On Morphology and Strain Field of Ge/Si(001) Islands According to TEM Phase Imaging Method

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Selective growth of tensily strained Si1−yCy films on patterned Si substrates

International audienceAdvanced structures with poly-Si gates, Si3N4 spacers, and shallow trench isolation (STI) areas were used for elaborating the selective growth of Si1−yCy films into recessed source and drain (S/D).Selective Si1−yCy films were grown by repeated cycles consisting of two distinct steps: a non-selective CVD growth of Si1−yCy layers, and a chemical vapor etching with hydrochloric gas. This cyclic deposition/etching process has been experimented at 600 °C with a methylsilane/(methylsilane+trisilane+hydrogen) mass flow ratio (SiCH6 MFR) equal to 2.8×10−4 used for Si0.99C0.01 film deposition. Regarding etching step, a pure HCl gas/(hydrogen) mass flow ratio (HCl MFR) was about 4.3×10−1. We should note that the poly-crystalline Si1−yCy layers are etched more rapidly than the mono-crystalline layers. The etching rate ratio between poly and mono areas induces the capability, by cyclic process, to remove the deposited poly-crystalline Si1−yCy layers on the dielectric areas (STI, spacers) selectively versus the recessed mono-crystalline Si1−yCy layers. A global time process, of about 3 h, resulted in 50 nm thick Si0.99C0.01 films selectively grown into recessed S/D.The new TEM technique of dark-field holography was used to determine a mapping of the strain at transistor level (within Si channel among S/D). The tensile stress of about 0.2 GPa has been measured within Si channel (300 nm length) among recessed Si0.985C0.015 films

Determination of strain within Si1-yCy layers grown by CVD on a Si substrate

International audienceIn this work, we performed quantitative measurements of strain in structures consisting of a 30 nm-thick Si1-yCy layer grown by chemical vapour deposition (CVD) on a Si (001) substrate at 550 or 600°C. The total C concentration varies from 0.67 to 1.97% that was measured by SIMS. Geometric phase analysis (GPA) of high resolution transmission electron microscopy (HR TEM) cross-section images and convergent beam electron diffraction (CBED) were used to deduce the strain within these Si1-yCy layers. Finite-element simulations were carried out to estimate the impact of strain relaxation in thin areas of a specimen. These results were compared with the data obtained by high resolution X-ray diffraction and Raman spectroscopy and with the predictions of elasticity theory. Particular interest is paid to the formation of the structural defects within Si1-yCy layers as a function of a C concentration, growth temperature and incorporated strain. Both cross-sectional and plan-view TEM specimen configurations were used to obtain quantitative information on the defect size distribution, their density and structure

The role of eclipses and european observers in the development of ‘modern astronomy’ in Thailand

‘Modern astronomy’ was introduced to Siam (present-day Thailand) (Siam officially changed its name to Thailand in 1939) when the Belgian Jesuit missionary-astronomer Father Antoine Thomas carried out stellar and lunar eclipse observations during 1681 and 1682 in order to determine the latitude and longitude of Ayutthaya. Three years later a contingent of French Jesuit missionary astronomers observed a total lunar eclipse from Lop Buri, which marked the start of an intensive two-and-a-half year period of observational activity at Lop Buri under the sponsorship of King Narai. During this interval, a partial solar eclipse and two further lunar eclipses were observed from a number of different observing sites. Although a substantial astronomical observatory was constructed in Lop Buri and this was used by French Jesuit missionary-astronomers, ‘modern astronomy’ ended suddenly in 1688 when King Narai died and most Western missionary-astronomers were expelled from Siam. ‘Modern astronomy’ only re-emerged in Siam after a hiatus of almost 200 years when another royal supporter of astronomy, King Rama IV, invited French astronomers to observe the total solar eclipse of 18 August 1868 from Siam, and his son, King Rama V, hosted British astronomers during the 6 April 1875 total solar eclipse. Thailand’s romance with total solar eclipses continued during the 9 May 1929 solar eclipse when King Rama VII visited British and German astronomers based near Siam’s southern border, and this was the catalyst required for the birth of home-grown ‘modern astronomy’. Soon after, Siam’s first astronomy classes began at Chulalongkorn University, and in 1944 this university hosted Siam’s first professional astronomer when Rawee Bhavilai, a solar specialist, joined the Physics Department. The latest phase in the professionalisation of astronomy occurred in 2009 when the Government approval the formation of the National Astronomical Research Institute of Thailand (NARIT). In this paper we trace the critical roles that solar and lunar eclipses played in the emergence and final adoption of ‘modern astronomy’ in Thailand from 1682 through to the present day