Research Terms
This nano-acoustic resonator employs a ferroelectric transducer to enable the radio frequency (RF) front-end module necessary for the realization of 5G wireless communication networks. The majority of Americans today use a cellphone as a primary source for wireless communication. Each cellphone has at least 40-50 bulk acoustic resonator-based RF filters; these are used in Wi-Fi, GPS, Bluetooth, data/voice transceivers. In 2018, 440 million users subscribed to wireless carriers in the United States and this number keeps increasing. With the advent of the internet of things, more “smart” cars and household devices are communicating among themselves, and this requires our wireless networks to handle more users/devices at increasingly higher speeds. To prevent interference between devices and to increase data speed significantly, communication networks aim to scale the frequencies of certain wireless communication signals to extremely high frequencies in the millimeter wave (mm-wave) spectrum. In order to enable operation at mm-wave frequencies, the piezoelectric transducers used in the bulk acoustic resonator technology need to be miniaturized to sub-100nm thickness. Available thin-film resonator technology cannot achieve this thickness miniaturization because of their inherent material processing limitations such as nucleation, crystallization and texture development at such low thicknesses. Therefore, on scaling to the mm-wave frequency spectrum, the current piezoelectric films cannot preserve the critical electromechanical properties necessary for the effective operation of resonant devices.
Researchers at the University of Florida have developed a nano-acoustic resonator with a thin film ferroelectric transducer that exhibits superior piezoelectricity even at thicknesses less than 10 nm. This nanoscale resonator technology is capable of extreme frequency scaling, thus enabling 5G mm-wave wireless mobile systems.
Nano-acoustic resonator that achieves extreme frequency scaling for faster, clearer wireless communications
This nano-electro-mechanical (NEM) resonator creates monolithic cm- and mm-wave RF front ends and frequency references for 5G wireless communications systems. Resonators consist of a piezoelectric material in between two electrodes. The frequency of a bulk acoustic resonator is inversely proportional to its piezoelectric film thickness. For a resonator to operate in the mm-wave spectrum, the piezoelectric film thickness must be less than 100nm. This resonator uses an atomically engineered hafnium-zirconium oxide (Hf0.5Zr0.502) ferroelectric transducer. An atomic layer deposition process forms the Hf0.5Zr0.502 layer, ensuring better control of the thickness and uniformity of the film. This layer has a thickness in the range of 2nm to 20nm, well below the maximum thickness limit for mm-wave signal processing. Hf0.5Zr0.502 is already available in the current CMOS process material bank. Thus, with Hf0.5Zr0.502 transducer, this nano-acoustic resonator enables the first monolithic integration of acoustic frequency references/RF filters on chips operating in mm-wave bands.
By employing a transparent inert liquid as the constraining surface, this stereolithography 3D printing system can fabricate even large-scale and ultra-high-aspect features continuously without a need for scaffolding or support. Stereolithography uses photopolymerization to create solid objects. Exposing liquid resin to UV light in specific locations creates a solid object defined by the patterned UV light. In conventional stereolithography approaches, the polymerization of resin occurs at a solid interface (transparent window). The solid interface is needed in order to constrain the liquid resin into a predefined layer thickness. A major disadvantage of polymerization at a solid interface is the adhesion (stiction) of the solid object to the solid window interface. As a consequence, large peel forces must be applied to separate the solid object from the solid window interface. The peel force is proportional to area of the 3D object. These peel forces lead to poor process reliability, failed or defective objects, and a need for support or scaffolding structures to prevent the object from breaking during the fabrication process. In addition, because of the requirement for the peeling process, the object must be grown in discrete layers.
Researchers at the University of Florida have developed a stereolithography 3D printing system that enables polymerization at a liquid interface. This system employs a transparent inert liquid used as a constraining surface during the stereolithography process, in contrast to the solid interface used in conventional approaches. Due to the inherent deformability of the inert liquid, the peel forces of the photopolymerized object from the interface are negligible. In addition, polymerization at a liquid interface allows 3D objects to grow continuously (layer-less) as opposed to layer-by-layer (discrete layers) thus reducing total fabrication time. This system has the advantages of being able to fabricate objects with large-area and ultra-high-aspect features, and it also improves process reliability without a need for support or scaffolding. Fabrication of 3D objects both on the macro and micro scale benefits from photopolymerization at the liquid interface.
Continuous, UV-curing, 3D printer that produces large and ultra-high-aspect ratio layer-less objects
The transparent inert liquid forms a layer adjacent to the liquid resin interface. The inert liquid constrains the liquid resin between the previously polymerized layer. During UV polymerization, the inert liquid remains in its liquid state and prevents a finite thickness of resin directly at the inert liquid-resin interface from being polymerized. Thus, researchers can grow 3D objects continuously without stiction. Minimal stiction during separation from the liquid interface facilitates layer-by-layer printing of an object, resulting in a layer-by-layer growth of the 3D object.
This implantable neural electrode device serves as a potential therapy for patients suffering from a host of neurological disorders in the central or peripheral nervous system. According to a report by the World Health Organization, neurological disorders ranging from migraines to epilepsy and dementia, affect up to one billion people worldwide, and that number is expected to rise as populations age. Researchers at the University of Florida have developed a device that far surpasses any available therapy because it enables unprecedented miniaturization and minimal power consumption. This wireless, implantable system increases health safety and convenience compared to existing external, bulky devices.
A technology in neuroprosthetics that serves as a potential therapy for patients suffering from a host of neurological disorders in the central or peripheral nervous system
This fully-integrated, implantable neural electrode system has low power consumption. The system utilizes an interface with neural tissue for recording, as well as stimulating, neural activity in a research subject or patient. With the use of the flexible substrate as a hybrid platform to integrate the electrodes, the amplification and signal processing electronics, and the wireless transmission and power management electronics, this therapy far surpasses anything currently available. The electrodes are integrated as a single unit with the flexible substrate while the electronics are optimized separately and then hybrid packaged. Constructing the component separately allows for more efficient and cost effective fabrication.
This device uses sensors to accurately and quickly process wall shear-stress in applications for the aircraft industry. The measurement of skin friction drag is vitally important to the aircraft industry, and skin friction drag causes an estimated 50 percent of the total vehicle drag for a typical transport aircraft. The macro-scale measurement systems that are widely in use cannot sufficiently meet the demands for directly obtaining accurate shear stress data. And while optical-MEMS-based laser-Doppler anemometers have shown promise, they lack the ability to generate small measurement volumes in high numbers.
Researchers at the University of Florida have created a floating-element shear stress sensor that allows direct, high temperature measurements of skin friction. This device allows for quick, accurate quantitative measurements and covers high-ranging temperatures, providing advantages in efficiency, applicability, and functionality when compared to available shear-stress sensing systems.
A sensing system that accurately and quickly processes wall shear-stress in aircraft industry applications
This sensing system uses floating-element shear stress sensors that enable the direct, high temperature measurement of skin friction based on geometric and/or interferometric optical techniques. Since they use materials able to transmit, absorb, or reflect optical signals, the sensors maintain functionality at higher temperatures. Additionally, the use of high-temperature materials such as sapphire allows use of the sensing system at a distance for various temperature-sensitive electronics.
This hafnium oxide ferroelectric thin film increases ferroelectricity and thermal retention for manufacturing ferroelectric random-access memory (FeRAM). Ferroelectric random-access memory (FeRAM) is a promising emerging technology. It displays significantly lower operation voltage, read/write times, and higher endurance than flash memory. However, current FeRAM technologies suffer from poor scalability and difficulty integrating into the complementary metal-oxide semiconductor (CMOS) process, an instrumental component of modern wireless communications. Ferroelectric hafnium oxide is a new and growing field offering a solution.
Hafnium oxide-based ferroelectric thin films have been explored over the last decade since discovering silicon-doped hafnium oxide could produce a hysteresis and remanent polarization. In varying the silicone doping, it results in an array of films from ferroelectric to anti-ferroelectric. Ferroelectric hafnium is highly CMOS compatible, with its ultra-thin nature providing excellent scalability for a wide range of applications.
Researchers at the University of Florida have developed a hafnium oxide ferroelectric thin film through in situ hydrogen plasma treatment. It increases the efficacy of ferroelectric film production and ensures higher ferroelectricity and thermal retention.
Hafnium oxide ferroelectric thin films for manufacturing ferroelectric random-access memory (FeRAM), increasing ferroelectricity and thermal retention
Hafnium oxide-based ferroelectric thin films have expanded capabilities for complementary metal-oxide semiconductor (CMOS) applications. Applying oxygen (O2) and the sequential O2, hydrogen (H2) plasma oxidation controls the behavior of the resulting films from anti-ferroelectric to ferroelectric. For the sequential O2, H2 plasma films, the application of the O2 plasma occurs after the precursor pulse, followed by the H2 plasma. Using O2 and sequential O2, H2 plasma during the atomic layer depositions (ALD) offers significant tuning of the film properties from anti-ferroelectric to ferroelectric. It partially reduces the previously deposited oxide, generating oxygen vaccines and enhancing the orthorhombic phase. Adding hydrogen plasma during the atomic layer deposition improves the remanent polarization and thermal retention of the resulting ferroelectric films.
