Transport Properties Of MoS₂ Nanodevices From First Principles

Developing new devices based on new materials,new structures and new principles,breaking through Boltzmann limits,and preparation smaller scale and lower power consumption information processor components are the core issues in the design of integrated circuits.Two-dimensional materials with excellent properties play an important role in the preparation of sub-10 nanodevices.They have unique electrical,optical,magnetic and thermal properties different from bulk materials.Therefore,two-dimensional nanomaterials have great potential for applications and can play a huge role in promoting the development of multifunctional materials and devices.Among many two-dimensional materials,MoS₂ have outstanding properties.The semiconductor phase(2H)of it has a direct band gap,with the width is 1.8e V.It is potential substitute for Si materials.In this work,the first-principle method based on density functional theory(DFT)combined with the non-equilibrium Green's function(NEGF)was used to simulate the transport properties of 2H-phase MoS₂ connected to a semi-infinite 1T-phase MoS₂ lead.The main contents are:1.The research progress and basic properties of MoS₂ are introduced,and the methods and software used in theoretical calculation are briefly introduced.The method of calculating the transport properties of nanodevices under the applied bias voltage is summarized.2.Using DFT-NEGF method,the transport properties of MoS₂ nanodevices with different lengths were studied.It is found that the smallest channel length of MoS₂-based devices without leakage current is 2.189nm,marking this length as the miniaturization ultimate limit for a traditional logical junction based on electron.The transmission characteristic curve shows that the Schottky contact of the junction will change to the typical Ohmic character when the gate voltage is above 0.4V with a fixed bias voltage of 0.6V.The results will provide guiding significance for designing two-dimensional nanodevices in future studies.3.Using DFT-NEGF method,the transport properties of MoS₂nanoribbons with different widths were studied.It is found that the 1T/2H interface of MoS₂nanoribbons has a low tunnel barrier and even becomes Ohmic without Schottky barrier.The transmission characteristic curve shows that the width is 1.264nm,the negative differential resistance effect appears when the bias voltage is less than 1V,and the current through the MoS₂nanoribbons decreases with the decrease of the width.The results of this study have some guiding significance for the design of MoS₂ devices with high'on'current.4.Using DFT-NEGF method,the transport properties of MoS₂ nanoribbons adsorbed NH₃,NO₂ were studied.It is found that MoS₂ nanoribbons sensitive to NO₂ gas.The transmission characteristic curves show that the NH₃adsorbed nanoribbons have similar current characteristics to the gas-free nanoribbons when the bias voltage is less than 0.5V.The current of the nanoribbons adsorbed with NO₂ is always zero,which is different from that of the MoS₂ nanoribbons without adsorbed gas.The results show that MoS₂ nanoribbon has good application potential in NO₂ gas sensor.