Fabrication process for cantilevers with integrated tunnel junctions

Abstract

The authors have developed a process for making submicron cantilevers, clamped beams, and more complicated electromechanical structures that carry integrated electrical leads. Such objects are useful as test structures for measuring the electrical properties of molecular sized objects, as high frequency electromechanical components for radio frequency and microwave applications, and as sensor components for studying fluctuations in small systems. Their process uses two realigned electron beam lithography steps, a thin-film angled deposition system, and differential removal of sacrificial aluminum layers to produce freely suspended submicron electromechanical components. The authors have produced cantilevers and beams on a variety of substrates (silica, silicon, and polyimide) and have produced insulating, conductive, and multilayer electromechanical structures. The process allows the use of essentially any material that can be deposited from a thermal or electron-beam deposition source. The authors have integrated mechanically adjustable gold-vacuum-gold contacts onto the cantilevers and have demonstrated vacuum tunneling. The behavior of these contacts indicates an exponential dependence on tunneling gap. The authors have demonstrated electrostatic control over the tunnel gap spacing as well.