Photodetector for scanning probe microscope

Patent metadata

Field	Value
Publication number	US-11169176-B2
Application number	US-202117193267-A
Country	US
Kind code	B2
Filing date	Mar 5, 2021
Priority date	Mar 5, 2020
Publication date	Nov 9, 2021
Grant date	Nov 9, 2021

Abstract

A detector device is presented for use in a surface probing system. The detector device comprises an integral semiconductor structure configured to define a cantilever and tip probe assembly, comprising at least one tip formed on the cantilever, wherein an apex portion of said at least one tip is configured as an apertured photodetector comprising a layered structure formed with an aperture of subwavelength dimensions and defining at least one depletion region and an electrical circuit, said subwavelength aperture allowing collection of evanescent waves created at a surface region and interaction of collected evanescent waves with the at least one depletion region thereby causing direct conversion of the collected evanescent waves into electric signals being read by the electrical circuit within said tip apex portion, said integral semiconductor structure being thereby capable of concurrently monitoring topographic and optical properties of the surface being scanned by the tip.

First claim

The invention claimed is:

1. A detector device for use in a surface probing system, the detector device comprising an integral semiconductor structure configured to define a cantilever and tip probe assembly, comprising at least one tip formed on the cantilever, wherein an apex portion of said at least one tip, by which the probe assembly scans a surface being probed, is configured as an apertured photodetector comprising a layered structure formed with an aperture of subwavelength dimensions and defining at least one depletion region and an electrical circuit, said subwavelength aperture allowing collection of evanescent waves created at a surface region in response to external illumination and interaction of collected evanescent waves with the at least one depletion region thereby causing direct conversion of the collected evanescent waves into electric signals being read by the electrical circuit within said apex portion of the tip, said integral semiconductor structure being thereby configured and operable for concurrently monitoring topographic and optical properties of the surface being scanned by said apex portion of the tip.

2. The detector device according to claim 1 , wherein the electric circuit comprises electric contact layers extending from the apex portion of the tip along a surface of the cantilever and tip probe assembly to be received at a signal detector.

3. The detector device according to claim 2 , wherein the layered structure is configured as a metal-oxide-semiconductor (MOS) structure, defining at least one MOS unit, and an electrical contact layer.

4. The detector device according to claim 2 , wherein said apertured photodetector is fabricated at the apex portion of the tip made of semiconductor material, by applying the following processing of the tip:
performing Atomic Layer Deposition of a passivation layer on a portion of said apex region of the tip,
depositing by sputtering reflective and conductive layer on said passivation layer,
applying FIB processing to said portion of the apex region of the tip to deposit electrically conductive opaque layer and form the aperture in the semiconductor material of the tip.

5. The detector device according to claim 4 , wherein: said semiconductor material of the tip is silicon; the passivation layer is Al 2 O 3 ; the reflective and conductive layer is Al; and the electrically conductive opaque layer is platinum.

6. The detector device according to claim 5 , wherein: said passivation layer Al 2 O 3 has a thickness of about 50 nm; said reflective and conductive layer Al has a thickness of about 200 nm; and the platinum opaque layer has a thickness of about 100 nm.

7. The detector device according to claim 6 , wherein the apertures has a dimension less than 100 nm.

8. The detector device according to claim 4 , wherein said FIB processing comprises: ablation of the tip to form an initial silicon aperture size of 100 nm, followed by the deposition of the platinum opaque layer; and drilling to define the silicon aperture of a dimension less than 100 nm.

9. The detector device according to claim 1 , wherein said cantilever and tip probe assembly comprises at least one additional tip on said cantilever.

10. The detector device according to claim 9 , wherein said at least one additional tip on said cantilever is configured for monitoring topographic properties of the surface being scanned.

11. The detector device according to claim 9 , wherein apex regions of at least two tips on the cantilever comprise apertured photodetectors configured to collect and detect different wavelengths, respectively, the detector device being thereby having spectrometer functionality.

12. The detector device according to claim 1 , wherein the aperture has elongated geometry and is operable as a polarizer.

13. The detector device according to claim 1 , wherein the cantilever and tip assembly is configured to detect different polarization components of the evanescent waves being collected, the detector device thereby having a polarimeter functionality.

14. The device according to claim 13 , wherein the layered structure of the photodetector at the apex region of the tip comprises a patterned electrically conductive layer defining four spaced-apart electrically conductive segments, thereby forming four depletion regions for polarized detection and four electric signal read channels, thereby enabling measurement of angles of rotation of polarized illuminating light caused by interaction with the surface being scanned.

15. An AFM-NSOM dual-mode detector device comprising: an integral semiconductor structure configured to define a cantilever and tip assembly comprising at least one tip configured and operable as an AFM probe for monitoring topography properties of a surface being scanned by the tip, wherein an apex portion of said at least one tip is configured as an apertured photodetector having a metal-oxide-semiconductor layered structure formed with an aperture of a subwavelength dimensions adapted to collect evanescent waves created at a surface region in response to external illumination and directly convert collected evanescent waves into electric signals being read by an electrical circuit within the apex portion of the tip, said apex region of the tip being thereby configured and operable as an NSOM probe, while maintaining the cantilever and tip assembly operation as the AFM probe.

16. A surface probing system comprising the detector device of claim 1 .

17. A surface probing system comprising the AFM-NSOM dual-mode detection system of claim 15 .

18. A surface probing system comprising:
a light source unit configured and operable to produce pulsed illumination on a surface being scanned,
a detector device comprising an integral semiconductor structure configured to define a cantilever and tip probe assembly, comprising at least one tip formed on the cantilever, wherein an apex portion of said at least one tip is configured as an apertured photodetector comprising a metal-oxide-semiconductor layered structure formed with an aperture of subwavelength dimensions allowing collection of evanescent waves created at a surface region in response to the pulsed illumination and direct conversion of the collected evanescent waves into electric signals being read by an electrical circuit within said apex portion of the tip, said integral semiconductor structure being thereby configured and operable for concurrently monitoring topographic and optical properties of the surface being scanned by said apex portion of the tip.

19. A method for fabricating a detector device of claim 1 , the method comprising:
providing the cantilever and tip probe assembly made of silicon material;
processing the apex region of the tip, to form said apertured photodetector, said processing comprising: performing Atomic Layer Deposition of a passivation layer on a portion of said apex region of the tip, depositing reflective and conductive layer on said passivation layer, and applying FIB processing to said portion of the apex region of the tip to deposit electrically conductive opaque layer and form the aperture in the semiconductor material.

Assignees

• Univ Bar Ilan
• Jerusalem College Of Tech Jct Lev Academic Center

Inventors

• Zalevsky Zeev
• Chelly Avraham
• Karsenty Avi

Classifications

• G01Q60/06

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

• G01Q70/06

  Probe tip arrays · CPC title

• G01Q60/22 Primary

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

• G01Q70/10

  Shape or taper · CPC title