Distance-controlled tunneling transducer and direct access storage unit employing the transducer

Abstract

A distance-controlled tunneling transducer comprises a plurality of tunnel tips arranged in an array at a tunneling distance from an electrically conductive surface of a storage medium. Each tip is attached to a respective cantilever beam permitting the distance between each tip and the surface to be individually pre-adjusted electrostatically. Arranged in juxtaposition with each cantilever beam is an active control circuit for adjusting the tip-to-surface distance during operation of the storage unit, thus preventing crashes of the associated tip into possible asperities on the surface of the recording medium. Each control circuit is designed such that its operating voltage concurrently serves to pre-adjust its associated cantilever beam and to maintain the tip-to-surface distance essentially constant.

What is claimed is: 
     
       1. A direct access storage unit comprising a recording medium; a plurality of tunnel tips arranged on a transducer in proximity to said recording medium, and means for generating a .[.mutual.]. periodic displacement between said recording medium and said transducer, wherein each tip is operated as a detector for the current flowing across a gap (Z G ) between said tip and a surface of said recording medium, and wherein each tip is attached to a respective cantilever beam with the .[.mutual.]. distance between said tip and the surface of the recording medium being adjustable by electrostatic means, characterized in that each tip is associated with an active control circuit integrated on said transducer in proximity to the respective cantilever beam associated with a particular tip and comprising a transistor, a load resistance, and a capacitance, and that the circuit is connected such that the supply voltage (U 0 ) creating the current across the gap between said tip and the surface of said recording medium also serves to adjust, during operation, the gap distance (Z G ) between said tip and the surface of said recording medium. .Iadd.2. A direct access storage unit comprising a recording medium, one or more tips arranged on a transducer in proximity to said recording medium, and means for generating a displacement beetween said recording medium and said transducer, wherein each tip is operated as a detector for a current flowing across a gap distance (Z g ) between each said tip and a surface of said recording medium, and wherein each tip is attached to a respective cantilever beam with the gap distance (Z g ) between each said tip and the surface of the recording medium being adjustable, characterized in that each tip is associated with an active control circuit integrated on said transducer in proximity to the respective cantilever beam associated with the particular tip and comprising a transistor, a load resistance, and a capacitance, and that the circuit is connected such that the supply voltage (U 0 ) creating the current across the gap distance (Z g ) between said tip and the surface of said recording medium also serves to adjust, during operation, the gap distance (Z g ) between said tip and the surface of said 
     
     
        recording medium..Iaddend..Iadd.3.  The direct access storage unit of claim 2, further comprising an electrostatic means for adjusting the gap distance (Z g ) between the recording medium and the tip..Iaddend..Iadd.4. The direct access storage unit of claim 2, further comprising a piezo means for adjusting the gap distance (Z g ) between the recording medium and the tip..Iaddend..Iadd.5. The direct access storage unit of claim 2, wherein the gap distance (Z g ) between the recording medium and the tip is less than 20 nm..Iaddend..Iadd.6. The direct access storage unit of claim 2, wherein the gap distance (Z g ) between the recording medium and the tip is less than 2 nm..Iaddend..Iadd.7. The direct access storage unit of claim 2, wherein the active control circuit comprises an open loop circuit..Iaddend..Iadd.8. The direct access storage unit of claim 2, wherein the means for generating a displacement allows each tip to scan a plurality of concentric circles of tracks on the surface of the recording medium..Iaddend.