| As a typical semiconductor material,monocrystalline silicon is widely used in aerospace,integrated circuits,infrared detection,and micromechanical systems(MEMS).Monocrystalline silicon materials are prone to brittle fracture and micro-crack damage at room temperature,which largely restricts its cutting efficiency and use in complex and harsh environments.At the same time,with the continuous development of aerospace and other fields,deep space exploration,infrared optics and other technologies have increasingly higher requirements for the efficiency and quality of complex surface creation under monocrystalline silicon substrates and the serviceability under complex and harsh conditions..Therefore,research on material properties and testing technology under complex and harsh environments has become a hot topic and difficulty in the international frontier and a major national demand.The high temperature environment can greatly improve the plasticity of monocrystalline silicon,and it has important application value to accurately characterize the mechanical properties and fracture behavior of monocrystalline silicon from room temperature to high temperature.Due to its rich test content and convenient test process,high-temperature indentation testing technology has great advantages in the study of high-temperature mechanical properties of materials.However,the current domestic related testing technology is relatively late,and the existing high-temperature indentation testing instruments are not yet perfect.In order to guide actual production and application,it is urgent to advance the research of testing instruments and error correction methods on the basis of the existing high temperature indentation testing technology to accurately characterize the mechanical properties,micro deformation behavior and fracture behavior of monocrystalline silicon materials at room temperature and high temperature.Based on the existing high-temperature micro-nano indentation test equipment,this paper has carried out calibration and debugging work,combined with actual working conditions and simulation calculation,comprehensively analyzed the influence of various factors on the contact thermal drift in the high-temperature indentation test process,and proposed the thermal drift the detection and correction methods ensure the reliability of the instrument and the accuracy of the test results.Subsequently,based on the self-made hightemperature indentation test device and the commercial nanoindenter,the indentation test of different indentation scales and different temperatures was carried out on monocrystalline silicon,and the mechanical properties were combined with Raman spectroscopy and other analysis.Methods The microscopic deformation mechanism of monocrystalline silicon was studied.The crack growth process of monocrystalline silicon at different temperatures is discussed by means of simulation calculation.The main research contents of this article include:(1)The research progress of high temperature indentation test technology and monocrystalline silicon performance test at home and abroad is briefly analyzed,and the Oliver-Pharr method and fracture toughness test method of indentation test are summarized.According to the existing high temperature indentation test device,the load,displacement and other sensors and temperature control unit are calibrated,and the flexibility of the whole machine frame is corrected and calibrated by the direct calibration method.After the calibration,the standard hardness block is used to test to ensure Test the reliability of the device.(2)Aiming at the problem of contact thermal drift in high-temperature indentation testing,a mechanical-thermal coupling simulation model was established,and the thermal drift and its influencing factors were studied.It is found that the use of a low thermal conductivity indenter,a higher loading and unloading rate and a smaller indentation dimension can effectively reduce the thermal drift.The actual temperature difference between the indenter of the existing indentation test device and the sample at different temperatures was accurately measured,combined with experiments and simulation calculations,the elimination and correction of thermal drift during the test were analyzed,and long-term precontact was found It can effectively remove the influence of thermal drift on the test.At the same time,the method of correcting the curve by measuring the drift rate during the unloading stage of the high-temperature indentation test can greatly improve the test accuracy.(3)Based on the self-made high-temperature indentation test device and the commercial indenter,the nano-micro scale cross-scale indentation test of monocrystalline silicon with different orientations at room temperature was carried out,and the characteristics were characterized by <100>,<110> and different indentation scales.The hardness and elastic modulus of <111> oriented monocrystalline silicon materials are analyzed.The size effect of indentation of different oriented monocrystalline silicon materials is analyzed,and it is found that it shows obvious size effect at room temperature,and the <100> orientation is the most significant.Combined with optical microscope,the fracture toughness and critical crack load of monocrystalline silicon in various orientations were characterized.Combined with microscope and Raman microscopy,the fracture behavior and phase change products of monocrystalline silicon materials under different loads and different types of indenters were analyzed.The effects of indentation loading and unloading rates on the indentation phase change products and fracture behavior of monocrystalline silicon were studied respectively.It was found that adjusting the loading and unloading rates had significant effects on the phase transition behavior and indentation fracture behavior of monocrystalline silicon.Combined with experiments,a cohesive force simulation model for simulating the crack growth of Vickers and Bosch indentation was established,and the stress distribution of monocrystalline silicon material and the process of crack derivation and growth during the indentation process were analyzed.Finally,the effect of doping phosphorus(P)element on the mechanical properties of silicon is studied through experiments.The results show that doping increases the hardness of silicon,but reduces its fracture toughness.(4)Based on the self-made high temperature indentation test device,the high temperature indentation test of <100> and <111> oriented monocrystalline silicon was carried out,and the hardness and elastic modulus of monocrystalline silicon at different temperatures from room temperature to 600? were obtained,and The indentation work of <100> oriented monocrystalline silicon was analyzed at different temperatures,and the crack morphology and characteristic size of the crack were characterized by an optical microscope.It was found that the monocrystalline silicon gradually no longer fractures with the increase of temperature,and an obvious brittle-ductile transition has occurred.Combining scanning electron microscopy and Raman spectroscopy to study the microscopic deformation behavior of monocrystalline silicon at different temperatures,it is found that the plastic deformation of monocrystalline silicon gradually transitions from phase transition behavior to dislocation slip behavior at high temperatures.Finally,the cohesion simulation was used to study the crack propagation process of monocrystalline silicon material at high temperature,and it was found that it no longer produces mid-position cracks at high temperature,only radial cracks,and at 600? high temperature,under 3N load indentation Monocrystalline silicon exhibits complete plastic deformation,and no cracks have been generated or expanded. |
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