M. Luna

Publications (9)8.42 Total impact

• Article: Interaction forces and conduction properties between multi wall carbon nanotube tips and Au(111).

  M Luna, P J de Pablo, J Colchero, J Gomez-Herrero, A M Baro, H Tokumoto, S P Jarvis
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  ABSTRACT: We have studied the interaction forces and electrical conduction properties arising between multiwall carbon nanotube tips and the Au(111) surface in air, by means of amplitude modulation scanning force microscopy, also called intermittent contact. We have centered our work on tips with metallic electronic structure and for the specific parameters used we have found a preliminary interaction range where there is no contact between tip and surface. Stable imaging in this non-contact range is possible with multiwall carbon nanotube tips. These tips have also been used to obtain simultaneous topographic and current maps of the surface. They show excellent properties as tips due to their high aspect ratio and durability, as a result of their elastic and non-reactive properties. Correspondingly, multiwall carbon nanotube tips allow high resolution local analysis of electrical conductivity on a nanometer scale.
  Ultramicroscopy 08/2003; 96(1):83-92. · 2.47 Impact Factor
• Article: Tip-sample interaction in tapping-mode scanning force microscopy

  P. J. de Pablo, J. Colchero, M. Luna, J. Gómez-Herrero, A. M. Baró
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  ABSTRACT: Tip-sample interaction in intermittent contact scanning force microscopy, also called tapping mode, is experimentally studied to determine under which conditions tip-sample contact is established. Force vs distance curves are made while the cantilever is oscillating at its resonance frequency. Cantilevers with different force constants driven at different oscillation amplitudes have been used. In addition, samples with different hardness, such as silicon oxide, glass, and highly orientated pyrolytic graphite were taken as sample surface. From the analysis of the data we conclude that by choosing appropriate operating conditions, tip-sample contact can be avoided. This operating regime is of general interest in scanning force microscopy, since it allows imaging of even the softest samples.
  Phys. Rev. B. 05/2000; 61(20).
• Article: Adsorption of Water on Solid Surfaces Studied by Scanning Force Microscopy

  A. Gil, J. Colchero, M. Luna, J. Gómez-Herrero, A. M. Baró
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  ABSTRACT: Tip−sample interaction of an oscillating tip near a surface is determined. The experimental results show that the presence of the surface can be detected without mechanically touching the surface. By adjusting the appropriate operating conditions of a scanning force microscope setup, tip−sample contact can be avoided during imaging at atmospheric pressure. This allows study of even the softest samples. In the present work, we demonstrate that molecularly thin water films can be imaged with nanometer resolution on different substrates such as mica, gold, and highly oriented pyrolitic graphite. Correspondingly, scanning force microscopy can be used to investigate wetting properties of liquids with very high spatial resolution.
  04/2000;
• Article: Study of Water Droplets and Films on Graphite by Noncontact Scanning Force Microscopy

  M. Luna, J. Colchero, A. M. Baró
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  ABSTRACT: The scope of the noncontact scanning force microscopy technique concerning the analysis of fragile and weakly attached samples is shown by proving its ability to investigate the water−graphite interface. After a macroscopic quantity of purified water has been shacked out from the graphite surface, a noncontact image taken in air at a relative humidity value of 60% reveals nanodroplets attached to the steps. In a high relative humidity atmosphere (>90%), water adsorbs on the surface forming flat rounded islands of 5 nm in height that transform to 2 nm high islands when the relative humidity stabilizes to 90%. This process is induced by the presence of the scanning tip. Desorption of the water present on the surface is achieved after the exposure of the sample to a dry atmosphere for several hours. The adsorption−desorption cycle is reversible.
  10/1999;
• Article: Observation of Liquid Neck Formation with Scanning Force Microscopy Techniques

  J. Colchero, A. Storch, M. Luna, J. Gómez Herrero, A. M. Baró
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  ABSTRACT: In the present work, we describe a technique to measure the tip−sample interaction in a scanning force microscope setup with high precision. Essentially, the force exerted on the cantilever is acquired simultaneously with a spectrum of the cantilever. This technique is applied to study the behavior of the microscope setup as the tip approaches a sample surface in ambient conditions. The measured interaction can only be understood assuming the formation of a liquid neck and the presence of a thin liquid film on the tip as well as on the sample.
  04/1998;
• Article: Lock‐in technique for measuring friction on a nanometer scale

  J. Colchero, M. Luna, A. M. Baró
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  ABSTRACT: A method for measuring friction forces on a nanometer scale is described. This method combines a lock‐in technique with scanning force and friction microscopy. Essentially, a lock‐in amplifier is used to determine the amplitude of the friction loop, which is measured at high frequency. To demonstrate the capability of this method, the dependence of the friction force with normal load is measured and a two dimensional image is presented. © 1996 American Institute of Physics.
  Applied Physics Letters 05/1996; 68(20):2896-2898. · 3.84 Impact Factor
• Article: Application of non-contact scanning force microscopy to the study of water adsorption on graphite, gold and mica

  M Luna, J Colchero, A Gil, J Gómez-Herrero, A.M Baró
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  ABSTRACT: The tip of an oscillating cantilever experiences a strong variation of energy dissipation with the distance just before contacting the surface. This allows scanning force microscopy (SFM) imaging in non-contact mode with high resolution. The potential of this mode is demonstrated by the study of an extremely soft and easily detachable sample such as water adsorbed on graphite, gold and mica substrates. Flat layers of water, ranging in height from molecular dimensions to several bilayers, are observed on the different surfaces studied.
  Applied Surface Science 157(4):393-397. · 2.10 Impact Factor
• Article: Preparation of STM W tips and characterization by FEM, TEM and SEM

  J. Méndez, M. Luna, A.M. Baró
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  ABSTRACT: We have used an oxygen at high temperature (1300 K) in order to sharpen W tips suitable for STM operation. Starting from an electrochemically etched tip his procedure gives a finger-like tip as can be observed by SEM. We also measure the Fowler-Nordheim plots of field-emitted electrons. Analysis of these data allows a precise characterization of the tip sharpness parameters that we correlate with TEM images.
  Surface Science. 266:294-298.
• Article: Intermittent contact scanning force microscopy: The role of the liquid necks

  M Luna, J Colchero, A M Baró
  Applied Physics Letters. 72(26):3461-3463.