Method Article
Optical characterizations of few-layer NiI2 by magneto-optical-electric joint-measurement scanning imaging system
https://doi.org/10.21203/rs.3.pex-2277/v1
This work is licensed under a CC BY 4.0 License
This protocol has been posted on Protocol Exchange, an open repository of community-contributed protocols sponsored by Nature Portfolio. These protocols are posted directly on the Protocol Exchange by authors and are made freely available to the scientific community for use and comment.
posted
You are reading this latest protocol version
As an advanced imaging system, the magneto-optical-electric joint-measurement scanning imaging system (MOEJSI) brings spectroscopic techniques with unmatched spatial resolution to very low temperature, high magnetic field and high electric field measurements.
magneto-optical-electric joint-measurements
two dimensional ferromagnetic
two dimensional ferroelectric
mutual control
Sample fabrication: NiI2 flakes were prepared by a normal and widely-used mechanical exfoliation method. The few-layer NiI2 were exfoliated via PDMS films in a glovebox from NiI2 bulk crystals, synthesized by chemical vapor transport method from elemental precursors with molar ratio Ni:I = 1:2. All exfoliated hBN, NiI2 and graphene flakes were transferred onto pre-patterned Au electrodes on SiO2/Si substrates one by one to create a heterostructure in glovebox and were further in-situ loaded into a microscopy optical cryostat for optical measurements in the glovebox. The whole process of NiI2 sample fabrication and measurement were kept out of atmosphere.
Optical measurements by the magneto-optical-electric joint-measurement scanning imaging system (MOEJSI):
As an advanced imaging system, the magneto-optical-electric joint-measurement scanning imaging system (MOEJSI) brings spectroscopic techniques with unmatched spatial resolution to very low temperature, high magnetic field and high electric field measurements. It was developed for investigating the magnetic and ferroelectric properties and their mutual control through magneto-optical-electric joint-measurements, besides Raman and photoluminescence features. In particular, the reflective magnetic circular dichroism (RMCD) loops and imaging, linear dichroism (LD) imaging and polarization-electric field (P-E) hysteresis loop can be achieved when simultaneously applied high magnetic field (7 T) and electric field (100 V) at low temperature of 10 K.
The MOEJSI system is built based on a Witec alpha 300R Plus low-wavenumber confocal Raman imaging microscope, which is integrated with a closed cycle superconducting magnet (7 T) with a room temperature bore and a closed cycle cryogen-free microscopy optical cryostat (10 K) with coaxial cables assemblies, as shown in Fig. 1a. This system achieves multi-field coupling of magnetic fields, electric fields and optical fields and realize high speed, sensitivity and resolution. For use in the room temperature bore superconducting magnet, an extended snout sample mount is specially designed for the cryogen-free microscopy optical cryostat (Fig. 1b). The microscopy optical cryostat directly anchored on the XY scanning stage of Witec Raman system for scanning imaging. The objective mounted in a lens tube and the extended snout enter into the room-temperature bore from top and bottom, respectively (Fig. 1b and 1c).
For RMCD and LD measurements, a free-space 532 nm laser of ~2 μW was linearly polarized at 45° to the photoelastic modulator (PEM) slow axis and sinusoidally phase-modulated by PEM (RMCD: 50 KHz; LD: 100 KHz), with a maximum retardance of λ/4 for RMCD and λ/2 for LD. The light was further reflected by a non-polarizing beamsplitter cube (R/T = 30/70) and then directly focused onto samples by along working distance 50× objective (Zeiss, WD = 9.1 mm, NA = 0.55). The reflected beam which was collected by the same objective passed through the same non-polarizing beamsplitter cube and was detected by a photomultiplier (PMT). The PMT and PEM coupled with lock-in amplifier and Witec scanning imaging system (Fig. 2 and 3).
Optical characterizations of few-layer NiI2 by magneto-optical-electric joint-measurement scanning imaging system
This protocol has been posted on Protocol Exchange, an open repository of community-contributed protocols sponsored by Nature Portfolio. These protocols are posted directly on the Protocol Exchange by authors and are made freely available to the scientific community for use and comment.
posted
You are reading this latest protocol version