NL2010334C2

NL2010334C2 - Terahertz scanning probe microscope.

Info

Publication number: NL2010334C2
Application number: NL2010334A
Authority: NL
Inventors: Teunis Martien Klapwijk
Original assignee: Univ Delft Tech
Priority date: 2013-02-20
Filing date: 2013-02-20
Publication date: 2014-08-21
Also published as: WO2014129896A1

Abstract

The invention provides aterahertz scanning probe microscope setup comprising (i) a terahertz radiation source configured to generate terahertz radiation; (ii) a terahertz lens configured to receive at least part of the terahertz radiation from the terahertz radiation source; (iii) a cantilever unit comprising a cantilever with at its distal end an electrically conductive tip, a slot-line basedleaky wave antenna configured to receive at least part of the focused terahertz radiation, a stripline electrode with a terahertz radiation receiving part wave antenna and with a tip part in electrical conductive connection with the electrically conductive tip; (iv) a terahertz radiation receiver, configured to receive via the leaky wave antenna returning terahertz radiation from a sample.

Description

Terahertz scanning probe microscope

FIELD OF THE INVENTION

The invention relates to a scanning probe microscope setup and to a method to probe a sample with sub millimeter radiation.

BACKGROUND OF THE INVENTION

Scanning probe microscopy (SPM) is a branch of microscopy that forms images of the surface of a sample using a physical probe that scans the sample. An image of the surface can be obtained by moving the probe, often in the form of a tip or needle, in a raster scan of the sample and evaluating the probe-surface interaction as a function of position. SPM was founded with the invention of the scanning tunneling microscope in 1981. Scanning probe microscopy is known since the 80's, when the first scanning tunneling microscope was built at IBM in Zürich (Switzerland).

Atomic Force Microscopy (AFM) is a later development of scanning probe microscopy. In general, the AFM consists of a cantilever with a sharp tip (probe) at its end that is used to scan a surface of a sample. When the tip is brought into proximity of a sample surface, forces between the tip and the sample lead to a deflection of the cantilever. Along with force, additional quantities may simultaneously be measured through the use of specialized types of probes. Typically, the deflection of the cantilever is measured using a laser spot reflected from the top surface of the cantilever into an optical sensor (e.g. CCD), though other methods for evaluation the deflection are also known in the art.

US 2010218286 (US Patent 8266718) describes a microwave microscope including a probe tip electrode vertically positionable over a sample and projecting downwardly from the end of a cantilever. A transmission line connecting the tip electrode to the electronic control system extends along the cantilever and is separated from a ground plane at the bottom of the cantilever by a dielectric layer. The probe tip may be vertically tapped near or at the sample surface at a low frequency and the microwave signal reflected from the tip/sample interaction is demodulated at the low frequency. Alternatively, a low-frequency electrical signal is also a non-linear electrical element associated with the probe tip to non-linearly interact with the applied microwave signal and the reflected non-linear microwave signal is detected at the low frequency.

SUMMARY OF THE INVENTION

An important frontier in condensed matter physics is the understanding of quantum materials in which different ground states compete, leading to electronic inhomogeneity and the concept of ‘quantum electronic liquid crystals’. The challenge for experiments is to measure the local electrodynamic properties in materials, which are electronically inhomogeneous, but atomically homogeneous. Despite of the fact that on an atomic level the materials can be fully homogeneous, uniformly amorphous or uniformly crystalline, the electronic properties vary with position. It is possible to have a mixture of superconducting and antiferromagnetic properties or of ferromagnetic and antiferromagnetic properties. This mixture and the concomitant topological structures such as edge states, domain walls and exotic surfaces have emerged as an important theme of the field, dominating the transport properties and the electrodynamic response. It reflects the breakdown of the conventional paradigm of solid-state physics that the periodic lattice and the atomic orbitals determine the properties of materials. Instead the properties beyond the atomic scale, on the larger mesoscopic scale, have become crucial. In many cases the material behaves more in analogy to soft condensed matter, such as the classical molecular liquid crystals, and behaves as quantum electronic liquid crystals.

Understanding and measuring these electronic inhomogeneities is at the center of interest for many of the new materials. Various experimental techniques are being applied such as for example angle-resolved photoemission spectroscopy (ARPES), neutronscattering, and electrodynamic response with optical experiments, all lacking the needed spatial resolution. A rewarding and powerful route is the direct study of the local properties by scanning tunneling microscopy (STM) including spectroscopy. This technique has been very successful in identifying the electronic inhomogeneities in conducting materials and will, despite of the fact that it is only sensitive to the surface and cannot be used with an insulator, continue to play an important role.

The materials envisioned here are usually doped Mott-insulators, and the many properties emerge by doping providing a rich phase diagram including metallic, ferromagnetic, superconducting and antiferromagnetic states and the peculiar pseudo-gap phase. Experiments need to be able to shed light on this rich variety, which include, apart from conducting states, also a large variety of non-conducting states. A (partially) related problem is the so-called superconducting-insulator transition observed in strongly disordered conventional superconductors. In these systems the competition between Anderson-localization and superconductivity leads to the formation of electronic inhomogeneity which is likely to persist into the insulating state. Understanding these complex materials with their rich variety of properties will be a major step forward in our conceptual framework and will lay the groundwork for optimizing these materials and harvesting their properties for future technology. Several other classes of materials that depend on local conductivities or local dielectric constants are optically and electronically active polymers, as well as biological materials. In addition, in many cases unique electronic properties are buried in an insulating matrix and are not accessible with scanning probes which are only sensitive to the surface. Access to local electrodynamic properties is a widely felt need.

As indicated above, US2010218286 describes a microwave microscope including a probe tip electrode vertically positionable over a sample and projecting downwardly from the end of a cantilever. A transmission line connecting the tip electrode to the electronic control system extends along the cantilever and is separated from a ground plane at the bottom of the cantilever by a dielectric layer. A frequency indicated in this document seems to be in the range of 0.5-10 GHz.

As described herein, for further characterization of materials an extension to the terahertz range would be desirable. Hence, we propose to expand the frequency range upwards to the 100’s of GHz to about 1 THz, or even more like up to 2 THz, or even up to 10 THz, e.g. desired to study materials with conductivities in the 1 to 10+5 S/m range, close to fully metallic. With the present systems this is however not possible as too much radiation is dissipated due to transport and/or passing junctions.

Hence, it is an aspect of the invention to provide an alternative scanning probe microscope setup and/or an alternative method for probing a sample with submillimeter wavelength radiation, which preferably further at least partly obviate one or more of above-described drawbacks.

A new technique, amongst others suitable to determine these local variations of the electronic properties, is proposed. The central objective is to measure with nanometer-scale spatial resolution the frequency-dependent (electrodynamic) properties, such as complex dielectric constant and complex conductivity of quantum materials, as well as polymeric and biological materials at frequencies in the THz range. The terahertz (THz) range is herein especially defined as 0.1-20 THz, like especially 0.1-10 THz, even more especially 0.5-10 THz.

With the herein proposed instrument it will become possible to determine for a range of materials the local (and possibly frequency-dependent) electromagnetic properties, such as the dielectric constant and conductivity. Through this technique it will now be possible to study the local properties of new materials and even getting access to the local energy-scales of their excitations. The envisioned device builds on US 2010218286 (US 8266718) and extends it from the microwave frequency range to the THz frequency range. As indicated above, one can no longer transmit the signal from a piece of room temperature electronics in the conventional way through coaxial cables, because of the increased losses. The problem to be solved is how to apply and minimize losses of this THz signal in the various components, such as the cantilever and in the coupling of the signal.

The proposed solution is to use an antenna-leaky lens combination and to make the antenna an integral part of the (circuit that forms the) cantilever. In this way, THz radiation can be coupled into the cantilever (and via the tip to the sample) via the leaky lens, which focuses the received THz radiation in the antenna. Hence, the terahertz lens is configured in the terahertz scanning probe microscope setup, or on the cantilever unit part, with the focal point in the antenna (or in the attachable cantilever unit part with antenna).

The antenna is herein also indicated as leaky-wave antenna. The antenna is especially a slot-line based antenna. The slot-line is designed to facilitate generation of a propagating THz wave at one or more frequencies in the THz range.

Hence, in a first aspect the invention provides a terahertz scanning probe microscope setup comprising (i) a terahertz radiation source configured to generate terahertz radiation; (ii) a terahertz lens (herein also indicated as "lens" or “leaky lens”) configured to receive at least part of the terahertz radiation from the terahertz radiation source and configured to focus at least part of said terahertz radiation to provide focused terahertz radiation; (iii) a cantilever unit comprising a cantilever with (at its distal end) an electrically conductive tip (herein also indicated as "tip"), a slot-line based leaky wave antenna (herein also indicated as "leaky wave antenna" or "antenna") configured to receive at least part of the focused terahertz radiation, a stripline electrode with a terahertz radiation receiving part, configured to receive terahertz radiation from the slot-line based leak wave antenna, and with a tip part in electrical conductive connection with the electrically conductive tip; (iv) a terahertz radiation receiver unit (herein also indicated as "receiver" or "detector"), configured to receive, for instance via the leaky wave antenna, returning terahertz radiation from a sample (under investigation with the electrically conductive tip). In an embodiment, the terahertz radiation source is an optional part of the setup, i.e. in an embodiment such setup is provided with at least components ii-iii, and optionally one or more of components i en iv. In such embodiment, e.g. the terahertz lens may be configured to receive terahertz radiation from a terahertz radiation source (such as e.g. defined below).

In a further aspect, the invention also provides a method to probe a sample with terahertz radiation, wherein the method comprises providing terahertz radiation to said sample via the electrically conductive tip of the terahertz scanning probe microscope setup as defined herein, and retrieving a terahertz signal from said sample with a terahertz radiation receiver unit configured to receive a terahertz signal from said sample, for instance via the leaky wave antenna, or via an on-chip heterodyne system. In such method, especially the herein defined terahertz scanning probe microscope setup may be applied. The terahertz scanning probe microscope setup may be configured to receive returning terahertz radiation from said sample (under investigation with the electrically conductive tip) via the cantilever unit, including optionally via the terahertz lens.

Especially, the terahertz scanning probe microscope setup is an atomic force microscope (AFM) setup.

Advantageously, this scanning probe setup, as well the method, enlarge the present possibilities to probe samples, and especially (electronic properties of) samples that are bad or even substantially not conductive. Therefore, the terahertz scanning probe microscope setup as described herein or the method to probe a sample with terahertz radiation as defined herein, may for instance be used for one or more of the following: studying a complex quantum material, studying electronic behavior of a conductive material, studying electronic behavior of a non-conductive material, studying a disordered superconducting material, studying the quantum Hall effect of a material, studying giant magnetic resistance of a material, studying colossal magnetic resistance of a material. However, other applications are also possible.

The terahertz lens is used as a leaky lens, and the THz wave(s) generated downstream of the lens are received by the antenna, wherein a THz wave is generated. In a first experiment, it was possible to couple in the terahertz lens and thereby in the antenna terahertz radiation within a substantial part of THz range of specific interest of 0.1-10 THz. The lens is herein also indicated as leaky lens, and the combination of antenna and terahertz lens is herein also indicated as antenna-leaky lens combination. Hence, the terahertz lens is especially designed to focus terahertz radiation having focal abilities for frequencies within a substantial part of THz range of specific interest of 0.1-10 THz.

The terms “upstream” and “downstream” relate to an arrangement of items or features relative to the propagation of radiation from a radiation generating means (here e.g. the terahertz radiation source), wherein relative to a first position within the propagation path from the radiation generating means, a second position in the propagation closer to the radiation generating means is “upstream”, and a third position within the beam of light further away from the light generating means is “downstream”. Note that the propagation direction is followed when determining upstream and downstream.

The antenna-leaky lens combination is amongst others described in US2012088459 (EP2175522), and by A. Neto et al. in (1) " UWB, Non Dispersive Radiation From the Planarly Fed Leaky Lens Antenna— Part 1: Theory and Design", in IEEE Transactions on Antennas and Propagation, Date of Publication: July 2010, Volume: 58, Issue: 7, Page(s): 2238 - 2247; (2) "UWB, Non Dispersive Radiation From the Planarly Fed Leaky Lens Antenna—Part IF Demonstrators and Measurements" in IEEE Transactions on Antennas and Propagation, Date of Publication: July 2010, Volume: 58, Issue: 7, Page(s): 2248 - 2258; and (3) US2012/0088459 (EP2175522), which are all incorporated herein by reference. These references especially describe the transfer of THz radiation from the antenna in the leaky lens, whereas in the present invention, especially the lens is used to couple the THz radiation into the antenna. US20120088459, e.g. describes a device with a substrate lens antenna, which uses a lens shaped dielectric body located on top of a planar feed antenna. A leaky wave antenna structure is used as feed antenna. The leaky wave antenna structure has a feed input and a first and second wave propagation branch extending from the feed input. The lens shaped dielectric body has a plane surface containing a focal point of the lens shaped dielectric body, the plane surface located adjacent the first plane, with the focal point adjacent the position of the feed input. Preferably the lens shaped dielectric body is spaced from the leaky wave structure at a sufficient distance to remove most of the propagation speed reduction effect of the dielectric on wave propagation along the leaky wave antenna. This helps to suppress undesirable side-lobes.

Hence, in an embodiment, the antenna-leaky lens combination, as e.g. described by Neto et al. (see above) is arranged as an integrable part of the circuit that forms the cantilever.

In a specific embodiment, the terahertz lens comprises a shaped dielectric body, especially a hyper hemispherical body, which may be of silicon or aluminum oxide, and which lens may have a diameter selected from the range of 1-5 mm, such as in the range of 2-4 mm. Therefore, especially the terahertz lens comprises a hyper hemispherical silicon or aluminum oxide lens having a diameter selected from the range of 1-5 mm. At least part of the shaped dielectric body may also comprise a (multi-layer) coating, with thin dielectric layers with suitable dielectric constants to serve as an anti-reflection coating. Such coating may further enable a reduction of loss from the surface of the lens.

Dependent upon the THz source, instead of a hyper hemispherical lens also a collimating lens may be applied.

As indicated above and further elucidated below, the antenna can be used to couple the focused THz radiation from the THz lens into the cantilever. Hence, the antenna is especially integrated in the cantilever. The cantilever is part of the cantilever unit, which at least comprises also the tip (see below). Between the lens and the antenna there is a gap, which is in general filled with a gas, especially air, but may also consist of a material with a dielectric constant substantially lower than that of the lens material, such as e.g. a polymer (such as for instance a (suitable) adhesive). The antenna is embedded in the cantilever, and especially, the cantilever is not in physical contact with the antenna. The cantilever below the lens especially comprises a thin metallic layer on a (planar) substrate, comprising the slot-line based antenna (as a kind of recess in the thin metallic layer). Hence, there is also a gap between the cantilever and the lens; this gap (dl) may be in the range of about 1-1000 pm, especially in the range of about 10-500 pm, such as 10-50 pm. For high frequency THz radiation, the gap will be relatively small; for low frequency THz radiation, the gap may be relatively large. As indicated above, this gap may at least partly be filled with a material with a dielectric constant that is smaller than that of the lens material, especially at least 20% smaller.

The total distance (h2) from the terahertz lens and the bottom of the slot-line based antenna, i.e. the top of the planar substrate, may be in the same range, as the depth (h2) of the slot-line based antenna will (only) be in the order of 10 nm - 10 pm, such as 50 nm - 2 pm, like up to 1 pm. Further, the walls of the antenna may comprise an electrically conductive material, e.g. selected from the group consisting of e.g. aluminum metal, tantalum, and copper, gold, tantalum, niobium or niobiumtitaniumnitride, especially a superconducting material.

The term “antenna” may also refer to a plurality of antennas. Further, the term “slot-line” may also refer to a plurality of slot-lines. Two or more of such slot-lines may be parallel, but may also be arranged in e.g. an X-like shape. The slot-line may especially be rectangular, but may optionally also be curved or bent. Especially, the slot-line is a cavity (line) in an electrically conductive material. Such antennas are e.g. also described in US

8283619 or EP 1213787. Especially, the antenna is adapted for receiving terahertz radiation (from the leaky THz lens).

In general, the slot-line based antenna may have any shape, especially a rectangular shape. Hence, in a specific embodiment the slot-line based leaky wave antenna comprises a rectangular channel with a length (1) in the range of 30 micrometer - 1 mm, a width (wl) in the range of 1-100 micrometer, especially 3-50 pm, a wall height (hi), alternatively called thickness of metallic layer, in the range of 10 nm - 10 pm, especially 50 nm - 2 pm, wherein the channel bottom and the terahertz lens have a distance in the range of 1-1000 pm, such as 10-500 pm (see above).

Optionally, one or more of the channel wall and the channel bottom comprises the terahertz radiation receiving part, although other configurations are also possible (see below). Further, more than one antenna may be applied. Hence, the term "antenna" may also relate to a plurality of antennas. The antenna may further have a narrowing in the middle of the antenna, which may facilitate to concentrate the electrical field in the antenna. For instance, a bow-tie antenna may be applied. The slotline-based antenna is in general a recession in an electrically conductive electrode on a substrate (or support), with the substrate providing the bottom of the slot-line based antenna. The substrate especially comprises a dielectric material.

As indicated above, the lens also may also comprise a dielectric material. Especially, the dielectric constant of the substrate (ε) is smaller than the dielectric constant of the lens. For instance, the lens may be of aluminum oxide, and the substrate may be silicon dioxide.

Terahertz radiation may e.g. be generated with a carcinotron (backward wave oscillator (BWO)), a multiplier-chain attached to a Gunn-oscillator, a quantum cascade laser, a photo-mixer, a free electron laser, a femto second laser, a gas laser, etc., like a tunable terahertz laser, such as e.g. from Toptica, a photo conductive (PC) antenna, etc. Terahertz transmission spectroscopy can be performed using either pulsed or continuous wave (cw) terahertz radiation, depending upon the desired application. Especially pulsed terahertz radiation may be applied, to observe transient and other dynamic phenomena. The terahertz radiation source may especially be able to generate in a frequency range that cover at least 10% of the range of 0.1-1 THz, especially at least 10% of the range of 0.1-10 THz, even more especially at least 20% of these ranges respectively. For instance, the terahertz radiation source may be tunable within the range of 0.1-4 THz, which is about 40% of the 0.1-10 THz range. Hence, in an embodiment the terahertz scanning probe microscope setup comprises a terahertz radiation source configured to provide terahertz radiation over at least 10% of the range of 0.1-10 THz.

As will be clear to the person skilled in the art, the cantilever needs some length to allow deflection. The part of cantilever unit below the lens may be stiff (non-deflectable), but seen from the probe head, beyond the lens up to the distal end, the cantilever may be deflectable. This part may in an embodiment have a length in the range of 30-800 pm, especially 40-400 pm. The terahertz radiation is to be transported from the antenna to the tip. To this end, an (electrically) conductor is used, especially in the form of a stripline, between the tip, which is (also) electrically conductive) and the antenna. As indicated above, the (stripline) electrode comprises a terahertz radiation receiving part, configured to receive terahertz radiation from the slot-line based leak wave antenna, and a tip part in electrical conductive connection with the electrically conductive tip. The electrically conductive tip may especially comprise a Pt tip.

The term "stripline" may also refer to a plurality of striplines. In general, the stripline comprise two electrically conductive conductors, which are separated by an insulator (dielectric). In a specific embodiment, the stripline may comprise three electrically conductive conductors, each separated by an insulator.

Transfer of the electromagnetic signal (THz signal)that is generated within the antenna to the stripline electrode (see below) can especially be done to integrate part of the stripline electrode in the wall(s) and/or bottom of the cavity of the slot-line based antenna. However, alternatively or additionally, the stripline may comprise an antenna configured to receive the THz radiation within the slot-line based antenna. To this end, the stripline may comprise a radial probe. The radial probe may especially comprise an extension of a stripline electrode having the shape of a circle sector, having a radius (r2) and an opening angle, suitable to receive THz radiation from the slot-line based antenna. The radius of the radial probe may be in the range of 10-500 pm and the opening angle (Θ) may be in the range of 5-180°. Especially, the radius of the radial probe may be in the range of 50-400 pm and the opening angle may be in the range of 80-100°, especially 85-95°.

In this way, THz radiation from the THz source is focused by the THz lens (especially at a focal point within the slot-line based antenna), transferred to the slot-line based antenna, via the terahertz receiving part of the stripline, transferred via the stripline to the tip part, and from the tip part to the tip, and finally from the tip to a sample.

The terahertz receiving part and an electrically conductive conductor of the stripline may be a single entity. For instance, part of the stripline may be a wall or bottom (part) of the slot-line based antenna. However, the terahertz receiving part may also comprise a radial probe (see also above), which is not necessarily in electrically conductive contact with one or more of the antenna wall and the antenna bottom.

The stripline may extend over a substantial length of the cantilever, such as over at least 50% of its length, especially at least 75% of its length. In general, at least one electrode of the stripline will over a substantial part of its length be embedded in one or more other material, or be sandwiched between one or more other materials, such as over at least 50% of its length, especially at least 75% of its length.

The stripline may comprise any electrical conductive material. One option that appears to work well is an aluminum stripline. However, also other options are possible, like tantalum, copper, gold, niobium, niobium titanium nitride, other alloys, etc., especially also superconducting ones. It may especially be advantageous to confine a propagating electromagnetic field of terahertz radiation in a space with sub-wavelength dimensions. This can be achieved by using a conductor having a cross-section with sub-wavelength structures that are smaller than the smallest wavelength of the guided radiation. For instance, terahertz radiation with a frequency of 100 GHz corresponding to the longest wavelength of terahertz radiation has a wavelength in free space of 1 mm. Thus, the conductor should comprise a structure smaller than 1 mm, like e.g. the height of the conductor.

In an aspect, the conductor may include a core structure and at least one confinement structure, wherein the confinement structure extends continuously along a longitudinal direction of the conductor, such as described in WO2012049587. In this way a type of laminate or coaxial system may be created. The confinement structure refers to a structure on a surface of the core structure, by which terahertz radiation can be confined. Since the confinement structure extends continuously along the length of the conductor, the cross- sectional shape of the wire remains constant at any point along the length of the wire. By these means, terahertz waves can be guided with low losses. Preferably, also the confinement structure has at least one dimension with sub-wavelength dimension. Hence, the cross-section of the confinement structure has at least one portion, which is smaller than a wavelength of the guided electromagnetic waves. In case that a large bandwidth of electromagnetic waves is guided, the confinement structure may have at least one dimension smaller than the smallest wavelength of the bandwidth. Preferably, dimensions of the confinement structure in the cross-section are smaller than the width of the core structure. At least one of the core structure and the confinement structure may be made of a conducting material and/or a semi-conductor material. If the core structure and/or the confinement stmcture are made of a conducting material, this may include any metal, preferably copper or stainless steel. When using a semi-conductor for at least one of the core structure and the confinement structure, the electrical characteristics of the wire may be adjusted using doping agents. Possibly, the core structure and the confinement structure are made of the same material. However, the confinement structure may also comprise an insulator.

Especially advantageous appears to be a system wherein the stripline electrode is at least partly comprised by a sandwich structure comprising a first conductor, a first isolator (“confinement structure”), a stripline electrode conductor, a second isolator (“confinement structure”) and a second conductor. The various thicknesses, dielectric constants, mechanical strengths and processability are important criteria to meet in order to minimize losses, impedance-match and optimize the tip-diameter in conjunction. Such type of sandwich structure can be considered an analogue of a coax cable. Characteristic materials that may be applied for the stripline electrode conductor are aluminum, or e.g. tantalum, copper, gold, niobium, niobium titanium nitride and other alloys; characteristic materials for the first conductor and second conductor are e.g. tantalum, copper, gold, niobium, niobium titanium nitride and other alloys; characteristic materials for the first isolator and second isolator are e.g. silicon, silicon nitride, silicon oxynitride, silicon-oxide, aluminum oxide, and aluminum nitride.

Other stripline geometries and background information may for instance be found in THz Wave propagation on Strip Lines: Devices, Properties, and Applications, by YutakaKadoya et al., Radio Engineering, vol. 17, no. 2, June 2008, p. 48-55.

In general scanning probe microscopy, especially AFM, is applied at room temperature. However, also lower temperature measurements are possible. Especially cryogenic temperatures like liquid nitrogen or sub liquid nitrogen temperatures, like liquid helium temperatures may also be applied, alternatively supplied through a closed-cycle refrigerator or a solid-state cooler. In such instance it may especially be beneficial to use a stripline that comprises a superconducting material, like yttrium barium copper oxide (YBCO) or niobium nitride (NbN) or niobium titanium nitride (NbTiN).

Therefore, the scanning probe microscope unit may further comprise a cryogenic unit, configured to cool the cantilever, and thereby allow an even better transport of the terahertz radiation through the stripline in the cantilever. Likewise, the method of the invention may further comprise cooling the cantilever to cryogenic temperatures. Hence, in a specific embodiment the stripline electrode conductor comprises a superconducting material, and the terahertz scanning probe microscope setup further comprises a cryogenic unit configured to cool the cantilever. Referring to the above described sandwich type of system with a first and a second conductor, that may especially be used to shield the stripline and confine the terahertz radiation, one or more of the first conductor, the stripline electrode conductor, and the second conductor may (thus) especially (also) comprise (each independently) a superconducting material, especially at least the stripline electrode conductor comprises a superconducting material.

Terahertz radiation from the sample, such as reflected THz radiation, follows the same way back, but may either be received by a receiver unit via the leaky lens or may from the antenna (not only travel to the leaky lens, but), or alternatively or additionally via another part of the cantilever, be fed to an electronic circuit (at least partly) integrated in the cantilever unit.

Hence, in an embodiment the terahertz radiation receiver unit is configured to receive returning terahertz radiation downstream from the terahertz lens. Hence, in an embodiment the terahertz radiation receiver unit may be configured to receive a terahertz signal from sample downstream from the terahertz lens. To this end optionally a terahertz radiation separator, a splitter, may be used to separate the returning terahertz radiation downstream from the lens (note that this is upstream for the terahertz radiation being transported from the THz radiation source to the lens) from the terahertz radiation travelling from the radiation source to the lens. In this way, the terahertz radiation receiver unit is configured to receive downstream from the terahertz lens returning terahertz radiation from the sample (that is probed by the tip and propagates through the stripline electrode, which is comprised by the cantilever unit.

In yet another embodiment, the terahertz radiation receiver unit comprises a terahertz processing unit integrated in the cantilever unit. Terahertz radiation receiver units are known in the art, and are for instance available from Gentec Electro Optics. In addition in particular state-of-the-art superconducting circuitry is known by specialists in the detection and processing of faint THz signals from astronomical objects in the universe.

Another possibility to consider is on-chip filtering (here, as indicated above, an electronic circuit may be used that, in an embodiment, is at least partly integrated in the cantilever unit). Also a (room temperature) heterodyne system based super lattice multiplier might also be an approach to be considered. The on-chip filtering or heterodyne system maybe included in a unit which is configured in electrical communication with the stripline, and which may be in physical connection with the cantilever.

The terahertz radiation receiver unit may comprise a photo conductive antenna, a non-linear element (such as a Schottky barrier diode), a thermal detector such as a bolometer, pyroelectric detector, or a Golay cell, and a heterodyne receiver (see also above).

The method of the invention may further comprise processing the terahertz signal from the sample. The setup may additionally comprise a control unit, which may include the functionality of processing the terahertz signal of the sample. Alternatively or additionally the control unit may be configured to control one or more of the terahertz radiation source, the cantilever (like in conventional scanning probe systems the functionality to control the cantilever in the z-direction), the sample and cantilever (tip) relative to each other in xy-direction(s) (such as with an xy-table), the terahertz radiation receiver unit, a cryogenic unit, etc.

The use of the leaky lens in the present configuration with a gap between the leaky lens and the antenna allows configuration with specific advantages. In an embodiment the cantilever can be a disposable item, while maintaining good coupling. The outcome in an embodiment can be (1) an item comprising a THz lens-coupling (or other attachment device) arrangement as part of an add-on for an atomic force microscope (AFM) such as the Asylum Research model Cypher; (2) a cantilever, containing striplines, but with an antenna arrangement and a clamping arrangement (or other attachment device) compatible with the lens-coupling arrangement as defined in (1); (3) a cantilever with superconducting striplines also compatible with (1).

The cantilever may advantageously be a disposable item because it is often encountered that the delicate tip is damaged during operation. For properly aligning the disposable cantilever with antenna to the lens with sufficient accuracy an alignment chip may be applied. Hence, in a further aspect, the invention also provides an alignment chip configured to align a cantilever (see also below) or (part of a) cantilever unit to the THz lenscoupling arrangement,

Hence, in an embodiment, the cantilever unit further comprises the terahertz lens, wherein the cantilever unit further comprises an attachment device (such as a clamping arrangement) configured to attach the cantilever unit to a probe head of the terahertz scanning probe microscope setup. This can be used as (part of) an add-on for an atomic force microscope (AFM). In a further embodiment, the cantilever unit comprises a first cantilever unit part, wherein said first cantilever unit part comprises the terahertz lens and an attachment device configured to attach the first cantilever unit part to a probe head of the terahertz scanning probe microscope setup, wherein the cantilever unit further comprises a second cantilever unit part comprising said cantilever with at its distal end said electrically conductive tip, said slot-line based leaky wave antenna configured to receive at least part of the focused terahertz radiation, said stripline electrode with said terahertz radiation receiving part configured to receive terahertz radiation from the slot-line based leak wave antenna and with said tip part in electrical conductive connection with the electrically conductive tip, wherein the second cantilever unit part further comprises an attachment device configured to attach the second cantilever unit part to the first cantilever unit part. In fact, this is an add-on (for an atomic force microscope (AFM)) that allows a further add on in the form as a disposable cantilever.

The invention is further directed to such items per se. Hence, in a further aspect the invention also provides a cantilever unit part (especially configured (to be used) for a terahertz scanning probe microscope setup, such as defined herein) comprising a cantilever with at its distal end an electrically conductive tip, a slot-line based leaky wave antenna, a stripline electrode with a terahertz radiation receiving part, configured to receive terahertz radiation from the slot-line based leak wave antenna, and with a tip part in electrical conductive connection with the electrically conductive tip. In a further aspect, the invention also provides a cantilever unit part (especially configured (to be used) for a terahertz scanning probe microscope setup, such as defined herein) comprising a terahertz lens and an attachment device configured to attach the cantilever unit part to a probe head of a terahertz scanning probe microscope setup, wherein the cantilever unit part is further configured to accommodate a further cantilever unit part as defined above.

Hence, in an embodiment one or more of the cantilever unit, the first cantilever unit part and the second cantilever unit part, may be configured as “snap-on” devices, which may be connected to existing AFM (which may especially be configured to host one or more of such snap-on devices). As indicated above, such parts are especially configured (to be used) for a terahertz scanning probe microscope setup, such as defined herein.

The term “substantially” herein, such as in “substantially consists”, will be understood by the person skilled in the art. The term “substantially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term “substantially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” includes also embodiments wherein the term “comprises” means “consists of’. The term "and/or" especially indicates "one or more of'. Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

The devices or apparatus herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

The invention further applies to an apparatus or device comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterising features described in the description and/or shown in the attached drawings. The various aspects discussed in this patent can be combined in order to provide additional advantages. Furthermore, some of the features can form the basis for one or more divisional applications.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figs.la-ld schematically depict some aspects of the scanning probe microscope and cantilever unit as described herein;

Figs. 2a-2e schematically depict some further aspects of embodiments with special attention to antenna aspects;

Figs. 3a-3d schematically depict some further aspects of embodiments with special attention to antenna aspects; and

Fig. 4 schematically depicts a specific variant of the lens with laser hole.

The drawings are not necessarily on scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Figs, la-Id schematically depict a terahertz scanning probe microscope setup 100 and/or various aspects thereof. In these figures is focused on an AFM application. Fig. la schematically depicts an embodiment of such scanning probe microscope setup 100 in general. The scanning probe microscope setup 100 comprises amongst others a terahertz radiation source 400 configured to generate terahertz radiation 410.

The scanning probe microscope setup 100 further comprises a terahertz lens 50, of which embodiments are depicted in more detail in figs lb-ld. The terahertz lens 50 is configured to receive at least part of the terahertz radiation 410 from the terahertz radiation source 400. Further, this terahertz lens is configured to focus at least part of said terahertz radiation to provide focused terahertz radiation 420 (see fig. lb). The focus of the terahertz lens is especially within the antenna. Hence, the lens dimensions, antenna dimensions and relative position may depend upon the desired frequency or frequency range to be applied.

The scanning probe microscope setup 100 further comprises a cantilever unit 300 comprising a cantilever 310 with at its distal end 311 an electrically conductive tip 320, such as from Pt. The cantilever 310 comprises a slot-line based leaky wave antenna 340, which will be described below.

The scanning probe microscope setup 100 further comprises a terahertz radiation receiver unit 500, configured to receive, for instance via the leaky wave antenna 340 (see below), returning terahertz radiation from a sample. This radiation receiver unit may be a terahertz diode, but may also be an electronic circuit at least partly embedded in the cantilever unit, especially the cantilever 310.

Further, the scanning probe microscope setup 100 may comprise a control unit 600, which may be configured to control one or more mechanically or electronically or optically variable items, such as e.g. the probe head or cantilever head, which is indicated with reference 200, an xy-table or scanner, indicated with reference 120, a laser 700, configured to generate laser light 710 at the end of the cantilever for measuring deflection of the cantilever 310 with a laser light receiver 720, an (optional) cryogenic unit 800, which may be configured to cool the cantilever, etc. etc.

In fig. la, reference 210 indicates the z-stage, and, as indicated above, reference 120 indicates the xy-stage or xy-scanner. In this way, the needle or electrically conductive tip, indicated with reference 320, can be moved in the z-direction and the needle and sample, indicated with reference 10, can be moved relative to each other in the xy-direction(s), respectively.

Reference 140 indicates a frame, and reference 130 indicates a chuck.

Fig. lb schematically depicts in more detail the cantilever head 300 attached to the probe head 200 (of the latter only part is shown). Here, it is shown that the scanning probe microscope setup 100 further comprises a slot-line based leaky wave antenna 340 configured to receive at least part of the focused terahertz radiation 420. As shown, the terahertz lens 50 is configured to receive at least part of the terahertz radiation 410 from the terahertz radiation source 400. Further, this terahertz lens is configured to focus at least part of said terahertz radiation to provide focused terahertz radiation 420. The terahertz lens 50 may have a lens diameter dl in the range of about 1-5 mm. Here, by way of example a hyper hemispherical lens is schematically depicted.

Further, it is shown (Fig.lc) that the scanning probe microscope setup 100, especially the cantilever 310, further comprises a stripline electrode 330. This stripline electrode 330 comprises a terahertz radiation receiving part 337, configured to receive terahertz radiation from the slot-line based leak wave antenna 340, and a tip part 338 in electrical conductive connection with the electrically conductive tip 320.

Between the cantilever 310 and the leaky lens 50 is a gap, indicated with height (or distance) dl. This distance allows an evanescent terahertz wave downstream of the leaky lens 50. The cantilever 310 further comprises downstream of the lens 50 the slot-line based leaky wave antenna 340. This antenna 340 is in general a rectangular slot (here seen along the axis of elongation, with a length lc (see fig. 2a) in the range of 30 pm - 1 mm, and a width wl in the range of 1-100 pm. The height hi of the slot-line based antenna 340 is in the range of 10 nm - 10 pm. The total distance from the substrate bottom of the metallic thin film layer to the leaky lens 50 is indicated with reference h2=dl+hl is in the range of 1-1000 pm. The total length of the cantilever from proximal end 312 to distal end 311 may be in the range of 100 pm-1 mm.

Reference 390 (and 392) indicate(s) one or more attachment units that may be used to arrange a (disposable) cantilever 310 (without lens 50) to the cantilever unit (with lens 50, but without cantilever 310). Such attachment units 390 (and 392) may include one or more of a clamping unit, a magnet, etc. Fig. lb schematically shows a cantilever unit part 370 that may be attached to an existing AFM as add-on. In an embodiment, this cantilever unit part 370 may consist of two or more parts, of which embodiments are schematically shown in figs, lc and Id. Fig. lc schematically depicts a cantilever unit part 371 comprising the cantilever 310 with at its distal end 311 the electrically conductive tip 320, the slot-line based leaky wave antenna 340, the stripline electrode 330 with the terahertz radiation receiving part 337, configured to receive terahertz radiation from the slot-line based leak wave antenna 340, and with the tip part (338) in electrical conductive connection with the electrically conductive tip (320). This cantilever unit part may be attached to an existing AFM with (already) includes the terahertz lens 50. To this end, the cantilever unit part and/or the cantilever unit may comprise one or more attachment devices 390. Reference 392 indicates attachment devices for attaching the cantilever unit part 371 to the (rest of the) cantilever. Reference 360 indicates a support or substrate, which is in general a dielectric.

At the terahertz receiving part, the stripline electrode receives the terahertz radiation from the antenna. In an embodiment, a physical connection between the antenna (wall or bottom) is made with a connector 33, which may be an electrically connective part or extending part from a stripline electrode. This connector "probes" the terahertz radiation in the antenna 340.

Fig. Id schematically shows a cantilever unit part (372) comprising the terahertz lens 50 and an attachment device (391) configured to attach the cantilever unit part to a probe head (200) of a terahertz scanning probe microscope setup (100), wherein the cantilever unit part is further configured to accommodate a further cantilever unit part, such as schematically depicted in fig. lc as cantilever unit part 371.

Referring to fig. lc, the embodiment depicted shows a sandwich structure 30. Note however that the cantilever unit part 371 is not limited to this specific variant. Here, the stripline electrode 330 is at least partly comprised by this sandwich structure 30 comprising a first conductor 331, a first isolator 332, a stripline electrode conductor 333 (central conductor), a second isolator 334 and a second conductor 335. The stripline electrode conductor material, and optionally one or more of the first conductor 331 and the second conductor 335, may e.g. A1 metal or a superconductor. In general, the stripline comprises (at least) two (parallel) arranged electrodes, separated by a dielectric.

As indicated above the terahertz scanning probe microscope setup 100 may thus be configured to receive returning terahertz radiation from the sample 10 (under investigation with the electrically conductive tip) via the cantilever unit 300, including optionally via the antenna and terahertz lens 50 (“leaky lens).

Figs. 2a-2c schematically depict embodiments of the antenna and it surroundings. Reference 361 indicates a substrate, especially a dielectric, on which (and in which), an electrically conductive material is applied, which is indicated with reference 1330. This conductive material may for instance be the first conductor 331. Within this electrically conductive material, a hole or recess is made in the form of the antenna. The walls of the antenna thus especially comprise the electrically conductive material; the bottom of the antenna 340 especially may comprise the dielectric (material). With a dashed line, the lens, over the antenna is depicted. Hence, when going along a line perpendicular to the plane of the drawing, first the lens is seen, then the electrically conductive material with antenna, and there below the substrate 361. The slot-line based antenna has a length lc and a width wl (see also above) and a height hi. Figs. 2b and 2c schematically depict two cross-sections at AA' and BB', respectively.

Fig. 2d schematically depicts a specific variant of the antenna, having a central narrowing having a length 12, which narrows down to a central part having a width w2 and a length wp. In an embodiment, the dimensions are lc is in the range of 1-5 mm, 12 is in the range of 6-120 pm, wl is in the range of 5-80 pm, the height hi (perpendicular to the plane, see fig 2b), is in the range of 10 nm - 10 pm, and the length wp of the narrow part is in the range of 0-50 pm. For instance, wp may be nearly 0 pm.

Fig. 2e may be the same embodiment as fig. 2a, but now in cross-sectional view (like fig. 2b), with the lens arranged over the antenna 340.

Fig. 3a may be same embodiment as fig. 2a, but now with a cantilever integrated. Again, this is a very schematic drawing. The second conductor 335 is integrated in the cantilever from the terahertz receiving part 337, at or close to the antenna 340, to the tip part 338. The first conductor 331 and the second conductor are entirely separated by the insulator (or insulating substrate) 361, except from optionally a small conductive connection at the terahertz receiving part 337 (see below). Cross sections are shown in fig. 3b, with AA' differing from fig. 2b because of the second conductor 335. Cross-section CC' is a cross-section at the terahertz receiving part where the two conductors are electrically connected via an electrically conductive connector 33. This may be a connector having a cross-sectional area (in the plane of the cantilever) in the range of 1-100 pm2. Cross-section DD' is a cross section at the cantilever, and cross-section EE' is a cross section at the cantilever distal end 311. As indicated above, optionally a third conductor is arranged parallel to the first conductor 331 and the second conductor 335. One of the conductors, here the second conductor 335 is in electrical contact with the electrical conductive tip 320. The tip may be of an electrical conductive material or may comprise an electrical conductive coating. Suitable materials are e.g. Pt, and other metals, which can be sharpened sufficiently.

Fig. 3c schematically depicts another variant how terahertz radiation from the slot-line based antenna 340 can be transferred to the (second) conductor 333. Here, instead of a physical connection between the first and the second conductor, the second conductor includes a radial probe which is suitable for probing the THz radiation from the antenna. This radial probe may have a radius r2, which may be in the range of 10-500 pm, and an openings angle Θ (circle section) in the range of 5-180°. Fig. 3d shows again schematically some cross-sections.

As the terahertz lens 340 may be relatively bulky compared to the cantilever 310, in a specific embodiment, the terahertz lens 340 extends over a substantial part of the cantilever, or even beyond the distal end 331. This may complicate a deflection measurement with a laser, assuming AFM. Hence, in an embodiment, the lens 340 comprises a through hole 53 facilitating propagation of laser light through the lens to the distal end 311 of the cantilever for deflection measurements. The through hole 53 may have a diameter d2 in the range of e.g. 0.5-100 pm, especially 1-50 pm. Alternatively, deflection may be measured by measuring from below.

Hence, in an embodiment the invention provides a terahertz scanning probe microscope setup comprising (i) a terahertz radiation source configured to generate terahertz radiation; (ii) a terahertz lens configured to receive at least part of the terahertz radiation from the terahertz radiation source; (iii) a cantilever unit comprising a cantilever with at its distal end an electrically conductive tip, a slot-line based leaky wave antenna configured to receive at least part of the focused terahertz radiation, a stripline electrode with a terahertz radiation receiving part wave antenna and with a tip part in electrical conductive connection with the electrically conductive tip; (iv) a terahertz radiation receiver, configured to receive via the leaky wave antenna returning terahertz radiation from a sample.

Claims

A terahertz scanning probe microscope device (100) comprising: (i) a terahertz radiation source (400) configured to generate terahertz radiation (410), (ii) a terahertz lens (50) configured to at least a portion of the terahertz radiation (410) receive from the terahertz radiation source (400) and configured to focus at least a portion of said terahertz radiation to provide focused terahertz radiation (420); (iii) a leaf spring ("cantilever") unit (300) comprising a leaf spring (310) having at its distal end (311) an electrically conductive tip (320), a slot-line-leaking wave antenna (340) configured to receive at least a portion of the focused terahertz radiation (420), a stripline electrode (330) with a terahertz radiation receiving portion (337) configured to receive terahertz radiation from the slotted line-leaking wave antenna (340), and a tip portion (338) in electrical conductive connection to the electrically conductive tip (320), (iv) a terahertz radiation receiver (500) configured to receive recurring terahertz radiation from a sample.

The terahertz scanning probe microscope device (100) according to claim 1, wherein the stripline electrode (330) is at least partially comprised of a sandwich structure (30) comprising a first conductor (331), a first insulator (332), a stripline electrode conductor (333), a second insulator (334) and a second conductor (335).

The terahertz scanning probe microscope device (100) according to any one of the preceding claims, wherein the stripline electrode (330) comprises a superconducting material, and wherein the terahertz scanning probe microscope device (100) further comprises a cryogenic unit (800) configured to cooling the leaf spring (310).

The terahertz scanning probe microscope device (100) according to claim 3, wherein the first conductor (331) and the second conductor (335) comprise a superconducting material.

The terahertz scanning probe microscope device (100) according to any of the preceding claims, wherein the terahertz radiation source (400) comprises a carcinotron, a multiplier circuit on a Gunn oscillator, a quantum cascade laser, a photo mixer, or a gas laser, and wherein the terahertz radiation source (400) is configured to provide terahertz radiation selected from the range of 0.1-10 THz.

The terahertz scanning probe microscope device (100) according to any of the preceding claims, wherein the terahertz lens (50) comprises a hyper hemispherical silicon or aluminum oxide lens with a diameter selected from the range of 1-5 mm.

The terahertz scanning probe microscope device (100) according to any of the preceding claims, wherein the slot-line-leaking wave antenna (340) comprises a rectangular channel with a length (1) in the range of 1-5 mm, a width (w1) in the range of 6-120 µm, a wall height (h1) in the range of 10 nm-10 µm, the channel bottom and the terahertz lens (50) a distance in the range of 10-50 µm, where the channel wall an electrically conductive material, and wherein one or more of the channel wall and the channel bottom comprises the terahertz radiation receiving part (337).

The terahertz scanning probe microscope device (100) according to any of the preceding claims, wherein the conductive tip comprises a Pt tip.

The terahertz scanning probe microscope device (100) according to any of the preceding claims, wherein the leaf spring unit (300) further comprises the terahertz lens (50), wherein the leaf spring unit further comprises a mounting device configured to attach the leaf spring unit (300) to a measuring head (200) of the terahertz scanning probe microscope device (100).

The terahertz scanning probe microscope device (100) according to any of the preceding claims, wherein the leaf spring unit (300) comprises a first leaf spring unit part, the first leaf spring unit part comprising the terahertz lens (50) and a mounting device configured to attach the first leaf spring unit part to a measuring head ( 200) of the terahertz scanning probe microscope device (100), wherein the leaf spring unit (300) further comprises a second leaf spring unit part comprising the leaf spring (310) with the electrically conductive tip (320) mentioned at the distal end (311), the slot line-leaking wave antenna (340) is configured to receive at least a portion of the focused terahertz radiation (420), the stripline electrode (330) having said terahertz radiation recording part (337) configured to terahertz radiation from the slot-line leak wave antenna (340), and wherein the tip portion (338) is in electrically conductive connection with the electric g is a guiding tip (320), wherein the second leaf spring unit part further comprises an attachment device configured to connect the second leaf spring unit part to the first leaf spring unit part.

The terahertz scanning probe microscope device (100) according to any of the preceding claims, wherein the terahertz radiation receiver (500) is adapted to receive terahertz radiation returning downstream of the terahertz lens (50).

The terahertz scanning probe microscope apparatus (100) according to any of the preceding claims, wherein the terahertz radiation receiver (500) comprises a terahertz processing unit integrated in the leaf spring unit (300).

The terahertz scanning probe microscope device (100) according to any of the preceding claims, wherein the terahertz scanning probe microscope device (100) is an atomic force microscope (AFM) device.

A leaf spring unit part (371) comprising a leaf spring (310) having an electrically conductive tip (320) at the distal end (311), a slit-line-leaking wave antenna (340), a stripline electrode (330) with a terahertz radiation receiving part (337) configured to receive terahertz radiation from the slot-line leak wave antenna (340), and a tip portion (338) in electrical conductive communication with the electrically conductive tip (320).

A leaf spring unit part (372) comprising a terahertz lens (50) and a mounting device configured to mount the leaf spring unit part to a measuring head (200) of a terahertz scanning probe microscope device (100), the leaf spring unit part (372) further configured to have a further receiving leaf spring unit part (371) as defined in claim 14.

A method for measuring a terahertz radiation sample (10), the method providing terahertz radiation to a sample via the electrically conductive tip (320) of the terahertz scanning probe microscope device (100) according to any of claims 1-13 and receiving terahertz signal from the sample with a terahertz radiation receiver (500) configured to receive a signal from terahertz sample via the leaf spring unit (300).

The method of claim 16, wherein the terahertz scanning probe microscope device (100) comprises a terahertz radiation source (400) configured to provide terahertz radiation over at least 10% of the range of 0.1-10 THz.

The method of any one of claims 16-17, further comprising cooling the leaf spring (310) to cryogenic temperatures.

The method of any one of claims 16-18, further comprising processing a terahertz signal from the sample.

The method of any one of claims 16-20, wherein the terahertz radiation receiver (500) is configured to receive a terahertz signal from the sample (10) downstream of the terahertz lens (50).

Use of the terahertz scanning probe microscope device (100) according to any of claims 1-13 or the method for measuring a sample (10) with terahertz radiation according to any of claims 16-20 for one or more of the following: study of a complex quantum material, study of the electronic behavior of a conductive material, study of the electronic behavior of a non-conductive material, study of an unordered superconducting material, study of a quantum Hall effect of a material, study of a large magnetic resistance of a material, study of a colossal magnetic resistance of a material.