When an energetic ion penetrates through an interface between a thin film (of species A) and a substrate (of species B), ion induced atomic mixing may result in an intermixed region (which contains A and B) near the interface. Most ion beam mixing experiments have been directed toward metal-silicon systems, silicide phases are generally obtained, and they are the same as those formed by thermal treatment.Recent emergence of silicide compound as contact material in silicon microelectronic devices is mainly due to the superiority of the silicide-silicon interface in terms of uniformity and thermal stability. It is of great interest to understand the kinetics of the interfacial reactions to provide insights into the nature of ion beam-solid interactions as well as to explore its practical applications in device technology.About 500 Å thick molybdenum was chemical vapor deposited in hydrogen ambient on (001) n-type silicon wafer with substrate temperature maintained at 650-700°C. Samples were supplied by D. M. Brown of General Electric Research & Development Laboratory, Schenectady, NY.
AbstractErbium doping of silicon and silicon carbide using implantation followed by ion beam induced epitaxial crystallization (IBIEC) is investigated. The implanted concentration of Er was 1.4 at% in both cases. In Si(100), Rutherford backscattering/channeling revealed that about 40% of the Er atoms evolved upon rapid thermal annealing from an undetermined position (room temperature) to an interstitial tetrahedral position (650°C) and finally to a substitutional position (950°C). The remaining Er atoms were presumably trapped in the small precipitates visible in high resolution transmission electron microscopy. The photoluminescence at 1.54 μπι of Er3+ is enhanced with annealing and persists up to room temperature after a 950 °C 1 min anneal. The high concentration of optically active Er atoms is illustrated by the lack of saturation of the photoluminescence at high pumping excitation intensity. Erbium was also implanted into cubic silicon carbide films prepared by chemical vapor deposition on Si at 900 °C. Both solid phase epitaxy (SPE) and IBIEC were performed. After a 950°C anneal, the low temperature photoluminescence at 1.54 μιη after IBIEC was five times higher in SiC than in silicon. The difference in photoluminescence linewidth between IBIEC (broad lines) and SPE (sharp lines) is explained in terms of interactions between optically active erbium atoms.
ABSTRACTIon-beam induced epitaxial crystallization of thin amorphous silicon layers at {100} and {110} crystalline/amorphous interfaces exhibits no orientation dependencies, whereas at a {111} crystalline/amorphous interface a weak orientation dependency relative to thermal-induced epitaxial crystallization is observed. This behavior supports an interpretation in which the thermal crystallization process is dominated by the need to form interfacial defects and/or growth sites and in the ion-beam experiment this formation process ocurrs athermally. It is thought that the observed orientation dependent regrowth on a {111} substrate relative to a {100} (or {110}) substrate is associated with the special correlated atomic sequencing which is believed to control solid-phase epitaxial crystallization at a {111) crystalline/amorphous interface.
Abstract
It is shown that star disclinations can be a significant source of
stress in chemical vapor deposited (CVD) diamond. This purely geometrical
origin contrasts with other sources of stress that have been proposed
previously. The effectiveness is demonstrated of the use of electron
irradiation using a transmission electron microscope (TEM) to displace atoms
from their equilibrium sites to investigate intrinsic defects and impurities
in CVD diamond. After irradiation, the samples are studied by low
temperature photoluminescence microscopy using UV or blue laser
illumination. Results are given that are interpreted as arising from
isolated <100> split self-interstitials and positively charged single
vacancies. Negatively charged single vacancies can also be revealed by this
technique. Nitrogen and boron impurities may also be studied similarly. In
addition, a newly developed liquid gallium source scanned ion beam mass
spectrometry (SIMS) instrument has been used to map out the B distribution
in B doped CVD diamond specimens. The results are supported by micro-Raman
spectroscopy.
Mapping of polarization and detrapping effects in synthetic single crystal chemical vapor deposited diamond by ion beam induced charge imaging