Optimized Parameters for Identifying Layer Number of Few Layer Chromium Tri-iodide from Theoretical Perspective: Implications for Two-Dimensional Spintronics
2020
Chromium
tri-iodide (CrI3), a recently discovered two-dimensional
ferromagnetic material for spintronics, has attracted great attention
because of its intriguing physical properties, such as insulating
character, layer-dependent magnetism, and out-of-plane magnetic easy
axis. However, the instability of few layer CrI3 under
ambient conditions hinders layer-number characterization by atomic
force microscopy, which prevents the exploration of layer-dependent
properties and applications. Here, we theoretically propose that the
layer number of few layer CrI3 can be identified by optical-contrast
and Raman-intensity ratio methods. In the optical contrast method,
by using an appropriate monochromatic incident light, the contrast
of few layer CrI3 on an SiO2/Si substrate can
be maximized. Thicknesses of 75–90, 230–270, and 385–450
nm of SiO2 are suitable for obtaining optimized optical
contrast. The Raman intensity ratio between few layer CrI3 and an SiO2/Si substrate is sensitive to the variation
in thickness of the flakes and can be used for CrI3 layer
number characterization. This work provides two accurate, nondestructive,
and efficient methods to identify the layer number of few layer CrI3 and the corresponding optimized parameters, such as SiO2 thickness and light wavelength, for two-dimensional spintronic
applications.
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