Emerging Technologies 2018 Session Listing
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Session B1: Nanoscale Devices and Technologies
Start Time: 13:30, Wednesday, May 09
Room: Sutcliffe B
Chaired by Shankar Rananavare, Portland State University (email@example.com)
- 13:30 Maxime Hugues, CNRS-CRHEA
The development of AlGaN/GaN and ZnMgO/ZnO heterostructures for THz devices
During the last 20 years, wide bandgap materials (GaN and ZnO) have attracted a large interest for electronic and optoelectronic devices. The efforts on nitrides development have successfully allowed the commercialization of efficient blue and white light emitting diodes but also high-frequency and high-power transistors. On the other hand, despite really attractive potential for optoelectronic and sensing applications the development of ZnO devices has been strongly limited by the p-type doping issue.
Unipolar (i.e. only dealing with electrons) emitters and detectors based on quantum cascade structures have been widely developed in "classical" III-V materials. While it allows to fully covering the mid-infrared range, the device performances strongly degrade for the 1-10 Terahertz (THz) spectrum part. Here, we will show how wide bandgap material properties could overcome the intrinsic limitations of the classical material.
First, we will demonstrate that wide bandgap heterostructures fulfill the high control and quality level requirements of quantum cascade devices. This is particularly true for homoepitaxial ZnO since molecular beam epitaxy allows getting defect density, surface roughness, and residual doping, comparable to the state-of-the-art of GaAs. Then, we will give an overview of the main intersubband transition results obtained with these two wide bandgap families.
This work is funded by the French National Agency under "OptoTeraGaN" project (ANR-15-CE24-0002) and by EU commission under the H2020 FET-OPEN program; project "ZOTERAC" FET-OPEN 6655107.
- 13:50 Ji Ung Lee, SUNY Polytechnic Institute
Reconfigurable logic devices in 2D materials
- 14:10 Matthew Spencer, Harvey Mudd College
Evaluating electromechanical sequential logic
Nanoelectromechanical (NEM) switches have a set of switching characteristics which make them intriguing candidates for low power computing, but which make the design of sequential logic difficult. NEM switches display zero off state leakage, which allows NEM circuits to exhibit very low energy per operation, but NEM logic circuits must be designed to accommodate the long mechanical delay of NEM switches. This is especially apparent in sequential logic, where incorporating NEM flip-flops designed in the same way as CMOS flip-flops triples the delay of a well designed NEM pipeline stage. This talk will re-introduce the rudiments of NEM logic circuit design, discuss the challenges of designing NEM flip-flops, survey the NEM flops in literature, propose NEM sequential logic circuits which are capable of preserving the performance of combinational NEM logic, and demonstrate that proposal in simulation using a Verilog- A model of the NEM switch.
- 14:30 Toshiyuki Tsuchiya, Kyoto University
Measurement of energy carrier transportation across fracture fabricated nanogap on MEMS
Energy transportation across narrow gap less than 100nm attracts peoples to develop new nano materials, devices and systems. To investigate and apply the transportation, large (larger than micrometers square) and narrow (less than 100nm) uniform gap is needed but it is difficult to fabricate with conventional micro- and nano-fabrication technologies. We have proposed "fracture fabrication", in which cleavage of single crystal silicon on (111) plane is used. A beam with a notch is fractured by applying a tensile force along longitudinal direction and is separated into two pieces at the notch. The cleavage plane is atomically smooth and corresponding fracture surfaces are identical with each other and conformal gap can be formed. The beam is integrated to a MEMS structure, which may equip various functions, such as an actuator for fracture force generation and gap control after cleavage, a sensor for force, displacement and temperature measurement, and electrodes for current measurement. Using the structure, electron and phonon transportation, as well as attraction force is easily measured just after creating gap. We have succeeded in measuring field emission current through 100nm scale nanogap  and its gap-size dependency.
 A. Banerjee, et al., Jpn. J. Appl. Phys. 56 (2017) 06GF06.
- 14:50 COFFEE BREAK
(Mt. Curie Foyer)
- 15:30 Jan Dubowski, Université de Sherbrooke
Electrical characterization of digitally photocorroding GaAs/AlGaAs quantum well microstructures
Reproducible etching of semiconducting materials with atomic level depth resolution is of high interest to the advancement of technologies addressing fabrication of low-dimensional devices, tunability of their optoelectronic properties and precise control of device surface structure. The so-called digital etching requires specialized and expensive equipment, and relies on ex situ calibration processes. We have proposed that III-V semiconductor materials with negligible dark corrosion could be subjected to a controlled photocorrosion monitored in situ with the photoluminescence (PL) effect. The advantage of this approach is that photo-induced digital etching is achieved without the need of changing the environment — a procedure that, normally, is required for removing the product of a self-limiting reaction. The accumulated results indicate that the digital photocorrosion (DIP) process of GaAs/AlGaAs quantum well microstructures could be carried with sub-monolayer precision and simultaneously monitored with PL. Recently, we have demonstrated that DIP could also be monitored with open circuit potential (OCP) measured between the photocorroding semiconductor surface and an Ag/AgCl reference electrode installed in the sample chamber. The excellent correlation between the position of both PL and OCP maxima that reveal the location of GaAsAlGaAs interfaces, indicates that the DPC process could be monitored in situ for materials that do not exhibit measurable PL emission.
- 15:50 Edmond Cretu, University of British Columbia
with M. Manav and S. Phani
High sensitivity sensing through mode localization in weakly-coupled resonators
Energy (or mode) localization phenomena has been well known in acoustic resonators, and the study of a related concept in solid state physics, the Anderson localization, has led to a Nobel prize. As a symmetry-breaking phenomena, mode localization is extremely sensitive to perturbations induced asymmetries, and it started being exploited in both MEMS sensors or even highly sensitive circuits used in instrumentation. We will discuss the mechanisms of mode localization, and the experimental validation as a measuring technique in both weakly-coupled MEMS resonators and capacitive readout circuits.
- 16:10 Krishna Saraswat, Stanford University
Emerging interconnect technologies for nanoelectronics
Modern electronics has advanced at a tremendous pace over the course of the last half century primarily due to enhanced performance of MOS transistors due to dimension scaling, introduction of new materials and novel device structures. However, while this has enhanced the transistor performance, the opposite is true for the copper interconnects that link these transistors. Looking into the future the relentless scaling paradigm is threatened by the limits of copper/low-k interconnects, including excessive power dissipation, insufficient communication bandwidth, and signal latency for both off-chip and on- chip applications. Many of these obstacles stem from the physical limitations of copper/low-k electrical wires, namely the increase in copper resistivity, as wire dimensions and grain size become comparable to the bulk mean free path of electrons in copper and the dielectric capacitance. Thus, it is imperative to examine alternate interconnect schemes and explore possible advantages of novel potential candidates. This talk will address effects of scaling on the performance of Cu/low-k interconnects, alternate interconnect schemes: carbon nanotubes (CNT), graphene, optical interconnect, three-dimensional (3-D) integration and heterogeneous integration of these technologies on the silicon platform. Performance comparison of these technologies with Cu/low-k interconnects will be discussed.
- 16:30 Clara Santato, École Polytechnique de Montréal
with T. Lan
Electrolyte-gated transistors based on organic semiconductors: bridging redox properties, charge carrier transport and device performance
The n-type organic semiconductor phenyl-C61-butyric acid methyl ester (PCBM), a soluble fullerene derivative well investigated for organic solar cells and transistors, can undergo several successive reversible, diffusion-controlled, one-electron reduction processes.
We exploited such processes to shed light on the correlation between electron transfer properties, ionic and electronic transport as well as device performance in ionic liquid (IL)-gated transistors. IL-gated transistors are a particular type of electrolyte-gated transistors (EGTs), which exploit electrical double layers, forming at the interface between an ion-including medium and a semiconductor, to modulate the electrical conductance in the transistor channel. The high capacitance (typically 10~40 μF cm-2) of thin electrical double layers (ca 2-4 nm- thick) permits to reach high charge carrier density in EGT semiconducting channels (ca 1015 cm-2), at low operating voltages (as low as 0.1-0.5 V).
Our results show that features like the size of the doping ions as well as the presence in their molecular structure of aromatic groups affect the doping mechanism in the transistor channel material. Such mechanism can be two-dimensional (surface-confined) or three- dimensional (bulk) electrochemical doping. 2D doping is expected to be favored with high steric hindrance ions whereas 3D doping is favored by small ions, possibly featuring an aromatic structure facilitating their intercalation in the p-p structure of the organic semiconducting films.
We observed that, if the n-doping of the PCBM is pursued beyond the first electrochemical process, the transistor current vs gate-source voltage plots in the ionic liquid [PYR14][TFSI] feature a maximum that points to the presence of finite windows of high conductivity in IL- gated PCBM transistors.
 T. Lan, F. Soavi, M. Marcaccio, P.-L. Brunner, J. Sayago and C. Santato, Chem Comm. 2018 (DOI: 10.1039/C8CC03090A).  (a) Bryan D. Paulsen and C. Daniel Frisbie, J. Phys. Chem. C., 2012, 116, 3132. (b) D. Ofer, R. M. Crooks and M. S. Wrighton, J. Am. Chem. Soc., 1990, 112, 22.
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