NL2024739B1 - Ultrasonic subsurface imaging microscopy device and method - Google Patents

Ultrasonic subsurface imaging microscopy device and method Download PDF

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Publication number
NL2024739B1
NL2024739B1 NL2024739A NL2024739A NL2024739B1 NL 2024739 B1 NL2024739 B1 NL 2024739B1 NL 2024739 A NL2024739 A NL 2024739A NL 2024739 A NL2024739 A NL 2024739A NL 2024739 B1 NL2024739 B1 NL 2024739B1
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Netherlands
Prior art keywords
probe
tip
sample
pulses
subsurface imaging
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NL2024739A
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Dutch (nl)
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Jan Verbiest Gerard
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Univ Delft Tech
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Priority to NL2024739A priority Critical patent/NL2024739B1/en
Priority to PCT/EP2021/051497 priority patent/WO2021148632A1/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/043—Analysing solids in the interior, e.g. by shear waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/06—Visualisation of the interior, e.g. acoustic microscopy
    • G01N29/0654—Imaging
    • G01N29/0681—Imaging by acoustic microscopy, e.g. scanning acoustic microscopy
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/07—Analysing solids by measuring propagation velocity or propagation time of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/22—Details, e.g. general constructional or apparatus details
    • G01N29/24—Probes
    • G01N29/2418—Probes using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
    • G01Q60/00—Particular types of SPM [Scanning Probe Microscopy] or microscopes; Essential components thereof
    • G01Q60/24—AFM [Atomic Force Microscopy] or apparatus therefor, e.g. AFM probes
    • G01Q60/32—AC mode
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
    • G01S15/8906—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
    • G01S15/8909—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques using a static transducer configuration
    • G01S15/8911—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques using a static transducer configuration using a single transducer for transmission and reception
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S15/00—Systems using the reflection or reradiation of acoustic waves, e.g. sonar systems
    • G01S15/88—Sonar systems specially adapted for specific applications
    • G01S15/89—Sonar systems specially adapted for specific applications for mapping or imaging
    • G01S15/8906—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques
    • G01S15/8965—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques using acousto-optical or acousto-electronic conversion techniques
    • G01S15/8968—Short-range imaging systems; Acoustic microscope systems using pulse-echo techniques using acousto-optical or acousto-electronic conversion techniques using acoustical modulation of a light beam
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
    • G01S7/52023—Details of receivers
    • G01S7/52036—Details of receivers using analysis of echo signal for target characterisation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
    • G01S7/52079—Constructional features
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/52—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00
    • G01S7/52017—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S15/00 particularly adapted to short-range imaging
    • G01S7/52085—Details related to the ultrasound signal acquisition, e.g. scan sequences
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/1702—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids
    • G01N2021/1706—Systems in which incident light is modified in accordance with the properties of the material investigated with opto-acoustic detection, e.g. for gases or analysing solids in solids
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/01—Indexing codes associated with the measuring variable
    • G01N2291/011—Velocity or travel time
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/02—Indexing codes associated with the analysed material
    • G01N2291/023—Solids
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/042—Wave modes
    • G01N2291/0422—Shear waves, transverse waves, horizontally polarised waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/044—Internal reflections (echoes), e.g. on walls or defects
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/10—Number of transducers
    • G01N2291/101—Number of transducers one transducer

Abstract

The invention relates to an ultrasonic subsurface imaging Inicroscopy device, and. a method. of using such a device. The device comprises a probe, a laser beam source and a detector. The probe comprises a tip arranged at a first 5 surface of the probe, and an illumination area arranged at a second surface of the probe. The laser beam source is configured for generating short pulses of laser light, and for directing' said. short pulses of laser light onto the illumination area of the probe for generating acoustic pulses 10 in the probe. The probe is configured to guide said acoustic pulses towards an end of the tip which faces away from said probe. The detector is configured for time—resolved detection of acoustic vibrations in said. tip and/or said. probe in between subsequent acoustic pulses, in particular acoustic 15 vibration from reflections of said generated acoustic pulses from subsurface structures in a sample.

Description

No. P137685NL00 Ultrasonic subsurface imaging microscopy device and method
FIELD OF THE INVENTION The present invention relates to an ultrasonic subsurface imaging microscopy device. More particular, the invention relates to a device for scanning ultrasonic subsurface imaging, which uses features of an Atomic Force Microscope (AFM). In addition, the present invention relates to a method for subsurface imaging using an ultrasonic subsurface imaging microscopy device.
BACKGROUND A method to perform sub-surface detection of nanostructures in a sample, using an Atomic Force Microscopy (AFM) device is for example described in W02018/134011. The AFM device comprising a probe holder having a probe with a cantilever and a probe tip arranged on the cantilever. According to the method, the probe tip and a sample are moved relative to each other in one or more directions parallel to the surface for scanning of the surface with the probe tip. During this scanning, the motion of the probe tip relative to the probe holder is monitored with a tip position detector for obtaining an output signal. During said scanning, acoustic vibrations are induced in the probe tip by applying at least a first and second acoustic input signal to the probe. The first and second acoustic input signal respectively comprising a first and a second signal component at mutually different frequencies above 1 GHz, differing by less than 1 GHz, thereby obtaining a mixed acoustic signal that comprises a third signal component having a frequency equal to the difference between the frequencies of the first and second signal. Such a method of detection is also known as a heterodyne detection method.
It is noted that Wo2018/132011 also described an example in which the first and second input signals are provided by a pulsed laser source. The pulsed laser source provide an intensity varied pulsed laser beam, wherein the intensity of the laser beam has the frequency components of the first and second input signals. WO2018/132011 also teaches to used first and second signals having frequencies above 1 GHz to circumvent parasitic mechanical vibrations.
SUMMARY OF THE INVENTION A disadvantage of the known method to perform sub- surface detection of nanostructures in a sample, using an Atomic Force Microscopy (AFM) device as described in W02018/132011 is, that the method is based on the use of a mixed acoustic signal that comprises a third signal component having a frequency equal to the difference of the first and second signal. Such a third signal is generated by a non- linear mixing of the first and second signal by the tip- sample interaction. Although, one can make a mapping of changes of the output signal as a function of the position on the sample, it is not straight forward to attribute these changes to actual subsurface structures. In addition, there is no clear relation between the observed contrast and the depth of the subsurface features. Only detailed prior knowledge may allow a quantitative analysis.
It is an object of the present invention to provide a device and method for ultrasonic subsurface imaging which at least partially solves at least one of the above identified disadvantages at least partially.
According to a first aspect, an ultrasonic subsurface imaging microscopy device comprising: a probe comprising a tip arranged at a first surface of the probe, and an illumination area arranged at a second surface of the probe, a laser beam source configured for generating short pulses of laser light, and for directing said short pulses of laser light onto the illumination area of the probe for generating acoustic pulses in the probe, wherein the probe is configured to guide said acoustic pulses towards an end of the tip which faces away from said probe, a detector configured for time-resolved detection of acoustic vibrations in said tip and/or said probe in between subsequent acoustic pulses generated by the short pulses of laser light.
In use, the tip of the probe is arranged against or close to a surface of a sample, such that the acoustic pulses can be transferred from the tip into the sample. The part of the acoustic pulses which is transferred into the sample, will travel through the sample and will be reflected at positions inside the sample where the mass density, the elasticity and/or absorption of the material changes, such as subsurface structures. The reflected acoustic pulses travel back towards the tip, where they are picked-up by the tip. The reflected acoustic pulses travel through the tip and/or probe, and can be detected by the detector, at least in between subsequent acoustic pulses generated by the short pulses of laser light. Due to the time-resolved detection, the time difference between the generated acoustic pulse in the probe and the occurrence of a reflected acoustic pulses from a structure inside the sample can be determined, which time difference provides a measure for the position and depth of the subsurface structure.
Accordingly, the device of the present invention uses a pulse-echo technique, which is much more straight forward to analyse than the heterodyne measuring technique as described in W02018/132011. Moreover, when the velocity of sound in the sample is known, the actual depth of the structure can easily be calculated from the time difference between the generated acoustic pulse in the probe and the occurrence of a reflected acoustic pulses.
By using very short pulses of laser light and a high speed time-resolved detection, a device according to the invention can detect and locate subsurface structures more accurately, and preferably visualize subsurface structures with sub micrometer resolution, and preferably with nanometer resolution.
In an embodiment, the detector for time-resolved detection of acoustic vibrations in said tip and/or said probe comprises a light source which is configured for generating an optical sensing beam and for directing said optical sensing beam to incident on the probe, and an optical sensor which is configured for sensing a reflected beam of the optical sensing beam reflected from said probe. Accordingly, acoustic vibrations in said tip and/or said probe can be sensed by the optical sensor via changes in the intensity and/or position of the reflected beam. Preferably, said detector is configured to detect changes in the reflectivity of the surface of the probe where the optical sensing beam incidents on. The changes of the reflectivity of the surface of the probe contains information of the acoustic waves in the probe. In addition or alternatively, said detector is preferably configured so that the reflected beam can sense stress and/or strain waves in the tip and/or probe, for example by utilising a photo-elastic effect or for example by sensing surface waves at the surface of the probe at which the optical sensing beam is reflected.
In an embodiment, the optical sensing beam also comprises a pulsed optical sensing beam, wherein the light source is configured to provide a time delay between the short pulses of laser light and the pulsed optical sensing beam. Preferably the time delay 1s adjustable, in particular in order to probe for reflections coming from different depths in the sample. A pulsed optical sensing beam is highly preferred for detecting acoustic vibrations with high frequencies. Preferably, the frequencies of the acoustic vibrations used in the device of the present invention are 5 very high (in the GHz range) in order to obtain a desired depth resolution. In order to detect acoustic vibrations with such high frequencies, one can use a pulsed optical sensing beam in order to probe the reflectivity of the probe during a time period which is defined by the pulse duration of the pulsed optical sensing beam. By changing or shifting the delay-time between the short pulses of laser light and the pulsed optical sensing beam for subsequent generations of acoustic vibrations, the reflections of the high frequency acoustic vibrations at internal structures in the sample can be reconstructed.
In an embodiment, the light source is configured for directing said optical sensing beam to incident on the illumination area of the probe. Preferably, the energy in the optical sensing beam is much smaller than the energy in the short pulses of laser light, in particular such that the optical sensing beam substantially does not generate acoustic vibrations in the probe or tip, or generates acoustic vibration in the probe or tip with a negligible intensity.
In an embodiment, the light source is configured to be at least part of the laser beam source, wherein the laser beam source is configured for generating both the short pulses of laser light and the optical sensing beam. Preferably, the laser beam source is configured to provide an adjustable time-delay between the short pulses of laser light and the optical sensing beam, in particular in order to probe for reflections coming from different depths in the sample.
In an embodiment, the laser beam source comprises a pulsed laser, preferably a pulsed laser configured for generating light pulses with a duration of approximately 10 nano seconds or shorter, more preferably for generating light pulses with a duration shorter than 10 pico seconds, more preferably for generating light pulses with a duration shorter than 100 femto seconds. Such short light pulses allow to generate short acoustic pulses in the probe, which are highly suitable for time-resolved detection, such as in pulse-echo measuring techniques, in order to obtain the desired depth resolution.
Preferably the laser beam source is configured so that the time between two adjacent pulses is much larger than the duration of the light pulses. Preferably the time between two adjacent light pulses is more than 10 times the duration of said light pulses, more preferably the time between two adjacent light pulses is more than 100 times the duration of said light pulses. Accordingly, the time between pulses is readily available to detect acoustic reflections in the sample without interference of acoustic pulses generated by subsequent light pulses.
In an embodiment, the device comprises a sample holder, wherein the sample holder is configured to hold a sample and to position the sample in between the sample holder and the probe, wherein the probe is arranged such that the first surface and the tip are facing towards the sample holder.
In an embodiment, the first surface and the second surface are arranged at opposite sides of the probe.
Accordingly, the acoustic pulses generated at the illumination area on the second surface can travel straight through the probe to the opposite first surface comprising the tip.
In an embodiment, said tip comprises a centre line, wherein the centre line of the tip traverses said illumination area. Preferably, said illumination area extends at least partially perpendicular to said centre line. Accordingly, the acoustic pulses can travel into the tip and to the end of said tip which faces away from the probe.
In an embodiment, the probe comprises a cantilever. Cantilevers with a sharp tip on one side are for example used in Atomic Force Microscopes (AFM) and are readily available and can be used in the ultrasonic subsurface imaging microscopy device of the present invention.
The diameter of an AFM tip is typically 20nm, and is typically much smaller than the optical wavelengths used for imaging.
Accordingly, the lateral resolution of the ultrasonic subsurface imaging microscopy device of the present invention can be much larger or higher than the resolution of an optical microscope.
The large lateral resolution of an AFM allows to resolve smaller details when compared to an optical microscope.
For example, an AFM may resolve details in the order of approximately 10 nanometres, whereas an optical microscope may resolve details in the order or approximately 500 nanometres.
In an embodiment, the ultrasonic subsurface imaging microscopy device further comprises a probe holder, wherein the cantilever is fixed to the probe holder such that the tip is arranged spaced apart from said probe holder, and wherein the light source and/or the optical sensor are configured for measuring the position of the tip relative to the probe holder.
In addition to the ultrasound detection with the optical sensing beam, a significant part of the optical sensing beam is just reflected of the probe surface.
Any deflection of the cantilever due to tip-sample forces will change the amplitude and phase of the reflected optical sensing beam.
As the deflection of the cantilever varies on a much slower (>us) time scale {micro seconds or larger) compared to the time scale of the acoustic vibrations (pico second or nano second) as measured by the optical sensing beam, the optical sensing beam can also be used to perform feedback on the AFM cantilever while simultaneously performing the optical reflectivity (= GHz ultrasound) measurements.
This low frequency signal in the optical sensing beam due to the deflection of the cantilever can be used as input for the regular z-feedback of the AFM to keep the deflection, amplitude, or frequency of the cantilever constant.
It is noted that also the reflected short pulses of laser light from the laser beam source can be used in a similar way to provide information about a movement of the tip and/or probe by sensing changes in the position of the reflected beam. In a further embodiment, the ultrasonic subsurface imaging microscopy device further comprises a probe holder, wherein the cantilever is fixed to the probe holder such that the tip is arranged spaced apart from said probe holder, and a tip position detector for measuring the position of the tip relative to the probe holder. The tip position detector allows to measure a deflection of the cantilever, and thus to determine a force between the tip and a sample, preferably in a similar way as in an Atomic Force Microscope. An advantage of using a cantilever from an Atomic Force Microscope is, that the Atomic Force Microscope allows to determine the force with which the sharp tip rests on the surface of the sample, and/or to keep the force with which the sharp tip rests on the surface of the sample substantially constant. Accordingly, the tip can be positioned in contact with a sample in a reliable and reproducible way. In addition or alternatively, the device according to this embodiment allows to set the force between the tip and the sample to obtain an optimised transmission of the acoustic pulses from the tip into the sample, and/or an optimised picking up of reflected acoustic pulses from the sample into the tip.
In an embodiment, the tip position detector comprises a second light source which is configured for generating a second optical sensing beam and for directing said second optical sensing beam to incident on the probe, and a second optical sensor which is configured for sensing a reflected beam of the second optical sensing beam reflected from said probe. In an embodiment, the second light source is configured for directing said second optical sensing beam to incident on the second surface of the probe. Any deflection of the cantilever due to tip-sample forces will change the amplitude and phase of the reflected second optical sensing beam, and the second optical sensing beam can be used as a dedicated tip position detector to perform feedback on the
AFM cantilever. This dedicated tip positioning detector can be used as input for the regular z-feedback of the AFM to keep the deflection, amplitude, or frequency of the cantilever constant.
In an embodiment, the ultrasonic subsurface imaging microscopy device comprises an actuator cooperating with at least one of the probe or a sample holder for moving the tip and a sample relative to each other in one or more directions, preferably one or more directions substantially parallel to a surface of the sample. Accordingly, the actuator allows to scan the surface of the sample with the tip in order to sense subsurface structures in the sample at multiple positions over the sample.
In an embodiment, the ultrasonic subsurface imaging microscopy device is configured so that the central axis of the tip of the probe crosses the surface of the sample to be measured at an angle in a range between 65 and 90 degrees, preferably at an angle in a range between 72 and 82 degrees, more preferably at an angle approximately equal to 77 degrees.
This is in particular advantageous when the probe and tip are arranged on or part of a cantilever which is held at a proximal end of the cantilever by a cantilever holder, in particular wherein the probe and tip are arranged at a distal end of the cantilever. In such an embodiment, the tilting of the cantilever with a well-known angle with respect to the surface of the sample holder, can prevent that the base of the cantilever and the cantilever holder will not come into accidental contact with the sample. Since the tip usually extends in a direction substantially perpendicular to a longitudinal axis of the cantilever, the tilting of the cantilever also yields a tiling of the central axis of the tip, as in this embodiment.
In addition or alternatively, the cantilever comprises a longitudinal axis, wherein said longitudinal axis of the cantilever is arranged at an angle smaller than 35 degrees, preferably at an angel in a ranged between 5 and 25 degrees, more preferably at an angle approximately equal to
13 degrees, with respect to a surface parallel to a surface of the sample holder.
In an embodiment, the cantilever comprises a surface structure which is configure to reflect the traveling of phononic waves through said cantilever. Due to this reflecting surface structure which blocks the traveling of phononic waves through said cantilever, an interference of these phononic waves with the detection of acoustic reflections from subsurface structures in a sample can be reduced.
According to a second aspect, the present invention provides a method for ultrasonic subsurface detection of structure in a sample using an ultrasonic subsurface imaging microscopy device as described above, or an embodiment of said ultrasonic subsurface imaging microscopy device as described above.
The various aspects and features described and shown in the specification can be applied, individually, wherever possible. These individual aspects, in particular the aspects and features described in the attached dependent claims, can be made subject of divisional patent applications.
BRIEF DESCRIPTION OF THE DRAWINGS The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings, in which: Figure 1 shows a schematic representation of a first example of a device according to the invention, Figure 2 shows a schematic representation of a second example of a device according to the invention, Figure 3 shows a schematic representation of a third example of a device according to the invention, Figures 4A, 4B and 4C show a detail of a first example of a probe with a tip for use in a device of the invention, Figures SA and 5B show a schematic representation of the working of the probe and tip, and Figure 6, shows a detail of a second example of a probe with a tip for use in the device of the invention.
DETAILED DESCRIPTION OF THE INVENTION Ultrasound imaging, as commonly used in hospitals for imaging for example unborn babies in their mother’s womb, in limited in spatial and depth resolution by the wavelength of the ultrasound waves. As the wavelength ranges from 10 micrometers to several millimeters, ultrasound imaging as we know it cannot be utilized to image features at the sub-micro meter scale.
The present invention provides a device to overcome this limitation, and an example of such a device is described below with reference to figure 1.
Figure 1 shows a schematic representation of a first example of an ultrasonic subsurface imaging microscopy device 1 according to the present invention.
The device comprises a sample holder 2 for holding a sample 3, and a probe 4 comprising a tip 6. The tip 6 is arranged at a side of the probe 4 facing the sample holder
2. The probe 4 and the tip 6 are configured for in use contacting the surface of the sample 3. The tip 6 is arranged at a first surface 41 of the probe 4, and an illumination area arranged at a second surface 42 of the probe 4. As schematically shown in figure 1, the first surface 41 and the second surface 42 are arranged at opposite sides of the probe
4.
The device further comprises a probe holder 7. The probe 4 is connected to the probe holder 7 by means of a cantilever 5, wherein the cantilever 5 is connected to the probe holder 7 such that the tip 6 is arranged spaced apart from said probe holder 7.
In order to detect subsurface structures in the sample 3 at various position over the sample, the holder 7 and/or the sample holder 2 comprises a scanning device which is configured for moving the sample 3 and the tip 6 with respect to each other, which allows to scan over the surface of the sample 3 in order to search for the presence of subsurface structures in the sample 3. The device further comprises a laser beam source 3 configured for generating short pulses of laser light 9, and for directing said short pulses of laser light onto the illumination area 42 of the probe 4 for generating acoustic pulses in the probe 4. The probe 4 is configured to guide said acoustic pulses towards an end 61 of the tip 6 which faces away from said probe 4. When the tip 6 of the probe 4 contacts the sample 3, the acoustic pulses can at least partially be transmitted from the end 61 of the tip 6 into the sample 3, and reflected acoustic pulses from the sample 3 can at least partially be transmitted into the tip 6. Furthermore, the device comprises a detector configured for time-resolved detection of acoustic vibrations in said tip 6 and/or said probe 4. In this example, the detector comprises a detector laser beam source 10 which is configured for directing an optical sensing beam 11 of laser light onto the illumination area 42 of the probe 4, which optical sensing beam 11 is reflected on the illumination area 42, and the reflected optical sensing beam 11 is directed to a sensor 12. It is highly preferred to use a pulsed optical sensing beam 11 comprising short pulses of light, wherein a time delay between the pulses of the optical sensing beam 11 and the short pulses of laser light 9 from the laser beam source 8 is adjustable.
When acoustic vibrations in said probe 4 reach the illumination area 42, the illumination area 42 on second surface of the probe 4 will experience a short-term change in the surface properties and/or a deformation of the surface, which will induce a short-term change in the reflection of the optical sensing beam 11, for example due to a change in the reflectivity of the illumination area 42 induced by the acoustic vibrations, which can be detected by the sensor 12. This will be explained in more detail below with reference to figures 3 and 4.
In addition or alternatively, the sensor 12 can be configured to sense stress and/or strain waves in the second surface 42 of the probe 4, for example by utilising a photo- elastic effect or for example by sensing surface waves at the second surface 42 of the probe 4 at which the optical sensing beam 11 is reflected. It is noted that in this example, the optical sensing beam 11 is directed onto the illumination area 42. However, the optical sensing beam may also be directed in a different part of the probe 4, as long as the surface where the optical sensing beam 11 impinges on the probe 4, is affected by the acoustic vibrations in said probe 4. As schematically shown in figure 1, the cantilever 5 is arranged at an angle a with respect to the surface of the sample 3, so that the cantilever 5 and/or the probe holder 7 are at least substantially kept clear from the sample 3. In an exemplary embodiment the angle a is around or equal to 13 degrees. It 1s further noted that the detector can also be configured to operate as a tip position detector for measuring the position of the tip 6 relative to the probe holder 7, and thus for measuring a change in the position and/or shape of the illumination area 42 of the probe 4 due to a deformation of the cantilever 5. Any deflection of the cantilever 5 due to tip-sample forces will change the position, amplitude or phase of the reflected optical sensing beam 11 at the sensor 12, and the optical sensing beam 11 can be used as a tip position detector to perform feedback on the AFM cantilever
5. Accordingly, in addition to sensing acoustic vibrations in the probe 4, the signals from the sensor 12 can be used as input for the regular z-feedback of the AFM to keep the deflection, amplitude, or frequency of the cantilever 5 constant.
Figure 2 shows a schematic representation of a second example of an ultrasonic subsurface imaging microscopy device 1’ according to the present invention.
As in the first example, the device 1’ comprises a laser beam source 8 configured for generating a laser beam 9 with short pulses of laser light, and for directing said short pulses of laser light onto the illumination area 42 of the probe 4 for generating acoustic pulses in the probe 4. The laser beam 9 with high power short pulses of laser light is herewith referred to as the ‘pump beam’. The probe 4 is configured to guide said acoustic pulses towards an end 61 of the tip 6 which faces away from said probe 4. In addition, the laser beam source 8 is configured to also generate a low power pulsed optical sensing beam 97, also referred to as the ‘probe beam’ . Furthermore, the laser beam source 8 is configured to emit the low power laser pulses of the probe beam after a certain time delay after the emission of the high power laser pulses of the pump beam.
The time delay is adjustable in order to probe for echoes of the acoustic pulse which arrive at the illumination area 42 after reflection from subsurface structures at various depths in the sample.
The energy in the pulses of the probe beam is much smaller than the energy in the short pulses of laser light in the pump beam, in particular such that the probe beam substantially does not generate acoustic vibrations in the probe or tip, or generates acoustic vibration in the probe or tip with a negligible intensity.
As schematically shown in figure 2, at least a part of the probe beam 9’ is reflected on the illumination area 42, and the reflected beam 13 is directed to a sensor 14. It is noted, that also part of the high power pulses from the pump beam may be reflected at the illumination area 42 and may be directed towards the sensor 14. In order to circumvent that this reflection from the high power pulses reaches the sensor 14, the laser beam source 8 is configured such that the polarisation direction of the probe beam is perpendicular to the polarisation direction of the pump bean,
and a polarizing filter is arranged in front of the sensor 14 which only transmits the reflected light from the probe beam. In an alternative embodiment, the pump beam and the probe beam are configured to have different optical wavelengths, which allows to separate the pump beam and the probe beam due to their difference in wavelength, for example using a color filter, in order to ensure that the reflections of the pump beam does not reach the sensor. When acoustic vibrations in said probe 4 reach the illumination area 42, the illumination area 42 on second surface of the probe 4 will experience a short-term change in the surface properties and/or a deformation of the surface, which will induce a short-term change in the reflection of the optical sensing beam 11, in particular due to a change in the reflectivity of the illumination area 42 induced by the acoustic vibrations, which can be detected by the sensor
12. It is noted that the detector can also be configured to operate as a tip position detector for measuring the position of the tip 6 relative to the probe holder 7, and thus for measuring a change in the position and/or shape of the illumination area 42 of the probe 4 due to a deformation of the cantilever 5. Any deflection of the cantilever 5 due to tip-sample forces will change the position, amplitude or phase of the reflected probe beam 13 at the sensor 14, and the probe beam 13 can be used as a tip position detector to perform feedback on the AFM cantilever 5. Accordingly, in addition to sensing acoustic vibrations in the probe 4, the signals from the sensor 14 can be used as input for the regular z-feedback of the AFM to keep the deflection, amplitude, or frequency of the cantilever 5 constant. Figure 3 shows a schematic representation of a third example of an ultrasonic subsurface imaging microscopy device 17” according to the present invention. As in the first and second example, the device 1” comprises a laser beam source 8 configured for generating a laser beam 9 with short pulses of laser light, and for directing said short pulses of laser light onto the illumination area 42 of the probe 4 for generating acoustic pulses in the probe 4. The laser beam 9 with high power short pulses of laser light is herewith referred to as the ‘pump beam’ . The probe 4 is configured to guide said acoustic pulses towards an end 61 of the tip 6 which faces away from said probe 4. In addition, the laser beam source 8 is configured to also generate a low power pulsed optical sensing beam 97, also referred to as the ‘probe beam’. Furthermore, the laser beam source 8 is configured to emit the low power laser pulses of the probe beam after a certain time delay after the emission of the high power laser pulses of the pump beam. The time delay is adjustable in order to probe for echoes of the acoustic pulse which arrive at the illumination area 42 after reflection from subsurface structures at various depths in the sample. The energy in the pulses of the probe beam is much smaller than the energy in the short pulses of laser light in the pump beam, in particular such that the probe beam substantially does not generate acoustic vibrations in the probe or tip, or generates acoustic vibration in the probe or tip with a negligible intensity. As schematically shown in figure 2, at least a part of the probe beam 9’ is reflected on the illumination area 42, and the reflected beam 13 is directed to a sensor 14. When acoustic vibrations in said probe 4 reach the illumination area 42, the illumination area 42 on second surface of the probe 4 will experience a short-term change in the surface properties and/or a deformation of the surface, which will induce a short-term change in the reflection of the optical sensing beam 11, in particular due to a change in the reflectivity of the illumination area 42 induced by the acoustic vibrations, which can be detected by the sensor
12. The device according to this third example comprises a separate Lip position detector comprising a light source 20 for generating a laser beam 21, which need not be a pulses laser beam, and a position sensor 22, which is arranged to receive a part of the laser beam 21 which has been reflected on the second surface of the probe 4. Accordingly, by detecting changes in the position of the reflected laser beam 21 at the position sensor 22, the tip position detector can measure the position of the tip © relative to the probe holder 7, and thus can measure a change in the position and/or shape of the second surface of the probe 4 due to a deformation of the cantilever 5. Any deflection of the cantilever 5 due to tip-sample forces will change the position, amplitude or phase of the reflected laser beam 21 at the position sensor 22, and the tip position detector is thus configured to perform feedback on the AFM cantilever 5. Accordingly, in addition to sensing acoustic vibrations in the probe 4 by the reflection of the probe beam 13 using the sensor 14, the signals from a separate position sensor 22 can be used as input for the regular z-feedback of the AFM to keep the deflection, amplitude, or frequency of the cantilever 5 constant.
Figure 4A shows a schematic isometric view of a probe 4 as being part of a cantilever 5 for an atomic force microscope. Figures 4B and 4C show a schematic cross-section along the line IIIB-IIIB in figure 4A. The tip 6 is arranged at a first surface 41 of the probe 4, and an illumination area 42 arranged at a second surface 43 of the probe 4. Again, the first surface 41 and the second surface 43 are arranged at opposite sides of the probe 4. The tip 6 comprises a centre line 62, and is arranged such that the centre line 62 traverses said illumination area 42, preferably wherein the centre line 62 traverses the illumination area 42 substantially at the centre 44 thereof. In this example, the illumination area 42 extends substantially perpendicular to said centre line 62 of the tip 6.
In the example, the laser beam source 8 comprises a pulsed laser for generating high power light pulses 81 with a duration of approximately 10 nano seconds or shorter, more preferably for generating light pulses with a duration equal or shorter than 1 pico seconds, more preferably for generating light pulses with a duration equal or shorter than 100 femto seconds. When such an ultra-short light pulse 81 (smaller or equal to 100 femto seconds) irradiates the illumination area 42, the ultra-fast heating and cooling of the illumination area 42 produces stress waves 15 with a wavelength of approximately 10 nanometers (which corresponds to a frequency of more than 10 GHz) in the probe 4. The stress waves 15 will travel to the apex 61 of the tip 6, where they will partly be reflected and partly be transmitted into a sample 3 at a position where the tip 6 touches a surface of the sample 3 to produce the stress waves 16 in the sample 3. The stress waves 16 transmitted into the sample 3 will be scattered and/or reflected on the internal structure in the sample 3 due to differences in the speed of sound caused by variations in mass density, elasticity and/or absorption. The reflected stress waves 17 coming from the internal structure (echoes) of the sample 3 are (partially) picked-up by the apex 61 of the tip 6 and will travel through the tip 6 towards the probe 4 where they can be detected, for example using a detector beam 11, 9’ and a sensor 12, 14 as described above. The detector beam 97,11 comprises a low power pulses 82 which impinge on the probe 4 after a certain time delay At after the high power laser pulses 81. The time delay At is adjustable in order to probe for echoes of the acoustic pulse which arrive at the illumination area 42 after reflection from subsurface structures at various depths in the sample.
By using ultrashort high power laser pulses 81 and low power detector pulses 32, the device of the present invention can perform ultrasound sonography. By varying the position of the tip 6 and the sample 3 with respect to each other, the device can perform ultrasound imaging.
Preferably, the device comprises an Atomic Force Microscope (AFM) with a cantilever 5 which comprises a tip © which is configured for performing Atomic Force Microscopy. The sharp tip 61 of the AFM probe ensures nanometer spatial resolution over the area of the sample 3, whereas the ultrashort stress waves 15, 16 enable nanometer depth resolution. By varying the position of the cantilever 5 with respect to the sample 3, the device according to this example of the invention can perform ultrasound imaging. It is noted that the tip 6 of the probe 4 should contact the sample 3 in order to transmit the acoustic waves.
This can be in a contact mode of the AFM or in a tapping mode of the AFM. During the tapping mode, the tip 6 is also for some time in contact with the surface during the oscillation period.
Figures 5A and 5B show a schematic representation of the working of the probe and tip for detecting a subsurface structure 33 in the sample 3. As described above, stress waves produced by irradiation of the illumination area 43 by ultra- short laser pulses 81, will travel to the apex 61 of the tip 6, where they will partly be reflected and partly be transmitted into a sample 3 at a position where the tip 6 touches a surface of the sample 3.
The stress waves reflected at the apex 61 of the tip 6 travel back to the probe 4 where they can be detected, for example using a detector beam 11, 9’ and a sensor 12, 14 as described above, to generate a first signal 611 at a time delay tl.
The stress waves transmitted into the sample 3 produce stress waves in the sample 3 which will be at least partially reflected at a boundary surface 331 of a subsurface structure 33. The reflected stress waves coming from the internal structures 33 or back surface 34 of the sample 3 will arrive back at the tip 6 at a certain time depending on the distance 31, 32 between the apex 61 of the tip 6 and the boundary surface 331 and/or the back surface 34 of the sample 3, and the speed of sound in the sample 3 and/or in the internal structures 33.
When the tip 6 of is arranged above the subsurface structure 33, a first reflection of the stress wave will arrive back at the tip 6 and generates a first reflection signal 311 at a time delay t2. Subsequently, this first reflection is again partially reflected at the upper surface 35 of the sample, travels back to the subsurface structure 33, is again partially reflected at the boundary surface 311, travels back to the upper surface 35 to arrive at the tip 6 to generate a second reflection signal 312 at a time delay t4. This ringing process may repeat itself to generate a third reflection signal 313 at a time delay t6, etc.
When the tip 6 of is arranged at a position of the sample without a subsurface structure 33, the stress wave will be reflected at least at the back surface 34 of the sample 3, and a first reflection of the stress wave will arrive back at the tip 6 and generates a first reflection signal 321 at a time delay t3. Subsequently, this first reflection is again partially reflected at the upper surface 35 of the sample, travels back to the back surface 34, is again partially reflected, travels back to the upper surface 35 to arrive at the tip 6 to generate a second reflection signal 322 at a time delay t5. This ringing process may repeat itself to generate a third reflection signal 323 at a time delay t7, etc.
Because the distance 32 between the front surface 35 and the back surface 34, and the distance 31 between the front surface 35 and the boundary surface 311 is larger, time t3 is larger than t2.
It is noted that in case the speed of sound in the sample 3 is known, the distance between the boundary surface 311 and the upper surface 35 can be calculated from the time difference between tl and t2. In addition or alternatively, using several samples with a controlled thickness allows to calibrate the device by establishing a relation between the time difference between tl and t3 as a function of the thickness of the sample corresponding to the measurements at the appropriate time delays.
It is further noted that when the tip 6 is arranged above the internal structure 33, the resulting signal may also comprise a combination of a partial reflection at the boundary surface 311 and a partial reflection at the back surface 34. In case the sample comprises several boundary surfaces at various depths in the sample, the signals of all these reflections will result in a complicated signal comprising the sum of the various reflections. Such a complicated signal can at least partially be disentangled by using the above described ringing effect.
In order to reduce an interference between the detection of the reflected stress waves with a subsequent laser pulse 81, the laser beam source is preferably configured so that the time between two adjacent laser pulses 81 is much larger than the duration of the laser pulses 81 , preferably wherein the time between two adjacent light pulses 81 is more than 10 times the duration of said light pulses 81, more preferably the time between two adjacent light pulses 81 is more than 100 times the duration of said light pulses 81.
Preferably, the time between subsequent laser pulses 81 is large enough to detect at least the signals 311, 321 of the first reflected stress wave, but preferably to also detect one or more ringing signals 312, 322; 313, 323.
It is noted that ultrashort laser pulses, for example with a pulse duration of smaller than 100 femto seconds, yield an ultrafast heating and cooling of the illumination area which may yield GHz acoustic waves, for example with a frequency between 10 - 100 GHz. Using high- speed time-resolved detection can provide the required depth resolution. For example, when the time-resolved detection is capable of measuring a time delay of 1 pico seconds, this corresponds to a depth resolution of approximately 1 nm (in silicon) for detecting an echo. Accordingly, when using a sampling frequency of 100 GHz, a depth resolution of approximately 10 nm can be obtained (in silicon).
Accordingly, the ultrasonic subsurface imaging microscopy device working at GHz frequencies allows to obtain a depth resolution smaller than the wavelength of visible light. In addition, when combining the ultrasonic subsurface imaging microscopy device with an Atomic Force Microscope, the lateral resolution (in the plane of the surface of the sample) can be as low as approximately 5 nm (standard AFM resolution).
The detected signals as a function of the time delay and the position can be transformed into a 3D image of the sample using an appropriate algorithm. It is noted that the present invention allows the 3D visualisation of sample that are opaque for light or charged particles/wave (such as electrons) commonly used for imaging.
When the probe 4 is part of a cantilever 5, such as a cantilever for an AFM, the stress waves generated at the illumination area 42 will also partially travel along the cantilever 5 as stress wave and/or phononic surface waves, and may yield reflected stress waves and/or phononic surface waves from a reflection in the cantilever 5 which may interfere with the reflected stress waves from the sample 3. Accordingly, figure 6 shows a schematic view of a second example of a probe 4 with a tip 6, arranged at a modified cantilever 5’, wherein this cantilever 5’ comprises a surface structure 51 which is configure to reflect the traveling of phononic waves through said cantilever 5’. Due to this reflective surface structure 51 which blocks the traveling of phononic waves through said cantilever 5’, an interference of phononic waves with the detection of acoustic reflections from subsurface structures in a sample 3 is reduced.
In summary, the present invention relates to an ultrasonic subsurface imaging microscopy device, and a method of using such a device. The device comprises a probe, a laser beam source and a detector. The probe comprises a tip arranged at a first surface of the probe, and an illumination area arranged at a second surface of the probe. The laser beam source is configured for generating short pulses of laser light, and for directing said short pulses of laser light onto the illumination area of the probe for generating acoustic pulses in the probe. The probe is configured to guide said acoustic pulses towards an end of the tip which faces away from said probe. The detector is configured for time- resolved detection of acoustic vibrations in said tip and/or said probe, in particular acoustic vibration from reflections of said generated acoustic pulses from subsurface structures in a sample.
It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and 1s not meant to limit the scope of the invention. From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the scope of the present invention as defined in the claims.

Claims (18)

CONCLUSIESCONCLUSIONS 1. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak omvattende: een sonde omvattende een tip die aan een eerste oppervlak van de sonde is geplaatst, en een belichtingsvlak dat aan een tweede oppervlak van de sonde is geplaatst, gen bron voor een laserbundel die geconfigureerd is voor het genereren van korte pulsen van laserlicht, en voor het richten van de genoemde korte pulsen van laserlicht op het belichtingsvlak van de sonde voor het genereren van akoestische pulsen in de sonde, waarbij de sonde is geconfigureerd om de genoemde akoestische pulsen naar een uiteinde van de tip te leiden dat van de sonde af gekeerd is, een detector die geconfigureerd is voor tijd- opgeloste detectie van akoestische vibraties in de tip en/of in de sonde tussen opeenvolgende akoestische pulsen.An ultrasonic microscopy device for subsurface imaging comprising: a probe comprising a tip disposed on a first surface of the probe, and an illumination plane disposed on a second surface of the probe, a laser beam source configured to generate short pulses of laser light, and for directing said short pulses of laser light onto the exposure plane of the probe to generate acoustic pulses in the probe, the probe being configured to direct said acoustic pulses to directing an end of the tip facing away from the probe, a detector configured for time-resolved detection of acoustic vibrations in the tip and/or in the probe between successive acoustic pulses. 2. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens conclusie 1, waarbij de detector voor tijd-opgeloste detectie van akoestische vibraties in de tip en/of in de sonde een lichtbron omvat die geconfigureerd is voor het opwekken van een optische meetbundel en voor het richten van de optische meetbundel om op de sonde te vallen, en een optische sensor die geconfigureerd is voor het waarnemen van een gereflecteerde bundel van de optische meetbundel die van de sonde gereflecteerd is.The subsurface imaging ultrasonic microscopy apparatus of claim 1, wherein the detector for time-resolved detection of acoustic vibrations in the tip and/or in the probe comprises a light source configured to generate an optical measurement beam and for directing the measurement optical beam to impinge on the probe, and an optical sensor configured to detect a reflected beam of the measurement optical beam reflected from the probe. 3. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens conclusie 2, waarbij de optische meetbundel verder een gepulste optische meetbundel omvat, waarbij de lichtbron is geconfigureerd om een tijdvertraging tussen de korte pulsen van laserlicht en de gepulste optische meetbundel te verschaffen, bij voorkeur waarbij de tijdvertraging instelbaar is.The subsurface imaging ultrasonic microscopy apparatus of claim 2, wherein the measurement optical beam further comprises a pulsed measurement optical beam, the light source configured to provide a time delay between the short pulses of laser light and the pulsed measurement optical beam, preferably wherein the time delay is adjustable. 4. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens conclusie 2 of 3, waarbij de lichtbron geconfigureerd is om de optische meetbundel te richten zodat deze invalt op het belichtingsvlak van de sonde.The subsurface imaging ultrasonic microscopy apparatus of claim 2 or 3, wherein the light source is configured to direct the measurement optical beam to be incident on the exposure plane of the probe. 5. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens conclusie 2, 3 of 4, waarbij de lichtbron is geconfigureerd om ten minste een deel te zijn van de bron voor een laserbundel, waarbij de bron voor een laserbundel geconfigureerd is voor het genereren van de korte pulsen van laser licht en de optische meetbundel.The subsurface imaging ultrasonic microscopy apparatus of claim 2, 3 or 4, wherein the light source is configured to be at least a portion of the laser beam source, the laser beam source being configured to generate the short pulses of laser light and the optical measurement beam. 6. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens één van de conclusies 1 — 5, waarbij de bron voor een laserbundel een gepulste laser omvat, bij voorkeur een gepulste laser die geconfigureerd is voor het genereren van lichtpulsen met een duur van ongeveer 10 nanoseconden or korter, meer bij voorkeur voor het genereren van lichtpulsen met een duur van korter dan 10 picoseconden, meer bij voorkeur voor het genereren van lichtpulsen met een duur korter dan 100 femtoseconden.A subsurface imaging ultrasonic microscopy apparatus according to any one of claims 1 to 5, wherein the laser beam source comprises a pulsed laser, preferably a pulsed laser configured to generate pulses of light with a duration of about 10 nanoseconds or less, more preferably to generate light pulses with a duration of less than 10 picoseconds, more preferably to generate light pulses with a duration of less than 100 femtoseconds. 7. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens één van de conclusies 1 — 6, waarbij het apparaat een monsterhouder omvat, waarbij de monsterhouder is geconfigureerd om een monster te houden en om het monster te positioneren tussen de monsterhouder en de sonde, waarbij de sonde zodanig geplaatst is dat het eerste oppervlak en de tip naar de monsterhouder gekeerd zijn.The ultrasonic microscopy apparatus for subsurface imaging according to any one of claims 1 to 6, wherein the apparatus comprises a sample holder, the sample holder configured to hold a sample and to position the sample between the sample holder and the probe, with the probe positioned so that the first surface and tip face the sample holder. 8. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens één van de conclusies 1 — 7, waarbij het eerste oppervlak en het tweede oppervlak geplaatst zijn aan tegenovergelegen zijden van de sonde.The subsurface imaging ultrasonic microscopy apparatus according to any one of claims 1 to 7, wherein the first surface and the second surface are located on opposite sides of the probe. 9. Ultrasoon microscopie-apparaat voor beeldvorming onder een oppervlak volgens één van de conclusies 1 - 8, waarbij de tip een hartlijn omvat, waarbij de hartlijn van de tip het belichtingsvlak doorkruist, bij voorkeur waarbij het belichtingsvlak zich ten minste ten dele loodrecht op de hartlijn uitstrekt.An ultrasonic microscopy device for subsurface imaging according to any one of claims 1-8, wherein the tip comprises an axis, the axis of the tip intersecting the exposure plane, preferably wherein the exposure plane is at least partially perpendicular to the centerline extends. 10. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens één van de conclusies 1 - 9, waarbij de sonde een cantilever omvatThe ultrasonic microscopy device for subsurface imaging according to any one of claims 1 to 9, wherein the probe comprises a cantilever 11. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens conclusie 10, indien afhankelijk van conclusie 7, waarbij de cantilever een longitudinale as omvat, waarbij de longitudinale as van de cantilever onder een hoek kleiner dan 35 graden, bij voorkeur onder een hoek in een bereik tussen 5 en 25 graden, meer bij voorkeur onder een hoek ongeveer gelijk aan 13 graden geplaatst is met betrekking tot een oppervlak parallel aan een oppervlak van de monsterhouder.The ultrasonic microscopy device for subsurface imaging according to claim 10, when dependent on claim 7, wherein the cantilever comprises a longitudinal axis, the longitudinal axis of the cantilever at an angle of less than 35 degrees, preferably at a angle in a range between 5 and 25 degrees, more preferably at an angle approximately equal to 13 degrees, with respect to a surface parallel to a surface of the sample holder. 12. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens conclusie 10 of 11, waarbij de cantilever een oppervlaktestructuur omvat die geconfigureerd is om het voorplanten van fonon-golven door de cantilever te blokkeren.The subsurface imaging ultrasonic microscopy apparatus of claim 10 or 11, wherein the cantilever comprises a surface structure configured to block the propagation of phonon waves through the cantilever. 13. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens conclusie 10, 11 of 12, waarbij het ultrasoon microscopie-apparaat voor beeldvorming onder een oppervlak verder omvat: een sonde-houder, waarbij de cantilever bevestigd is aan de sonde-houder zodat dat tip op afstand geplaatst is van de sonde-houder, en waarbij de lichtbron en/of de optische sensor geconfigureerd zijn voor het meten van de positie van de tip ten opzichte van de sonde-houder.The subsurface imaging ultrasonic microscopy apparatus of claim 10, 11 or 12, wherein the subsurface imaging ultrasonic microscopy apparatus further comprises: a probe holder, the cantilever being attached to the probe holder such that said tip is spaced from the probe holder, and wherein the light source and/or the optical sensor are configured to measure the position of the tip relative to the probe holder. 14. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens conclusie 10, 11 or 12, waarbij het ultrasoon microscopie-apparaat voor beeldvorming onder een oppervlak verder omvat een sonde-houder, waarbij de cantilever bevestigd is aan de sonde-houder zodat dat tip op afstand geplaatst is van de sonde-houder, en een tip-positie-detector voor het meten van de positie van de tip ten opzichte van de sonde-houder.The subsurface imaging ultrasonic microscopy apparatus of claim 10, 11 or 12, wherein the subsurface imaging ultrasonic microscopy apparatus further comprises a probe holder, the cantilever being attached to the probe holder such that that tip is spaced from the probe holder, and a tip position detector for measuring the position of the tip relative to the probe holder. 15. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens conclusie 14, waarbij de tip-positie-detector een tweede lichtbron omvat die geconfigureerd is voor het genereren van een tweede optische meetbundel en voor het richten van de tweede optische om op de sonde in te vallen, en een tweede optische sensor die geconfigureerd is voor het waarnemen van een gereflecteerde bundel van de tweede optische meetbundel die van de sonde gereflecteerd is.The subsurface imaging ultrasonic microscopy apparatus of claim 14, wherein the tip position detector comprises a second light source configured to generate a second optical measurement beam and direct the second optical beam onto the probe, and a second optical sensor configured to detect a reflected beam from the second measurement optical beam reflected from the probe. 16. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens conclusie 15, waarbij de tweede lichtbron geconfigureerd is om de tweede optische meetbundel te richten zodat deze invalt op het tweede oppervlak van de sonde.The subsurface imaging ultrasonic microscopy apparatus of claim 15, wherein the second light source is configured to direct the second measurement optical beam to be incident on the second surface of the probe. 17. Ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak volgens één van de conclusies 1 “16, waarbij het ultrasoon microscopie-apparaat voor beeld- vorming onder een oppervlak een aandrijving omvat die samenwerkt met ten minste één van de sonde en de monsterhouder voor het verplaatsen van de tip en het monster ten opzichte van elkaar in één or meer richtingen, bij voorkeur één of meer richtingen in hoofdzaak parallel aan een oppervlak van het monster.The subsurface imaging ultrasonic microscopy device of any one of claims 1 to 16, wherein the subsurface imaging ultrasonic microscopy device comprises a drive cooperating with at least one of the probe and the sample holder for moving the tip and sample relative to each other in one or more directions, preferably one or more directions substantially parallel to a surface of the sample. 18. Werkwijze voor het ultrasoon detecteren van een structuur in een monster gebruik makende van een ultrasoon microscopie-apparaat voor beeldvorming onder een oppervlak volgens één van de conclusies 1 - 17.A method for ultrasonically detecting a structure in a sample using a subsurface imaging ultrasonic microscopy apparatus according to any one of claims 1 to 17.
NL2024739A 2020-01-23 2020-01-23 Ultrasonic subsurface imaging microscopy device and method NL2024739B1 (en)

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