![]() An air gap, instead of a solid dielectric, provides minimal capacitive coupling between the bridge and the 2D electron gas (2DEG) in the quantum well underneath, for a given gap height. We require the gates to be electrically connected while keeping the potential in the 1D channel as uniform as possible along its whole length. Each device consists of a large number of identical channels organized into multiple sets of parallel wires to enhance the tunneling current. A 1D electron channel is formed underneath the narrow region between each pair of metallic gates when they are negatively biased. The substrate is a GaAs/AlGaAs heterostructure that contains two parallel quantum wells separated by a 14 nm-thick tunnel barrier, which allows electron tunneling. Figure 1(a) demonstrates the geometry of the array under a scanning electron microscope (SEM). The development of our air-bridge technique was motivated by the need to fabricate arrays of 1D channels in order to study the exotic properties of electron-electron interactions, specifically regarding non-Fermi-liquid behavior and the Luttinger liquid model. hence making it unsuitable for dense sub-micron patterns. ![]() Brewer, in Electron-Beam Technology in Microelectronic Fabrication (Īcademic Press, 1980). ![]() One drawback of cross-linking, however, is that it is susceptible to pattern distortion due to swelling of the resist, 12 12. Photo-resist can be partially cross-linked and later removed to form an air gap below the bridge. While NIL simplifies repeated fabrication, its complexity is unsuitable for rapid iteration of research prototypes. for example, demonstrated a process with nanoimprint lithography (NIL) for monolithic microwave integrated circuits with air-bridges. Various methods have been employed for the fabrication of these bridges: Li et al., 10 10.ħ8, 3322 (2001). Here, however, even though workable techniques have already been proposed in the literature, their significant degree of complexity means that, in practice, they are still rarely used. where the bridge played a crucial role in connecting a central gate while leaving the interference path undisturbed, and superconducting microwave circuits based on coplanar waveguides, where the use of bridges prevents the propagation of parasitic modes, hence reducing the amount of loss and decoherence. Air-bridge structures have also been used in quantum-dot interference devices, 4–6 4.ĩ3, 121412 (2016). polymer resist (PMMA) has been used as a patterned insulator under metal bridges for studying quantum ring structures and antidots.
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