Professor William Kaden

University of Central Florida

Friday, October 6

11:00 a.m.

214 Mudd and Zoom

Single-crystalline metallic nanowires: Exploring emerging paradigm shifts in charge-transport through next generation CMOS interconnect technology

Abstract:Increasing resistivity of polycrystalline copper interconnects as wire width and height drop to and below the electron mean free path (EMFP) with Moore’s law scaling has long been known as the gating factor limiting microprocessor clock speed and, more recently, power consumption/heat generation. However, soon this scaling can lead to a paradigm shift as the lengths of the interconnects also approach and drop below EMFP dimensions. Shorter transport length presents an opportunity to leverage ballistic contributions to conductance to achieve energy-efficient computing, but only to the extent that non-phonon contributions to nanowire resistivity (primarily electron scattering from surfaces and grain boundaries) can be minimized. This additional scattering decreases the effective EMFP, restricting the potential for ballistic and partial ballistic transport to occur. Scattering from grain boundaries, which single-crystal nanowires do not contain, has been attributed to more than half of the copper resistivity increases relevant to polycrystalline interconnects. While experimental evidence of ballistic transport has been studied and successfully modelled at point contacts (often formed by deliberately crashing an STM tip into a conducting support to form point contacts of ill-defined shape and cross-sectional area), device scale demonstrations of this phenomenon and complications arising from mixed mode transport within nanowires of well-defined dimensions have thus far gone unreported. In this presentation, we will present structure-conductivity relationships for Ru(0001) thin-films and nanowires of varied dimensions to explore and further develop existing models of transport in the near/sub-EMFP size regime. This will include and overview of several approaches used to meet disparate materials science challenges associated with heteroepitaxial growth of metals on oxides and vice-versa; wire patterning techniques needed to explore wires oriented along varied crystallographic directions; characterization approaches used to establish key materials properties such as composition, crystal structure, physical dimensions, and defect typing and quantification; a phenomenological study of changes in surface-scattering specularity as a function of (often reversible) changes in processing conditions, and direct evidence suggesting the onset of low-temperature, ballistic transport through sub-100 nm long Ru nanowires grown and patterned on Al2O3(0001) substrates.

ZOOM:

https://columbiauniversity.zoom.us/j/93373131305?pwd=cDlsdFBHZ2FrVE81UTA4U1ZMQlpNUT09


 

Bio: Dr. Kaden is an associate professor of physics at the University of Central Florida where he has specialized in the growth and characterization of single-crystalline thin-films suitable for advancing research and development across several disparate fields of study since 2015. This work has focused increasingly on the development and characterization of single-crystalline nanowire devices suitable for studying effects associated with transitions from Ohmic to ballistic transport for wires compatible with existing and soon-to-exist CMOS interconnect geometries and length scales. Prior to UCF, Dr. Kaden completed a postdoctoral research fellowship at the Fritz Haber Institute of the Max Planck Society in Berlin, Germany from 2010 – 2014, where he focused on the heteroepitaxial growth and characterization of ultrathin oxide films on metallic substrates. Dr. Kaden completed a PhD in Chemistry at the University of Utah in 2010, which focused on the unique surface chemistry of atomically size-selected metal clusters within the non-monotonically scaling size regime (<30 atoms).”