Notes: We report spectroscopic ellipsometry (SE) studies on (Si)2(Ge)12, (Si)6(Ge)2, and (Si)12(Ge)2 short period superlattices (SLs) whose optical response has not been reported yet. Multilayer calculations enabled us to determine the dielectric response of the superlattice layers. We report the clear observation of splitting of the E2 peak in (Si)m(Ge)n superlattices contrary to the previous SE report that the separation was observed only in larger period SLs. © 1997 American Institute of Physics.

Notes: The determination of the above band gap optical properties of zincblende Cd1−xMgxTe (0≤x≤0.5) ternary alloys are reported on. Using the parabolic-band critical point model, room-temperature critical point energies of the E0, E0+Δ0, E1, E1+Δ1, E2, and E0′ interband transitions from numerically calculated second energy derivatives of ellipsometric spectra were obtained. The presence of two distinct structures in the E2 feature for x〉0 was also observed. © 1997 American Institute of Physics.

Notes: We report monolayer-by-monolayer epitaxy of GaAs at 650 °C using surface photoabsorption (SPA) to monitor growth. Our results show, as confirmed by photoluminescence measurements, the possibility of growing highly accurate quantum well heterostructures by metal–organic chemical-vapor deposition at conventional growth temperatures. In addition, we observe a continuous increase of the SPA signal during trimethylgallium exposure that cannot be explained by present growth models. © 1996 American Institute of Physics.

Notes: Nanoemulsions have recently become increasingly important as potential vehicles for the controlled delivery of cosmetics and for the optimized dispersion of active ingredients in particular skin layers. The preparation of conventional nanoemulsions requires mainly high-pressure homogenization, which is unproductive and requires high energy due to its lower efficiency, limiting their practical applications. In order to solve these problems novel nanoemulsions were studied using a model system of pseudo-ternary water/emulsifier/paraffin oil. Nanoemulsions were prepared by stirring a mixture of the tocopherol-containing block co-polymer emulsifier PPG-20 Tocophereth-50, paraffin oil, and distilled water at the Θ-point using weight fractions of the dispersed phase (φ) of 0.31 to 0.82 and an emulsifier content of 1.0 to 9 wt.%. The emulsifying property of PPG-20 Tocophereth-50 in nanoemulsions was compared with that of the conventional emulsifiers Tocophereth-43, a mixture of polysorbate 60 and sesquioleate (3/1), and phospholipids. Also the emulsifying property of PPG-20 Tocophereth-50 in the more hydrophilic oils caprylic/capric triglyceride and octyldodecanol was compared with that in paraffin oil. The stability and morphology of the resulting nanoemulsions were studied by visual inspection, optical microscopy, particle size analysis, and cryo-scanning electron microscopy. In the nanoemulsion systems containing caprylic/capric triglyceride and octyldodecanol, respectively, as an oil phase PPG-20 Tocophereth-50 showed emulsification properties similar to those in paraffin oil. The conventional emulsifiers Tocophereth-43, a mixture of polysorbate 60 and sesquioleate (3/1), and phospholipids did not give nanoemulsions with high-speed stirring. The block co-polymer nonionic emulsifier PPG-20 Tocophereth-50 was found to produce stable nanoemulsions of mean droplet diameters ranging from 204 to 499 nm. The emulsification method of high-speed stirring at the Θ-point using PPG-20 Tocophereth-50 was found to be very effective for the preparation of stable nanoemulsions useful for applications in skincare cosmetics, cosmeceuticals, and drugs.

Notes: Surface morphology characteristics and electron emission properties of boron-doped polycrystalline diamond thin films grown by microwave plasma-assisted chemical-vapor deposition were investigated using an ultra-high-vacuum scanning tunneling microscope. Small secondary grains with average size less than 10 nm were observed to be on top of the isolated crystal surfaces. The current imaging tunneling spectroscopy (CITS) study revealed that high electron emission occurred at some crystalline facets while others showed relatively no measurable electron emission. The CITS study at high magnification also indicated that the electron emission was initiated at the grain boundaries rather than at the top of the grains. This observation suggests that the electrons transport through the grain-boundary conductive channels and preferentially emit at the low electron affinity facets. © 1999 American Institute of Physics.

Notes: We report highly accurate dielectric function data for ZnTe. These data were made possible by the high quality of the heteroepitaxial material and the development of a chemical etching procedure for producing abrupt surfaces on ZnTe; they provided the first observation of the E0+Δ0 structure in ZnTe by spectroscopic ellipsometry and evidence for several contributions to the E2 structure. Accurate critical point energies were obtained by Fourier analysis. © 1997 American Institute of Physics.

Notes: The investigation of As desorption from the (001) InP during metalorganic chemical vapor deposition was performed using surface photoabsorption (SPA). The behavior of the monochromatic SPA signal showed a clear existence of a metastable state after the AsH3 was turned off. SPA spectra at each stable surface were taken to confirm the interpretation. This result indicates that the previous criterion to measure the amount of As/P exchange reaction is not necessarily correct and that the As-desorption process should be understood as a two-step process. © 2002 American Institute of Physics.

Notes: We examine various ZnSe spectra to obtain that which best represents the dielectric response ε of ZnSe. The measured evolution of pseudodielectric function 〈ε〉 data with chemical etching shows that the natural overlayer on ZnSe can be modeled accurately only if we assume that it contains amorphous Se. Hence previous assumptions made in correcting 〈ε〉 mathematically are not correct, and data obtained on stripped samples yield the best representation of ε. © 2000 American Institute of Physics.