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

Abstract

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 MIIM (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 °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 ∼80 Ω (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.

Oxides for Rectenna Technology

“…Other oxides that have been considered for inclusion in MIM diodes include ZnO [81,82], V 2 O 5 [20,83], SiO 2 [84,85], Nb 2 O 5 [86,87], CuO [8], TiO 2 [69], Cr 2 O 3 [88], HfO 2 [89] and Sc 2 O 3 [90]. A simple process for fabricating planar-type MIM tunneling diodes using electron beam writing and a boiling water oxidation process has been proposed, achieving high diode sensitivity of −31 V −1 for Poly Si/PolySi [85] and −14.5 V −1 for PolySi/Au electrodes [84] but too high R 0 .…”

“…These features have made ALD the most compatible insulator deposition technique in MIM fabrication. In addition, some other techniques have also been investigated for oxide deposition in MIM diodes, such as Langmuir-Blodgett [63,82]. Although this method facilitates easy and low-cost oxide deposition with appropriate thickness control, it has been mostly used to fabricate organic material-based insulator films [29].…”

Unique supramolecular assembly through Langmuir – Blodgett (LB) technique

“…Various metals have been deposited onto cadmium stearate (CdSt 2 ) LB films to have metal-insulator-semiconductor (MIS) structures [104]. LB films of ZnO has been used to fabricate metal-insulator-metal tunnel diode [105]. This types of diodes have great potential for use in infrared detection and energy harvesting applications.…”

Quantum‐Tunneling Metal‐Insulator‐Metal Diodes Made by Rapid Atmospheric Pressure Chemical Vapor Deposition

“…Some deposition processes have been introduced to fabricate thin films at atmospheric pressure for nanoelectronic devices that utilize quantum phenomena. Thermal and anodic oxidation, for example, have been used to grow thin CrO x and Nb 2 O 5 films on Cr and Nb layers for MIM diodes; atmospheric pressure metal organic vapor phase epitaxial growth (AP‐MOVPE), or atmospheric pressure metal organic chemical vapor deposition (AP‐MOCVD), has been used to fabricate InGaAsP multiquantum‐well structures for optical devices; the Langmuir Blodgett technique was used to deposit a ZnO film for a MIM diode; and a chemical vapor deposition (CVD) furnace operated at atmospheric pressure has been used to deposit a TiO 2 film in a tunneling transistor . The need for high temperatures, specific metal films for oxidation, and complex compound precursors in these techniques, as well as challenges in reproducibility, highlight the need for new methods to reliably deposit enabling films for cost‐effective quantum devices.…”