Fabrication and Characterization of ZnO Langmuir-Blodgett Film and Its Use in Metal-Insulator-Metal Tunnel Diode

Metal-insulator-metal tunnel diodes have great potential for use in infrared detection and energy harvesting applications. The quantum based tunneling mechanism of electrons in MIM (metal-insulator-metal) or MIINI (metal-insulator-insulator-metal) diodes can facilitate rectification at THz frequencies. In this study, the required nanometer thin insulating layer (I) in the MIM diode structure was fabricated using the Langmuir-Blodgett technique. The zinc stearate LB film was deposited on Au/Cr coated quartz, FTO, and silicon substrates, and then heat treated by varying the temperature from 100 to 550 degrees C to obtain nanometer thin ZnO layers. The thin films were characterized by XRD, AFM, FTIR, and cyclic voltammetry methods. The final MIM structure was fabricated by depositing chromium/nickel over the ZnO on Au/Cr film. The current voltage (I-V) characteristics of the diode showed that the conduction mechanism is electron tunneling through the thin insulating layer. The sensitivity of the diodes was as high as 32 V-1. The diode resistance was, similar to 80 Omega (at a bias voltage of 0.78 V), and the rectification ratio at that bias point was about 12 (for a voltage swing of +/- 200 mV). The diode response exhibited significant nonlinearity and high asymmetry at the bias point, very desirable diode performance parameters for IR detection applications.