Single-phase Si1−x−yGexSny alloys with random diamond cubic structures are created on Si(100) via ultrahigh vacuum chemical vapor deposition reactions of SnD4 with SiH3GeH3 at 350 °C. Commensurate heteroepitaxy is facilitated by Ge1−xSnx buffer layers, which act as templates that can conform structurally and absorb the differential strain imposed by the more rigid Si and Si–Ge–Sn materials. The crystal structure, elemental distribution and morphological properties of the Si1−x−yGexSny/Ge1−xSnx heterostructures are characterized by high-resolution electron microscopy, including electron energy loss nanospectroscopy, x-ray diffraction (rocking curves) and atomic force microscopy. These techniques demonstrate growth of perfectly epitaxial, uniform and highly aligned layers with atomically smooth surfaces and monocrystalline structures that have lattice constants close to that of Ge. Rutherford backscattering ion channeling shows that the constituent elements occupy random substitutional sites in the same average diamond cubic lattice and the Raman shifts are consistent with the lattice expansion produced by the Sn incorporation into SiGe tetrahedral sites.

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This paper describes the testbed telesurgery system that was developed in MIT's Human Machine Systems Laboratory. This system was used to investigate the effects of communication time delays on controller stability and on the performance of surgical tasks. The system includes a bilateral force-reflecting teleoperator system, interchangeable surgical tools, audio and video communication between the master and slave sites, and methods to generate time delays between the sites. To compensate for the time delays, various control schemes were investigated, leading to the development and selection of fuzzy sliding control (FSC). With a stable teleoperator system, experiments in performing a variety of surgical exercises were conducted. These looked at the performance of a team of a telesurgeon and local assistant given a number of different time-delay scenarios, including synchronous and asynchronous force and audio/video feedback. The results of the research project include the development of the novel FSC algorithm, data on how time delays degrade performance of surgical tasks, and recommendations on how telesurgery should be performed to accommodate telecommunication time delays.