| Atomic force microscope (AFM) thermomechanical data storage involves the recording of digital information as submicron data pits on a rotating substrate at very high densities, up to 30 Gbit/sq.in. In a typical implementation, the sharp tip of a micromachined AFM cantilever is kept in contact with a spinning polycarbonate disk by a weak loading force. For writing, the cantilever tip is heated above the glass transition temperature of polycarbonate to melt data pits onto the substrate. For reading, the cantilever deflection is measured as the tip rides over the pits. This work describes recent developments in AFM thermomechanical data storage, including the integration of heating and deflection-sensing elements onto the micromachined cantilevers.; Single-crystal silicon cantilevers 1 micron thick have been demonstrated for use in AFM thermomechanical data storage. Cantilevers with integrated piezoresistive sensors were fabricated with measured sensitivities {dollar}Delta R/R{dollar} up to 0.75 ppm per angstrom, in close agreement with theoretical predictions. Separate cantilevers with integrated resistive heaters were fabricated. Electrical and thermal measurements on these heaters matched ANSYS simulations. Geometric variants of the cantilever were also tested to study the dependence of thermal time constant on device parameters. Time constants as low as 1 microsecond were achieved. A thermodynamic model was developed based on the cantilever's geometry and material properties, and was shown to predict device behavior accurately. A comprehensive understanding of cantilever functionality allowed the cantilever to be optimized for fast thermal writing.; A novel dual-axis piezoresistive cantilever has also been developed for AFM data tracking. The device allows simultaneous, independent detection of vertical and lateral forces. The vertical force sensor of the cantilever can be used for data readback and loading force control, while the lateral force sensor can be used for data groove edge detection and tracking. The device consists of a flat, triangular probe with a sharp tip, connected to the support by four parallel high-aspect-ratio ribs. Using a special oblique ion implant technique, piezoresistors are fabricated on the horizontal surface of the triangular probe and the vertical sidewalls of the ribs, facilitating orthogonal force sensing. Groove tracking on a spinning disk has been demonstrated. |
