Max Rudolph Lorenz

Atomic force microscopy of polymeric liquid films

We demonstrate the use of the atomic force microscope (AFM) for studying perfluoropolyether polymer liquid films as thin as ∼20 A. With the AFM we are able to measure three distinct properties of the liquid film: (1) its thickness when the thickness of liquid on the AFM tip is taken into account, (2) the meniscus force acting on the AFM tip as a function of depth into the liquid film, and (3) the topography of the liquid/air interface. All three of these measurements can be done with a very high lateral resolution, ∼1000 A, demonstrating the unique capability of AFM for studying liquid films. With AFM we have observed several interesting properties of these polymeric liquid films. First films thinner than ∼300 A are fairly uniformly distributed, while films thicker than ∼300 A slowly dewet the surface. Second, by measuring the meniscus radius of liquid in a micron sized hole on the surface, we can determine the disjoining pressure in a thin liquid film.

Ultrathin particulate magnetic recording media (abstract)

This paper presents a novel method of producing an ultrathin and highly oriented particulate magnetic recording medium. The process involves the laying down of a monolayer of magnetically aligned particles where the thickness of the layer is limited only by the diameter of the magnetic particles. Thus, using commercially available magnetic particles, a 50–100‐nm‐thick magnetic layer can be produced. The particle deposition process depends on electrostatic interactions of charged particles with an oppositely charged disk surface in an aqueous medium. In order to reduce the tendency of the magnetic particles to aggregate, the particles are stabilized by adsorbed colloidal silica. Particle volume concentration (PVC) is higher than usually realized with conventional particulate media and it was measured in excess of 50%. A typical particulate monolayer has an Ms of 1.6×10−3 emu/cm2 and the orientation ratio (Mr/Ms) of 4–4.5. Resolution, at 150‐nm flying height, was measured at 1200 fc/mm with a high signal‐to...

Visible Light from Semiconductors Luminescence from p-n junctions and potential uses of solid state light sources are discussed

Electroluminescence from semiconductor diode light sources can occur as a result of the application of a direct current at a low voltage to a suitably doped crystal containing a p-n junction. In recent years, it has become apparent that in some materials the efficiency of conversion of electric energy to visible light can be appreciably high. Since light-emitting diodes are compatible with the present electronic circuitry, they have many potential applications.