Ilan Golecki

Single‐crystalline, epitaxial cubic SiC films grown on (100) Si at 750 °C by chemical vapor deposition

Single‐crystalline, epitaxial cubic (100) SiC films have been grown on (100) Si substrates at 750 °C by low‐pressure chemical vapor deposition, using methylsilane, SiCH3H3, a single precursor with a Si:C ratio of 1:1, and H2. This epitaxial growth temperature is the lowest reported to date. The films were characterized by means of transmission electron microscopy, x‐ray diffraction, infrared transmission, four‐point probe and other methods. Based on double‐crystal x‐ray diffractometry, the crystalline quality of our films is equivalent to that of commercial films of similar thickness. The letter describes the novel growth apparatus used and the properties of the films.

Rapid vapor-phase densification of refractory composites

Abstract The status of vapor-phase routes for the rapid densification of high-temperature composite materials, primarily ceramic-matrix composites, is reviewed. Conventional densification of composites such as carbon-carbon and SiC-SiC is accomplished by isothermal, isobaric chemical vapor infiltration (CVI), either alone or in combination with liquid resin impregnation and thermal annealing. These are multi-step processes which take from several hundred to thousands of hours at high temperature. In this paper we review approaches designed to significantly reduce the processing time and the number of steps required for densification, while producing materials with the desired properties. We describe techniques such as inductively-heated thermal-gradient isobaric CVI, radiantly-heated isothermal and thermal-gradient forced-flow CVI, liquid-immersion thermal-gradient CVI and plasma-enhanced CVI. Different heating methods, such as radiative and inductive, and both hot-wall and cold-wall reactors are compared. Available material properties of composites produced by these techniques are given.

Rapid densification of porous carbon–carbon composites by thermal‐gradient chemical vapor infiltration

Porous carbon–carbon preforms, 10.8 cm o.d.×4.4 cm i.d.×3.0 cm thick have been densified in a one‐cycle, 26 h process. The disks are heated by induction, creating an inside‐out thermal gradient, and are exposed to cyclopentane vapor in a water‐cooled vacuum chamber. Rough‐laminar carbon microstructure is obtained; a compressive strength of 268 MPa is measured at 1.79 g/ cm3 density. The densification rate is monitored in real time. The precursor utilization efficiency is 20%–30%. Our patented process can be applied to other materials, has significant scale‐up potential and is economically competitive.

Epitaxial Monocrystalline SiC Films Grown on Si by Low-Pressure Chemical Vapor Deposition at 750°C

Monocrystalline, epitaxial cubic (100) SiC films have been grown on monocrystalline (100) Si substrates at 750°C, the lowest epitaxial growth temperature reported to date. The films were grown by low-pressure chemical vapor deposition, using methylsilane, SiCH 3 H 3 , a single precursor with a Si:C ratio of 1:1, and H 2 . The films were characterized by means of transmission electron microscopy, single- and double-crystal X-ray diffraction, infra-red absorption, ellipsometry, thickness measurements, four-point probe measurements, and other methods. Based on X-ray diffractometry, the crystalline quality of our films is equivalent to that of commercial films of similar thickness. We describe the novel growth apparatus used in this study and the properties of the films.