US5025153A
Expired / Lapsed
US
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Scanning tunneling spectroscope and a spectroscopic information detection method
Assignee: Olympus Corp
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Filing: 1990-07-06
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Granted: 1991-06-18
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Expires: 2010-07-06
Abstract
Abstract A scanning tunnel spectroscope comprises a generator for applying a bias voltage (V T ) of a sin wave between a sample and probe, an I-V converter for converting a tunnel current flowing when the probe is set close to the sample, to a tunnel current representing voltage singal (I T ), a detector for detecting the absolute value of the voltage signal (I t ), and a servo circuit for servo-controlling a distance between the sample and probe using the absolute value with the servo time constant set larger than five times the period of the bias voltage. The information concerning the unevenness of the sample is obtained based on an output of the servo control means. A unit is provided for effecting the analog operation to derive a differential conductance based on the tunnel current on the real time basis and measuring the unevenness data and differential conductance between the sample and probe kept constant.
Inventors
- 👤 Takao Okada
- 👤 Akira Yagi
- 👤 Seizo Morita
- 👤 Nobuo Mikoshiba
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 18:50
CPC Classifications
G; G01; G01Q; G01Q60/00; G01Q60/10; G01Q60/12; Y; Y10; Y10S; Y10S977/00; Y10S977/84; Y10S977/849; Y10S977/85; Y10S977/851; Y10S977/86; Y10S977/861
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
171 words
A scanning tunnel spectroscope comprising a probe settable close to a sample; means for applying a bias voltage (V T ) of a preset waveform varying with time in a constant period between said sample and probe; means for current-voltage converting a tunnel current flowing when said probe is set close to said sample, to a tunnel current signal (I T ); means for detecting the absolute value of the tunnel current signal (I T ); means for servo-controlling a distance between said sample and probe using the absolute value with the servo time constant set larger than five times the period of the bias voltage; means for obtaining information concerning the unevenness of said sample based on an output of said servo control means; and means for effecting the analog operation to derive a differential conductance based on the tunnel current on the real time basis and measuring the unevenness data and differential conductance data on the real time basis with the distance between said sample and probe kept constant.
Claim 2
Dependent Claim
171 words
A scanning tunnel spectroscope comprising a probe settable close to a sample; means for applying a bias voltage (V T ) of a preset waveform varying with time in a constant period between said sample and probe; means for current-voltage converting a tunnel current flowing when said probe is set close to said sample, to a tunnel current signal (I T ); means for detecting the absolute value of the tunnel current signal (I T ); means for servo-controlling a distance between said sample and probe using the absolute value with the servo time constant set larger than five times the period of the bias voltage; means for obtaining information concerning the unevenness of said sample based on an output of said servo control means; and means for effecting the analog operation to derive a differential conductance based on the tunnel current on the real time basis and measuring the unevenness data and differential conductance data on the real time basis with the distance between said sample and probe kept constant.
Claim 3
Dependent Claim
47 words
A scanning tunnel spectroscope according to claim 1, wherein said detecting means includes means for detecting the fundamental frequency component of the bias voltage in the tunnel current signal and said servo control means controls the distance between said sample and probe using the fundamental frequency component.
Claim 4
Dependent Claim
20 words
A scanning tunnel spectroscope according to claim 1, wherein said bias voltage application means includes a sine wave voltage generator.
Claim 5
Dependent Claim
60 words
A scanning tunnel spectroscope according to claim 1, wherein said real-time measuring means includes a differentiating circuit for differentiating the tunnel current signal (I T ) and bias voltage (V T ) with respect to time and a division circuit for deriving a differential conductance (∂I T /∂V T ) based on the time-differentiated values on the real time basis.
Claim 6
Dependent Claim
72 words
A scanning tunnel spectroscope according to claim 1, wherein said real-time measuring means includes a logarithm amplifier means for deriving the logarithms of the tunnel current signal (I T ) and the bias voltage (V T ), and means for differentiating the logarithms with respect to time and subjecting the differentiated values to to a dividing operation to derive the differential conductance (∂I T /∂V T /I/V) on the real time basis.
Claim 7
Dependent Claim
76 words
A scanning tunnel spectroscope according to claim 1, further comprising means for holding only differential conductance data which is included in local differential conductance data output on the real time basis from said real-time measuring means at a desired voltage within the range of the bias voltage amplitude and which corresponds to a specified bias voltage based on the output voltage and the direction of variation in the output voltage from said bias voltage application means.
Claim 8
Dependent Claim
62 words
A scanning tunnel spectroscope according to claim 1, further comprising means for sampling and holding local differential conductance data output on the real time basis from said real-time measuring means at at least one desired voltage within the range of the bias voltage amplitude at a desired timing in a constant period of an output voltage from said bias voltage application means.
Claim 9
Dependent Claim
39 words
A scanning tunnel spectroscope according to claim 1, further comprising a phase compensation circuit for setting the tunnel current signal (I T ) and bias voltage (V T ) supplied to said real-time measuring means in-phase with each other.
Claim 10
Dependent Claim
50 words
A scanning tunnel spectroscope according to claim 1, further comprising means for removing a signal having a phase different from that of the bias voltage appearing in the tunnel current voltage from the current-voltage converting means due to a conductivity coupling between means for supporting the probe and the sample.
Claim 11
Dependent Claim
173 words
A scanning tunnel spectroscope comprising: means for applying a bias voltage (V T ) of a preset waveform varying with time in a constant period between a sample and probe; means for adding a D.C. offset voltage to said bias voltage to make the bias voltage positive or negative; means for current-voltage converting a tunnel current flowing when the probe is set close to the sample, to a tunnel current signal (I T ); means for servo-controlling a distance between said sample and probe using the tunnel current signal (I T ) with the servo time constant set larger than five times the period of the bias voltage; means for obtaining information concerning the unevenness of said sample based on an output of said servo control means; and means for effecting the analog operation to derive a differential conductance based on the tunnel current on the real time basis and measuring the unevenness data and differential conductance data on the real time basis with the distance between said sample and probe kept constant.
Claim 12
Dependent Claim
173 words
A scanning tunnel spectroscope comprising: means for applying a bias voltage (V T ) of a preset waveform varying with time in a constant period between a sample and probe; means for adding a D.C. offset voltage to said bias voltage to make the bias voltage positive or negative; means for current-voltage converting a tunnel current flowing when the probe is set close to the sample, to a tunnel current signal (I T ); means for servo-controlling a distance between said sample and probe using the tunnel current signal (I T ) with the servo time constant set larger than five times the period of the bias voltage; means for obtaining information concerning the unevenness of said sample based on an output of said servo control means; and means for effecting the analog operation to derive a differential conductance based on the tunnel current on the real time basis and measuring the unevenness data and differential conductance data on the real time basis with the distance between said sample and probe kept constant.
Claim 13
Dependent Claim
149 words
A scanning tunnel spectroscope in which a bias voltage (V T ) is applied between a sample and a probe, and a tunnel current (I T ) signal corresponding to a tunnel current flowing between the sample and the probe is detected to servo-operate the probe by means of an X, Y and Z finely driving mechanism, comprising: means for applying a Z axis variation voltage (ΔV Z ) having a period less than 1/5 of a servo time constant to said finely driving mechanism to finely move said probe in a Z direction; and analog operation means for receiving the Z axis variation voltage (ΔV Z ) and the tunnel current signal (I T ) to derive a barrier height (φ or √φ); wherein an unevenness image is derived from the servo output and a barrier height image is derived from an output of said analog operation means.
Claim 14
Dependent Claim
149 words
A scanning tunnel spectroscope in which a bias voltage (V T ) is applied between a sample and a probe, and a tunnel current (I T ) signal corresponding to a tunnel current flowing between the sample and the probe is detected to servo-operate the probe by means of an X, Y and Z finely driving mechanism, comprising: means for applying a Z axis variation voltage (ΔV Z ) having a period less than 1/5 of a servo time constant to said finely driving mechanism to finely move said probe in a Z direction; and analog operation means for receiving the Z axis variation voltage (ΔV Z ) and the tunnel current signal (I T ) to derive a barrier height (φ or √φ); wherein an unevenness image is derived from the servo output and a barrier height image is derived from an output of said analog operation means.
Claim 15
Dependent Claim
166 words
A scanning tunnel spectroscopic information detecting method comprising the steps of: applying a bias voltage (V T ) of a preset waveform varying with time in a constant period between a sample and a probe and detecting the absolute value of a tunnel current voltage signal (I T ) corresponding to a tunnel current flowing when said sample and probe are set close to each other; servo-controlling a distance between said sample and probe using said absolute value while the time constant of a servo circuit is set to prevent the distance between said sample and probe from being influenced by oscillation of the bias voltage; deriving information concerning the unevenness of said sample from an output of said servo control circuit; and effecting the analog operation to derive a differential conductance based on the tunnel current on the real time basis and measuring the unevenness data and differential conductance data on the real time basis with the distance between said sample and probe kept constant.
Claim 16
Dependent Claim
166 words
A scanning tunnel spectroscopic information detecting method comprising the steps of: applying a bias voltage (V T ) of a preset waveform varying with time in a constant period between a sample and a probe and detecting the absolute value of a tunnel current voltage signal (I T ) corresponding to a tunnel current flowing when said sample and probe are set close to each other; servo-controlling a distance between said sample and probe using said absolute value while the time constant of a servo circuit is set to prevent the distance between said sample and probe from being influenced by oscillation of the bias voltage; deriving information concerning the unevenness of said sample from an output of said servo control circuit; and effecting the analog operation to derive a differential conductance based on the tunnel current on the real time basis and measuring the unevenness data and differential conductance data on the real time basis with the distance between said sample and probe kept constant.
Claim 17
Dependent Claim
47 words
A scanning tunnel spectroscopic information detecting method according to claim 12, wherein said servo-controlling step includes a step of effecting the servo-control for a distance between said sample and probe using the fundamental frequency component of the bias voltage at a tunnel current signal (I T ).
Claim 18
Dependent Claim
20 words
A scanning tunnel spectroscopic information detecting method according to claim 12, wherein said bias voltage is a sine wave voltage.
Claim 19
Dependent Claim
55 words
A scanning tunnel spectroscopic information detecting method according to claim 12, wherein said step of real-time measuring the differential conductance data includes a step of deriving differential conductance data at at least one specified bias voltage signal from the local differential conductance data at a desired voltage within the range of the bias voltage amplitude.
Claim 20
Dependent Claim
40 words
A scanning tunnel spectroscopic information detecting method according to claim 12, further comprising a step of setting the tunnel current signal and the bias voltage signal in-phase with each other before said step of real-time measuring the differential conductance data.
Claim 21
Dependent Claim
41 words
A scanning tunnel spectroscopic information detecting method according to claim 12, further comprising a step for removing a capacitive component of a current generated between means for supporting the probe and the sample, from the tunnel current signal (I T ).
Claim 22
Dependent Claim
171 words
A scanning tunnel spectroscopic information detecting method comprising the steps of: adding an offset voltage to a bias voltage (V T ) of a preset waveform varying with time in a constant period to make the sign of the bias voltage positive or negative, applying the added voltage between a sample and a probe and detecting a tunnel current flowing when said sample and probe are set close to each other; servo-controlling a distance between said sample and probe using the tunnel current while the time constant of a servo circuit is set to prevent the distance between said sample and probe from being influenced by oscillation of the bias voltage; deriving information concerning the unevenness of said sample from an output of said servo control circuit; and effecting the analog operation to derive a differential conductance based on the tunnel current on the real time basis and measuring the unevenness data and differential conductance data on the real time basis with the distance between said sample and probe kept constant.
Claim 23
Dependent Claim
171 words
A scanning tunnel spectroscopic information detecting method comprising the steps of: adding an offset voltage to a bias voltage (V T ) of a preset waveform varying with time in a constant period to make the sign of the bias voltage positive or negative, applying the added voltage between a sample and a probe and detecting a tunnel current flowing when said sample and probe are set close to each other; servo-controlling a distance between said sample and probe using the tunnel current while the time constant of a servo circuit is set to prevent the distance between said sample and probe from being influenced by oscillation of the bias voltage; deriving information concerning the unevenness of said sample from an output of said servo control circuit; and effecting the analog operation to derive a differential conductance based on the tunnel current on the real time basis and measuring the unevenness data and differential conductance data on the real time basis with the distance between said sample and probe kept constant.
Claim 24
Dependent Claim
77 words
In a current-voltage converting circuit which on a base of a modified alternating current signal applied on a load having a variable resistance, current-voltage converts a detected current flowing the resistance component of the load, the improvement in which the detected current is treated by a phase-shifter and an amplifier and compared with the modified alternating current signal so that a current component flowing a capacitive component generated by the load is removed from the detected current.
Claim 25
Dependent Claim
77 words
In a current-voltage converting circuit which on a base of a modified alternating current signal applied on a load having a variable resistance, current-voltage converts a detected current flowing the resistance component of the load, the improvement in which the detected current is treated by a phase-shifter and an amplifier and compared with the modified alternating current signal so that a current component flowing a capacitive component generated by the load is removed from the detected current.
Claim 26
Dependent Claim
27 words
A circuit according to claim 19, wherein said load is a load between an STM probe and a sample, and said detected current is a tunnel current.
References Cited (Backward Citations)
US4870352A
Cited
US4894537A
Cited
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