| 1. |
- Banuazizi, Seyed Amir Hossein, et al.
(author)
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Order of magnitude improvement of nano-contact spin torque nano-oscillator performance
- 2017
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In: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 9:5, s. 1896-1900
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Journal article (peer-reviewed)abstract
- Spin torque nano-oscillators (STNO) represent a unique class of nano-scale microwave signal generators and offer a combination of intriguing properties, such as nano sized footprint, ultrafast modulation rates, and highly tunable microwave frequencies from 100 MHz to close to 100 GHz. However, their low output power and relatively high threshold current still limit their applicability and must be improved. In this study, we investigate the influence of the bottom Cu electrode thickness (t(Cu)) in nano-contact STNOs based on Co/Cu/NiFe GMR stacks and with nano-contact diameters ranging from 60 to 500 nm. Increasing t(Cu) from 10 to 70 nm results in a 40% reduction of the threshold current, an order of magnitude higher microwave output power, and close to two orders of magnitude better power conversion efficiency. Numerical simulations of the current distribution suggest that these dramatic improvements originate from a strongly reduced lateral current spread in the magneto-dynamically active region.
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| 2. |
- A. M. Naiini, Maziar, 1980-
(author)
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Horizontal Slot Waveguides for Silicon Photonics Back-End Integration
- 2014
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Doctoral thesis (other academic/artistic)abstract
- This thesis presents the development of integrated silicon photonic devices. These devices are compatible with the present and near future CMOS technology. High-khorizontal grating couplers and waveguides are proposed. This work consists of simulations and device design, as well as the layout for the fabrication process, device fabrication, process development, characterization instrument development and electro-optical characterizations.The work demonstrates an alternative solution to costly silicon-on-insulator photonics. The proposed solution uses bulk silicon wafers and thin film deposited waveguides. Back-end deposited horizontal slot grating couplers and waveguides are realized by multi-layers of amorphous silicon and high-k materials.The achievements of this work include: A theoretical study of fully etched slot grating couplers with Al2O3, HfO2 and AIN, an optical study of the high-k films with spectroscopic ellipsometry, an experimental demonstration of fully etched SiO2 single slot grating couplers and double slot Al2O3 grating couplers, a practical demonstration of horizontal double slot high-k waveguides, partially etched Al2O3 single slot grating couplers, a study of a scheme for integration of the double slot Al2O3 waveguides with selectively grown germanium PIN photodetectors, realization of test chips for the integrated germanium photodetectors, and study of integration with graphene photodetectors through embedding the graphene into a high-k slot layer.From an application point of view, these high-k slot waveguides add more functionality to the current silicon photonics. The presented devices can be used for low cost photonics applications. Also alternative optical materials can be used in the context of this photonics platform.With the robust design, the grating couplers result in improved yield and a more cost effective solution is realized for integration of the waveguides with the germanium and graphene photodetectors.
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| 3. |
- Banuazizi, Seyed Amir Hossein, et al.
(author)
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Control of thermal budget in nanocontact spin-torque nano-oscillators
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Other publication (other academic/artistic)abstract
- We investigate the influence of the bottom Cu electrode thickness (tCu) in nanocontact spin-torque nano-oscillators (NC-STNOs) based on Si/SiO2/Pd(8)/Cu(tCu)/Co(8)/Cu(7)/NiFe(4.5)/Cu(3)/Pd(3) GMR stacks on the thermal budget of the magnetodynamically active region. Increasing tCu from 10 to 70 nm results in a ~50% reduction in Joule heating in both the Co and NiFe layers, which directly improves the microwave output stability and linewidth. Numerical simulations of the NC-STNO current distribution suggest that this improvement originates from a strongly reduced lateral current spread in the top ferromagnetic layer and a reduction in the device's resistance.
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| 4. |
- Li, Jiantong, et al.
(author)
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Inkjet Printing of MoS2
- 2014
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In: Advanced Functional Materials. - : Wiley-VCH Verlagsgesellschaft. - 1616-301X .- 1616-3028. ; 24:41, s. 6524-6531
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Journal article (peer-reviewed)abstract
- A simple and efficient inkjet printing technology is developed for molybdenum disulfide (MoS2), one of the most attractive two-dimensional layered materials. The technology effectively addresses critical issues associated with normal MoS2 liquid dispersions (such as incompatible rheology, low concentration, and solvent toxicity), and hence can directly and reliably write uniform patterns of high-quality (5-7 nm thick) MoS2 nanosheets at a resolution of tens of micrometers. The technology efficiency facilitates the integration of printed MoS2 patterns with other components (such as electrodes), and hence allows fabricating various functional devices, including thin film transistors, photoluminescence patterns, and photodetectors, in a simple, massive and cost-effective manner while retains the unique properties of MoS2. The technology has great potential in a variety of applications, such as photonics, optoelectronics, sensors, and energy storage.
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| 5. |
- Naiini, Maziar M., et al.
(author)
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ALD high-k layer grating couplers for single and double slot on-chip SOI photonics
- 2012
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In: Solid-State Electronics. - : Elsevier BV. - 0038-1101 .- 1879-2405. ; 74, s. 58-63
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Journal article (peer-reviewed)abstract
- State of the art grating couplers for horizontal single and double slot waveguides are presented; in these devices the input signal is transmitted from a single mode optical fiber to silicon on insulator slot waveguide. In the waveguides, atomic layer deposited (ALD) high-k dielectrics form the low refractive index slot. It is demonstrated that a fully etched design combined with precision of ALD result in highly reproducible devices with theoretical efficiency variations less than 1%. Devices have a peak calculated coupling efficiency of 24% at 1.55 mu m. In order to achieve an optimal design, optical properties of high-k films are studied by spectroscopic ellipsometry. Measured refractive indices show variations from reference values, originated from film variation in densities. Chips with a test slot material are fabricated and the optical efficiency of the couplers is characterized. The maximum measured coupling efficiency of the couplers is 18.5%.
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| 6. |
- Naiini, Maziar M., et al.
(author)
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CMOS compatible ALD high-k double slot grating couplers for on-chip optical interconnects
- 2012
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In: Solid-State Device Research Conference (ESSDERC), 2012 Proceedings of the European. - : IEEE. - 9781467317078 ; , s. 93-96
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Conference paper (peer-reviewed)abstract
- Silicon-on-insulator(SOI) novel on-chip grating couplers for double slot high-k waveguides are experimentally demonstrated. The devices were fabricated with standard CMOS process technology. The grating couplers were designed for the best performance at the C-band communication range. Two thin layers of aluminum oxide formed the slot region of the waveguide. The high-k layers were deposited using the atomic layer deposition (ALD) method. A reliable process was realized by etching the structures to the buried oxide. Effect of the top oxide cladding layer on the efficiency was studied. The grating couplers had a measured efficiency of 22% at 1.55μm wavelength. This efficiency is competitive to other results reported by other groups.
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| 7. |
- Naiini, Maziar M., et al.
(author)
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Double slot high-k waveguide grating couplers for silicon photonics
- 2012
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In: Device Research Conference (DRC), 2012 70th Annual. - : IEEE. - 9781467311618 ; , s. 69-70
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Conference paper (peer-reviewed)abstract
- Novel on-chip double slot high-k waveguide grating couplers have been successfully fabricated, and characterized. Silicon cannot yet be directly used for light generation and modulation in photonic devices because of its weak nonlinear optical effects. Slot waveguide is a solution to this problem, this structure consists of silicon and low refractive index material layers as the active material[1, 2]. Previously, grating couplers were demonstrated for horizontal single slot SiO 2 waveguides [3, 4]. Double slot waveguide is of great interest since the confinement of the optical power in the active material is significantly larger. Atomic layer deposited (ALD) high-k aluminum oxide (Al 2O 3) was used as the slot layer because of a superior layer quality and thickness uniformity. The ultimate goal of this work is the demonstration of the highly reproducible on-chip photonic devices.
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| 8. |
- Naiini, Maziar M., et al.
(author)
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Embedded Graphene Photodetectors for Silicon Photonics
- 2014
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In: Device Research Conference (DRC), 2014 72nd Annual. - : IEEE conference proceedings. - 9781479954056 ; , s. 43-44
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Conference paper (peer-reviewed)abstract
- Graphene has extraordinary electronic and optoelectronic properties such as high carrier mobility, large charge-carrier concentrations, tunability via electrostatic doping, wavelength-independent absorption, and relatively low dissipation rates [1]. The combination of its electro-optical properties with its manufacturability and CMOS integrability makes graphene an extremely promising candidate for active photonic devices [2,3]. Because of its two-dimensional appearance, graphene has a limited light absorption, which is not enough to fulfill the requirements of silicon photonics technology. Recently, the integration of graphene with silicon waveguides [4,5] has been shown for on-chip applications [6]. In these solutions graphene is placed on top and outside of the waveguide yielding only limited light-graphene interaction. We introduce novel photo-detector architecture by embedding CVD-graphene inside the slot layer of deposited high-k slot waveguides that are compatible with back-end-of-the-line manufacturing of photonic integrated circuits (PICs). This approach leads to a high light-graphene interaction due to the high mode concentration in the slot region[7]. This results in enhanced absorption and enables a very compact photodetector design.
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| 9. |
- Naiini, Maziar M., et al.
(author)
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Integrating 3D PIN germanium detectors with high-k ALD fabricated slot waveguides
- 2014
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In: ULIS 2014 - 2014 15th International Conference on Ultimate Integration on Silicon. - : IEEE Computer Society. ; , s. 45-48
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Conference paper (peer-reviewed)abstract
- A novel device technology for photonics integrated circuits (PICs) is presented. In this work germanium PIN photodetectors are embedded in back-end deposited high-k slot waveguides. The waveguides are fabricated using chemical vapor deposited amorphous silicon and atomic layer deposition of Al 2O3 thin films. The germanium PIN stack is selectively grown on a bulk silicon substrate. The detectors are butt coupled to the slot waveguides. Using our selective germanium growth and interconnect technology we study a 3D multilayer photonic integration for CMOS back-end of the line (BEOL) process. Finally we demonstrate the fabrication of a photonic chip deploying this technology platform.
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