tailieunhanh - Crystalline Silicon Properties and Uses Part 4

Tham khảo tài liệu 'crystalline silicon properties and uses part 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 64 Crystalline Silicon - Properties and Uses Kemmerich 1990 Alexander 1991 Alexander Teichler 1991 2000 . Plastic deformation introduces a variety of EPR-active defects in Si. Some of them denoted as Si-K1 Si-K2 Si-Y and Si-R have been identified to be associated with the dislocation core others namely Si-K3 Si-K4 and Si-K5 with deformation-induced point defect clusters Alexander Teichler 1991 . Si-K6 and Si-K7 are ascribed to impurity atoms in the dislocation core. It was concluded that all EPR active centers attributed to dislocations belong to vacancies introduced into the core of the 30 partials forming screw dislocations. There is hitherto no satisfying explanation why paramagnetic centers are not observable for 60 dislocations and therefore 90 partials . EPR requires defined charge states of defects which can be different for 60 and screw dislocations. Properties of deep levels generated by lattice defects are also investigated by deep level transient spectroscopy DLTS introduced by Lang 1974 . The method probes changes of the capacity of the space charge region of a diode caused by reloading of deep levels. For point defects emission and capture rate are linearly dependent on the occupation ratio of the defect level so that capacitance transients are exponentially dependent on time during capture and emission. The analysis of the DLTS-line variations with correlation frequency and filling pulse duration is then straightforward and yields the level of the defect ionization enthalpy and entropy its electron or hole capture cross section and its concentration Schroder Cerva 2002 . For dislocations line charge fluctuations modify the electron emission resulting in a non-exponential transient and gives rise to a broadening of the corresponding DLTS line Figielski 1990 . Some important features such as the C-line in n-type silicon the F-line in p-type Si as well as B- and D-line in plastically deformed Si were analyzed in detail for a review see . Schroter .