Fundamental/theoretical Understanding of the RRAM Switching Mechanism (Hynix)

Principal Investigator: Yoshio Nishi

Team: Yoshio Nishi, Blanka Magyari-Kope and Daniel Duncan

Scope: This project aims at in-depth understanding of RRAM switching mechanism, leading to predictive accelerated retention and endurance testing as well as providing direction for material/device structure optimization.

Engineering of Graphene Bandgap and Growth (GRC 2011 OJ 2124)

Principal Investigator: Yoshio Nishi

Team: Marjan Aslani, Michael Garner

Scope: This project will evaluate the potential for strain to generate a bandgap, explore techniques to induce strain through structures and process and evaluate the effect of high κ dielectric deposition on the electrical and electronic properties of strained graphene.



Feasibility Research of RRAM for Neuromorphic Circuits Applications

Principal Investigator: Yoshio Nishi

Team: Bohchang Kim, Dan Duncan

Scope: Explore potential of RRAM devices for possible neuromorphic circuits application, by looking into pulse writing characteristics with multi-level programming.

Study of Metal Work Function in Metal/Dielectric Structure – Electrical, Structural, and Stability Properties

Principal Investigators: Yoshio Nishi

Team: Kyoung-Ryul Yoon, Mike Deal

Scope: This project investigates fundamental mechanisms and behaviors of several solid-solid interfaces such as metal- dielectrics, metal-2D material contacts as well as metal-semiconductor both experimentally and theoretically.

Fundamental study on thermoelectric conversion of heat to electricity

Principal Investigators: Yoshio Nishi

Team: Yeji Kim

Scope: Flexible Thermoelectric Harvesting Devices.

Commercially available thermoelectric devices are costly and hard to scale up. We have been investigating low-cost and flexible film-type thermoelectric devices which can be attachable to various wasted heat sources including the human body to convert body heat to electricity. We have already developed hybrid sheets containing carbon nanotubes (CNTs) and organic materials as thermoelectric materials in which CNTs and organic materials can provide higher electric conductivity and lower thermal conductivity, respectively. By controlling materials composition, we expect to i) realize a reduction of battery power dependence; ii) develop a fully wireless system; iii) reduce maintenance costs by continuous use of human body heat, and iv) reduce the environmental impact of hazardous chemicals used to produce energy for the devices.

Initiative for Nanoscale Materials and Processes, INMP Phase 3 (Industry Group)

Principal Investigators: Yoshio Nishi (EE), Paul McIntyre (MSE) and Krishna Saraswat (EE)

Team:PIs, Bruce Clemens (MSE), H.-S. Philip Wong (EE), Mike Deal (EE)

Scope: This project is aimed at fundamental understandings of metal gate/high K dielectrics/high mobility channel structure at atomic/molecular levels to provide in-depth knowledge and discovery for ITRS 10 nm node and beyond CMOS technology, including TMD, graphene based materials and devices.

Nishi group’s contribution to this Initiative includes metal gate work function engineering and fundamental study for metal-insulator/semiconductor interfaces. Metal/metal bilayer structures can be used to adjust the gate electrode work function over a 1eV range for a variety of metals by controlling the thickness of the bottom metal layer. Current year’s focus is to investigate interface work function for metal-insulator and metal-TMD interfaces.

Nonvolatile Memory Technology Research Initiative (Industry Group)

Principal Investigators: Yoshio Nishi (EE), Krishna Saraswat (EE), H.-S. Philip Wong (EE), Simon Wong (EE)

Scope: This initiative for non-volatile memory research pursues technical feasibility at the device level, circuit/system level as well as develop a fundamental understanding for a variety of new non-volatile memory phenomena, materials and processes. We propose several connected research themes showing (i) how scalable are the various resistance switch materials and mechanisms from fundamental physical understanding point of view (ii) how selector devices can be integrated with resistive switches in crosspoint arrays (iii) how cell and circuit innovations can improve performance and (iv) how bulk and interface effects control reliability and endurance. The scope of the initiative is for 5 years aiming at possible infusion into sub-10nm ITRS nodes and beyond.

Nishi group’s contribution will be in the area of resistance change memory with metal oxides such as TiO2, Al2O3, Ta2O5, HfO2 as the switching materials, and look into physical mechanism for switching, endurance, retention, effect of doping and oxide-electrode interactions both theoretical and experimental research.

Ab Initio Modeling Research on Defects, Interfaces and Contact Resistances in 2D Material Systems

Principal Investigator: Yoshio Nishi (EE)

Team: Blanka Magyari-Kope

Scope: The fabrication of integrated devices and circuits based on single-layer 2D materials has been recently achieved with high mobility, on/off current ratio and density achievements. Metal contacts to 2D materials systems, due to the electron injection process, were found however to play a crucial role in the overall performance of these materials. For example the observed electron mobility in single-layer devices has been lower than expected, and possible explanations were linked to the work function values of the metals. Defects in the 2D material itself also significantly affect the transport properties. It has been found that for low carrier densities, the transport exhibits nearest-neighbour hopping at high temperatures and variable-range hopping at low temperatures via localized gap states induced for example by sulfur vacancies in MoS2. Based on the fundamental understanding of the atomic interactions in the contact regions, we are working on deriving mobility enhancement guidelines to be implemented in future devices.