Archive for the ‘Nano Blog’ Category

Zheng et al. demonstrated Ge-MOSFET with negligible C−V hysteresis, extremely low leakage, and superior equivalent oxide thickness by the aid of a fluorinated epitaxial graphene on Ge as an oxygen diffusion barrier to successfully prevent the formation of unstable germanium oxide between the Ge channel and the HfO2 gate oxide.  Read the original article: Xiaohu Zheng et al., Adv. Funct. Mater. 2015, 25, 1805–1813 (Posted by Yonhua Tzeng)

a) Schematic diagram showing the implementation of FGra as the diffusion barrier layer between the Ge substrate and HfO 2 dielectric layer in the Ge-based MOS device: (step 1) direct growth of continuous monolayer graphene on Ge; (step 2) FGra synthesized by exposure to SF 6 plasma; (step 3) dielectric deposition on FGra/Ge by atomic layer deposition; (step 4) MOS device completed by standard semiconductor manufacturing processes. b) Cross-sectional high-resolution TEM of the gate stack showing the absence of interfacial oxide formation in the presence of FGra and schematic diagram showing retarded diffusion in the vicinity of high- k /Ge interface.  (Credit Xiaohu Zheng et al., Adv. Funct. Mater. 2015, 25, 1805–1813 with permission)

Xiangping Li et al. demonstrated write-once holograms for wide-angle and full-colour three-dimensional images using subwavelength-scale pulsed femtosecond laser reduction of graphene oxide to enable multilevel optical index modulation and restoration of  vectorial wavefronts of polarization discernible images through the vectorial diffraction of a reconstruction beam. Read the original article: Li et al., Nature Communication  (2015) (Posted by Y. Tzeng)

Alice Gaudin et al. used squalenoyl adenosine nanoparticles of the size of ∼120 nm as a neuroprotective drug to deliver therapeutic amounts of drugs by intravenous injection for treating nervous system after stroke and spinal cord injury of mice. Read the original article: Nature Nanotechnology, doi:10.1038/nnano.2014.274  (Posted by Y. Tzeng)

Boyd et al. of California Institute of Technology demonstrated a microwave plasma-enhanced CVD chemistry in gas mixtures of hydrogen, methane, and nitrogen that grows graphene on copper foils at temperatures lower than 420 °C exhibiting sub-nanometer smoothness, excellent crystalline quality, low strain, few defects and room-temperature electron mobility up to (6.0±1.0) × 10000 cm² V⁻¹ s⁻¹.  Read the original article: NATURE COMMUNICATIONS doi:10.1038/ncomms7620  ( Posted by Y. Tzeng)

Te-Fu Yeh et al. of National Cheng Kung University in Tainan, Taiwan invented nitrogen-doped graphene oxide quantum dots containing p-n type photochemical diodes, which catalyze water-splitting under visible-light irradiation mimicking biological photosynthesis. Read the original article and report: Advanced Materials doi/10.1002/adma.201305299, NCKU Research Express

(Upper) Nitrogen-doped graphene oxide quantum dots. (Lower) quantum dot p-n diode  for water splitting. Credit : Te-Fu Yeh et al., Advanced Materials  (Posted by Y. Tzeng)

Pojen Chuang et al. of National Cheng Kung University in Tainan, Taiwan and his co-workers used two quantum point contacts as spin injectors and detectors to achieve complete control of the electron spins (spin injection, manipulation and detection) in a purely electrical all-semiconductor spin field-effect transistor which is compatible with large-scale integration and promising for future spintronics based information processing.  Read the original article: Pojen Chuang, Sheng-Chin Ho, L. W. Smith, F. Sfigakis, M. Pepper, Chin-Hung Chen , Ju-Chun Fan , J. P. Griffiths, I. Farrer, H. E. Beere, G. A. C. Jones, D. A. Ritchie and Tse-Ming Chen. All-electric all-semiconductor spin field-effect transistors. Nature Nanotechnology DOI: 10.1038/NNANO.2014.296  (Posted by Y. Tzeng)

Kolkowitz et al. of Harvard University used nitrogen-vacancy centers in diamond to make single-spin qubits for measuring Johnson noise thermally induced in a conductive silver film in the vicinity indicating that nanoscale quantum systems may be controlled by nearby electrodes. Read the original article: Thermally induced electrical currents, known as Johnson noise, cause fluctuating electric and magnetic fields in proximity to a conductor. These fluctuations are intrinsically related to the conductivity of the metal. We use single-spin qubits associated with nitrogen-vacancy centers in diamond to probe Johnson noise in the vicinity of conductive silver films. Measurements of polycrystalline silver films over a range of distances (20 to 200 nanometers) and temperatures (10 to 300 kelvin) are consistent with the classically expected behavior of the magnetic fluctuations. However, we find that Johnson noise is markedly suppressed next to single-crystal films, indicative of a substantial deviation from Ohm’s law at length scales below the electron mean free path. Our results are consistent with a generalized model that accounts for the ballistic motion of electrons in the metal, indicating that under the appropriate conditions, nearby electrodes may be used for controlling nanoscale optoelectronic, atomic, and solid-state quantum systems. Science 6 March 2015: Vol. 347 no. 6226 pp. 1129-1132, DOI: 10.1126/science.aaa4298  (Posted by Y. Tzeng)

Tuncay Ozel et al. of Northwestern University demonstrated a core/shell semiconductor nanowire with an embedded plasmonic nanoring, which could not be fabricated by any previously known method, using templated electrochemical synthesis termed as coaxial lithography.    Read the original article: Nature Nanotechnology  doi:10.1038/nnano.2015.33 (Posted by Y. Tzeng)

Professor Koh and his team at University of Texas at Arlington reported in Nature Communication a means of enabling electrons to transport at room temperature like electrons do at very low temperatures with little energy loss by passing electrons through an energy filter made of a quantum well.  The team has received funding to apply the discovery to high-density transistors made in the form of nanopillars. Read the original reports: Nanotechnology aids in cooling electrons without external sources,  Energy-filtered cold electron transport at room temperature.

(a) Left: the double-barrier tunnel junction (DBTJ) structure.  (a) Right: DBTJ structure with a quantum well inserted between the source and tunnelling barrier 1. (b) Schematic of the DBTJ structure with the energy filter inserted. Top: cross-sectional view. The dotted arrows indicate electron tunnelling paths. Bottom: three-dimensional view of one device unit. The schematics are not to scale. Credit Koh et al., Nature Communication.  (Posted by Y. Tzeng)

NIST scientists prove that the propagation time of entanglement between two distant particles for sharing data across a quantum system grows only as a power of the system size instead of logarithmically. The finding implies that quantum processors will be slower than previously predicted. (Posted by Ed. Perkins, Y. Tzeng)