Structure and characteristics of laser crystallized thin amorphous Si films

AbstractPure amorphous Si thin films deposited on oxidized crystalline Si surface (111) were crystallized by picosecond UV laser pulses. The Raman scattering spectra show that pulse energy of 330 mJ/cm2 is enough to fully crystallize Si film and further increase of the energy does not improve crystallinity. A large grained polycrystalline Si was obtained as revealed by surface analysis. A significant increase in carrier mobility was observed after laser crystallization

Sulfides of the Modern Kamchatka Hydrothermal Systems

ABSTRACT Sulfides pyrite, melnikovite-pyrite, marcasite, sphalerite, chalcopyrite, galena, cinnabar, coloradoite, metacinnabar are precipitating at the modern geothermal systems of Kamchatka: Kireunsky, Dvukhyurtochny and Apapel'sky in Central Kamchatka, Vilyuchinsky and Mutnovsky in Southern Kamchatka. Ore deposits are spatially associated with hydrothermal springs. Pyrite is the most common mineral precipitated at the discharge of hydrothermal style. It varies in mode of occurrence, size, inner structure, chemical composition and microstructure. Frequently pyrite occurs as framboids, idiomorphic crystals and their aggregates. By chemical composition, two varieties of pyrite are observed: homogeneous and heterogeneous. Heterogeneity of composition is due to impurities of As, Cu, Sb, Hg and Ag. Au as impurity in pyrite was relieved only in pyrite from Voinovsky hot springs in Southern Kamchatka. Cinnabar is the next most common occurring mineral at the modern hydrothermal systems in Kamchatka. Chalcopyrite, galena, sphalerite and gold are rare minerals. The modern hydrothermal systems in Kamchatka provide the opportunity to study sulfide typomorphism and physico-chemical conditions of the deposition mechanism. We suppose that some of them are the elements of the long-life ore generating hydrothermal systems

Recommended reading list of early publications on atomic layer deposition-Outcome of the "Virtual Project on the History of ALD"

Atomic layer deposition (ALD), a gas-phase thin film deposition technique based on repeated, self-terminating gas-solid reactions, has become the method of choice in semiconductor manufacturing and many other technological areas for depositing thin conformal inorganic material layers for various applications. ALD has been discovered and developed independently, at least twice, under different names: atomic layer epitaxy (ALE) and molecular layering. ALE, dating back to 1974 in Finland, has been commonly known as the origin of ALD, while work done since the 1960s in the Soviet Union under the name "molecular layering" (and sometimes other names) has remained much less known. The virtual project on the history of ALD (VPHA) is a volunteer-based effort with open participation, set up to make the early days of ALD more transparent. In VPHA, started in July 2013, the target is to list, read and comment on all early ALD academic and patent literature up to 1986. VPHA has resulted in two essays and several presentations at international conferences. This paper, based on a poster presentation at the 16th International Conference on Atomic Layer Deposition in Dublin, Ireland, 2016, presents a recommended reading list of early ALD publications, created collectively by the VPHA participants through voting. The list contains 22 publications from Finland, Japan, Soviet Union, United Kingdom, and United States. Up to now, a balanced overview regarding the early history of ALD has been missing; the current list is an attempt to remedy this deficiency. (C) 2016 Author(s).Peer reviewe

Chemical Vapour Deposition of sp2 Hybridised Boron Nitride

The aim of this work was to develop a chemical vapour deposition process and understand the growth of sp2 hybridised Boron Nitride (sp2-BN). Thus, the growth on different substrates together with the variation of growth parameters was investigated in details and is presented in the papers included in this thesis. Deposited films of sp2-BN were characterised with the purpose to determine optimal deposition process parameters for the growth of high crystal quality thin films with further investigations of chemical composition, morphology and other properties important for the implementation of this material towards electronic, optoelectronic devices and devices based on graphene/BN heterostructures. For the growth of sp2-BN triethyl boron and ammonia were employed as B and N precursors, respectively. Pure H2 as carrier gas is found to be necessary for the growth of crystalline sp2-BN. Addition of small amount of silane to the gas mixture improves the crystalline quality of the growing sp2-BN film. It was observed that for the growth of crystalline sp2-BN on c-axis oriented α-Al2O3 a thin and strained AlN buffer layer is needed to support epitaxial growth of sp2-BN, while it was possible to deposit rhombohedral BN (r-BN) on various polytypes of SiC without the need for a buffer layer. The growth temperature suitable for the growth of  crystalline sp2-BN is 1500 °C. Nevertheless, the growth of crystalline sp2-BN was also observed on α-Al2O3 with an AlN buffer layer at a lower temperature of 1200 °C. Growth at this low temperature was found to be hardly controllable due to the low amount of Si that is necessary at this temperature and its accumulation in the reaction cell. When SiC was used as a substrate at the growth temperature of 1200 °C, no crystalline sp2-BN was formed, according to X-ray diffraction. Crystalline structure investigations of the deposited films showed formation of twinned r-BN on both substrates used. Additionally, it was found that the growth on α-Al2O3 with an AlN buffer layer starts with the formation of hexagonal BN (h-BN) for a thickness of around 4 nm. The formation of h-BN was observed at growth temperatures of 1200 °C and 1500 °C on α-Al2O3 with AlN buffer layer while there were no traces of h-BN found in the films deposited on SiC substrates in the temperature range between 1200 °C and 1700 °C. As an explanation for such growth behaviour, reproduction of the substrate crystal stacking is suggested.  Nucleation and growth mechanism are investigated and presented in the papers included in this thesis

Spread of COVID-19 in the Russian regions in 2020: factors of excess mortality

The paper identifies major factors associated with the pandemic spread in the Russian regions, using econometric models and nonlinear «Random Forest» models to assess their significance. The study is based on data of the Russian regions for March-December 2020, a balanced panel sample included 780 observations. Prevalence of the pandemic was estimated based on the excess mortality rate. The study has identified a positive relationship between excess mortality and the share of migrants and a negative relationship between excess mortality and the share of pensioners in the region. Importance of climatic factors has been confirmed: high temperatures, other things being equal, reduce excess mortality, while high humidity, on the contrary, increases it. Excess mortality is higher in the regions with lower population mobility. Mortality is higher in the regions with high per capita incomes and regions with significant unemployment. Vice versa, excess mortality is lower in the regions with better doctor and nurse staffing levels. The study results show that in case of repeated waves of the epidemic or emergence of new viruses, public health policy should be geographically differentiated. Priority should be given to epidemiological situation in the regions with humid climate and low temperatures, high incomes, intensive migration, and high unemployment rates. Significant investments in medical education, higher number of medical specialists and their more even distribution across regions are required. This approach turns out to be more effective in terms of reducing mortality rather than restrictions on population mobility