2.2 dB and a 1-dB bandwidth of 72.9 nm was achieved in the representative device. Over several chips across the wafer, we measured a median peak coupling efficiency of -2.1 dB and median 1-dB bandwidth of 70.8 nm. The measurements had good correspondence with simulation.