Growth, Properties, and Applications of Al1-xScxN Thin Films

Member for

3 years
Submitted by lleblanc on Thu, 02/14/2019 - 08:16

Paul Muralt

Electroceramic Thin Films Group, EPFL, Lausanne, Switzerland

The discovery of enhanced piezoelectricity in solid solutions of AlN and ScN [1] is certainly one of the most important events in piezoelectric MEMS. As compared to pure AlN, it brought a crucial factor 2 to 3 improvement in a number of figures of merit governing the performance of MEMS devices. The aim of this tutorial is to give an overview of the present knowledge about this material, its synthesis as thin film, its properties, and demonstrated device performance. Growth issues, phase stability of metastable AlScN, and the disturbing formation of abnormally oriented grains in otherwise perfect (0001)-textured columnar microstructures are addressed.[2] Piezoelectric and dielectric properties obtained from experiments are compared with results from density functional theory.[3] Figure of merits for a number of applications are presented and compared with the ones of AlN and PZT thin films.[4] In ultrasonic devices for communication and sensors, AlScN will replace in many cases AlN. The higher coupling factors allow for the exploitation of new resonator types that previously did not reach a high enough coupling. This is the case for instance with Lamb wave resonators. The strong coupling will also help to push thin film SAW devices for wireless sensors with identification tags. A darker side of AlScN lies in its strong chemical stability. It is in fact difficult to etch the material in a selective way. This hampers for the time being the achievement of precisely patterned structures in microsonic devices with micron feature sizes. In this regard, we have to wait until industrial efforts will overcome this problem.

Is it now the right time for FM MEMS inertial sensors?

Member for

3 years
Submitted by lleblanc on Wed, 01/16/2019 - 11:15

Giacomo Langfelder

Politecnico di Milano

Through a few decades, AM MEMS inertial sensors have seen enormous evolution and progress from the device topology, electronic circuits and packaging points of view, and have historically led the development of micromachining fabrication processes. The continuous demand for new functionalities and fields of application is now challenging some fundamental limits that the traditional capacitive transduction intrinsically shows.

The tutorial will briefly review the physics and working principle behind capacitive AM MEMS accelerometers and gyroscopes, with a focus on typical sources of offset drift and scale-factor drift. A system-level vision will be adopted to clarify trade-offs between sensors parameters (area), electronics parameters (consumption), packaging parameters (pressure and co-integration needs) and final performance (noise, linearity, full-scale).

The discussion will then move to alternative working principles based on frequency modulated sensing, which claim help from the frequency-control community for the development of next-generation inertial units.

Ferroelectric Thin Films for Acoustic Applications

Member for

3 years
Submitted by lleblanc on Wed, 01/16/2019 - 11:14

Ausrine Bartasyte

FEMTO-ST Institute, University of Franche-Comté

The next generation of high –frequency wide-band RF filters or frequency-agile filters are urgently needed for the development of 5G infrastructures/networks/communications. This motivates further development of acoustic wave devices based on piezoelectric/ferroelectric thin films of alkali metal niobates (LiNbO3, LiTaO3, etc.), adapted to the high-frequency applications. In this tutorial, the requirements, challenges and achievements in the ferroelectric thin films and their integration with silicon technology and with acoustic devices will be presented in detail. The basic principles of crystallization and epitaxial/textured film growth used to control the film quality, morphology, roughness and orientation will be introduced. The deposition techniques enabling the control of film composition/nonstoichiometry of volatile alkali metal oxides & the methods of compositional analysis will be compared. Future prospects of potential applications and the expected performances of thin film devices are overviewed, as well.

Resonant Micro/Nanoelectromechanical Systems (M/NEMS) for Quantum Engineering

Member for

3 years
Submitted by lleblanc on Wed, 01/16/2019 - 11:12

Philip Feng

Electrical Engineering, Case School of Engineering, Case Western Reserve University

An essential theme of the ongoing ‘second quantum revolution’ is to realize human-made structures and devices where ‘quantum phenomena’ can be sustained and harnessed to enable radically new approaches to information processing. These require exquisite creation and scalable fabrication of atom-like devices, design and engineering of new information carriers and transduction schemes. Only recently have quantum phenomena been incorporated into technologies for next-generation computers, sensors, and detectors that demonstrate performance characteristics rivaling those of their conventional counterparts, thus promising enormous potential for future quantum technologies. This tutorial aims to capture state-of-the-art knowledge of quantum materials, devices, and technology platforms. It will particularly focus on resonant micro/nanoelectromechanical systems (M/NEMS) in quantum regime, and their roles in quantum signal transduction, metrology, and development of hybrid quantum systems and networks.

Microacoustic Resonators

Member for

3 years
Submitted by lleblanc on Wed, 01/16/2019 - 11:11

Roy Olsson III

Department of Electrical and Systems Engineering at the University of Pennsylvania

This tutorial will cover the fundamentals, design, applications, and different types of microacoustic resonators, including bulk acoustic wave (BAW), piezoelectric Lamb wave, and silicon MEMS resonators. The key microacoustic resonator performance metrics will be identified and related to equivalent circuit models describing the resonator electromechanical response. We will explore the different types of microresonator vibration modes, transduction mechanisms, the different materials used to realize microresonators, and the impact of these choices on microacoustic resonator performance metrics such as electromechanical coupling, quality factor, linearity, thermal stability, and aging. We will discuss how to design microacoustic resonators to achieve a targeted response. Finally, we will learn to synthesize filter and oscillator circuits utilizing microacoustic resonators and to evaluate how microacoustic resonator properties translate to filter and oscillator performance.

Optical Time-Frequency Transfer Over Fiber and Free-Space

Member for

3 years
Submitted by lleblanc on Wed, 01/16/2019 - 11:09

Nathan Newbury

Applied Physics Division at NIST

Optically based methods of time-frequency transfer have been developed to support long distance connections between clocks over both fiber-optic networks and free-space (i.e. the air). As with optical clocks, these methods often exploit the high coherence possible with cavity-stabilized lasers and frequency combs. I will discuss and compare the approaches of optical time-frequency transfer over fiber optics and free space. The tutorial will discuss the basics of fiber-optic based methods, which are now well-developed and varied, and will then focus in more detail on recent work in free-space time-frequency transfer.

Time Transfer and Dissemination Using GNSS

Member for

3 years
Submitted by lleblanc on Wed, 01/16/2019 - 11:08

Stefania Römisch

Department of Electrical and Computer Engineering of University of Colorado at Boulder

The first use of Global Navigation Satellite Systems (GNSS) to compare two clocks at remote location happened more than 30 years ago, using the Global Positioning System (GPS). It allowed an order of magnitude improvement in clock comparisons with respect to Loran-C, with global coverage. Today, GNSS-based time transfer is still the technique used by most timing laboratories contributing to UTC (Universal Coordinate Time) with techniques like carrier-phase and all-in-view that have been developed in addition to the initial common-view method. GNSS also remains the most common means to disseminate UTC, generally using GNSS-disciplined oscillators.

This tutorial will explain the basic mechanism of time transfer using GNSS, with a look at the most recent opportunity of using timing information from satellites belonging to different constellations, and will describe the advantages and limitations of time dissemination using global satellite systems.

Atomic Time Scales

Member for

3 years
Submitted by lleblanc on Wed, 01/16/2019 - 10:49

Gérard Petit

Time Department, BIPM

Realizing a time scale means having at one’s disposal atomic clocks, a measurement system, and the capacity to process data to establish an ensemble time possibly steered on the international reference time UTC. The necessary tools to realize a time scale, mostly related to the algorithms, are reviewed. The tutorial presents in some detail the time scales under the responsibility of the BIPM (TAI, UTC, UTCr and TT(BIPM)) which all provide realizations of Terrestrial Time TT, a coordinate time of the geocentric system. The ensemble of atomic clocks, the time transfer techniques and the algorithms for TAI are presented along with the achieved performance in stability and in accuracy. TAI accuracy is provided by primary frequency standards (mostly Cs fountains) regularly operated in a number of contributing time laboratories and a few secondary frequency standards. Frequency standards also form the basis for TT(BIPM), the ultimate reference time coordinate produced by the BIPM. Finally, some information is given on upcoming and future developments of atomic clocks and time transfer techniques and on their potential impact on atomic timescales.

The Physics of Atomic Clocks

Member for

3 years
Submitted by lleblanc on Wed, 01/16/2019 - 10:47

Eric Burt

Principal Member Technical Staff
Jet Propulsion Laboratory, California Institute of Technology

The basic fundamentals of atomic clocks are derived from work performed by Rabi and Ramsey in the 1930’s on magnetic resonance. In this tutorial we will introduce magnetic resonance as it applies to clocks. In particular we will describe the types of internal atomic states used in atomic clocks and will describe the Bloch sphere and how it can be used to visualize various clock interrogation methods. We will then discuss the underlying principles of several key clock technologies including optical pumping, Lamb-Dicke confinement, laser-cooling, and both neutral atom and ion trapping. Finally, we will cover some of the primary systematic frequency shifts that atomic clocks experience. These include the magnetic Zeeman shift, electric effects such as the AC Stark shift, or light shift and its various orders, collision shifts, and the Doppler shift.

Phase Noise Measurement Techniques

Member for

3 years
Submitted by lleblanc on Wed, 01/16/2019 - 10:46

Archita Hati

Electronics Engineer
Time and Frequency Division of the National Institute of Standards and Technology

Noise, present everywhere, causes a signal source to deviate from its ideal performance. This noise introduces time dependent phase and amplitude fluctuations on the signal. The spectral purity of a frequency source can be characterized in terms of phase modulation (PM) and amplitude modulation (AM) noise. This tutorial will cover the basic theory of modulation noise, the origin of different noise types, and the effects of signal manipulation such as amplification, frequency translation, and multiplication on the spectral purity of a signal. Various phase noise measurement techniques will be discussed, in particular, advantages and drawbacks of the cross-spectrum technique.