Acquisition of an Ultrahigh Vacuum Scanning Tunneling Microscope for the Study of Surface Chemistry and Surface Physics

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0079796McEllistremThe scanning tunneling microscope has done much to broaden our understanding ofSemiconductors and metals, providing a unique view of material surfaces available by noother technique. Specifically, the microscope's ability to resolve individual surfaceatoms has lead to an improved understanding of the chemistry and physics of solidsurfaces. How a chemical reaction proceeds on a surface, or how different surface atomsdiffuse, segregate, or combine can be literally watched on an atomic scale. The awardedinstrument will be used to investigate the formation of metal silicides on silicon, sincemetal/semiconductor interfaces continue to impact device fabrication. At a morefundamental level, understanding the processes that lead to metal silicide formation willallow the controlled formation of nanoscale particles, particles that are driven to self-assembleby their reactivity. The instrument will also be used to investigate how reactions proceed on gallium nitride (from which electro-optic devices that emit in the blue/violet can be made). In particular, the dynamics of hydrogen on the gallium nitride surface is of technological interest, and can also be used as a probe of local surface reactivity. Since gallium nitride surfaces are also polar (N- vs. Ga-terminated), the impact of surface polarity on surface reactions will also be studied.Semiconductors are widely used in electronic and electro-optic devices. Nearly allcomputer chips, for example, are fabricated from silicon. Compound semiconductors(the so-called III-V semiconductors) are often found in devices which convert electricalenergy into light, namely light-emitting diodes, found in nearly all consumer electronics,and laser diodes, which form the heart of a solid state laser, the engine in laser printers and compact disc players. Research into semiconductors has lead to the development of faster, smaller computer chips (and thus computers), and novel electro-optic devices. The scanning tunneling microscope has done much to broaden our knowledge of semiconductors and metals, providing a unique view of material surfaces unavailable by any other technique. Specifically, this microscope is capable of attaining atomic resolution images of surfaces. With it, surface physics and chemistry can observed on an atomic scale. In short, how atoms move and distribute themselves on a surface, or how a chemical reaction proceeds on a surface, can be imaged directly with a scanning tunneling microscope. The awarded instrument will be used to further our understanding of how metals interact with silicon, and to investigate the surface chemistry of novel semiconductor materials used in electro-optic applications.