The preparation of flat H–Si(111) surfaces in 40% NH4F revisited

The reasons why ideally flat H–Si(111) surface can be prepared by NH₄F etching are investigated from correlation between AFM observations and experimental conditions used for etching. It is shown that pitting may be completely suppressed if a one side polished wafer is immersed in an oxygen free solution. An analytical electrochemical study of the (111) and rough face of the same n-Si wafer is presented to yield insight into observations.     

Single-step electrochemical nanolithography of metal thin films by localized etching with an AFM tip

This work introduces electrochemical nanolithography (ENL), a single-step method in which a metal thin film is locally etched without application of a mask on a 100?nm length scale with an electrochemical atomic force microscope (AFM). The method requires the application of ultra-short voltage pulses on the tip (nanosecond range duration, 2-4?V amplitude), while both the sample and the metalized tip are under independent potentiostatic control for full control of interface reactions in an AFM electrochemical cell. It is demonstrated that Cu films as well as Co and Cu/Co sandwich magnetic films can be patterned if negative voltage pulses are applied to the tip. This method also applies to films deposited on an insulating substrate. Moreover the lateral dimension of lithographed structures is tunable, from a few micrometers down to 150?nm, by appropriate choice of ENL conditions. Simulation of the dissolution process is discussed.     

Semiconductor electrode modifications: influence on the state distribution at the interface

Surface modifications including a surface preparation (etching, photoetching …) followed by electrodeposition of a discontinuous metal film are presented. Photocapacitance spectra and surface observations reveal that such a procedure is equivalent to modify both the energy and the spatial distribution of the interface states in the case of Pt and Ru.     

Modeling Methods for Reusable and Interoperable Virtual Entities in Multimedia Virtual Worlds

Virtual Worlds are facing several challenges to become a mature technology commonly used in their numerous potential applications such as games, training, education, health and collaborative work. Main challenges are the introduction of multimedia in virtual worlds and the decrease of the cost and the required time for their design, which remains an empirical process. This paper proposes a methodology for introducing multimedia and decreasing the cost and needed time. The main interest of the proposed methodology is to provide virtual worlds with multimedia, interoperability and reusability properties. Interoperability enables virtual entities belonging to virtual worlds independently designed (i.e., no prior explicit agreement exists between theirs respective designers) to interact with each others. Reusability enables virtual worlds designers to use a virtual entity pattern initially designed for a virtual world A to be used in the design of a new virtual world B. The originality of this methodology relies on multiagent concepts and learning techniques for avoiding prior complex specifications tasks to achieve interoperability and reusability of multimedia virtual entities in virtual worlds.