DISTRIBUTION OF DISLOCATIONS IN AlN CRYSTALS GROWN ON EVAPORATING SiC SUBSTRATES

By the use of high-resolution X-ray diffractometry and synchrotron radiation topography, the distribution of dislocations in AlN crystals grown on evaporating SiC substrates is studied. The growth of AlN layer in one process with the evaporation of SiC substrate gave the possibility to prevent the relaxation of thermal stresses through cracking of AlN during cooling the structure. The continuous 0.2-1.5 mm thick plates were used as the model objects for the study of dislocation structure near the AlN/SiC interface. Analysis of the broadening of the Bragg reflection peaks, the shape of scattering maps in reciprocal space and topographs showed that dislocations formed the mosaic structure, different from the distribution of threading dislocations in GaN epilayers. A theoretical model for misfit strain relaxation in the growing AlN layer is suggested. The results enable to clarify the dislocation processes during sublimation growth of industrial quality AlN crystals

Структурные особенности формирования цинкосодержащих наночастиц, полученных методом ионной имплантации в Si(001) и последующим термическим отжигом

This work deals with structural transformations in the near− surface layers of silicon after  ion beam synthesis of zinc−containing nanoparticles. Phase formation after  Zn + ion implantation and  two−stage O+ and Zn+ ion implantation followed by thermal annealing in a dry oxygen atmosphere was studied. To avoid amorphization, we heated the substrate to 350 °C during the implantation. After implantation, we annealed the samples for 1 h in a dry oxygen  atmosphere at 800  °C. The structure of the surface silicon layers was examined by X−ray diffraction and transmission electron microscopy. We show that a disturbed near  surface layer with a large  concentration of radiation induced defects appears as  a result  of 50 keV Zn+ ion implantation. In the  as−implanted specimens, metallic  Zn nanoparticles about 25 nm in size formed at a depth of 40 nm inside  the damaged silicon layer. Subsequent annealing at 800 °C in a dry oxygenatmosphere produced structural changes in the defect layer, formed Zn2SiO4 nanoparticles at a depth of 25 nm with an average size of 3 nm and oxidized the existing Zn particles to form the Zn2SiO4  phase. The oxidation  of the metallic  Zn nanoparticles starts from the surface of the particles and leads to the formation of particles with a “core−shell” structure. Analysis of the phase composition of the silicon layer after O+ and  Zn+ ion two−stage implantation showed that Zn and  Zn2SiO4 particles formed in the  as−implanted state. Subsequent annealing at 800 °C in a dry oxygen  atmosphere increases the particle  size but does not change the phase composition of the near surface layer. ZnO nanoparticles were  not observed under the  experimental ion beam synthesis conditions.. Исследованы структурные превращения в приповерхностных слоях кремния после ионного  синтеза цинкосодержащих наночастиц. Рассмотрены процессы фазообразования после имплантации ионов Zn+ и двухстадийной последовательной имплантации ионами O+ и Zn+ с последующим термическим отжигом в атмосфере сухого кислорода. Для предотвращения аморфизации в процессе имплантации мишень подогревали до температуры 350 °С. После имплантации образцы подвергали термообработке в течение 1 ч в атмосфере сухого кислорода при температуре 800  °С. Структура поверхностных слоев кремния исследована методами рентгеновской дифрактометрии и просвечивающей электронной микроскопии. Показано, что в результате имплантации ионов Zn+ с энергией 50 кэВ в подложку монокристаллического кремния на поверхности образуется нарушенный слой с большой концентрацией радиационных дефектов. В приповерхностном слое кремния на глубине 40 нм формируются наночастицы металлического Zn размером порядка 25 нм. Последующий отжиг при температуре 800 °C в атмосфере сухого кислорода обуславливает структурные изменения в дефектном слое и образование в приповерхностном слое кремния на глубине 25 нм частиц Zn2SiO4  со средним размером 3 нм, а также окисление уже имеющихся частиц Zn с формированием фазы Zn2SiO4. Окисление наночастиц Zn начинается с поверхности и приводит к образованию частиц со структурой типа «ядро—оболочка». Исследование фазового состава приповерхностного слоя кремния после последовательной имплантации ионами О+ и Zn+ показало, что при таком способе имплантации сразу образуются частицы  двух фаз: Zn и Zn2SiO4. Последующий отжиг при температуре 800 °С в атмосфере сухого кислорода приводит к увеличению размеров частиц, но не изменяет фазового состава поверхностного слоя кремния. При данных условиях эксперимента в результате ионного  синтеза не наблюдали образования частиц ZnO

Indian Ocean grenadiers of the subgenus Coryphaenoides, genus Coryphaenoides (Macrouridae, Gadiformes, Pisces)

Volume: 48Start Page: 285End Page: 31

Structural properties of the formation of zinc-containing nanoparticles obtained by ion implantation in Si (001) and subsequent thermal annealing

This work deals with the study of structural transformations in the near-surface layers of silicon after ion beam synthesis of zinc-containing nanoparticles. Phase formation after implantation of Zn+ ions and two-stage implantation of O+ and Zn+ ions with subsequent thermal annealing in an atmosphere of dry oxygen has been considered. We heated the substrate to 350 °C during the implantation to avoid amorphization. After implantation, the specimens were annealed for 1 h in a dry oxygen atmosphere at 800 °C. Investigation of the structure of surface silicon layers has been carried out by X-ray diffractometry and transmission electron microscopy. We show that a damaged layer with a large concentration of radiation induced defects forms near the surface as a result of the implantation of Zn+ ions with an energy of 50 keV. In the as-implanted state, nanoparticles of metallic Zn with a size of about 25 nm form at a depth of 40 nm inside the damaged silicon layer. Subsequent annealing at 800 °C in a dry oxygen atmosphere leads to structural changes in the defect layer and the formation of Zn2SiO4 nanoparticles at a depth of 25 nm with an average size of 3 nm, as well as oxidation of the existing Zn particles to the Zn2SiO4 phase. The oxidation of the metallic Zn nanoparticles starts from the surface of the particles and leads to the formation of particles with a “core-shell” structure. Analysis of the phase composition of the silicon layer after two-stage implantation with O+ and Zn+ ions showed that Zn and Zn2SiO4 particles form in the as-implanted state. Subsequent annealing at 800 °C in a dry oxygen atmosphere leads to an increase in the particle size but does not change the phase composition of the near-surface layer. ZnO nanoparticles were not observed under these experimental conditions of ion beam synthesis