EP0290648A1
Expired / Lapsed
EP
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Atomic force sensor head for investigating the topography of a surface
Assignee: International Business Machines Corp
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Filing: 1987-05-12
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Granted: —
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Expires: 2007-05-12
Abstract
Abstract The atomic force sensor head comprises a cantilever beam (50) forming an integral part of a body (53) from which it extends such that it has a free end to carry a member (55) for interaction with a surface to be investigated. As said member (55) is brought close to said surface, atomic forces will cause a deflection of said cantilever (50). This deflection is translated into a variation of an electrical value, such as a capacitance. A capacitor (57) is formed by a pair of electrodes (51, 52) coated onto the cantilever beam (50) and said body (53), respectively. The deflection of said cantilever beam (50) causes a variation of the distance (s) between said electrodes (51, 52) and, hence, of the capacitance. An improvement of the sensitivity and stability of this arrangement is made possible by filling the gap between the said electrodes (51, 52) with materials (54, 56) having different dielectric constants and different thicknesses. With a relation of 1:10 of the dielectric constants and a thickness relation of 1:5, an improvement factor of about 40 can be obtained. A 55
Inventors
- 👤 Urs Theodor Dr. Dürig
- 👤 James Kazimierz Dr. Gimzewski
- 👤 Heinrich Dr. Rohrer
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 22:23
CPC Classifications
G; G01; G01Q; G01Q20/00; G01Q20/02; G01D; G01D5/00; G01D5/26; G01D5/266; G01Q20/04; G01Q60/00; G01Q60/24; G01Q60/38; G01R; G01R33/00; G01R33/02; G01R33/038; G01R33/0385; G11; G11B; G11B11/00; G11B11/002; G11B11/007; G11B11/10; G11B17/00; G11B17/32; G11B9/00; G11B9/12; G11B9/14; G11B9/1418
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
157 words
Atomic force sensor head comprising at least one cantilever beam (3, 30, 50, 70, 82, 92, 102, 112) fixed at one end and carrying an interaction member (2, 37, 55, 71, 81, 93, 101, 113) in a location distant from said fixed end for interaction with the surface of a sample (5, 38, 80, 95, 103, 108) to be investigated, and means (6, 29, 72-78, 86, 98) for detecting the deflection of said cantilever beam (3, 30, 50, 70, 82, 92, 102, 112) as said interaction member (2, 37, 55, 71, 81, 93, 101, 113) interacts with said investigated sample surface (5, 38, 80, 95, 103, 108), characterized in that said detection means (6, 29, 72-78, 86, 98) are designed to convert said deflection of said cantilever beam (3, 30, 50, 70, 82, 92, 102, 112) from its home position to a variation of an electrical value other than a tunneling current from an initial level thereof.
Claim 2
Dependent Claim
157 words
Atomic force sensor head comprising at least one cantilever beam (3, 30, 50, 70, 82, 92, 102, 112) fixed at one end and carrying an interaction member (2, 37, 55, 71, 81, 93, 101, 113) in a location distant from said fixed end for interaction with the surface of a sample (5, 38, 80, 95, 103, 108) to be investigated, and means (6, 29, 72-78, 86, 98) for detecting the deflection of said cantilever beam (3, 30, 50, 70, 82, 92, 102, 112) as said interaction member (2, 37, 55, 71, 81, 93, 101, 113) interacts with said investigated sample surface (5, 38, 80, 95, 103, 108), characterized in that said detection means (6, 29, 72-78, 86, 98) are designed to convert said deflection of said cantilever beam (3, 30, 50, 70, 82, 92, 102, 112) from its home position to a variation of an electrical value other than a tunneling current from an initial level thereof.
Claim 3
Dependent Claim
181 words
Sensor head in accordance with claim 1, characterized in that said interaction member consists of a pointed tip (2, 37, 55, 81 rigidly fixed on said cantilever beam (3, 30, 50, 82), that said detection means is designed as a capacitor (6, 29, 57, 87) comprising a pair of capacitor plates (7, 8; 32, 33; 51, 52; 82, 85) of which a first one (7, 32, 51, 82) forms an integral part with said cantilever beam (3, 30, 50, 82), while the second plate (8, 33, 52, 85) is mounted stationary opposite said first plate (7, 32, 51, 82), that both plates of said capacitor (6, 29, 57, 87) are connected to conventional capacitance measurement equipment, and that the output signal of said capacitance measurement equipment, representing a variation of the capacitance of said capacitor (6, 29, 57, 87) from an initial capacitance value, is supplied via a feedback control circuit (10; 35, 36; 43-46; 88) to a z-drive (12, 39, 89) for adjusting the z-distance of said tip (2, 37, 55, 81) from the investigated sample surface (5, 38, 80).
Claim 4
Dependent Claim
122 words
Sensor head in accordance with claim 1, characterized in that said cantilever beam (82; Fig.6) is attached to a rigidly supported frame member (83) an arm (84) of which carries a capacitor plate (85) at its free end and opposite the back of said cantilever beam (82), said plate (85) and said cantilever beam (82) forming a capacitor (87), that said cantilever beam (82) carries a pointed tip (81) which is supported at a distance on the order of one nanometer from the surface of a storage medium (80), and that a feedback circuit comprising a z-control unit (88) is provided for controlling the said z-distance by means of a z-jack (89) attached to the support (90) of said storage medium (80).
Claim 5
Dependent Claim
107 words
Sensor head in accordance with claim 1, characterized in that said cantilever beam (92; Fig.7) is attached to a rigidly supported frame member (83) an arm (84) of which carries a capacitor plate (85) at its free end and opposite the back of said cantilever beam (92), said plate (85) and said cantilever beam (92) forming a capacitor (87), and that said cantilever beam (92) carries an interaction member designed as a magnetic element (93) attached to the lower side (94) of said cantilever beam (92) and facing at a small distance (d) a magnetic storage medium (95) carrying at least one track of magnetic domains (96).
Claim 6
Dependent Claim
92 words
Sensor head in accordance with claim 2, characterized in that said cantilever beam (30; Fig.2) forms an integral part with the body (31) from which it extends, having an eigenfrequency on the order of 10 kHz and an effective spring constant of about 4 N/m, a width on the order of 100 µm, a thickness of about 15 um, and a length on the order of 1100 um, and that the spacing of said cantilever beam (30) at its free end from said body (31) is on the order of 10 um.
Claim 7
Dependent Claim
109 words
Sensor head in accordance with claim 2, characterized in that said cantilever beam (30) is mounted on top of a piezoelectric transducer (40, Fig.3) which rests on said body (31), said transducer (40) being connected to be excited by an excitation unit (41), that a voltage source (42) is connected between the capacitor plates (32, 33) carried by said cantilever beam (30) and said body (31) respectively, that the capacitor plate (32) attached to said cantilever beam (30) is connected to one input of a current/voltage converter (43), and that the output thereof is connected to an amplifier (44) which in turn is connected to said excitation unit (41).
Claim 8
Dependent Claim
52 words
Sensor head in accordance with claim 2, characterized in that the gap between the plates (51, 52) of said capacitor (57, Fig.4) is filled with at least two dielectric materials (54, 56) having different dielectric constants ( E1 , E2 ) and different relative thicknesses (s 1 ; s-s 1 ), respectively.
Claim 9
Dependent Claim
39 words
Sensor head in accordance with claim 7, characterized in that said dielectric materials (54, 56) have dielectric constants (∈ 1 ; E2 ) with a ≧ 1:10 relationship, and relative thicknesses (si; s-s 1 ), with a 1:5 relationship.
Claim 10
Dependent Claim
77 words
Sensor head in accordance with claim 1, characterized in that said interaction member is designed as a dielectric member (101, Fig.7) attached to the free end of said cantilever beam (102), that said dielectric member (101) carries an electrode (100) serving as a capacitor plate of a capacitor (C s ) the other plate of which is formed by the information pattern (103) carried by a record carrier (99) in operation passing underneath said dielectric member (101).
Claim 11
Dependent Claim
111 words
Sensor head in accordance with claim 1, characterized in that said interaction member is designed as a capacitor plate (111, Fig.9) attached to said cantilever beam (112) at the free end thereof, that said capacitor plate (111) carries a dielectric member (113) having a first dielectric constant ( E3 ), that said capacitor plate (111) is separated by an air gap (110, E2 = 1) from a storage medium (108) having an electrically conductive surface and forming the second plate of a capacitor, and that said storage medium (108) is coated with a soft dielectric medium (109, ∈ 1 ) smoothing out any possible corrugations (107) on said record carrier (108).
Claim 12
Dependent Claim
162 words
Sensor head in accordance with claim 1, characterized in that said interaction member is designed as pointed tip (71, Fig. 5) forming an integral part of said cantilever beam (70) which in turn extends from a body (74) across a via hole (75) therein, that said cantilever beam (70) carries a metal film (72), that said via hole (75) on the side of said body (74) opposite said cantilever beam (70) is closed with a half-transparent mirror (73), that a laser (76) is aligned with the axis of said via hole (75), that a beam splitter (77) is arranged at an angle in the path of the laser beam so as to deflect part of the light from said laser (76) onto a photodetector (78), the arrangement forming a Fabry-Perot interferometer with the value of the output signal from said photodetector (78) being a measure for the deflection of said cantilever beam (70) as its tip (71) interacts with a surface investigated.
References Cited (Backward Citations)
GB2150304A
Cited
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