The effect of vacancy defect on quantum capacitance, electronic and magnetic properties of Sc₂CF₂ monolayer

Abstract

Two-dimensional (2D) MXene materials have attracted much attention in recent years because of their excellent properties. In this paper, we theoretically investigated the quantum capacitance, electronic and optical properties of pristine Sc 2 CF 2 and the vacancy-doping Sc 2 CF 2 monolayers by first principles calculations. Pristine Sc 2 CF 2 is the most stable structure among the four investigated systems according to the analysis of binding energy, and the introduction of vacancy does not improve the stability of the system. The introduction of vacancy produced the defect energy levels, which pass through the Fermi energy level and result in the semiconductormetal transition. For Pristine Sc 2 CF 2 , the introduction of V Sc results in the strong magnetism with 1.0 μ B , which is mainly from the contribution of C-p z , Sc-d z2 , Sc-d xz states. The analysis of optical properties indicates that the introduction of the vacancy not only makes the system more sensitive to the infrared light, but also improves the reflectivity, especially in the infrared region. The introduction of vacancy improves the C diff of the systems at 0 V, and drastically increases the maximum C int of the vacancy-doping systems. Charge transfer is further explored. K E Y W O R D S electronic properties, first-principle calculations, optical properties, Sc 2 CF 2 MXene, vacancy defect 1 | INTRODUCTION With the rapid development of science and technology, the discovery of new functional materials plays an increasingly prominent role in scientific research [1]. Two-dimensional materials have attracted more and more attention because of their different characteristics from other materials [2]. Compared with other materials, 2D materials have superior electronic structure and physical properties [3]. 2D materials are proposed with the successful separation of graphene in 2004 [4, 5]. Some other 2D materials were later discovered, such as transition metal dichalcogenides (TMDs) [6] and layered double hydroxides (LDHs) [7]. The excellent properties of these materials make them show potential applications in energy storage [8], adsorption [9], catalysis [10,11], photoelectricity [12] and so on. However, there are some shortcomings in the practical application of these materials. Monolayer graphene has high carrier mobility, large specific surface area, excellent mechanical strength [13], but the characteristics of zero bandgap of graphene hinders its applications in nanoelectronics and optoelectronic devices [14]. Although MoS 2 (TMDs) has good semiconductor properties, the low carrier mobility cannot meet the requirements of high-speed electronic devices [15]. Therefore, it is necessary to design or find other materials with excellent properties to satisfy the requirement of electronic devices.MXene, a new large family of 2D materials, was exfoliated from ternary layered transition metal carbides and nitrides MAX (M n + 1 AX n , n = 1-3) phases by etching the intercalated "A" layers, where M represents a transition metal, X is a carbon or nitroge...

Optimizing the quantum capacitance of AsXBr/AsYBr ((X ≠ Y) = S, Se and Te) Janus heterostructures for high-performance supercapacitors

“…71 Additionally, our results were compared with the work of Cui et al on Janus Sc 2 CF 2 , which showed a quantum capacitance of 34.09 mF cm À2 at positive bias. 72 Our findings underscored the competitive nature of our S/Se and S/Te Janus heterostructures regarding quantum capacitance values.…”

Theoretical Studies on the Quantum Capacitance of Two-Dimensional Electrode Materials for Supercapacitors

“…Stanene is a novel material that has received increasing attention in recent years. It has been successfully realized by epitaxial growth on Bi 2 Te 3 (111) substrates [70][71][72]. Stanene exhibits several remarkable features, including large spin-orbit gaps, topological superconductivity, quantum anomalous Hall behavior, giant magnetoresistance, and efficient thermoelectricity [73].…”

“…Their results show that the maximum CQ value of Hf2C is 549 µF/cm 2 (0.56 V). At positive bias, the CQ of the Subsequently, Cui et al theoretically studied the C Q of Sc 2 CF 2 with different atomic vacancies (Figure 4c) [111]. They observe that, at positive bias, pristine Sc 2 CF 2 has almost no C Q , while the introduction of vacancies increases it.…”