Papers

AVS2001 Session PN-MoM: Atomic/Nano-scale Manipulation

Monday, October 29, 2001 9:40 AM in Room 133

Monday Morning

Start	Invited?	Item
9:40 AM		PN-MoM-1 The "Millipede" - More than 1000 Tips for parallel and dense AFM Data Storage P. Vettiger, G. Cross, M. Despont, U. Drechsler, U. Dürig, W. Häberle, M.I. Lutwyche, H.E. Rothuizen, R. Stutz, R. Widmer, G.K. Binnig (IBM Research, Zurich Research Laboratory, Switzerland); T. Albrecht (IBM Almaden Research Center) A MEMS-based AFM-array concept ("Millipede") for data storage of potentially ultrahigh density, terabit capacity, and high data rate is presented. Its storage potential has been demonstrated by a new thermomechanical local-probe technique to store, read-back and erase data in very thin polymer films. With this new technique, 30- to 40-nm-sized bit indentations of similar pitch size were made by a single cantilever/tip in a 50-nm-thin PMMA layer, resulting in a data storage density of 400-500 Gb/in.². High data rates are achieved by parallel operation of large 2D AFM arrays batch-fabricated by silicon surface-micromachining techniques. The VLSI of micro/nanomechanical devices (cantilevers/tips) on a single chip leads to the largest and densest 2D array of 32x32 (1024) AFM cantilevers with integrated write/read storage functionality ever built. Time-multiplexed electronics control the write/read storage cycles for parallel operation of the Millipede array chip. Initial areal densities of 100-200 Gb/in.² have been achieved with the 32x32 array chip, which has potential for further improvements.¹ This constitutes a major step towards future ultra-dense data storage with potential capacities beyond today's storage approaches. The Millipede concept focuses on a polymer storage media, but may be expanded to other media, and not excluding magnetics, provided suitable read/write functionality can be integrated into cantilevers and tips. We also envision that Millipede may open up new perspectives in nanoscale science and technology areas such as lithography, high-speed/large-scale imaging, molecular and atomic manipulation, biotechnology and many others. ¹P. Vettiger et al., IBM J. Res. Develop. 44, 323 (2000); M. I. Lutwyche et al., Appl. Phys. Lett. 77, 3299 (2000).
10:20 AM		PN-MoM-3 Attractive Mode Manipulation of Fullerenes on Si(100) D.L. Keeling, M.J. Humphry, P.H. Beton, P. Moriarty, M.A. Phillips (University of Nottingham, UK) Room temperature STM manipulation of C60 on silicon surfaces under ultra-high vacuum has been investigated. A new intrinsic attractive mode of manipulation has been observed for gap impedances 1-3GOhm in which molecules hop towards the tip in steps of 1-3 lattice constants. These effects are observed in both polarities although a greater stability and higher probability for attractive mode manipulation is observed for negative sample bias. A similar effect can give rise to a continuous dragging of the molecule while scanning, for which the displacement is parallel to the dimer rows. For lower gap impedance, ~1GOhm, repulsive manipulation, characterised by a sawtooth response of the tip similar to that reported by Bartels et.al., is observed in which the molecule is displaced across the surface in regular steps of 1 or 3 surface lattice constants. The response of molecules to manipulation is discussed in terms of a simple model for C60-Si(100) bonding in which two out of four Si-C bonds are broken during the manipulation process and a change in molecular orientation accompanies tip induced displacement.
10:40 AM		PN-MoM-4 Reliable Nanofabrication Method on Au Cluster Films in a Non-contact Mode with an Atomic Force Microscope K.-H. Park, J.Y. Kim, J.S. Ha, K.-B. Song (ETRI, Republic of Korea) Many kinds of nanofabrication methods have been studied on metal films using scanning probe microscopy so far. However, they are still far from the practical application for the data storage or lithography. Scanning tunneling microscopy(STM) is not an adequate technique because it reliably operates only at ultra high vacuum (UHV) and the throughput is very low.¹ Contact mode fabrication methods of atomic force microscopy (AFM) also have shortcomings because the mechanical contact between the tip and the samples induces a significant damage to the tip apex causing the serious tip wear. Here, we devised a new reliable fabrication method by applying a local field on granular Au nanocluster films using conducting AFM tips in a noncontact mode. Au cluster thin films (10-50 nm) were deposited on silicons and glass substrates through the gas evaporation process under the partial Ar pressure of several mbar. The granular morphologies of the films are observed by STM at UHV in situ, and then the samples were transferred to an air ambient stage for AFM analysis. A reproducible creation of Au bits was obtained with the lateral dimension of 100 nm on granular films. The critical voltage for the fabrication is much larger than the case in a contact mode with some variation depending on the conductivity of the films. The reliability of nanofabrication is attributed to the field induced migration and current induced sintering mechanism without the contact process between the tip and samples. The near-field optical properties of fabricated structures are investigated in a view of an optical data storage. ¹ ¹ K.-H. Park et al., Appl. Phys. Lett. v75, 139 (1999)
11:00 AM		PN-MoM-5 Creating Nanoscale Patterns by Arranging Gold Nanocolloids with an AFM S. Hsieh, S. Meltzer (University of Southern California); C.R.C. Wang (National Chung Cheng University, Taiwan); A.A.G. Requicha, B.E. Koel (University of Southern California) Combining lithography methods and controlled positioning and manipulation of nanosized building blocks is a promising technique for building future nanoscale devices, e.g., SETs or near-field photonic waveguides. Gold colloids can be fabricated in well-defined shapes and sizes and are therefore ideal components for such devices. We extended the capabilities demonstrated in this field by demonstrating the manipulation of Au nanorods and spherical particles by utilizing atomic force microscopy (AFM). For anchoring of Au nanorods and subsequent manipulation, the choice of adhesive layer is crucial. 3-Mercaptopropylmethyldimeoxysilane (MPMDMS) self- assembled layers adhere to the colloid particles and still allow their lateral manipulation. The colloids can be pushed by exerting a controlled lateral force on the particles with an AFM tip. Off-center pushing results in rotation of the nanorods. The parameters for successful manipulation of nanorods and spherical particles will be compared. These techniques for arranging nanoparticles and nanorods should be useful for fabricating new nanostructures or incorporating such nanoparticles into pre-fabricated structures.
11:20 AM		PN-MoM-6 Dynamics and Manipulation of Surface Electronic States R. Berndt (University of Kiel, Germany) We discuss two recent applications of scanning tunneling spectroscopy of surface electronic states. First, a long standing discrepancy between experimental and theoretical values for the lifetimes of holes in the surface state electron bands on noble metal surfaces is resolved with both found to have been in error. The ability of the scanning tunneling microscope to verify surface quality before taking spectroscopic measurements is exploited to remove the effects of defect scattering on experimental lifetimes. A theoretical treatment of inelastic electron-electron scattering is developed which explicitly includes intra-band transitions within the surface state band. In our model two-dimensional decay channels dominate the electron-electron interactions that contribute to the hole decay, screened by the electron states of the underlying three-dimensional electron system. Second, from a single Mn adsorbate placed within a geometrical array of adatoms on Ag(111) modification of the electronic structure is observed. The changes result from coupling between the adsorbate level and surface electronic states of the substrate. These surface states are scattered coherently within the adatom array, mediating the presence and shape of the array to the adsorbate within. The dimension and geometry of the adatom array thus provide a degree of control over the induced changes.