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Notes: The interaction of molecular sulfur with the GaAs(100) surface has been investigated by reflectance anisotropy spectroscopy (RAS). The use of arsenic-capped GaAs(100) surfaces provided a means to study the interaction of sulfur with both the arsenic-rich (2×4) and gallium-rich (4×1) surface reconstructions. A sulfur flux was generated in ultra-high-vacuum (UHV) by the thermal decomposition of silver sulfide. The room-temperature deposition of a 1–2 monolayer saturation coverage of sulfur on both arsenic- and gallium-rich surfaces produces a (1×1) low-energy electron-diffraction pattern. This surface displays a strongly anisotropic optical response with RAS spectra which contain two clear features at 3.5 and 5.2 eV. These features become more pronounced as the sulfur-covered surface is annealed up to 500 °C where the surface displays a (2×1) reconstruction. The origin of these spectral features is believed to be due to optical transitions related to the sulfur dimers which are formed on this surface. The extent of the reduction in surface band bending induced by the sulfur coverage can be monitored by measuring the magnitude of the linear electro-optic feature which appears prominently in the RAS spectra of high-doped GaAs samples. © 1995 American Institute of Physics.

Notes: In this paper it is demonstrated that Raman spectroscopy can be used for in situ online monitoring of semiconductor layer growth. For this purpose an ultra-high-vacuum chamber was designed to suit molecular beam epitaxial growth as well as simultaneous optical measurements utilizing a multichannel detection Raman system. As a result Raman spectra can be taken while growth progresses. As shown by the example of InSb growth, they provide information on the interface chemistry, crystal quality of the growing layer, and the growth mode as well.

Notes: Synopsis Assessing accurately the pH of axillary eccrine sweat is of vital importance in the antiperspirant industry. Eccrine sweat pH is a critical parameter in determining the effectiveness of antiperspirants; antiperspirant salts dissolve in sweat and diffuse into the sweat glands, where the resultant acidic solution hydrolyses in more alkaline sweat forming an amorphous metal hydroxide gel, thereby restricting the flow of eccrine sweat. Comparison of the skin surface and sweat pH of males and females reported in the literature shows that, although consistent male/female differences have been observed on the forearm, determination of significant gender-based pH differences across other sites are less conclusive. Studies on the back and infra-mammary regions exhibited significant gender differences in skin surface pH, whereas those on the forehead, cheek, neck and inguinal area showed no such difference. With regard to the axilla specifically, four studies have been reported, three showing no significant difference in axillary skin surface pH and one indicating that females have an eccrine sweat pH of 7 and males have a sweat pH of 5.6.This paper describes a series of carefully controlled studies aimed at assessing potential gender differences in eccrine sweat and skin surface pH following exposure to a variety of temperature, humidity and time conditions. The results highlight the importance of controlling precisely the time of investigation, site of measurement and, most importantly, the necessity to pre-equilibrate samples in 40 mmHg carbon dioxide (equivalent to arterial CO2 tension (pCO2)) before determining sweat pH. When these parameters are controlled no gender differences in axillary sweat or skin surface pH are observed. Large differences in eccrine sweat and skin surface pH are found, however, between the vault (hairy region) and fossa (non-hairy region) of the axilla. Résumé La détermination précise du pH de la sueur au niveau des aisselles est de première importance dans l’industrie des antitranspirants. Le pH de la sueur est un paramètre clef affectant l’efficacité des produits antitranspirants; ceux-ci agissent par diffusion d’une solution d’actifs antitranspirants dans les glandes sudoripares où ils sont hydrolysés et forment un gel amorphe d’hydroxyde métallique limitant ainsi le flux de transpiration. Une comparaison des données publiées dans la littérature sur le pH de la peau et de la sueur chez les hommes et les femmes, révèle que bien que des différences hommes/femmes aient été observées de façon consistente sur l’avant-bras, la différenciation par sexe est moins marquée pour les autres parties du corps. Les études sur le dos et les régions infra-mammaires montrent des différences significatives du pH de la peau; en revanche, celles sur le front, les joues, le cou et la région inguinale ne font apparaitre aucune différence. En ce qui concerne les aisselles, sur quatre études publiées, trois ne montrent aucune différence significative de pH de la sueur et la quatrième indique un pH de 7,0 pour les femmes et de 5,6 pour les hommes, soit une concentration en ions H+ 10 fois plus élevée chez les hommes.Cet article décrit une série d’études méticuleusement controllées visant àévaluer les différences hommes/femmes du pH de la sueur et de la peau en fonction des conditions de temperature, d’humidité et de temps d’exposition. Les résultats démontrent l’importance du contrôle de la durée et du site de mesure et plus particuliérement la nécessité de pré-équilibrer les échantillons à 40 mmHg de dioxide de carbone (équivalent à la tension artérielle de CO2 (pCO2)) avant la mesure de pH. Lorsque ces paramètres sont contrôlés, aucune différence de pH n’est observée entre hommes et femmes au niveau de l’aisselle, ni pour la sueur, ni à la surface de la peau; cependant, des différences importantes sont observées entre la voûte (région pileuse) et la fosse (région non pileuse).

Notes: Low-temperature hydrophobic bonding is an enabling technology allowing the fabrication of device structures. Current research into improvement of hydrophobic bonding has focused on the elimination of thermally generated voids. It has been observed that a regular grid etched into the bonding interface can eliminate the thermally generated voids. By manipulation of patterns etched into the bond interface, it was possible to ascertain that the diffusion of interfacial gasses that form the thermally generated voids is enhanced along the 〈110〉 directions. This is shown by an analysis of the void density at various locations in relation to the etched trenches at the bonded interface. Void density between trenches is shown to be 12% of the void density near trenches but nto along a 〈110〉 direction.