The basic structure of the nanowire devices is based on a sandwich geometry in which a nanowire (n-type zinc oxide) is placed between the substrate (heavily doped p-type silicon) and a top metallic contact, using spin-on glass as an insulating spacer layer to prevent the metal contact from shorting to the substrate (as shown in (a) and (b)). This allows for uniform injection of current along the length of the nanowire. A finished wafer using the team's method is shown in (c), with a typical device shown in (d). Note that a stray nanowire intercepts the device on the upper part of (d). The oval feature surrounding the stray nanowire is due to the varying thickness of the spin-on glass film. When a voltage is applied to this device, it emits ultraviolet light (as shown in image (e) obtained with a CCD camera) with a peak wavelength of ~380 nm.

Courtesy of the lab of Federico Capasso, Harvard School of Engineering and Applied Sciences