Near field sensor with cantilever and tip containing optical pat

Details Near field sensor with cantilever and tip containing optical pat Near field sensor with cantilever and tip containing optical pat

1996-02-23

1998-06-23

Westin, Edward P.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

250306, H01J 314

Patent

active

057708568

DESCRIPTION:

BRIEF SUMMARY
This application claims benefit of international application PCT/GB 94/01586 filed Jul. 22, 1994.
This Invention relates to optical equipment and more particularly, though not exclusively, to optical devices and equipment with integrated photodetection means and/or processing means; or devices or equipment having a direct link to processing means, hereinafter referred to as an intelligent optical sensor.
Near field Scanning Tunneling Microscopy (STM) and related techniques have been proposed during the last ten years to image material surfaces at a scale below the traditional, optical microscopy range, that is at, or around, the atomic scale.
Scanning Near Field Microscopy has become well established in the ten years since the invention of Scanning Tunneling Microscopes (STM) by the Nobel prize winners Binnig and Rohrer (1984). The basic idea was to control the position of a probe (or antenna) in the vicinity of a surface, using high precision piezo-electric micro-actuators and feedback electronic control of a tunnel electron current between the surface under inspection and the probe (or antenna). More generally a so-called "proximity function" was used to control the distance between the probe and the surface, as with Atomic Force Microscopy (AFM) and related techniques.
Scanning Tunneling Microscopes have made it possible to obtain microscope images of very high resolution, without using either destructive electrons or a vacuum. More recently it has become possible, with computer assistance, to manipulate individual atoms in order to build tiny objects. The impetus is therefore now on micro-fabrication and corresponding instruments able to operate on such a micro scale.
Scanning Tunneling Microscopes (STM) and related techniques suffer from their extreme specification. Thus although they are very well adapted to the atomic scale, they are not easily extended to larger dimensions because of the limited size of the so called critical distance d.sub.c of the proximity function. Typically the critical distance, d.sub.c, is in the range 0.1 nm<d.sub.c <5 nm and it is within this range that STM's are intended to operate. Mesoscopic objects, which are typically of the order of tens of nanometers (hundreds of .ANG.), cannot easily be observed by STM, especially if the surface to be inspected is atomically rough. More recently a new technique has been proposed which relies on the so called photon near field proximity function instead of the electronic one. This technique is fairly easily adapted to the mesoscopic domain (10 nm<d.sub.c <250 nm) because of a larger value of d.sub.c.
Even more recently a particular technique has arisen which is called Photon Scanning Tunneling Microscopy (PSTM) or Scanning Near Field Optical Microscopy (SNOM). These two techniques, PSTM and SNOM, are related by the ability of very small apex optical systems to receive, or to emit, photons in the near field. For the sake of simplicity the present invention will be described with reference to the case of PSTM, given that SNOM situation operates in a substantially reciprocal manner, it will be appreciated that the invention is also applicable to SNOM.
The main difference between classical STM and PSTM relies on the much extended proximity function of PSTM, which makes it possible to control the position of a probe in an approximate range of 10 to 200 nm instead of 0.1 nm to 5 nm for STM. This is an advantage if larger scale investigations are intended on a micron scale.
It is emphasised that very small objects, that is smaller than about 0.5 .mu.m in size, cannot be seen using classical optical means of microscopy, nor can they be studied conveniently by electron microscopy. Thus making use of, observing and/or manipulating such small objects, has been extremely difficult, if not impossible. Also because of the relatively large "size" of a photon it was very difficult to establish a specific relationship with small light emitters such as nanometric lasers or luminescent molecules. Similarly the problem is experienced with l

REFERENCES:
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patent: 5289004 (1994-02-01), Okada et al.
patent: 5304795 (1994-04-01), Fujihira et al.
patent: 5354985 (1994-10-01), Quate

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