With the rapid development of the semiconductor industry, the size of electronic devices has entered the nano-scale, making the design and application of molecular devices as an important direction to guide the development of new semiconductor materials. Atomic-level simulations of quantum mechanics for related materials and devices are increasingly important. As a new functional material, two-dimensional materials have received extensive attention in recent years. For this reason, scientists hope that low-power electronic devices made from graphene and related two-dimensional materials will bring vitality to the electronics industry and bring revolutionary technologies and products. MXene is a new type of two-dimensional material similar to graphene. Its excellent carrier mobility and semiconducting properties make it an outstanding application potential in molecular devices. MXene is derived from a ternary layered cermet Mn+1AXn phase (M is a transition metal element, A is a main group element, X is C or N, and n is generally 1 to 3, forming a MAX phase). One can extract this layered transition metal carbide or carbonitride Mn+1XnTz material by extracting weaker A-site elements (such as Al atoms) in the MAX phase, where Tz refers to surface groups (such as O2- , OH-, F-, NH3, NH4+). MXene materials have the advantages of simple preparation, easy control, and easy device operation, but they still lack a very in-depth performance research. Recently, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, used a first-principles method that combines density functional theory and unbalanced Green's function to perform in-depth and systematic theoretical research on the charge transport properties of Ti2CO2 MXene nanobelts. Studies have shown that: (1) The energy gap of Ti2CO2 nanobelts can be controlled by changing the width or orientation of the nanoribbons. The energy gap of the asymmetrical armchair nanoribbons decreases with increasing width; the energy gap for the zigzag Ti2CO2 nanoribbons is small or even zero. Also, the quantum-defining effect has a large effect on its energy gap: Symmetrical armchair-shaped nanoribbons produce edge bands in their energy gaps. (2) Considering the charge transport behavior of Ti2CO2 nanoribbon molecular devices with different widths, the current-voltage curves of zigzag and armchair nanoribbon devices are obtained. It is found that Ti2CO2 nanobelt molecular devices have a good negative differential resistance phenomenon. As shown in the figure, in the armchair-shaped Ti2CO2 nanoribbon, because the band gap of the energy band has a certain size, the corresponding molecular device also has a corresponding turn-on voltage. Only when the voltage exceeds this threshold voltage, the current will be generated. . In this work, the researchers also carefully studied the theoretical mechanism of the negative differential resistance phenomenon of Ti2CO2 nanobelt molecular devices, and proposed that the device behaves differently between the conduction band and the valence band of the left and right electrodes under different bias voltages. Matching, which will cause the current to drop. Negative differential resistance appears. In summary, based on its good charge transport properties, this research has taken the first step toward using semiconductor MXene materials as functional molecular devices. This research work was received and published by Journal of Physical Chemical C (J. Phys. Chem. C 2016, 120, 17143−17152).
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