Optical And Electrical Properties Of Two Dimensional Transition Metal Dichalcogenides Materials

The studies of two-dimensional(2D)materials quickly spread to the whole physics,marking the arrival of the "two-dimensional materials era",since Geim group first found the single atomic layer graphene in 2004.Transition metal dichalcogenides(TMDs)materials are a branch of 2D materials,which can be divided into three types according to the different arrangement of atoms,including 2H-TMDs,1T-TMDs and 1T'-TMDs.So TMDs have many unique physical properties in optics,optoelectronics and electricity,which are considered to be one of the most important materials in post-Moore law period.In this thesis,we further explore the application value of TMDs materials.The main content includes:1.A brief introduction about the research background of TMDs materials and the research progress based on the unique physical properties of TMDs materials in optics,optoelectronics and electricity.We also introduce some basic concepts about quantum dots and so on.2.An introduction of the preparation of TMDs materials,nanofabrication technologies and low-temperature measurements,such as several micron-transfer technologies,annealing process,a series of micro-nano fabrication technologies,and low-temperature platforms and measurement system.3.A brief introduction about the methods to improve the photoluminescence(PL)of TMDs materials.We studied the PL of monolayer MoS2 with gold particle under different polarized beams.By using radially-polarized beams,we demonstrate the PL enhancement of monolayer MoS2 hybridized with gold nanoparticle is improved by about 2-fold compared with linearly-polarized beams.We further studied the PL enhancement of monolayer MoS2 with gap plasmon structure.Based on the luminescence of 2D materials defects,we studied tne single quantum emitter of h-BN.4.An introduction of the schottky barrier between metals and semiconductors when they contact,and the defects of materials which influence the photoelectric properties of TMDs materials.To optimize these problems,we fabricated a h-BN/graphite/WSe2/h-BN sandwich structure,then explored the photocurrent,photoresponsivity,and external quantum efficiency of monolayer WSe2 p-n junction.Further,we fabricated a plasmonic array hybridized with this sandwich structure to promote the interaction of light with materials and observed an improvement of photocurrent and photoresponsivity.5.A brief introduction about the electrical properties of TMDs materials.We fabricated a field effect transistor on WSe2,which demonstrated high on-off ratio,electron mobility,and so on.Then a gate-defined quantum dot made on WSe2 was demonstrated,where Coulomb diamonds and Coulomb oscillations were found.The size of the quantum dot could be tuned by the voltages applied to top gates.Further,as lT'-TMDs materials have topological properties,we first fabricated a MoRe-MoTe2-MoRe superconducting Josephson junction and achieved some progress.The main innovations of this thesis are:1.We first studied the PL of monolayer MoS2 with gold particle under different polarized beams.By using radially-polarized beams,we demonstrate the PL enhancement of monolayer MoS2 hybridized with gold nanoparticle is improved by about 2-fold compared with linearly-polarized beams.And we further studied the PL enhancement of monolayer MoS2 with gap plasmon structure.2.We studied the single quantum emitter of h-BN based on the luminescence of 2D materials defects.3.We fabricated a h-BN/graphite/WSe2/h-BN sandwich structure,in order to decrease the contact resistance and materials defects.Then we explored the photocurrent,responsivity,and external quantum efficiency of monolayer WSe2 p-n junction.Further,we first fabricated a plasmonic array hybridized with this sandwich structure and observed the improvement of photocurrent and photoresponsivity of WSe2 p-n junction.4.We first fabricated a gate-defined quantum dot on WSe2 and observed the Coulomb diamonds and Coulomb oscillations of WSe2 quantum dot which the size of the quantum dot could be tuned by the voltages applied to top gates.Further,as 1T'-TMDs materials have topological properties,we first fabricated a MoRe-MoTe2-MoRe superconducting Josephson junction and achieved some progress.