NCAFM2023 Programme Booklet

FIBER-OPTIC INTERFEROMETER BASED ATOMIC FORCE MICROSCOPE INTEGRATED IN CRYOGEN-FREE DILUTION REFRIGERATOR

Binod DC 2 , Noah Austin-Bingamon 1 , and Yoichi Miyahara 1,2*

1 Department of Physics, Texas State University, San Marcos, Texas 78666, USA 2 Materials Science, Engineering and Commercialization program, Texas State University, San Marcos, Texas 78666, USA Email: yoichi.miyahara@txstate.edu

We present a cryogenic atomic force microscopy (AFM) system which is integrated in a cryogen-free dilution refrigerator with magnetic field up to 9 T (LD-250 Bluefors). A large internal volume of the cryostat allows the AFM unit to be installed on an efficient internal vibration isolation system, enabling the reduction of the mechanical vibration from the dry refrigerator. The vibration isolation system consists of a massive (over 10 kg) of copper block suspended by four springs whose extensions are nearly 250 mm, resulting in the vertical resonant frequency is as low as 1 Hz. Combined with the rigid design of custom piezo coarse positioners, the influence from the vibration from the pulse tube cooler is minimized. The AFM is equipped with a fiber-optic interferometer which is used for both detecting the cantilever deflection and exciting the cantilever oscillation [1]. The capability of optically exciting cantilever oscillation enables tunable cantilever quality factor and the clean cantilever resonance, which is crucial for single-electron sensitive electric force microscopy/spectroscopy [2,3,4]. We will present the details of the system and its performance. We gratefully acknowledge funding from NSF-PREM (DMR-2122041), NSF-CAREER (DMR-2044920) and NSF-MRI (DMR-2117438). This work is also supported by Texas State University. References [1] Y. Miyahara et al., “Optical excitation of atomic force microscopy cantilever for accurate spectroscopic measurements”, EPJ Tech. Instrum. 7 :2 (2020). [2] Y. Miyahara, A. Roy-Gobeil, and P. Grutter, "Quantum state readout of individual quantum dots by electrostatic force detection", Nanotechnology 28 , 1 (2017). [3] A. Labuda et al., "Decoupling conservative and dissipative forces in frequency modulation atomic force microscopy", Phys.Rev. B84 , 125433 (2011). [4] N. Austin-Bingamon, Binod DC, and Y. Miyahara, “Frequency and damping noise of atomic force microscopy cantilevers with optomechanically modified quality factor at low temperature”, 24th NC-AFM, (2023).

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