Bulletin of the American Physical Society
APS March Meeting 2021
Volume 66, Number 1
Monday–Friday, March 15–19, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session P59: Applications of Semiconductors, Dielectrics, and Complex OxidesLive
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Sponsoring Units: FIAP Chair: Nadine Gergel-Hackett, Mary Baldwin Coll |
Wednesday, March 17, 2021 3:00PM - 3:12PM Live |
P59.00001: Current-voltage characteristics of silicon nitride membranes in solution Itaru Yanagi, Ken-ichi Takeda Recently, the dielectric breakdown of insulating membranes in solution has been utilized to fabricate nanopore sensors for various molecular detection applications. Generally, the breakdown phenomenon of an insulator is thought to be strongly related to the behavior of the current through it. However, until now, the current through an insulating membrane in solution has rarely been measured. In this study, by using thin SiN membranes with large and precisely defined areas, we achieved accurate and reproducible measurements of the current-voltage (I-V) characteristics of SiN membranes in solution. From the shape of the I-V curves and their temperature dependence, the carrier conduction process in the membrane was found to be mainly governed by the Poole-Frenkel emission and tunnel conduction of the electrons which ions in solution transfer to the membrane. In addition, we investigated how the I-V characteristics and breakdown voltage changed in accordance with the changes in the solution pH, solute type, solute concentration and solvent type. |
Wednesday, March 17, 2021 3:12PM - 3:24PM Live |
P59.00002: Elastic Constants of Boron Arsenide and Boron Phosphide Crystals Sushant Mahat, Sheng Li, Hanlin Wu, Pawan Koirala, Bing Lv, David G. Cahill We report the elastic constants of boron arsenide and boron phosphide single crystals derived from Brillouin frequencies measured by picosecond interferometry. The synthesis of BAs and BP with thermal conductivity as high as 1000 and 540 Wm-1K-1, respectively, has made them into promising materials for thermal management. Accurate measurements of elastic constants are needed to assess the accuracy of computational modeling of the lattice dynamics. The crystals are cut and polished in different orientations to access waves travelling along different directions. The orientations of the surface normals are determined using electron backscattering diffraction. We studied the Brillouin frequencies of quasi longitudinal waves in five orientations each of BAs and BP crystals. The propagation directions and acoustic velocities are used to construct Christoffel equations which are then solved for the elastic constants. We report C11, C12, and C44 values of 291 ± 5 GPa, 76 ± 13 GPa, and 173 ± 6 GPa for BAs and 354 ± 5 GPa, 83 ± 15 GPa, and 190 ± 8 GPa for BP. Furthermore, we also demonstrate the utility of PI in studying optical and acoustic attenuation in these crystals. |
Wednesday, March 17, 2021 3:24PM - 3:36PM Not Participating |
P59.00003: Merging Bound States in the Continuum at Off-high Symmetry Points Meng Xiao, Meng Kang Bound states in the continuum (BICs) confine resonances embedded in continuous spectrum by eliminating the radiation loss. Merging multiple BICs provides a promising approach to further reduce the scattering losses caused by the fabrication errors. However, up to now, merging BICs are only limited to /Gamma point which restricts potential applications such as beam steering and directional vector beams. Here we propose a new approach to construct merging BICs at almost an arbitrary point in the reciprocal space. Our approach utilizes the topological feature of the BICs on photonic crystal slab, and we merge a Friedrich-Wintgen BIC and an accidental BIC. The Q factor of the resulting merging BIC decays much slower than both the original Friedrich-Wintgen BIC and accidental BIC. Since Friedrich-Wintgen BICs and accidental BICs are quite common on the band structure, our proposal provides a general approach to realize off-G merging BICs and can boost applications in various directions. |
Wednesday, March 17, 2021 3:36PM - 3:48PM Live |
P59.00004: Geometric tuning of stress in silicon nitride beam resonators David Hoch, Xiong Yao, Menno Poot Silicon nitride is a material with high intrinsic stress, ensuring very high quality factors in micro- and nanomechanical resonators. Typically, the film stress can only be changed via the deposition process. We control the SiN beam stress via the geometry. Our “S”-shaped beams are displaced in the center and thus longer than the distance between the two clamping points. When releasing the beams, they straighten and partially relax their stresses, which influences the dynamics of the devices. We used an integrated Mach-Zehnder interferometer to optically sense the driven motion of the suspended beams and studied the stress-dependence of the eigenfrequencies and quality factors. A clear dependence of the resonance frequency on the initial displacement and length is observed, and the results match finite element simulations. Finally, we studied the influence of different beam shapes on the mechanical properties. These devices will provide more insight in the role of stress in the damping of SiN resonators, and adds geometrically-tunable stress as a new degree of freedom for a variety of experiments in the field of optomechanics, such as synchronization. |
Wednesday, March 17, 2021 3:48PM - 4:00PM Live |
P59.00005: Alloying orthorhombic Ga2O3 with Al2O3 /In2O3 Sierra Seacat, John Lyons, Hartwin Peelaers Ga2O3 is a wide-bandgap semiconductor with promising applications in high-power devices and UV photodetectors. It occurs in several polymorphs, with monoclinic β-gallia as the thermodynamically stable phase. Other polymorphs of Ga2O3 can be stabilized as well, but are less studied. The κ-polymorph is of interest, as it possesses ferroelectric properties and exhibits large spontaneous electrical polarizations. |
Wednesday, March 17, 2021 4:00PM - 4:12PM Live |
P59.00006: Bound Charge Engineering: A Novel Approach to Strengthen Screening in Low-Dimensional Systems Raphaël J. Prentki, Mohammed Harb, Lei Liu, Hong Guo Low-dimensional materials, e.g. 2D semiconductors and nanowires (NWs), have garnered great interest owing to their prospects for nanoelectronics. However, these systems have fewer free charges than 3D counterparts, resulting in weak electrostatic screening. This leads to long depletion lengths at junctions, severe limits on device downscaling, and impairs operation of such systems as tunnel field-effect transistors (TFETs). Chemical doping is typically used to add free charges but compromises material and electrical properties at high concentrations. To resolve this problem, we introduce the idea of bound charge engineering (BCE), a novel approach of engineering surface bound charges to strengthen screening. Established by basic electrostatics, BCE is broadly applicable to low-dimensional systems. Through atomistic quantum transport simulations, we show that BCE greatly increases the on-off ratio and on-state current of silicon NW TFETs and may thereby pave a path toward improved low-power nanotransistors [1]. |
Wednesday, March 17, 2021 4:12PM - 4:24PM Live |
P59.00007: Towards High-Performance Monolayer Semiconductor Transistors with Semimetallic Ohmic Contact Yuxuan Lin, Cong Su, Pin-Chun Shen, Ang-Sheng Chou, Chao-Ching Cheng, Ji-Hoon Park, Ming-Hui Chiu, Ang-Yu Lu, Hao-Ling Tang, Ju Li, Alex K Zettl, Tomas Palacios, Lain-Jong Li, Jeffrey Bokor, Jing Kong Atomically thin two-dimensional (2D) semiconductors have great potential for realizing high-performance electronic devices. However, energy barriers at the metal-semiconductor interface, which fundamentally lead to high contact resistances and poor current-delivery capabilities, have restrained the advancement of 2D semiconductor transistors to date. Here, we report a novel ohmic contact technology between semimetallic bismuth and semiconducting monolayer transition metal dichalcogenides (TMDs) where the gap-state pinning is sufficiently suppressed and degenerate states in the TMD are spontaneously formed in contact with bismuth. Through this approach, we achieve zero Schottky barrier height, a record-low contact resistance (RC) of 123 Ω μm, and a record-high on-state current density (ION) of 1135 μA μm-1 on monolayer MoS2. We also demonstrate that excellent ohmic contacts can be formed on various monolayer semiconductors, including MoS2, WS2, and WSe2. Theoretical investigation show that ION is now limited by the self-heating effect and can be further optimized. This technology unveils the full potential of high-performance monolayer transistors that are on par with the state-of-the-art 3D semiconductors, enabling further device down-scaling and extending Moore’s Law. |
Wednesday, March 17, 2021 4:24PM - 4:36PM Live |
P59.00008: Outstanding dielectric properties of ultra-thin CaF2 dielectric films Chao Wen, Yury Y. llarionov, Werner Frammelsberger, Theresia Knobloch, Fei Hui, Tibor Grasser, Mario Lanza The integration of two-dimensional (2D) materials into microelectronic devices usually suffers from a problematic 2D/3D interface due to the dangling bonds at the 3D dielectric surfaces. One probable solution is to introduce 2D layered dielectrics, such as hexagonal boron nitride (h-BN), to form a clean Van der Waals structure. However, most of the reported h-BN based microelectronic devices are fabricated by non-scalable mechanical exfoliation method. When h-BN is synthesized by a scalable method, chemical vapor deposition (CVD), it shows a large amount of amorphous defects, reducing its dielectric strength. Compared to h-BN, calcium fluoride (CaF2) has a higher dielectric constant and can be deposited by molecular beam epitaxy (MBE) at 250 °C. Furthermore, the surface of CaF2 (111) is terminated by fluorine atoms, which results in a Van der Waals interface between the 2D material and the CaF2 (111). In our work, we found that ultra-thin CaF2 films synthesized by MBE show high homogeneity and low leakage currents. Moreover, CaF2 films show a strong dielectric strength (~ 27.8 ± 1.7 MV/cm), much higher than that of SiO2 (~ 20.3 ± 0.9 MV/cm). These outstanding electrical performances are related to the low amount of defects in the cubic ionic crystalline structure of CaF2. |
Wednesday, March 17, 2021 4:36PM - 4:48PM Live |
P59.00009: Overcoming Acoustoelectric Material Limits of Piezoelectric Resonators using Epitaxial Aluminum Nitride Wenwen Zhao, Mohammad Javad Asadi, Lei Li, Reet T Chaudhuri, Kazuki Nomoto, Huili Grace Xing, James C. Hwang, Debdeep Jena Advanced wireless communication systems require compact and effective filters in the 6-40 GHz frequency range. These frequencies are beyond the capacity of conventional surface acoustic-wave resonators, and are challenging for bulk acoustic-wave resonators. This is mainly because higher frequencies require thinner resonators, but the electrical and mechanical properties of aluminum-nitride thin films deposited by conventional sputtering technique degrade at sub-micrometer thicknesses. Taking advantage of epitaxial aluminum nitride developed for ultraviolet photonics and high-speed electronics, we have explored aluminum-nitride film-bulk acoustic resonators (FBARs) which can operate in the thickness-extension mode up to 40 GHz. These FBARs also provide the unique opportunity for monolithic integration with nitride-based semiconductor and superconductor devices in the future. |
Wednesday, March 17, 2021 4:48PM - 5:00PM Live |
P59.00010: Layer-dependent mechanical properties and enhanced plasticity in the van der Waals chromium trihalide magnets Fernando Cantos-Prieto, Alexey Falin, Martin Alliati, Dong Qian, Rui Zhang, Tao Tao, Matthew Barnett, Elton Santos, Luhua Li, Efren A Navarro-Moratalla The knowledge of the mechanical properties of 2D magnets provides valuable information for the development of magneto-mechanic theory and the construction of optimal strain-modulated magnetic devices. Despite seminal works studying the effect of pressure in 2D magnets, there has been no experimental study on the intrinsic mechanical properties of the chromium trihalides to the date. Here we report the room temperature values of the Young’s modulus and the fracture strength of CrI3 and CrCl3 from bulk down to the few-layer limit. The materials show a Young’s modulus (~50 GPa) / breaking strength (~5 GPa) ratio comparable to the best 2D materials, 50 times above that of any other polycrystalline bulk material, withstanding maximum strains of 6.5%. This enlarges the possibilities of application in mechanical and magnetostrictive devices, so far highly restricted to the semiconducting 2D materials. At the same time, these results place the bulk counterparts of the two atomically-thin crystals as strong candidates to show an enhanced plastic behavior, which we have qualitatively tested in the bulk form of the crystals. |
Wednesday, March 17, 2021 5:00PM - 5:12PM Live |
P59.00011: Localization of Filaments in Resistive Switching Devices by Ion Irradiation Nareg Ghazikhanian, Javier del Valle, Pavel Salev, Yoav Kalcheim, Coline Adda, Ivan Schuller Resistive switching (RS) in transition metal oxides could find applications in a wide range of electronic devices, from conventional binary memories to artificial neurons and synapses for hardware-level neuromorphic computing. Often, the RS occurs by the formation of low-resistance filaments that percolate between the device electrodes. Because the filaments appear at different locations and follow different paths in different devices, the device-to-device variability could be very large. This presents a serious challenge for building large-scale RS circuits. In this talk, we introduce a novel approach of using focused ion beam irradiation to “guide” the filament formation. We use the RS in vanadium oxides as a case study. We show that both the position and the shape of the filament could be controllably adjusted by a relatively low dose of Ga+ ion irradiation. Our work demonstrates that local irradiation is an efficient tool for fine-tuning the RS properties, which could provide a general solution in solving the device-to-device variability problem. |
Wednesday, March 17, 2021 5:12PM - 5:24PM Live |
P59.00012: Graphene based pH sensing with extremely high sensitivity Son Le, Seulki Cho, Arvind Balijepalli, Curt Richter We have reported pH sensors based on two-dimensional (2D) MoS2 dual-gated field-effect transistors (2D-MoS2 dual-FETs) with sensitivity that greatly surpasses the Nernst limit of 59 mV/pH [1]. To further improve device performance, we replaced the 2D-MoS2 channel with graphene which has a higher maximum quantum capacitance, higher current drive, and lower contact resistance. Our graphene dual-FETs featured asymmetric front-gate (ionic liquid) and back-gate (300 nm SiO2) capacitances which allowed a quantum capacitance limited signal amplification of up to ~500, a record result for a dual-FET with the given back-gate oxides. The low contact resistance of the graphene dual-FETs enables the devices to operate with two orders of magnitude lower drain voltage than comparable MoS2 devices. We benchmark graphene dual-FETs against 2D-MoS2 dual-FETs in sensitive pH measurements. The higher sensitivity, combined with a lower limit of detection make graphene dual-FETs a powerful tool for field monitoring of pH with wide ranging applications in biology, environmental monitoring and agriculture. |
Wednesday, March 17, 2021 5:24PM - 5:36PM Live |
P59.00013: Transfer-free fabrication of bottom-up graphene nanoribbon transistors Zafer Mutlu, Juan P Llinas, Peter Herman Jacobse, Ilya Piskun, Raymond Blackwell, Michael F Crommie, Felix Fischer, Jeffrey Bokor Bottom-up synthesis of graphene nanoribbons (GNRs) provides atomically precise control of widths and edges that give rise to a wide range of electronic properties promising for high-performance field-effect transistors (FETs). However, since the bottom-up synthesis commonly takes place on catalytic metallic surfaces, the integration of GNRs into such devices requires transfer onto insulating substrates, which remains one of the bottlenecks in the field. Here we present a transfer-free method for the placement of seven-atom wide armchair GNRs on insulators substrates. The method involves growing the GNRs on a thin gold film deposited onto an insulating layer followed by gentle wet etching of the gold, which leaves the nanoribbons to settle in place on the underlying insulating substrate. The structural integrity of the nanoribbons on the gold films is examined using Raman spectroscopy and scanning tunneling microscopy (STM), while Raman measurements after etching of the gold verify that the ribbons remain intact on the insulating substrate. We also demonstrate the transfer-free fabrication of short-channel ∼20 nm FETs with the nanoribbons. The on-state current performance is comparable to the transistors fabricated via the much less scalable transfer process. |
Wednesday, March 17, 2021 5:36PM - 5:48PM On Demand |
P59.00014: Enhanced band-to-band tunneling in direct-gap group-IV Ge1-xSnx alloys: impact of alloy band mixing Michael D. Dunne, Christopher Broderick, Mathieu Luisier, Eoin O'Reilly The indirect band gap of Ge limits applications in several classes of devices. Band structure engineering via alloying with Sn has demonstrated direct-gap behaviour, allowing to develop Si-compatible post-CMOS devices such as tunneling field-effect transistors (TFETs) [1]. |
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