Scattering-type scanning near-field optical microscopy with Akiyama piezo-probes

Patent metadata

Field	Value
Publication number	US-12247998-B2
Application number	US-202218694765-A
Country	US
Kind code	B2
Filing date	Sep 22, 2022
Priority date	Sep 22, 2021
Publication date	Mar 11, 2025
Grant date	Mar 11, 2025

Abstract

A scattering-type scanning near-field optical microscope at cryogenic temperatures (cryo-SNOM) configured with Akiyama probes for studying low energy excitations in quantum materials present in high magnetic fields. The s-SNOM is provided with atomic force microscopy (AFM) control, which predominantly utilizes a laser-based detection scheme for determining the cantilever tapping motion of metal-coated Akiyama probes, where the cantilever tapping motion is detected through a piezoelectric signal. The Akiyama-based cryo-SNOM attains high spatial resolution, good near-field contrast, and is able to perform imaging with a significantly more compact system capable of handling simultaneous demands of vibration isolation, low base temperature, precise nano-positioning, and optical access. Results establish the potential of s-SNOM based on self-sensing piezo-probes, which can easily accommodate near-IR and far-infrared wavelengths and high magnetic fields. Using a tuning fork-based Akiyama probe provides nano-imaging capability at room and low temperatures and is used for near-field photocurrent mapping.

First claim

What is claimed is:

1. An apparatus for detecting optical properties of a sample comprising:
a scattering-type scanning field near-field optical microscope having a self-sensing piezo-electric based probe including a cantilevered probe tip for probing the sample, the self-sensing piezo-electric based probe being driven using an electrical signal;
a system for applying coherent light upon a sample being probed by the driven self-sensing piezo-electric based probe, the self-sensing piezo-electric probe generating a modified electrical signal responsive to a topography of said sample being probed; and
a detector for imaging an optical property of the sample based on a coherent light-sample interaction in a near-field regime of the cantilevered probe tip interacting with said sample,
wherein the applied electrical signal defines a cantilever tapping frequency and amplitude for tuning the self-sensing piezo-electric based probe.

2. The apparatus as claimed in claim 1 , further comprising:
a processor circuit operable for controlling the electrical signal applied to the self-sensing piezo-electric based probe, said processor circuit further adapted to measure an optical property based on the modified electrical signal generated by said probe interacting with said sample.

3. The apparatus as claimed in claim 2 , wherein the self-sensing piezo-electric based probe comprises:
a tuning fork element adapted for oscillatory motion responsive to the driving electrical signal, wherein the cantilevered probe tip is attached to the tuning fork element, the tuning fork element adapted for translating a motion of the cantilevered probe tip in a direction orthogonal to the oscillatory motion of the tuning fork element.

4. The apparatus as claimed in claim 3 , further comprising:
one of: a focusing lens or a parabolic mirror for focusing the coherent light upon the sample at a tip location.

5. The apparatus as claimed in claim 4 adapted for implementation at either a room temperature environment or in a cryostat providing a low temperature and high magnetic field environment in a cryostat vacuum chamber, the apparatus being compacted for mounting within the cryostat vacuum chamber.

6. The apparatus as claimed in claim 5 , further comprising:
a sample platform for mounting the sample for a probing operation;
a first positioning system operatively connected to said sample platform for orienting said sample platform mounting said sample in three dimensions; and
a scanning device operatively connected to said sample platform for moving said sample platform in two dimensions during a probing operation.

7. The apparatus as claimed in claim 6 , further comprising:
a second positioning device operatively connected to one of said focusing lens or parabolic mirror for positioning said one of said focusing lens or said parabolic mirror in three dimensions for focusing the coherent light upon said sample.

8. The apparatus as claimed in claim 7 , further comprising:
a self-contained unit adapted for mounting within said cryostat vacuum chamber, said self-contained unit comprising:
a first vessel structure for enclosing the first positioning system and for enclosing said scanning device, the sample platform being located above the first vessel structure,
a first mounting structure for mounting the cantilevered probe tip of said self-sensing piezo-electric based probe above the sample platform;
a second vessel structure for enclosing the second positioning system; and
a second mounting structure for mounting the one of said focusing lens or parabolic mirror above the second vessel structure in proximity to said sample platform.

9. The apparatus as claimed in claim 8 , wherein said self-contained unit is adapted for placement within a pod mountable within said cryostat vacuum chamber, the pod defining a three-dimensional space for receiving said self-contained unit.

10. The apparatus as claimed in claim 5 , wherein the low temperature is less than 100° K and ranges from anywhere between 4° K-20° K.

11. The apparatus as claimed in claim 5 , wherein the high magnetic field ranges from between −7 T to +7 T.

12. The apparatus as claimed in claim 5 , wherein said applied coherent light upon the sample ranges from a near infrared frequency to Terahertz frequency.

13. The apparatus as claimed in claim 12 , wherein said system for applying coherent light upon a sample being probed comprises: an optical interferometer.

14. The apparatus as claimed in claim 5 , adapted for imaging tunable graphene plasmons due to inter-Landau level transitions with subwavelength resolution.

15. An apparatus for performing scattering-type scanning field near-field optical microscopy at cryogenic temperatures and in high magnetic fields, the apparatus comprising:
a scattering-type scanning field near-field optical microscope having a self-sensing piezo-electric based probe including a cantilevered probe tip for probing the sample, the self-sensing piezo-electric based probe being driven using an electrical signal;
a first system for applying coherent light upon a sample being probed by the driven self-sensing piezo-electric based probe, the self-sensing piezo-electric probe generating a modified electrical signal responsive to a topography of said sample being probed;
a second system for applying a magnetic field to said sample; and
an interferometer and detector for measuring optical properties of the sample based on light-sample interactions in the near-field regime of the cantilevered probe tip interacting with said sample,
wherein the applied electrical signal defines a cantilever tapping frequency and amplitude for driving the self-sensing piezo-electric based probe.

16. The apparatus as claimed in claim 15 , further comprising:
a processor circuit operable for controlling the electrical signal applied to the self-sensing piezo-electric based probe, said processor circuit further adapted to measure an optical property based on the modified electrical signal generated by said probe interacting with said sample.

17. The apparatus as claimed in claim 16 , wherein the self-sensing piezo-electric based probe comprises:
a tuning fork element adapted for oscillatory motion responsive to the driving electrical signal, wherein the cantilevered probe tip is attached to the tuning fork element, the tuning fork element adapted for translating a motion of the cantilevered probe tip in a direction orthogonal to the oscillatory motion of the tuning fork element.

18. The apparatus as claimed in claim 17 , further comprising:
a mirror for focusing the coherent light upon the sample at the tip location.

19. The apparatus as claimed in claim 18 adapted for implementation in a cryostat providing an environment for low temperatures and high magnetic fields, the apparatus being compacted for mounting within the cryostat.

20. The apparatus as claimed in claim 19 , wherein said detector is further configured for measuring a nanoscale level photocurrent at a near field regime generated at a sample structure responsive to said applied coherent light and applied magnetic field.

21. The apparatus as claimed in claim 20 , wherein said sample comprises a semiconductor device structure including a pair of contact electrodes, each electrode defining an edge, and said processor circuit further configured to map a plasmon excitation at a defined edge of the semiconductor device structure and its associated nanoscale level edge photocurrent.

Assignees

• Univ New York State Res Found
• Univ Yale

Inventors

• Dapolito Michael
• Liu Mengkun
• Chen Xinzhong
• Gozar Adrian

Classifications

• G01Q60/22

  Probes, their manufacture, or their related instrumentation, e.g. holders · CPC title

• G01Q60/06 Primary

  SNOM [Scanning Near-field Optical Microscopy] combined with AFM [Atomic Force Microscopy] · CPC title

• G01Q30/10

  Thermal environment · CPC title

• G01Q20/04

  Self-detecting probes, i.e. wherein the probe itself generates a signal representative of its position, e.g. piezoelectric gauge · CPC title

• G01Q10/045 Primary

  Self-actuating probes, i.e. wherein the actuating means for driving are part of the probe itself, e.g. piezoelectric means on a cantilever probe · CPC title