US 11,635,448 B2Granted

Heterodyne scanning probe microscopy method and scanning probe microscopy system

AssigneeNederlandse Organisatie voor toegepast-natuurwetenschappelijk onderzoek TNO

InventorsSri Ram Shankar Rajadurai, Daniele Piras, Kodai Hatakeyama, Paul Louis Maria Joseph Van Neer, Maarten Hubertus Van Es, Hamed Sadeghian Marnani, Marcus Johannes Van Der Lans

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Abstract

The present document relates to a heterodyne scanning probe microscopy (SPM) method for subsurface imaging, and includes: applying an acoustic input signal to a sample and sensing an acoustic output signal using a probe. The acoustic input signal comprises a plurality of signal components at unique frequencies, including a carrier frequency and at least two excitation frequencies. The carrier frequency and the excitation frequencies form a group of frequencies, which are distributed with an equal difference frequency between each two subsequent frequencies of the group. The difference frequency is below a sensitivity threshold frequency of the cantilever for enabling sensing of the acoustic output signal. The document also describes an SPM system.

Claims16

Dependent claims

A heterodyne scanning probe microscopy method for imaging structures below a surface of a sample, the method including:

applying, using a transducer, an acoustic input signal to the sample;
sensing an acoustic output signal using a probe, the probe including a cantilever and a probe tip, wherein the probe tip is in contact with the surface, wherein the acoustic output signal is representative of an amount of indentation of the surface by the probe tip in response to the acoustic input signal applied to the sample;
wherein the acoustic input signal comprises a plurality of signal components that each have a unique frequency, wherein the plurality of signal components comprise:
a base signal component at a carrier frequency;
and
a plurality of additional signal components having further excitation frequencies;
wherein the carrier frequency and the further excitation frequencies together form a group of frequencies, wherein frequencies of the group of frequencies are distributed with an equal difference frequency between each two subsequent frequencies of the group of frequencies;
wherein the equal difference frequency is a frequency below a sensitivity threshold frequency for enabling said sensing the acoustic output signal;
wherein the plurality of additional signal components are provided as sideband signal components such that in a frequency domain the further excitation frequencies of the sideband signal components are arranged at either side of the carrier frequency of the base signal component, and
wherein at least two sideband signal components are arranged at either side of the carrier frequency.

7 more elements

A scanning probe microscopy system for imaging structures on or below the surface of a sample, comprising a probe for scanning the sample surface, wherein the probe comprises a probe tip mounted on a cantilever, and wherein the probe is mounted on a sensing head arranged for bringing the probe tip in contact with the sampling surface,

the system further comprising a motion actuator for enabling motion of the probe relative to the sample, a transducer for applying an acoustic input signal to the sample, and a probe deflection sensor for producing a sensor signal indicative of an acoustic output signal received via the probe tip, wherein the acoustic output signal is representative of an amount of indentation of the surface by the probe tip in response to the acoustic input signal when it is in use applied to the sample;
wherein the transducer is arranged for producing the acoustic input signal such as to comprise a plurality of signal components that each have a unique frequency, wherein the plurality of signal components comprise:
a base signal component at a carrier frequency;
and
a plurality of additional signal components having further excitation frequencies;
wherein the carrier frequency and the further excitation frequencies together form a group of frequencies, wherein the frequencies of the group of frequencies are distributed with an equal difference frequency between each two subsequent frequencies of the group of frequencies;
and
wherein the equal difference frequency is a frequency below a sensitivity threshold frequency for enabling said sensing of the acoustic output signal;
wherein the plurality of additional signal components are provided as sideband signal components such that in a frequency domain the further excitation frequencies of the sideband signal components are arranged at either side of the carrier frequency of the base signal component, and
wherein at least two sideband signal components are arranged at either side of the carrier frequency.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 17/612,507Filed 22 May 2020
Priority: EP 1917556521 May 2019
Published: US 2022/0229088 A121 Jul 2022
Granted: 25 Apr 2023
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

G01Q 60/32
AFM [Atomic Force Microscopy] or apparatus therefor, e.g. AFM probes: aC mode
G01N 29/06
Analysing solids: visualisation of the interior, e.g. acoustic microscopy
G01N 29/0681
Imaging: by acoustic microscopy, e.g. scanning acoustic microscopy
G01N 29/343
With time characteristics: pulse waves, e.g. particular sequence of pulses, bursts