Columnar grains of PtSi and CrSi2 surrounded by high-quality epitaxial silicon are obtained by ultra-high vacuum codeposition of Si and metal in an approximately 10:1 ratio on Si(111) substrates heated to 610-840°C. This result is similar to that found previously for CoSi2 (a nearly-lattice-matched cubic-fluorite crystal) on Si(111), in spite of the respective orthorhombic and hexagonal structures of PtSi and CrSi2. The PtSi grains are epitaxial and have one of three variants of the relation defined by PtSi(010)//Si(111), with PtSi[001]//Si<110>.

We report the growth of structurally continuous, pinhole-free epitaxial YSi2−xfilms on Si(l1l) substrates as thin as 30Å. This is accomplished by depositing both yttrium andsiicon in the appropriate stoichiometric ratio onto substrates held near room temperature, which is apparently below the activation energy for the nucleation of a reaction between a deposited Y film and a Si substrate. Diffusion of Si atoms from an evaporation source into a thin Y layer occurs below this barrier energy, allowing the layer by layer formation of YSi2−x without the removal of silicon from the substrate, maintaining a relatively low interface free energy between the growing silicide film and the Si(lll) substrate. Samples have been annealed to 500-900°C to improve epitaxy without the creation of pinholes. Use of the template method allows for the growth of thicker films also free of pinholes.

Epitaxial TiSi2 films have been grown by molecular beam epitaxy (MBE) on atomically clean Si(111)-orientated substrates. The growth procedure involves the ambient temperature deposition of Ti films of 50Å thickness and annealing to 800°C. In situ low energy electron diffraction (LEED) and Auger electron spectroscopy (AES) techniques have been used to monitor the TiSi2 formation process. The epitaxial films have been identified as the C49 metastable phase by both Raman spectroscopy and electron diffraction. Plan view transmission electron microscopy shows three different connected island morphologies. The individual island structures are single crystal and are grown epitaxially with different crystallographic orientations. The orientational relationship of the largest islands is given by [3 1 1] C49 TiSi2//[112]Si and (130) C49 TiSi2//(l1 1)Si. High resolution transmission electron microscopy (HRTEM) cross-section shows a coherent interface extending over several hundred angstroms.

The epitaxial structure of ErSi2−x on Si(1 11) has been investigated using Rutherford backscattering (RBS) and transmission electron microscopy (TEM). Films 10 nm. thick show channeling minimum yields of 4% after room temperature deposition and annealing to 800°C. Plan view electron microscopy on ultrathin layers 0.5 nm. to 10 nm. thick reveals the formation of a complex microstructure involving vacancy ordering in these films. This superlattice structure is interpreted by considering domain formation and twinning in the heteroepitaxial ErSi2−x.

The orientation dependence of phase separation has been examined in detail in InGaAsP layers grown by liquid phase epitaxy on (001), (110), (111)In and (123) InP substrates. It is shown that phase separation is two-dimensional in nature and does not occur along the growth direction for the cases examined. Further, phase separation takes place along the soft directions lying in the growth plane. These results very strongly suggest that phase separation evolves at the surface while the layer is growing.

CuPt-type ordering characteristics of InGaAsP layers are presented. In addition, the Influence of growth temperature and growth rate on domain sizes have been investigated in GaInP2 layers. A model has been proposed to rationalize the formation of domains and involves steps present on the surface. Results suggest that ordering like phase separation occurs at the surface while the layers is being deposited. It is inferred that the two microstructural features evolve concomitantly at the surface during layer growth.