Raman spectra were taken of cubic boron nitride (c-BN) crystals with diameters between 100 nm and 1 mm. The Raman line shape of the optical phonons was found to become increasingly asymmetric towards lower frequency shifts, broader and weaker with decreasing crystal diameters. The results can be explained in terms of a spatial correlation model. The corresponding correlation lengths lie in the nanometer range, i.e. several orders of magnitude below the actual crystallite sizes as determined by electron microscopy, thus revealing a high defect density. An additional examined typical c-BN film on a Si(100) substrate exhibits even weaker and broader structures consistent with an even higher defect density.

We present angular-resolved valence-band spectroscopy data for the (3×2) and c(2×2) reconstructed (001) surface of cubic silicon carbide. The two reconstructions were prepared by annealing the sample in a flux of silicon atoms. In this way single domain reconstructed surfaces were achieved which was confirmed by low energy electron diffraction. The orientation of the surface unit cell with respect to the substrate orientation excludes the alternate dimer-row model for the (3×2) reconstruction of the surface. Angular-resolved valence-band spectra were recorded along the [11̄0] direction of the sample. Both surfaces reveal the photoemission characteristics known from angular integrating experiments. By comparison of the reconstructions, surface derived photoemission features were identified. In addition to the known V1 and V2 states of the (3×2) reconstruction, we found a surface feature V3 in a limited range of the surface Brillouin zone which is to our knowledge reported for the first time. The results are compared to ab initio calculations of the surface band structure. The data for the c(2×2) reconstructed surface are in accordance to calculations for the bridging dimer model. By comparing the data of the (3×2) structure to calculations of the (2×1) surface band structure, we found indications for an assignment of the V1 and V2 states to dangling bonds and silicon dimers, respectively.

Raman spectra in the region of the pentagonal pinch mode A g (2) of C 60 were taken in situ during the deposition of C 60 on the GaAs͑100͒ surface at different temperatures. For very low coverages, only the feature corresponding to the pentagonal pinch mode of pristine C 60 is visible. The onset of polymerization under laser irradiation occurred at thicknesses of about 15 nm which is attributed to a suppressive effect on the polymerization process due to the interaction of C 60 with the substrate surface. The line shape for the feature due to photopolymerized C 60 was different at each temperature indicating distinct polymeric states at different temperatures. These different states are discussed in comparison to recent theoretical calculations. Additionally, the photopolymerization due to irradiation after growth was investigated in situ.

The modification of clean GaAs͑100͒ surfaces by in situ deposition of molecular sulfur was investigated by soft x-ray photoemission spectroscopy. Upon S treatment of the clean GaAs͑100͒ sample at 435-455°C in ultrahigh vacuum the formation of a three monolayer thick gallium sulfide-like compound is observed, which exhibits a ͑2ϫ1͒ low-energy electron diffraction pattern. Due to the S modification on n-GaAs a reduction of the band bending by 0.35 eV is achieved, while the band bending on p-GaAs is increased by 0.17 eV. The subsequent Mg evaporation leads to the formation of a metal/semiconductor contact with a reacted magnesium sulfide-like compound at the interface. After 1 nm Mg deposition the Schottky barrier height of the S-modified Mg/n-GaAs(100) contact amounts to 0.44 eV, which is 0.18 eV lower than without S modification, while the Mg/p-GaAs͑100͒ Schottky contact exhibits an increase in the Schottky barrier height by 0.30 eV in comparison to the value of the unmodified Schottky contact ͑0.55 eV͒.

We are discussing the latest results in the field of Organic Vapor Phase Deposition (OVPD) on basis of our experimental data. In particular the use of carrier gas and its controlled mass flow are adding an additional parameter to control deposition rates in OLED manufacturing by OVPD. Many advantages offered by this key parameter in this technology like stable deposition rates, wide range of adjustable deposition rates and doping concentrations are discussed. A small molecule hybrid OLED (SM‐HLED) consisting of a polymer layer of PEDT:PSS and two small molecule layers of α‐NPD and Alq3 was fabricated by OVPD. For this 3‐layer device we observed a turn on voltage of 2.5 V, a luminance brightness of 100 cd/m2 at 5.2 V and 300 cd/m2 at 6.5 V. Furthermore a passive matrix OLED‐display (PMOLED‐display) was demonstrated by OVPD. The display had a turn‐on voltage of about 3.0 V and showed a very homogeneous light emission. These device characteristics confirm that OVPD is close to be comparable to Vacuum Thermal Evaporation (VTE).

Multiple internal reflection and transmission IR spectra of hydrophobic and hydrophilic Si wafers, Si wafers with thermally grown SiO 2 layers, and Si wafers bonded at high and room temperature were investigated. It was found that the surface of the as-prepared hydrophobic wafer is terminated by hydrogen and water molecules, while the IR spectra of hydrophilic wafer demonstrate only the presence of water molecules at the surface. IR spectra of Si wafers covered by a thermally grown SiO 2 layer exhibit a number of the strong absorption bands assigned to combinational phonon bands in SiO 2 . The wafer bonding leads to the appearance of siloxane and hydroxyl groups at the buried interface whose absorption bands were observed in IR spectra. A rearrangement of atoms at the buried interface takes place after annealing of Si bonded wafers. IR spectra of room temperature bonds show a large number of water molecules and presence of the hydrogen in the oxide layer at the interface.

The molecular-beam epitaxial growth of InAs on GaAs(100) was investigated in situ using reflection anisotropy spectroscopy (RAS) and simultaneously reflection high-energy electron diffraction. The RAS spectra of the GaAs c(4×4) and (2×4) and the InAs (4×2) and (2×4) reconstructions are reported. During InAs deposition, the RAS signal shows significant changes for InAs coverages as low as 1/6 of a monolayer. At this coverage surface reconstructions are responsible for the signal variation. For InAs coverages larger than four monolayers, the RAS signal is essentially determined by the anisotropic roughness of the three-dimensional growing surface. This is verified using a three-layer model which gives an excellent description of the experimental spectra at large coverages.

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