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On-Demand CMOS-Compatible Fabrication of Ultrathin Self-Aligned SiC Nanowire Arrays
摘要： The field of semiconductor nanowires (NWs) has become one of the most active and mature research areas. However, progress in this field has been limited, due to the difficulty in controlling the density, orientation, and placement of the individual NWs, parameters important for mass producing nanodevices. The work presented herein describes a novel nanosynthesis strategy for ultrathin self-aligned silicon carbide (SiC) NW arrays (≤ 20 nm width, 130 nm height and 200–600 nm variable periodicity), with high quality (~2 ? surface roughness, ~2.4 eV optical bandgap) and reproducibility at predetermined locations, using fabrication protocols compatible with silicon microelectronics. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopic ellipsometry, atomic force microscopy, X-ray diffractometry, and transmission electron microscopy studies show nanosynthesis of high-quality polycrystalline cubic 3C-SiC materials (average 5 nm grain size) with tailored properties. An extension of the nanofabrication process is presented for integrating technologically important erbium ions as emission centers at telecom C-band wavelengths. This integration allows for deterministic positioning of the ions and engineering of the ions’ spontaneous emission properties through the resulting NW-based photonic structures, both of which are critical to practical device fabrication for quantum information applications. This holistic approach can enable the development of new scalable SiC nanostructured materials for use in a plethora of emerging applications, such as NW-based sensing, single-photon sources, quantum LEDs, and quantum photonics.
关键词： silicon carbide,telecom wavelengths,nanofabrication,self-aligned nanowires,ultrathin nanowires,quantum photonics
更新于2025-09-10 09:29:36
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Optoelectronic properties of high-Si-content-Ge <sub/> 1 <i>?x</i> – <i>y</i> </sub> Si <sub/><i>x</i> </sub> Sn <i> <sub/>y</sub></i> /Ge <sub/> 1? <i>x</i> </sub> Sn <sub/><i>x</i> </sub> /Ge <sub/> 1? <i>x–y</i> </sub> Si <sub/><i>x</i> </sub> Sn <sub/><i>y</i> </sub> double heterostructure
摘要： The optoelectronic properties of Ge1?x?ySixSny/Ge1?xSnx/Ge1?x?ySixSny double heterostructures pseudomorphically grown on a Ge substrate were investigated. The photoluminescence (PL) intensity of the sample with Ge0.66Si0.23Sn0.11 cladding layers is three times larger compared to PL from structure with a Ge cladding layer, which can be attributed to higher energy band offsets at both conduction and valence band edges at the Ge0.91Sn0.09/Ge0.66Si0.23Sn0.11 interface. The PL spectrum of the sample with the Ge0.66Si0.23Sn0.11 cladding layer at room temperature can be deconvoluted into four components, and the origins of these components can be assigned to direct and indirect transitions by measuring the temperature dependence of each component’s intensity. In addition, we examined the formation and characterization of strain-relaxed Ge1?x?ySixSny/Ge1?xSnx/Ge1?x?ySixSny double heterostructures to relieve the compressive strain in the Ge1?xSnx layer. Stacking faults were observed in the Ge1?xSnx and Ge1?x?ySixSny layers. The PL peak intensity of the strain-relaxed Ge1?xSnx layer decreases by a factor of 1/20 compared to the PL peak intensity of the double heterostructure pseudomorphically grown on a Ge(001) substrate. In addition, PL intensity can be increased by post-deposition annealing owing to decreasing defects.
关键词： silicon,germanium,photoluminescence,heterostructure,tin
更新于2025-09-10 09:29:36
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Electronic structures and spectroscopic signatures of silicon-vacancy containing nanodiamonds
摘要： The presence of midgap states introduced by localized defects in wide-band-gap-doped semiconductors can strongly affect the electronic structure and optical properties of materials, generating a wide range of applications. Silicon-divacancy defects in diamond have been recently proposed for probing high-resolution pressure changes and performing quantum cryptography, making them good candidates to substitute for the more common nitrogen-vacancy centers. Using group-theory and ab initio electronic structure methods, the molecular origin of midgap states, zero-phonon line splitting, and size dependence of the electronic transitions involving the silicon-vacancy center is investigated in this paper. The effects of localized defects on the Raman vibrational and carbon K-edge x-ray absorption spectra are also explored for nanodiamonds. This paper presents an important analysis of the electronic and vibrational structures of nanosized semiconductors in the presence of midgap states due to localized defects, providing insight into possible mechanisms for modulating their optical properties.
关键词： midgap states,electronic structure,optical properties,nanodiamonds,Raman vibrational spectra,quantum cryptography,x-ray absorption spectra,silicon-vacancy defects
更新于2025-09-10 09:29:36
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Investigation of the performance of strain-engineered silicon nanowire field effect transistors (?-Si-NWFET) on IOS substrates
摘要： In the current work, a design space for developing the performance enhanced strain-engineered Si nanowire field-effect-transistors has been provided. The fraction of insertion of the nanowire channel into the Insulator-on-Silicon substrate with judicious selection of high-k gate insulators is used as the key design parameter. The combined effect of fractional insertion and gate insulators results in inducing stress into the nanowire channel and, depending on their selection, it changes from tensile to compressive. Such induced-stress alters the existing inherent phononic-stress, leading to the modification of the carrier transport in the device channel. The carrier transport behavior in such partially embedded nanowire FETs has been modeled by incorporating the relevant stress-related effects into the indigenously developed self-consistent quantum-electrostatic framework. These equations are solved by employing the non-equilibrium Green’s function formalism. The study shows the phonon scattering under tensile strain to occur at the expense of electron energy; however, the electrons can also gain energy during such scattering in compressive stress. Thus, the device current has been observed to increase with tensile stress and it achieves relatively smaller values when the inherent tensile phononic stress is balanced by the induced compressive stress. However, the current is finally observed to increase once the compressive stress overcomes the inherent tensile phononic stress. In general, the present devices exhibit promising Ion/Ioff ratio for all of the fractional insertions and gate dielectrics with a maximum Ioff of <10 nA/μm, threshold voltage of sub-0.3 V, gm of ～104 μS/μm, sub-threshold swing of ～100 mV/dec, and drain-induced-barrier-lowering of ～100 mV/V.
关键词： IOS substrates,high-k gate insulators,strain-engineered,silicon nanowire,non-equilibrium Green’s function,quantum-electrostatic framework,field-effect transistors
更新于2025-09-10 09:29:36
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Enhanced surface passivation of predictable quantum efficient detectors by silicon nitride and silicon oxynitride/silicon nitride stack
摘要： In this paper, we investigate three different passivating films for use in predictable quantum efficient detectors: two monolayer films of SiNx with different compositions and one double-layer stack of SiNxOy capped with SiNx, all deposited on very high resistivity silicon substrates. In addition to the conventional characterization methods, we also utilize the novel method of photoluminescence imaging under applied bias (PL-V) and high voltage soaking to modulate the fixed charge density Qf in the layers. All films exhibit very good passivating properties after deposition and annealing, with the oxynitride stack providing the best passivation, resulting in an effective carrier lifetime close to 20 ms. This value is explained by a relatively high fixed charge density of Qf = 1.12 × 1012 cm?2 and low interface defect density (S0,n = 6.0 × 102 cm/s), giving a chemical passivation which is an order of magnitude better than the investigated nitrides. Both nitride films were readily charged by voltage soaking, increasing the effective carrier lifetime by about 20%. Based on the passivating properties, photodetector device simulations predict that self-induced photodiodes made with any of these passivation layers will have an internal quantum deficiency well below 1 ppm for selected wavelengths at room temperature, and all the investigated materials are thus good candidates for use as passivating layers in such photodiodes.
关键词： photoluminescence imaging,surface passivation,silicon nitride,high voltage soaking,predictable quantum efficient detectors,silicon oxynitride
更新于2025-09-09 09:28:46
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Characterization of Evanescent Field Gas Sensor Structures Based on Silicon Photonics
摘要： Photonic sensors that operate in the mid-infrared spectral range are an emerging field for photonic microsystems. In this paper, we present a photonic gas sensor concept based on silicon waveguides using infrared evanescent field absorption. The waveguides were specifically designed for CO2 sensing at a wavelength of λ = 4.26 μm as possible application for the proposed sensor platform. The waveguide cross section as well as the substructure were investigated using finite-element simulations and the devised structures were fabricated using mass fabrication processes exclusively. In order to evaluate the potential for long interaction path lengths using polysilicon strip waveguides, a study on the intrinsic losses of polysilicon waveguides was conducted. The lowest intrinsic damping that was obtained for polysilicon strip waveguides was 3.98 dB/cm. Furthermore, the sensing capability of the devised waveguides was tested with quantitative CO2 measurements down to a concentration of 500 ppm CO2. From the quantitative measurements, the evanescent field ratio was estimated and was in the range between η = 14%–16%.
关键词： integrated silicon photonics,intrinsic losses,evanescent field absorption,silicon waveguide,Optical gas sensing
更新于2025-09-09 09:28:46
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Integrated Beam Scanning Silicon Lens Antenna at Submillimeter Wavelengths
摘要： This paper presents a lens antenna that scans the beam using an integrated piezo-motor at submillimeter wave frequencies. The lens antenna is based on the concept presented in [1], a leaky wave waveguide feed in order to achieve wide angle scanning and seamless integration with the receiver. The lens is translated from the origin of the waveguide producing the scanning of the beam over a 50 deg Field of View (FoV) (or about 6.25 beamwidths) with a maximum scanning loss of 1 dB. The lens movement is achieved with a piezoelectric motor that is integrated within the antenna and receiver block. A prototype was built and measured at 550 GHz achieving scanning beam angles close to 20 degrees with only 0.6 dB of loss. The scanning of the 50 deg FoV, which corresponds to a lens displacement of approximately 2 mm, takes about 0.9 s achieving a scanning rate of 0.75 Hz of the FoV. The accuracy in continuous mode of the piezo actuator has been measured to be less than 28μm in the worse of cases for displacements of 2 mm, which corresponds to a beam steering of 0.76 deg, much smaller than the antenna half power beamdwith of 8 deg.
关键词： leaky-wave waveguide feed,piezo-motor,Beam-scanning,submillimeter-wave,silicon lens
更新于2025-09-09 09:28:46
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Effect of deposition rate on the growth mechanism of microcrystalline silicon thin films using very high frequency PECVD
摘要： The intrinsic microcrystalline silicon thin films were deposited by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD). Two series of films with different deposition rate 0.30 nm/s and 1.94 nm/s were prepared. The film surface and gas phase reaction growth processes were monitored with real-time spectroscopic ellipsometry and optical emission spectroscopy. The effect of deposition rate on the microcrystalline silicon thin film growth mechanism has been studied. The microcrystalline silicon surface growth was analyzed with KPZ model. The results show that the growth exponent of β is 0.448 for the films with low deposition rate, and the growth exponent of β is 0.302 for the films with high deposition rate. The growth exponent does not increase with deposition rate, but declines. And the reasons for this phenomenon were explained.
关键词： Real time spectroscopic ellipsometry,Microcrystalline silicon,High rate deposition,Optical emission spectrum,Growth mechanism
更新于2025-09-09 09:28:46
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Three-mode multiplexer and demultiplexer utilizing trident and multimode couplers
摘要： In this paper, a simultaneous three-mode silicon (de)multiplexer using a trident coupler and a 3×3 multimode interference (MMI) is presented. The fundamental (TE0), first-order (TE1), and second-order (TE2) modes at the input are successfully demultiplexed and converted to three uniform fundamental modes (TE0) at the output ports. The device is designed and optimized by numerical simulation using three-dimensional beam propagation method together with effective index method. The three-mode (de)multiplexing is achieved over the whole C-band with small insertion loss (<0.9 dB) and crosstalk (<?17 dB). The proposed device also features with a small footprint (5 μm×400 μm) and a large fabrication tolerance against chip-size variations while maintaining the desired optical performance.
关键词： silicon photonics,Mode-division multiplexing,Y-junction coupler,planar lightwave circuits,mode conversion,multimode interference coupler
更新于2025-09-09 09:28:46
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Big Potential From Silicon-Based Porous Nanomaterials: In Field of Energy Storage and Sensors
摘要： Silicon nanoparticles (SiNPs) are the promising materials in the various applications due to their unique properties like large surface area, biocompatibility, stability, excellent optical and electrical properties. Surface, optical and electrical properties are highly dependent on particle size, doping of different materials and so on. Porous structures in silicon nanomaterials not only improve the specific surface area, adsorption, and photoluminescence efficiency but also provide numbers of voids as well as the high surface to volume ratio and enhance the adsorption ability. In this review, we focus on the significance of porous silicon/mesoporous silicon nanoparticles (pSiNPs/mSiNPs) in the applications of energy storage, sensors and bioscience. Silicon as anode material in the lithium-ion batteries (LIBs) faces a huge change in volume during charging/discharging which leads to cracking, electrical contact loss and unstable solid electrolyte interphase. To overcome challenges of Si anode in the LIBs, mSiNPs are the promising candidates with different structures and coating of different materials to enhance electrochemical properties. On the basis of optical properties with tunable wavelength, pSiNPs are catching good results in biosensors and gas sensors. The mSiNPs with different structures and modified surfaces are playing an important role in the detection of biomarkers, drug delivery and diagnosis of cancer and tumors.
关键词： lithium ion battery,silicon nanomaterials,bioapplication,porous structures,core shell
更新于2025-09-09 09:28:46