| With the rapid development of Aviation and Astronautics in recent years,equipments such as multi-band radar,optical guidance and detection,high-frequency communication and quantum communication,etc.,put forward the higher requirements of function comprehensive,integration and miniaturization,which also brings serious problems such as structure complexity,which increase the unit power and insufficient heat dissipation.As a result,it is urgent to have better solutions of materials and structural design of devices.The diamond materials,especially single crystal diamond(SCD),holding the excellent properties in thermal,mechanical,optical,electrical and quantum,can widely fulfill the various needs by advanced equipment manufacturing,large-flux thermal management,high-power optical windows and components,and other sophisticated technologies in the aerospace field,and become the key,even unique material solution.Among them,the preparation of diamond materials and devices with large size,high crystal quality and special structure is the core problem.However,at present,the most typical and mature SCD technologies,including high temperature and high pressure(HPHT)as well as chemical vapor deposition(CVD),are still restricted by the critical technic bottlenecks like small size,low crystal quality,single structure,etc.,which can not be achieved simultaneously owing to the imperfect preparation and processing technology,which hardly makes the original excellent performance of SCD to play their role.In order to solve the disharmony between large-scale,high-quality and complex structure SCD,a new concept of"Coessential-connection"is put forward based on the research of CVD diamond preparation technology,that is,the technology to reach large-size,multi-scale and 3D structure based on the effective coordinate and control of homoepitaxy and lateral connections of SCD growth.Such concept is not only applicable to the classic mosaic growth,but also widely covers the various subdivisions such as the diamond heteroepitaxy,as well as the growth of polycrystalline diamond(PCD),which can be regarded as a universal concept throughout almost the whole field of CVD diamond.Around the concept of"coessential-connection",main research content can be divides the into four parts:1.homoepitaxial dynamic,process and enhanced assisted environment,2.process and mechanism coessential-connection growth,3.the properties of coessential-connection diamond materials,and 4.the three-dimensional multi-scale structure technology and design.Detailed innovative achievements are described below:First of all,process of nucleation and surface relief evolution from island to step mode during the early stage of homoepitaxy was discusses.The distribution of defects and impurities on the interface caused by interruption of the deposition was explored,as well as the disturbance and recovery of the surface condition.In addition,high power density plasma environment required for high quality SCD homoepitaxial growth was studied and obtained,which provides the basic and principle support for diamond preparation.A very fast deposition rate of 36μm/h for PCD was achieved.Then,the concept of"coessential-connection"was generalized and proposed,with the analysis of microdynamical mechanisms and processes of interface formation by connection of nucleuses.The influence of deviation of diamond nucleation sizes and orientations on the interface condition were revealed.What’s more,the important procedure of“lateral growth”was also studied,indicating that from top to buttom of the side surface,the impurity concentration of SCD gradually increase,and transform into PCD/NCD near the buttom part,due to the strong gradient of plasma density and temperature gradient(150℃).After that,preparation technology was optimized for mosaic SCD,as a representative of high-quality coessential-connection diamond material.Attentions were paid to the influence of the defect enriched junction between the single pieces,together with the degradation of thermal conductivity properties.High quality junction interface was achieved,and a narrow interface of only 20μm stress and defect enriching zone was found,while the dislocation density increased to a magnitude of 10~7/cm~2.However the thermal property of overall material is still excellent,with a 2470W/mK therml conductivity measured crossing the interface,and only a minimal reduction in comparison with none interface region(2530W/mK).Inch level large sized coessential-connection SCD diamond was prepared and realized under the optimal growth conditions.At last,according to the requirement of multi-scale and multi structure materials in the field of aerospace,the three-dimensional structure of diamond in macro and nano scale was designed and fabricated by employing coessential-connection technology.Special performance of the relevant structure and its optimization were acquired,which paves the way of urgent demand for SCD material solutions with special and spacial structures. |
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