Composition Of Epitaxial Films Research Articles

Characterization of Hetero-Epitaxial Ge Films on Si Using Multiwavelength Micro-Raman Spectroscopy

To meet various physical property requirements of materials for advanced applications for specific devices, combinations of Si/Ge, Ge/Si, Si1-xGex/Si, are frequently introduced in the device fabrication process. Epitaxy, condensation and annealing processes are commonly used. Since a small variation in composition, strain and crystallinity can result in reduced device performance or failure, the composition, strain and crystallinity must be carefully monitored and controlled throughout the manufacturing process. We have studied the dependence of Ge and Si intermixing on annealing temperature and Raman excitation wavelength. Using multiwavelength Raman spectroscopy, we found Ge and Si intermixing in epitaxially grown Ge(100)/Si(100) after successive thermal anneals. Very strong dependence of signal-to-noise (S/N) ratio measurements on excitation wavelength and film structure was observed. Suitable excitation wavelengths must be chosen to properly characterize Si and Ge-based heteroepitaxial layers based on the thickness, stacking order and composition of epitaxial films having different optical properties at different wavelengths.

The dynamics of accumulation of electrically active radiation defects on implantation of graded-band-gap HgCdTe films grown by MBE

The dynamics of accumulation of electrically active radiation defects under ion doping of epitaxial Cd x Hg 1−x Te films is studied for various distributions of film composition in the implantation region. The epitaxial films were irradiated by boron ions at room temperature in the continuous regime, with the dose ranging within 1011−3·1015 cm−2, energy — 20–150 keV, and ion current density — j = 0.001–0.2 µA·cm−2. It is found that the natural logarithm of the introduction rate of electrically active radiation defects linearly depends on the epitaxial-film composition in the range of mean projected path of implanted ions. An analysis of the experimental data shows that the dynamics of accumulation of electrically active radiation defects is determined by the epitaxial-film composition in the implantation region.

Exploring Magnetic properties of Epitaxial Films and Superlattices

ABSTRACTRecent advances in spin-sensitive spectroscopie techniques combined with the rapidly expanding capabilities to synthesize novel materials utilizing molecular beam epitaxy (MBE) are stimulating new interest in magnetism and magnetic materials. Epitaxial growth offers opportunities to stabilize and study crystal phases of elemental magnetic materials which do not naturally occur in nature, and to vary the crystal parameters and composition of epitaxial films in precisely controlled ways. Multilayer superlattice films can also be fabricated using MBE. These structures offer unprecedented new opportunities to explore the relationship between crystal structure and various magnetic properties such as spontaneous magnetization, the Curie temperature and magnetic anisotropy in well characterized systems. The present paper reviews some of the more recent work on thin film magnetic systems including structure analysis of film quality, new techniques for probing the electronic and magnetic properties of the films and the important role large scale numerical calculations are beginning to play in guiding the choice of magnetic systems for study.