Gold and silver Schottky barriers on ZnS(110)

The evolution of the Schottky barrier between Au and Ag metal films and ZnS(110) has been studied using photoemission. Clean and well-ordered ZnS(110) surfaces were prepared by molecular beam epitaxy on cleaved GaP(110) surfaces. Chemical reaction and/or intermixing between the metal and substrate were not observed upon room temperature deposition. Substrate Zn 3d attenuation plots indicate that an initial layer-by-layer growth is followed by island growth at higher depositions. The Schottky barrier heights were found to be ΦAuB=2.19 and ΦAuB=1.81 eV, indicating a considerable dependence on metal work function. This observation agrees well with predictions of Schottky barrier heights based on the concept of metal-induced gap states and the influence of charge transfer based on electronegativities, and discussed in the light of current concepts of Schottky barrier characteristics

Zinc sulfide on GaP(110):Characterization of epitaxial growth and electronic structure

Epitaxial layers of ZnS were grown on cleaved GaP(110) surfaces by molecular beam epitaxy in an ultrahigh vacuum photoelectron spectrometer. The growth mode and the structure of the overlayer were studied by means of low‐energy electron diffraction (LEED) and core as well as valence level photoemission using synchrotron radiation. The attenuation of substrate core‐level intensities with ZnS deposition indicate layerwise growth. LEED demonstrates the growth of the cubic (zinc‐blende) phase as expected for substrate‐stabilized growth. A minor interface reaction is evident from changes in the appearance of the substrate (Ga 3d) and overlayer (S 2p) core levels with increasing thickness. S–Ga bonding was observed in a thin interfacial layer. The valence band offset for this lattice‐matched heterojunction interface system was determined, and found to be of the straddling type (type I); its magnitude is in agreement with predictions based on the dielectric midgap energy model. © 1996 American Vacuum Societ

Electronic band structure of zinc blende

The electronic bulk and surface band structure of cubic zinc sulphide (“zinc blende”) has been studied by angle-resolved photoelectron spectroscopy using synchrotron radiation. The s−p derived bands along the Γ−K−X high-symmetry direction have been determined, and the region of the Zn 3d line has been examined. Spectra at fixed photon energy and variation of polar electron emission angle were used to determine the dispersion of the surface states along the ¯Γ−¯X within the surface Brillouin zone. The experimental data for bulk and surface bands are compared with results of a recent density-functional calculation, which includes the interaction between the s−p and the cation d-derived states

Pulsed laser deposition of HfO 2 and Pr x O y high-k films on Si(100)

Abstract Pulsed laser deposition was used to grow thin films of the high-k materials praseodymium oxide (Pr x O y ) and hafnium oxide (HfO 2 ) on Si(100) due to its experimental simplicity and flexibility. Most important factors for technical application, such as film morphology and interface quality, were investigated by optical microscopy, atomic force microscopy and Raman spectroscopy. During the growth process typical splashes, originating from the laser-target interaction, are embedded into the growing layer. The size of these splashes appears to depend strongly on the laser wavelength (355, 532, 1064 nm). The microscopic morphology of layers of both materials shows a dependence on substrate temperature, which is much more pronounced in case of HfO 2 . Raman spectra of the films show relatively sharp phonon peaks, a single one for Pr x O y and a rich spectrum for HfO 2 , clearly evidencing crystalline areas. This is corroborated by substrate Raman spectra which indicate a stressed interface, pointing to epitaxial Pr x O y and HfO 2 film growth, respectively, during the initial stages of growth.