The Preparation And Studies Of Metal Dichalcogenides SnS_2-xSe_x And 1T-TaS_2-xSe_x

There are many interesting and novel physical properties in these layered metal dichalcogenides?LMDs?.The LMDs are attractive in both basic physical properties and application of functional materials.In the past few decades,studies of LMDs are always a hot research point.These LMDs have many potential application values in energy storage devices,electronic devices,sensors,lubricants and catalysts and also achieve many useful fundamental research results in superconducting materials,charge density wave materials and giant magnetoresistance materials simultaneously.In this dissertation,we choose SnS_2-xSe_x and 1T-TaS_2-xSe_x single crystals as research objects and carry out some related experimental researches,the research results are summarized as below:In the first chapter,we introduce the research progresses in the LMDs and two dimensional?2D?superconductors in recent years.Firstly,the experimental progresses in the fundamental physical properties and applied researches of the LMDs?such as WTe₂,MoS₂,WS₂ and NbSe₂?are introduced in detail.And then,the progresses of recent years in 2D superconductors?such as metal superconducting films,interfacial superconductors and exfoliated 2D superconductors?are presented clearly.In the second chapter,a sample and practical method of making 2D materials is presented in detail and this method is always called direct ethanol sonication method or liquid exfoliation method.First of all,the SnS_2-xSe_x single crystals are made through simplified Bridgman method and their basic structure informations are measured;afterwards,the 2D SnS_2-xSe_x few layers are made through sonication method in ethanol and the AFM results confirm that some of the 2D samples are even monolayers;finally,the sensor performances of the bulk and 2D samples are measured,showing that the 2D SnS_2-xSe_x samples are useful sensor materials with high sensitivity and rapid response ability.The liquid exfoliation method is additive free,high efficiency and low cost in the preparation process and it is useful in many fields,such as electronics,sensors,electrochemical analysis,fast test and energy storage and will promote the applications of LMDs.In the third chapter,the 1T-TaS_2-xSe_x,a typical LMDs,is our investigative object and its 2D superconducting few layers are got after the sonication procedure.In the first place,the single crystals are synthesized through chemical vapor transport method and its basic structure information and superconductive properties are measured,indicating its perfect crystallinity and superconductivity.After that,the 2D superconducting few layers are made through liquid exfoliation method and their thicknesses,confirmed by the AFM measurement,are between 0.89³ nm;at last,the self-assembled films are made after the drop of the dispersion of the 2D superconducting few layers and the transition temperature of TaS_1.5Se_0.5 self-assembled film is the same as its single crystal,meaning that the self-assembled experimental method can avoid the influences from the substrate.The liquid exfoliation method,which are perfect in making 2D superconducting few layers and can be used in electronics,sensors and flexible superconducting devices,has enough values to be further investigated.In the fourth chapter,we investigate the fast synthesis process of intercalated superconductor?SnSe₂?(C₁₀H₁₀Co)_0.3 by the sonication method and the fast synthesis method is very useful in the field of exploring new materials.First of all,the SnSe₂single crystals are synthesized through simplified Bridgman method;and then the acetonitrile solution of cobaltocene and SnSe₂ are mixed and sonicated at different temperatures and proper times;after that,the?SnSe₂?(C₁₀H₁₀Co)_0.3 superconductors are got successfully and its superconducting properties are perfect compared to the samples made by general solution intercalation in a long time.Exploring new superconducting materials are always a hot research point and the introduction of sonication in the reaction can reduce the reaction time significantly.This experimental project has remarkable values in the exploration of new layered superconductors and other similar functional materials.At last,we summarize this whole dissertation and outlook the follow up studies about experiment and application researches.