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Plasma-enhanced atomic layer deposition (PEALD) of ultrathin (∼7 nm) slightly Ti-rich Ba x Ti y O z (BTO) films with different Al-doping concentration ([Al]/([Al] + [Ba] + [Ti]) = 0 to 22 at%) was studied. In particular, the effects of Al-doping in BTO on compositional, crystallographic and electrical properties were investigated. Previously, BTO films with a Ti cation composition, [Ti]/([Ba] + [Ti]) = ∼60 at% was reported to be advantageous for crystallization, resulting in superior dielectric properties. These Ti-rich BTO films, however, suffered from high leakage currents, necessitating the change in its crystalline structure as well as elemental composition. By incorporating Al 2 O 3 into the BTO films, the leakage current can be controlled, where the BTO films with an Al-doping concentration of 12 at% showed a leakage current reduced by one order of magnitude compared to un-doped BTO (i.e., ∼10 −7 to ∼10 −6 A/cm 2 at +1.6 V) without a significant drop of the dielectric constant (43,un-doped to 40, Al-doped).

Nanoelectromechanical (NEM) relays show promise in a wide variety of low power applications. NEM relays have near-zero leakage current, in contrast to the relatively high leakage current of nanoscale CMOS transistors, thus enabling hybrid CMOS-NEM relay systems that are more energy efficient. If NEM relays can be fabricated in the back-end-of-line (BEOL) metallization process, they can be added to a CMOS integrated circuit without adding significantly to the die area. In this paper, we demonstrate a CMOS BEOL-compatible fabrication process of NEM relays with protected, buried interconnects. The NEM relay processing steps are at temperatures below 425 °C and all mechanical and chemical processing steps are designed to avoid damage to underlying CMOS transistors. We demonstrate a lateral relay with buried interconnect that switches for more than 1000 cycles with resistances below 300 kΩ in nitrogen at atmospheric pressure.

We demonstrate stable, atomically smooth monolayer oxidation of Si(111) using a remote plasma. Scanning tunneling microscopy (STM) confirms the atomically flat nature of the oxidized surface, while cross-sectional transmission electron microscopy (TEM) proves the monolayer to bilayer oxide thickness. Fourier transform infrared spectroscopy (FTIR) and atomic layer deposition (ALD) indicate oxygen is incorporated onto the silicon surface in the form of Si–O–Si and Si–OH bonds. The incorporation of Si–OH bonds is inferred by using TiCl4, a highly specific ALD precursor, for TiO2 ALD. This plasma technique provides precise control of the surface chemistry and yields abrupt yet stable SiO/Si interfaces. It enables production of atomically flat, ALD-active silicon surfaces that could serve as a well-defined platform for investigation of various surface chemistries via STM. Using this substrate, we present the first ever STM observations of ALD TiO2 on silicon oxide.

This letter describes the manufacture and performance of a monolithic double-layer silicon photonic crystal temperature sensor. The sensor is fabricated on standard silicon wafers using oxide passivation and a combination of isotropic and anisotropic etching, and mounted on the facet of a standard single-mode optical fiber using template-assisted epoxy bonding. The double-layer configuration leads to coupling of the guided resonances in the two photonic crystals and enables sharper resonances and consequently higher temperature sensitivity and better detection limit (0.011 °C) than the single-layer counterpart. We experimentally demonstrate that the sensor has a twofold increased temperature sensitivity in terms of reflectivity change at a fixed wavelength (-0.00576/°C), and report on electromagnetic simulations explaining the enhanced sensor operation. The photonic crystal fabrication method and template-assisted bonding enable batch-fabrication of the sensors. Their small size, robust construction, and fiber interface make the sensors promising for numerous applications, including sensing in harsh environments.

This study uses surface resistance of silicon dioxide and a charge-biased, microshell encapsulated, single-anchored double-ended tuning fork resonator (DETF) to measure relative humidity (RH). As relative humidity increases, the surface resistance of silicon dioxide decreases due to increasing amounts of water adsorbed on the surface. This decrease in surface resistance leads to a faster charge decay from a capacitor. The DETF resonator converts the amount of charge on the capacitor to a frequency shift, via the electrostatic spring softening term. This frequency shift can be characterized by either exponential fitting or slope fitting. The hysteresis was shown to be less than 0.15% RH. The relative humidity is determined from the slope or the decay time constant, with the precision of 1.3 × 10−3% RH for slope fitting and 1.3 × 10−4% RH for exponential fitting.

Laterally actuated polycrystalline silicon nanoelectromechanical (NEM) relays with enhanced electrical properties are presented. Due to surface oxidation of polysilicon in room ambient conditions, the relays have a high contact resistance (> 1 GΩ) that requires high drain bias (3-5 V) to break through. The addition of a platinum sidewall coating reduces the on-resistance and the required drain bias to as low as 3 kΩ and 0.1 V, respectively. The platinum coating's stability is demonstrated by two tests: first, a contact-and-hold test where the relay passes current (~1μA) for up to 155 min and, second, a hot cycling test where the relay survives for over 108cycles . The NEMS relays are simulated using finite-element analysis, and the models are verified against experimental tests. Furthermore, the relays are configured and tested as a 2 : 1 multiplexer to show their potential as a digital logic component.

This paper presents techniques for designing nanoelectromechanical relay-based logic circuits using six-terminal relays that behave as universal logic gates. With proper biasing, a compact 2-to-1 multiplexer can be implemented using a single six-terminal relay. Arbitrary combinational logic functions can then be implemented using well-known binary decision diagram (BDD) techniques. Compared to a CMOS-style implementation using four-terminal relays, the BDD-based implementation can result in lower area without major impact on performance metrics such as delay, and energy (when the relays are scaled to small dimensions). Although it is possible to implement any combinational circuit with a single mechanical delay, the relay count can be significantly reduced for complex logic functions by allowing multiple mechanical delays.

We demonstrate a temperature sensor consisting of a 2-D, Silicon (Si), Photonic Crystal (PC) attached to the facet of a standard single-mode optical fiber. The 2-D PC sensors are fabricated on standard Si wafers, using a single mask and a combination of isotropic and anisotropic etching, and microassembled onto the facets of the optical fibers by Si-welding. The temperature of the Si-PC sensor is monitored by measuring its reflectance spectrum in the 1250 to 1650 nm wavelength range. The measured reflectivity peak shift is 0.11 nm°C in the 100°C to 700°C temperature range. The observed spectral shift and temperature sensitivity are significantly higher than high-temperature fiber Bragg grating sensors, and comparable to long-period fiber gratings sensors. The high sensitivity, combined with compactness and robust structure, give these sensors strong potential for use in harsh environments.

Fiber optic sensors have applications in the measurement of a wide range of physical properties such as temperature, pressure, and refractive index. These sensors are immune to electromagnetic interference, made of high temperature dielectric materials and hence can be deployed in harsh environments where conventional electronics would fail. Photonic crystal (PC) fiber tip sensors are highly sensitive to changes in the refractive index and temperature while remaining compact and robust. In comparison to conventional fiber sensors such as fiber Bragg gratings (FBG) or long period fiber gratings (LPFG), they are attractive in several aspects. PC fiber tip sensors have better sensitivity to refractive index and temperature than FBG sensors and are have much smaller sensing volumes than FBGs and LPFGs. Their small size allows them to combine high sensitivity and structural robustness. The most attractive feature may be that PC fiber tip sensors also return a spectrally rich signal with independently shifting resonances that can be used to extract multiple physical properties of the measurand and distinguish between them. In this paper, we show that the PC fiber tip sensor is highly sensitive to the refractive index and temperature of the environment and that both parameters can be simultaneously determined using multiple wavelengths.

We report on the fabrication and characterization of large-area 2-D square arrays of subwavelength holes in Ag and Al films. Fabrication is based on thermal nanoimprint lithography and metal evaporation, without the need for etching, and is compatible with low-cost, large-scale production. Reflectance spectra for these arrays display an intensity minimum whose amplitude, center wavelength, and line width depend on the geometry of the array and the reflectivity of the metal film. By placing various fluids in contact with the subwavelength aperture arrays, we observe that the center wavelength of the reflectance minimum varies linearly with the refractive index of the fluid with a sensitivity of over 500 nm per refractive index unit. The surface plasmon theory is used to predict sensitivities to refractive index change with accuracies better than 0.5%.

In this paper, we quantitatively investigate with atom probe tomography, the effect of temperature on the interfacial transition layer suboxide species due to the thermal oxidation of silicon. The chemistry at the interface was measured with atomic scale resolution, and the changes in chemistry and intermixing at the interface were identified on a nanometer scale. We find an increase of suboxide (SiOx) concentration relative to SiO2 and increased oxygen ingress with elevated temperatures. Our experimental findings are in agreement with reactive force field molecular dynamics simulations. This work demonstrates the direct comparison between atom probe derived chemical profiles and atomistic-scale simulations for transitional interfacial layer of suboxides as a function of temperature.

Laterally actuated nanoelectromechanical relays with compliant source-drain contacts are presented. The relay sidewalls are coated with a 30 nm-thick conductive layer of titanium nitride (TiN) deposited using atomic layer deposition (ALD). By hollowing the tip of the relay, a flexible sidewall is formed from the thin TiN that results in a larger contact area and therefore improves the contact properties of the relay. This modification improves the on-state resistance (RON) and also provides better stability over a larger number of switching cycles compared to a rigid contact. The results of life-time tests show that the contact resistance increases with the number of switching cycles possibly due to degradation of the contact material. However, flexible contacts show improved contact resistance stability under cyclic contact.

We report the realization of coalescent free-standing ultra-thin (as thin as 5.5 nm) platinum layers deposited via plasma-enhanced atomic layer deposition and their characterization as an uncooled infrared detector. Such thin platinum thermistors enable a responsivity as high as 2 · 107 V/WA, an estimated noise equivalent temperature difference of 163 mK and thermal time constants on the order of 1 ms.

CuPc-based organic thin-film transistor (OTFT) with high-k dielectric HfAlO as gate dielectric prepared by atomic layer deposition has been fabricated. Experimental results show that the HfAlO-OTFT has higher mobility, smaller sub-threshold slope and larger on/off ratio than the HfO 2 sample. All these should be attributed to the addition of Al into the HfO 2 film confirmed by X-ray photoelectron spectroscopy, resulting in improved dielectric and interfacial properties. Moreover, the reliablity of the device upon exposure to air is investigated.

We report the use of an array of electrically gated ~200 nm solid-state pores as nanofluidic transistors to manipulate the capture and passage of DNA. The devices are capable of reversibly altering the rate of DNA capture by over three orders of magnitude using sub-1V biasing of a gate electrode. This efficient gating originates from the counter-balance of electrophoresis and electroosmosis, as revealed by quantitative numerical simulations. Such a reversible electronically-tuneable biomolecular switch may be used to manipulate nucleic acid delivery in a fluidic circuit, and its development is an important first step towards active control of DNA motion through solid-state nanopores for sensing applications.

While the literature is rich with data for the electrical behavior of nanotransistors based on semiconductor nanowires and carbon nanotubes, few data are available for ultrascaled metal interconnects that will be demanded by these devices. Atomic layer deposition (ALD), which uses a sequence of self-limiting surface reactions to achieve high-quality nanolayers, provides an unique opportunity to study the limits of electrical and thermal conduction in metal interconnects. This work measures and interprets the electrical and thermal conductivities of free-standing platinum films of thickness 7.3, 9.8, and 12.1 nm in the temperature range from 50 to 320 K. Conductivity data for the 7.3 nm bridge are reduced by 77.8% (electrical) and 66.3% (thermal) compared to bulk values due to electron scattering at material and grain boundaries. The measurement results indicate that the contribution of phonon conduction is significant in the total thermal conductivity of the ALD films.

We present a sensor capable of detecting solution-based nanoparticles using an optical fiber tip functionalized with a photonic crystal cavity. When sensor tips are retracted from a nanoparticle solution after being submerged, we find that a combination of convective fluid forces and optically-induced trapping cause an aggregation of nanoparticles to form directly on cavity surfaces. A simple readout of quantum dot photoluminescence coupled to the optical fiber shows that nanoparticle presence and concentration can be detected through modified cavity properties. Our sensor can detect both gold and iron oxide nanoparticles and can be utilized for molecular sensing applications in biomedicine., Comment: 13 pages, 5 figures

Nano-Electro-Mechanical (NEM) relays are nano-scale switches that can be mechanically actuated by an electrical signal. Unlike conventional CMOS transistors, NEM relays exhibit zero off-state leakage and very sharp on-off transitions. As a result, NEM relays can be potentially used to design highly energy-efficient digital systems. NEM relays are also excellent candidates for programmable routing switches in Field Programmable Gate Arrays (FPGAs) due to their potentially low on-state resistances despite their long mechanical delays. Low-temperature fabrication of NEM relays creates opportunities for their integration on top of silicon CMOS circuits. Hysteresis properties of NEM relays can enable their use as FPGA programmable routing switches without requiring additional routing SRAM cells. In this talk, we will present an overview of NEM relays and their use in digital system design, and discuss design considerations for hybrid CMOS-NEM FPGAs.

We investigate DNA passage through a nanofluidic transistor (NFT) composed of large diameter nanopores (~200nm) with an embedded metal gate. The nanopores are large enough to be made by currently available photolithography process for manufacturability. We observe that the NFT is capable of electrostatic control of DNA capture rate, the equivalent of current in the electron transistor, with similar operating principle as their electron device counterpart.

This paper demonstrates electrical results of an integrated Si CMOS-electrostatically actuated nanoelectromechanical (NEM) relay circuit. This is an initial step towards realizing previously proposed NEM-CMOS hybrid circuits that predict various benefits compared to CMOS-only circuits. In this work, an e-beam patterned laterally actuated Pt NEM relay is fabricated at CMOS-compatible temperatures (≤ 400 °C) on top of CMOS and is driven by an on-chip CMOS inverter at V DD = 6 V.

Laterally actuated nanoelectromechanical (NEM) relays are implemented using a polysilicon structural layer with hafnium oxide (HfO 2 ) and platinum dual sidewall layers. Atomic layer deposition (ALD) HfO 2 provides electrical isolation between the polysilicon beam structure and the sputtered platinum conductive channel. Dual sidewall devices are demonstrated using a Y-shaped device with two contacts that connect source and drain upon actuation. Fabricated devices show up to 1µA current passing between source and drain without beam current flow, confirming successful isolation.

Unlike a traditional capacitive pressure sensor, which uses the entire deflectable diaphragm as the electrode, this paper proposes the use of reduced electrode area to increase the fractional capacitance change and reduce the device's sensitivity to package stresses. Therefore, in addition to the low temperature sensitivity inherent in capacitive sensing, the proposed pressure sensor helps relax signal conditioning requirements typically associated with capacitive sensor interface circuitry.

We present a technique to increase carbon nanotube (CNT) density beyond the as-grown CNT density. We perform multiple transfers, whereby we transfer CNTs from several growth wafers onto the same target surface, thereby linearly increasing CNT density on the target substrate. This process, called transfer of nanotubes through multiple sacrificial layers, is highly scalable, and we demonstrate linear CNT density scaling up to 5 transfers. We also demonstrate that this linear CNT density increase results in an ideal linear increase in drain−source currents of carbon nanotube field effect transistors (CNFETs). Experimental results demonstrate that CNT density can be improved from 2 to 8 CNTs/μm, accompanied by an increase in drain−source CNFET current from 4.3 to 17.4 μA/μm.

This paper presents an uncooled infrared bolometer using a metal thin film that is formed by atomic layer deposition (ALD). Nanometer-thick freestanding layers enabled by ALD have the potential to improve the performance of bolometers with achieving low thermal conductance and near optimal optical properties. The fabrication and characterization of the first implementation are described as well as the electrical properties of ALD platinum films.

We demonstrate that monolithic 2-dimensional silicon photonic crystals confined to the facet of single-mode optical fibers are capable of determining refractive index and temperature of a sample simultaneously from reflectivity measured at two different wavelengths.

This paper reports on lateral nanoelectromechanical (NEM) relays based on variations of a two- or three-mask titanium nitride (TiN) sidewall stringer process. Electrically isolated TiN perimeter beams are fabricated from stringers formed on the inside walls of polysilicon trenches, yielding 200nm wide TiN fins and 200nm gaps; these dimensions are 3X smaller than the resolution limit of the optical lithography tool (600nm) utilized. The reduction in the operating voltage is about a factor of 5 compared to 600nm wide polysilicon beams. Simple scaling could potentially enable sub-1V operation. Five-terminal NEM relays demonstrate successful switching in both directions over 1000 DC-sweep cycles with low drain bias (100mV).

We demonstrate that monolithic 2-dimensional photonic crystals (PCs) confined to the facet, or tip, of single-mode optical fibers can be designed as highly sensitive temperature sensors. Monolithic 2-D photonic-crystals are fabricated on silicon wafers and subsequently released and micro-assembled onto the tip of optical fibers. The PC's reflection spectrum is modulated by the temperature of the sensor and its environment and shows sensitivity comparable to Fiber Bragg Gratings (FBGs). In contrast to FBGs, the compact sensing element is localized at the tip of the fiber and the active sensor element is a disk of 10µm diameter and 480 nm thickness. The sensor system is made of robust, high-temperature dielectric materials and therefore has the potential to be used for many applications including measurements in harsh environments.

We developed a new process for laser-printing a thin-film magnetic-polymer composite microstructural material directly onto planar silicon substrates and characterized its magnetic and mechanical properties. Using this technique we fabricated cantilever beams 100–2000µm long, 100–500µm wide, and 6–8µm thick. An external magnet was used to demonstrate actuation via magnetic field gradient forces, and a scanner was constructed able to deflect a laser beam 3°. This technique takes advantage of advances in commercial laser printing technology and is suitable for low-cost, low-temperature, large-area MEMS devices and rapid MEMS fabrication on a variety of substrates.

Packaging of microelectromechanical systems (MEMS) is a critical step in the transition from product development to production. This paper presents a robust, hermetically-sealed encapsulation method that can accommodate many traditional MEMS devices by allowing large lateral deflection structures within a clean environment. Using the new technology described in this paper, trench widths ranging from 1?m to 100?m were successfully encapsulated at the wafer level while maintaining devices as thick as 20?m. Devices produced with this method have proven durable enough to withstand harsh post-processing such as dicing and wire bonding. Two different types of MEMS resonators are also discussed, demonstrating the use of both large and small trench widths within the encapsulation.

We report on the experimental observation of the effect of periodic hole arrays in the infrared reflection spectra of suspended polycrystalline silicon carbide (poly-SiC) membranes. The poly-SiC was deposited by low pressure chemical vapor deposition (LPCVD), patterned with contact photolithography, and etched by reactive ion etching (RIE). The spectra are shown to be strongly dependent on the pitch and aperture size of the hole arrays, indicating poly-SiC has promise as a mid-IR optical material.

As Navy warships transition to the "Electric Ship"paradigm, technologies capable of automatically monitoring and remotely controlling the systems involved in distribution of electric power become a significant consideration for reducing manpower, improving reliability and facilitating Distance Support. DRS TCS has developed a network design, the "Networked Intelligent Instrumentation & Control System for Switchboards (NPCS) ", that is capable of providing automated monitoring and control of all the ship power systems from a centralized location. Notably, adding to the cost benefits of the approach, it is achieved through a dedicated Local Area Network (LAN), such as the US Navy's Fiber Optic Data Multiplex System (FODMS). Coupling this proposed system with advancements in current and developing sensor measuring technology also provides increased diagnostic capability and a drastic reduction in sensor component weight when compared with conventional techniques. This synergistic analysis and maintenance network provides a streamlined interface to power distribution equipment while providing an increased level of reliability and the capability to build on a rich feature set including data trending, power consumption analyses, and full reconfiguration of power distribution. It permits rapid reaction to emergency situations and user-friendly maintenance. Most importantly in an era of minimally manned ships, it has the potential to reduce traditional manpower requirements.

The first reported square array of subwavelength holes patterned with nanoimprint lithography in an aluminum film is presented. Optical modes vary linearly with the refractive index of the fluid in contact with the aluminum grating

We report on an Optical Add/Drop Multiplexer designed from a single Arrayed Waveguide Grating and a MEMS optical switch. Three different MEMS switches were tested, the most promising being a potentially integrable binary actuator array.

We demonstrate embedding of chiplets into wafers to bypass the monolithic integration challenges of combining micro-mechanical devices with active circuitry. Dry alignment is provided by passive guide tabs, which are created through polysilicon refill of frontside etched trenches. The guide tabs are compatible with further processing on the wafer. Precision chiplets are created by through-wafer etching. After chiplet drop-in, optical detection provides feedback of chiplet jamming, and horizontal driving of the chiplets finishes the zero insertion force assembly process. We demonstrate less than 2.5 µm of chiplet to substrate alignment error. Theoretical scaling of alignment accuracy reaches numbers comparable to photolithography, allowing high density interconnects for heterogeneous integration without precision manipulators.

We demonstrate a simple and rapid epoxy-based method for transferring photonic crystal cavities to the facets of optical fibers. Passive Si cavities were measured via fiber taper coupling as well as direct transmission from the fiber facet. Active quantum dot containing GaAs cavities showed photoluminescence that was collected both in free space and back through the original fiber. Cavities maintain a high quality factor (2000-4000) in both material systems. This new design architecture provides a practical mechanically stable platform for the integration of photonic crystal cavities with macroscale optics and opens the door for novel research on fiber-coupled cavity devices., Comment: 10 pages, 5 figures

This article describes direct laser printing of thin-film polymer onto rigid substrates for use as an etch mask or liftoff layer in patterning on-chip electrical components. Using this technique, the authors fabricated planar spiral inductors of 12×12mm2 with 2.5–5.5 turns producing series inductance Ls=80–180nH as well as planar interdigitated capacitors of 10×10mm2 with two to nine fingers producing series capacitance Cs=100–1600nF. This technique is a low cost, low temperature, rapid turn around, maskless, resist-free means of patterning device features as small as 130μm.