Direct Growth of Magnetic Non-van der Waals Cr₂X₃(X = S, Se, and Te) on SiO₂/Si Substrates through the Promotion of KOH

Abstract

Two-dimensional (2D) magnetic materials can be used to construct multifunctional electronic and spintronic devices attributed to their unique 2D restricted magnetic properties. However, some magnetic materials are non-van der Waals materials, and the substrate used in chemical vapor deposition (CVD) is usually a van der Waals substrate like mica. This kind of substrate can cause transfer problems and increase the complexity of equipment fabrication or magnetic measurement. It is meaningful to further optimize the current production process for realizing good repeatability and simple fabrication. Growing materials on SiO2/Si can directly make electronic devices and measure magnetic properties. Herein, we use potassium hydroxide to modify a SiO2/Si substrate and succeed in growing Cr2X3 (X = S, Se, and Te) directly on the SiO2/Si surface by a CVD method. OH– is attached to the surface of SiO2/Si, thereby inhibiting the growth of thin layered Cr2X3 along the [001] zone axis. Through density function theory calculation, it is verified that the formation energy of Cr2S3 and SiO2/Si heterojunction can be enlarged by introducing OH–, which is beneficial to the growth of Cr2X3 on the SiO2/Si surface. At the same time, we have also achieved Cr2S3 and Cr2Se3 with controlled size and thickness. The thinnest thickness of the three materials on SiO2/Si can be close to 1 unit cell. Cr2S3, Cr2Se3, and Cr2Te3 nanosheets exhibit ferrimagnetic, spin glass, and ferromagnetic behavior, respectively. This work can provide a new method for the growth of non-van der Waals 2D materials on SiO2/Si, and it is of great significance to the fabrication of spintronic devices.

Vacancy‐Ordered Superstructure‐Induced Delocalized States Enable Superior Sodium Ion Storage

“…Two peaks at 585.3 and 575.3 eV in the Cr 2p XPS spectrum are assigned to the Cr 2p 1/2 and 2p 3/2 orbitals of Cr 3+ , respectively (Figure 2h). [ 54 ] Two peaks in the S 2p spectrum at 160 and 162.1 eV correspond to the S 2p 3/2 and 2p 5/2 orbitals of S 2− (Figure 2i). [ 54 ] The specific surface area of Cr 2/3 S is tested according to the Brunauer–Emmett–Teller (BET) characterization (Figure 2j), Cr 2/3 S has a specific surface area of 1.9454 m 2 g −1 and for CrS is 0.9827 m 2 g −1 (Figure S8, Supporting Information).…”

Non‐van der Waals 2D Materials for Electrochemical Energy Storage

“…Several nvdW materials of the Cr n X family (X = S, Se, and Te) have been also synthesized via CVD. [ 65 ] The synthesis of ultrathin nanosheets (along with thicker flakes) of non‐layered γ‐CuI (a p‐type semiconductor with cubic zinc blende structure) on SiO 2 /Si substrate has been also reported using a physical vapor deposition process, with γ‐CuI powder as the precursor and argon as the carrier gas at ca. 400 °C.…”

Advanced Strategies in Synthesis of Two‐Dimensional Materials with Different Compositions and Phases

“…Moreover, the Cr 2 Te 3 with trigonal non-layered structure can not only be obtained via van der Waals (vdW) epitaxy on mica but also can be realized by adding KOH on SiO 2 / Si substrate. [64][65][66][67] Here, the effect of K + is reducing the migration energy of Cr and Te atoms, while the OH − can enlarge the formation energy between Cr 2 Te 3 and the substrate. 1T Cr 3 Te 4 , belonging to the P2/m space group, has been realized by the atmospheric pressure CVD method [39] (Figure 3h).…”