US 11,899,041 B2
Method for referencing a near-field measurement with drift and fluctuation correction
Ivan Malovichko, Haar (DE); Florian Huth, Haar (DE); Alexander A. Govyadinov, Haar (DE); and Marcus Diem, Haar (DE)
Assigned to ATTOCUBE SYSTEMS AG, Haar (DE)
Appl. No. 18/016,638
Filed by ATTOCUBE SYSTEMS AG, Haar (DE)
PCT Filed Jul. 16, 2021, PCT No. PCT/EP2021/069983
§ 371(c)(1), (2) Date Jan. 17, 2023,
PCT Pub. No. WO2022/013431, PCT Pub. Date Jan. 20, 2022.
Claims priority of application No. 20186521 (EP), filed on Jul. 17, 2020.
Prior Publication US 2023/0280369 A1, Sep. 7, 2023
Int. Cl. G01Q 60/22 (2010.01); G01Q 30/04 (2010.01)
CPC G01Q 60/22 (2013.01) [G01Q 30/04 (2013.01)] 16 Claims
OG exemplary drawing
 
1. Method for referencing a near-field measurement of a sample in a scattering type near field microscope comprising a probe and a sample, which method comprises the steps of
a) providing a modulation of the probe-sample distance z(t)=z0−A·cos(φ(t)) having an offset distance z0, phase φ(t), such that φ(t)=0 corresponds to the smallest probe-sample distance, and at a modulation frequency

OG Complex Work Unit Math
b) measuring the scattering signal S of the probe, and determining σn for different n as the scattering signal S demodulated at frequencies n*Ωn, n being an integer equal to or larger than 0, wherein σn is determined for at least M different frequencies n*Ω, and M being at least 2;
c) calculating a reference background σrbg as a linear combination of σn according to equation (II)
σrbg=ΣnAn·σn  (II)
wherein coefficients An of the respective frequencies n*Ω are to be chosen such that the relative contribution of the scattering signal for |φ(t)|<ε, wherein ε≤π, to the σrbg is made small over an oscillation cycle;
d) determining the near field signal σNF of a position of the sample using at least one harmonic of the modulation frequency Ω at a frequency m*Ω, m being an integer equal to or larger than 0, and
e) determining the referenced near-field signal σNFref of the position of the sample using the calculated reference background σrbg as a reference.