EP0223918A2
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EP
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Method and atomic force microscope for imaging surfaces with atomic resolution
Assignee: International Business Machines Corp
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Filing: 1986-07-25
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Granted: —
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Expires: 2006-07-25
Abstract
Abstract A sharp point (5) is brought so close to the surface of a sample (4) to be investigated that the forces occurring between the atoms at the apex of the point (5) and those at the surface cause a spring-like cantilever (7) to deflect. The cantilever (7) forms one electrode of a tunneling microscope, the other electrode being a sharp tip (8). The deflection of the cantilever (7) provokes a variation of the tunnel current, and that variation is used to generate a correction signal which can be employed to control the distance between said point (5) and the sample (4), in order, for example, to maintain the force between them constant as the point (5) is scanned across the surface of the sample (4) by means of an xyz-drive (3). In certain modes of operation, either the sample (4) of the cantilever (7) may be excited to oscillate in z-direction. If the oscillation is at the resonance frequency of the cantilever (7), the resolution is enhanced.
Inventors
- 👤 Gerd Karl Dr. Binnig
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-25 14:52
CPC Classifications
G; G01; G01Q; G01Q20/00; G01Q60/00; G01Q60/24; G01Q60/38
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
183 words
Method for generating a topographical image of a sample surface with a resolution better than 100 nm, characterized by the following steps: - bringing a sharp point (5) which is fixed to one end of a spring-like cantilever (7) so close to the surface of the sample (4) to be inspected that the forces occurring between the atoms at the apex of said point (5) and on the sample's surface are larger than 10⁻²⁰N such that the resulting force deflects said cantilever (7); - detecting the deflection of said cantilever (7) by means of a tunnel tip (8) arranged at tunnel distance from said cantilever (7); - maintaining the tunnel current flowing across the tunnel gap between said cantilever (7) and said tunnel tip (8) at a constant value by using any detected variations of the tunnel current to generate a correction signal; - using said correction signal for controlling the point/sample distance such that said correction signal is minimized, and for plotting versus a scan position signal representative of the current position of the point (5) with respect to the sample (4).
Claim 2
Dependent Claim
183 words
Method for generating a topographical image of a sample surface with a resolution better than 100 nm, characterized by the following steps: - bringing a sharp point (5) which is fixed to one end of a spring-like cantilever (7) so close to the surface of the sample (4) to be inspected that the forces occurring between the atoms at the apex of said point (5) and on the sample's surface are larger than 10⁻²⁰N such that the resulting force deflects said cantilever (7); - detecting the deflection of said cantilever (7) by means of a tunnel tip (8) arranged at tunnel distance from said cantilever (7); - maintaining the tunnel current flowing across the tunnel gap between said cantilever (7) and said tunnel tip (8) at a constant value by using any detected variations of the tunnel current to generate a correction signal; - using said correction signal for controlling the point/sample distance such that said correction signal is minimized, and for plotting versus a scan position signal representative of the current position of the point (5) with respect to the sample (4).
Claim 3
Dependent Claim
61 words
Method in accordance with claim 1, characterized in that the sample (4) is oscillated in z-direction by way of appropriately modulating the xyz-drive (3) on which it is held, at the eigen frequency of said cantilever (7) and with an amplitude between 0,1 and 1 nanometer, such that the cantilever (7) is caused to oscillate and thus modulate the tunnel current.
Claim 4
Dependent Claim
48 words
Method in accordance with claim 1, characterized in that said cantilever (7) is excited to oscillate in z-direction at an amplitude in the 0,01....0,1 nanometer range, and that an additional correction signal is derived from the changes of the said amplitude occurring as the sample (4) is scanned.
Claim 5
Dependent Claim
63 words
Method in accordance with claim 1, characterized in that said cantilever (7) is excited by means of a piezoelectric element (13) to which it is attached, to oscillate in z-direction at an amplitude in the 0,01...0,1 nanometer range, and that an additional correction signal is derived from the changes of the phase of the cantilever's oscillation occurring as the sample (4) is scanned.
Claim 6
Dependent Claim
68 words
Method in accordance with claim 1, characterized in that a predetermined percentage of said correction signal is fed back to the control mechanism (9) for the tunnel tip (8) while some other predetermined percentage of said correction signal is applied to the control mechanism (3) for the sample holder (3), such that the sample (4) and the tunnel tip (8) are driven in opposite directions for distance correction.
Claim 7
Dependent Claim
171 words
Atomic force microscope for performing the method of claim 1, and comprising a sample holder designed for moving the sample in xyz-directions by steps in the nanometer range, and a tunnel system including first and second tunnel electrodes and associated electronics for measuring the distance between said tunnel electrodes and for generating a correction signal in response to deviations of said distance from a predetermined value, characterized in that said sample holder (3) is arranged opposite a sharp point (5) fixed to one end of a spring-like cantilever (7) which forms/carries the first one of the electrodes of said tunnel system, the second tunnel electrode (8) being movably arranged to face said first tunnel electrode (7) with tunneling distance, said correction signal being applied to said sample holder (3) for maintaining the sample/point distance constant, said correction signal alos being applied to a graphic display unit which is further connected to a source of position signals derived from the scanning of said point (5) across the surface of the sample (4).
Claim 8
Dependent Claim
22 words
Microscope in accordance with claim 6, characterized in that said point (5) consists of a diamond needle attached to said cantilever (7).
Claim 9
Dependent Claim
36 words
Microscope in accordance with claim 6, characterized in that said cantilever (7) is fixed to a part (6) of a base (1) with a piezoelectric element (13) arranged between said cantilever (7) and said part (6).
Claim 10
Dependent Claim
29 words
Microscope in accordance with claim 6, characterized in that said sample holder (3) is supported by a base (1, 2) by means of a vibration damping cushion (11, 17).
Claim 11
Dependent Claim
68 words
Microscope in accordance with claim 9, characterized in that the sample holder (3) is attached to a supporting member (16) which in turn is fixed to said vibration damping cushion (17), and that a screw (14) is provided for coarse adjustment of said sample (4) with respect to said point (5) in z-direction, by way of moving said supporting member (16) against the resistence of said cushion (17).
Claim 12
Dependent Claim
55 words
Microscope in accordance with claim 6, characterized in that said cantilever (7) is with one end rigidly connected to a common base (1) which also carries, by means of interposed vibration damping cushions (17, 19), supporting members (16, 20) respectively supporting an xyz-drive and sample holder (3) and a z-drive and tunnel tip support (9).
Claim 13
Dependent Claim
46 words
Microscope in accordance with claim 6, characterized in that said cantilever (7) is electrically conductive on its side facing said tunnel tip (8) and that an electrical potential difference is maintained between said tunnel tip (8) and the side of the cantilever (7) which it faces.
Claim 14
Dependent Claim
22 words
Microscope in accordance with claim 6, characterized in that said cantilever (7) consists of a gold foil of about 25 micrometer thickness.
References Cited (Backward Citations)
No citation records indexed.
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