X-ray photoelectron spectroscopy reveals that the remarkable electronic quality of GaAs/sulfide interfaces can be ascribed to the formation of AsxSy phases which grow on an oxide-free GaAs surface. While one of these phases is akin to As2S3, another shows significant in-plane S—S bonding. Raman experiments indicate that the band bending on this disulfide- terminated surface has been reduced to 0.12 eV.

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We present Raman scattering data from GaAs samples whose surfaces had been treated with thin films of sodium sulfide nonahydride (Na2S⋅9H2O). Raman scattering provides a quantitative, contactless means of measuring the reduced barrier height associated with decreased density of GaAs surface states. For GaAs samples doped at levels of n≊1018 cm−3, the barrier height is reduced to 0.48±0.10 eV.

The analysis of local crystal orientation with micron spatial resolution is of prime importance in understanding the dynamics of crystal growth processes with potential for device applications. Examples of such processes are laser annealing, lateral epitaxial growth over oxides, and molecular-beam-epitaxial growth over structured substrates. We present here a nondestructive technique for obtaining such information based on polarization selective Raman scattering from near-diffraction limited O(1 μm) regions of the sample. Depth resolution is limited by the optical penetration depth at the laser wavelength, which is on the order of 1.0 μm for Si at visible wavelengths. By rastering the sample with respect to the probe laser beam, maps of the local crystal orientation can be obtained. Abrupt changes in crystal orientation at grain boundaries are readily apparent. This paper details the experimental apparatus and the method for extracting local crystal orientation information for the particular case of Si. Experiments on single crystals of known orientation are presented which confirm our theoretical predictions and serve to calibrate the technique. Practical examples of mapping of laser annealed silicon-on-oxide structures are given. The analysis shows the loss of the lateral epitaxial seed, with many grains exhibiting 〈110〉 surface normals, in agreement with qualitative results obtained from a destructive selective chemical-etching procedure. Signal intensities are such that orientation information at a single point can be recorded in less than 30 s, thus providing the potential for a real time in situ monitor of slow growth processes.

We have grown YBa2Cu3O7−x-PrBa2Cu3O7−y heterostructures with the perovskite a axis normal to the surface of a variety of (001) oriented substrates using the pulsed laser deposition technique. X-ray diffraction studies indicate little or no formation of the traditional c-axis normal orientation usually nucleated on these substrates, while ion channeling, transmission electron microscopy (TEM), and Raman scattering studies reveal a highly ordered crystalline structure similar in quality to that obtained in the best c-axis oriented films. Superconducting transition temperatures, for current transport in the plane of the films, consistently exceed 80 K, but are probably lower than the optimum 92 K transition expected for YBa2Cu3O7−x due to the presence of growth twin boundaries between grains with the c axis oriented along the two substrate directions.