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.

Thin film metal–insulator–metal (MIM) diodes have attracted significant attention for use in infrared energy harvesting and detection applications. As demonstrated over the past decades, MIM or metal-insulator-insulator-metal (MIIM) diodes can operate at the THz frequencies range by quantum tunneling of electrons. The aim of this work is to synthesize required ultra-thin insulating layers and fabricate MIM diodes using the Langmuir-Blodgett (LB) technique. The nickel stearate (NiSt) LB precursor film was deposited on glass, silicon (Si), ITO glass and gold coated silicon substrates. The photodesorption (UV exposure) and the thermodesorption (annealing at 100 °C and 350 °C) methods were used to remove organic components from the NiSt LB film and to achieve a uniform homogenous nickel oxide (NiO) film. These ultrathin NiO films were characterized by EDS, AFM, FTIR and cyclic voltammetry methods, respectively. The MIM diode was fabricated by depositing nickel (Ni) on the NiO film, all on a gold (Au) plated silicon (Si) substrate. The current (I)-voltage (V) characteristics of the fabricated diode were studied to understand the conduction mechanism assumed to be tunneling of electron through the ultra-thin insulating layer. The sensitivity of the diode was measured to be as high as 35 V-1. The diode resistance was ∼100 ohms (at a bias voltage of 0.60 V), and the rectification ratio was about 22 (for a signal voltage of ±200 mV). At the bias point, the diode response demonstrated significant non-linearity and high asymmetry, which are very desirable characteristics for applications in infrared detection and harvesting.

The scouring and bleaching performance of conventional process (hydrogen peroxide, sodium hydroxide), was compared to that of enzymatic process using enzyme (arylesterase) which catalyst the discontinuous peroxide reaction. The whiteness and reflectance% indicating bleaching performance and absorbency and weight loss % was used as a measure of the scouring performance. Comparison of these performance and the effects are analyzed by using graphical representation. The weight loss% of enzymatic process was less than conventional process. In conventional process the reflectance % and absorbency increased and whiteness decreased with the increasing of concentration of caustic soda and the aforementioned properties were increased with the increasing of concentration of H2O2. In enzymatic process the reflectance % of cotton fabric increased and whiteness and absorbency fluctuated with the increasing of concentration of enzyme. Meanwhile reflectance %, absorbency and whiteness increased with the increasing of concentration of hydrogen peroxide. Enzymatic process was found eco-friendly process as it was occurred in neutral pH and the COD of this process was less than conventional process. It was found that the enzymatic process was superior to the conventional process under the conditions studied. Keywords: Scouring, bleaching, conventional, enzymatic pretreatment.