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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Alex Zettl | 2/3 | https://en.wikipedia.org/wiki/Alex_Zettl | reference | science, encyclopedia | 2026-05-05T16:44:58.484535+00:00 | kb-cron |
== Selected research accomplishments == Access to Zettl's 600+ research publications, supplementary materials, and research highlights can be found at https://www.ocf.berkeley.edu/~jode/index.html. Charge density wave statics and nonlinear dynamics Zettl discovered chaotic response and period doubling routes to chaos in dynamic charge density wave (CDW) systems driven by an rf field, and found that mode locking completely freezes out all internal fluctuations of the collective mode condensate. He identified phase slip centers as the origin of so-called switching in CDWs. He discovered unusual electro-elastic coupling in CDW systems, and studied the evolution of the CDW order parameter as sample sizes approached the nm scale. For the 2D static CDW system TaS2, Zettl used cryogenic STM measurements to fully characterize domain structure, and to contrast bulk CDW parameters determined via x-ray scattering to surface CDW parameters established by STM. High temperature superconductors and fullerenes Zettl performed seminal isotope effect measurements in high temperature superconductors, including substituting oxygen, barium, and copper isotopes in Y-Ba-Cu-O, substituting oxygen isotopes in La-Sr-Cu-O, and substituting carbon and alkali isotopes in A3C60. These measurements placed severe constraints on the superconductivity mechanism, and revealed that superconductivity in the copper oxides was likely not phonon-mediated, but likely was phonon mediated in the fullerenes. Zettl was the first to intercalate high-Tc superconductors with foreign molecules which allowed Cu-O planes to be physically and electronically separated. Zettl also produced high quality single crystals of fullerene superconductors which facilitated a host of detailed transport and thermodynamic measurements. Zettl revealed the elastic properties of high-Tc materials, and determined the effective dimensionality of fullerene superconductors via paraconductivity measurements. Carbon and boron nitride nanotubes and related nanostructures Zettl has performed extensive studies on the mechanical and electronic properties of carbon nanotubes (CNTs). He created electronic devices from CNTs, including a rectifier and chemical sensor. From thermal conductivity measurements he extracted the linear-T behavior expected from the quantum of thermal conductance. He created a highly robust CNT-based electron field emission source. Zettl discovered that CNTs could be stable in a fully collapsed state, which led to a refined quantification of the interlayer interaction energy in graphite; this important parameter had previously been surprisingly ill-defined experimentally. Zettl was the first to synthesize boron nitride nanotubes (BNNTs), for which (in sharp contrast to CNTs), the electronic and optical properties are relatively insensitive to wall number, diameter, and chirality. Zettl also found different ways to efficiently synthesize BNNTs, along with related BN-based nanomaterials such as BN nanococoons and BN aerogels. He also developed methods to functionalize the outer surfaces of BNNTs, and fill them with foreign chemical species creating new structures including silocrystals. Zettl showed experimentally that an electric field could be used to modulate the electronic band gap of BNNTs (giant Stark effect). Nanoelectromechanical systems and advances in transmission electron microscopy Zettl developed the transmission electron microscope (TEM) nanomanipulator, which allowed electrical and mechanical stimulation of nanoscale samples while they were being imaged inside the TEM. The nanomanipulator could be configured as a mechanical and/or electrical probe placed with atomic precision, as a scanning tunneling microscope, or as an atomic force microscope with simultaneous force measurement capability. Zettl used the nanomanipulator to prove that multi-wall CNT were composed of nested concentric cylinders rather than scrolls, and he determined the fundamental frictional forces between the cylinders. This led to his invention of the rotational nanomotor that employed nanotube bearings. Other inventions by Zettl that resulted were surface-tension-powered relaxation oscillators, tunable resonators, nanocrystal-powered linear motors, a fully integrated nanoradio receiver, a nanoballoon actuator, and nano-scale electrical and thermal rheostats. Zettl used the nanomanipulator to perform the first electron holography experiments on nanoscale materials, which quantified quantum mechanical field emission from CNTs. Using an architecture similar to that of his nanoradio, Zettl created a nanoelectromechanical "balance" which had single atom mass sensitivity, and with which he observed atomic shot noise for the first time. He developed a suspended graphene membrane that allowed for nearly real-time TEM imaging of individual carbon atom dynamics, and other isolated atomic and molecular species. Zettl's development of the TEM graphene liquid cell and graphene flow cell brought ultra-high-resolution real-time liquid phase imaging to the TEM world. Zettl also developed nanomechanical biological probes, tailored nanopores, and highly efficient wideband graphene-based mechanical energy transducers. 2D materials Zettl has made key contributions to the synthesis and characterization of a host of 2D materials, including TaS2, MoS2, alloyed NbS2, NbSe2, and 2D quasicrystals. Zettl recently discovered a means to enhance and control quantum light emission in hexagonal-BN heterostructures, with implications for quantum information transmission and management. Isolation of 1D chains and topological materials In analogy to the isolation of 2D graphene from graphite, Zettl developed a method by which single or few chains of quasi 1D materials could be isolated and studied. He did this by synthesizing the materials in the confined (and protective) interior of CNTs and BNNTs. The method has yielded structures unknown in "bulk", with often interesting electronic properties (such as sharp metal-to-insulator transitions) and non-trivial topological properties. Atomically precise ultra-narrow nanoribbons were also created by Zettl via this confined growth method. Liquid electronics Using conducting nanoparticles softly "jammed" at the interface between two immiscible liquids, Zettl constructed electronic devices and "circuitry", thus realizing an effective paradigm for "all liquid electronics". Such constructs could facilitate easier reconfiguration or complete recycling of constituents once the circuit architecture becomes obsolete.
== Selected books, book chapters, and review articles == S. Saito and A. Zettl, eds. Carbon Nanotubes: Quantum Cylinders of Graphene. Contemporary Concepts of Condensed Matter Science, Volume 3, Pages 1–215 (2008)