Nur Syahirah Kamarozaman

Effect of Post-Deposition Annealing Process on the Resistive Switching Behaviour of TiO2 Thin Films by Sol-Gel Method

The paper presents the memristive behaviour of spin-coated titania thin films on ITO substrate. The sample was annealed in air ambient at different annealing temperature and duration of 250 and 450 °C for 20 and 60 min. The effect of post-annealing process to the physical thickness and crystallinity of the films towards switching behaviour was studied. It was found that the thickness and crystallinity of the films increases as the post annealing process increases. Sample annealed at 250 °C for 20 min with thinner film showed better switching behaviour even though the sample is still in amorphous form. Thus, in our work, we believed that the crystallinity of the films does not affect the switching behaviour of the sample. The reliability of device performance was studied by repeating the measurement for three times.

Sputtered titanium dioxide thin film for Extended-Gate FET sensor application

This paper presents an investigation on sputtered titanium dioxide (TiO2) thin film for application in the Extended-Gate Field Effect Transistor (EGFET) sensor application for pH detection. The TiO2 thin film was fabricated on conductive indium-tin oxide (ITO) covered glass by using RF Sputtering method. An EGFET proof-of-concept setup was constructed using a commercial FET as the transducer and the TiO2/ITO structure was used for the extended gate. The sensor measurement was taken using semiconductor device parametric analyzer, constant-current constant-voltage biasing interfacing circuit and data logger to obtain the sensitivity and the characteristics for output voltage with respect to time. TiO2 thin film on ITO glass as the sensing membrane was compared with a bare ITO glass substrate for the extended gate. The TiO2/ITO glass exhibited the sensitivity of 42.1 mV/pH and good linearity of 0.9997 in the sensing range pH4, pH7 and pH10 which was better than the bare ITO glass sensitivity of 31.3 mV/pH and the linearity of 0.9868.

Annealing temperature dependence of resistive switching behavior for sol-gel spin coated zinc oxide thin films

This work focuses on the resistive switching behavior of sol-gel spin coated zinc oxide (ZnO) thin films on ITO substrate. The deposited ZnO thin films were annealed at various temperatures from 300°C to 500°C in a furnace for 60 minutes in order to study the effect of annealing temperature on the resistive switching behavior of ZnO thin film. The electrical property of the thin film was characterized using 2-point probe current-voltage (I-V) measurement. The surface morphology and film thickness were examined and measured using atomic force microscopy (AFM) and surface profiler respectively. The I-V characteristic showed that the heat treatment on the ZnO thin films at 300 and 400°C resulted in the resistive switching characteristic behavior. Further increasing the temperature up to 500°C on the other hand leads to the formation of asymmetrical hysteresis loop.

Memristive Behavior of TiO2 Nanostructures Grown at Different Substrate Positioning by Immersion Method

In this paper, the physical characteristics and memristive behavior of TiO2 nanostructures grown at different substrate positioning by wet chemical solution were investigated. TiO2 thin film as a seed layer for TiO2 nanostructures growth was first deposited on ITO-coated substrate by RF magnetron sputtering method. TiO2 nanostructures were then grown by immersing the TiO2 thin film/ITO/glass sample in 10M NaOH solution at 80 °C while studying the effect of the substrate position to the nanostructure growth and thus its memristive behavior. Characterization on the growth morphology of TiO2 nanostructures was observed using scanning electron microscopy (FESEM). The current-voltage (I-V) measurement of the device was investigated for its memristive behavior. Different growth morphology of TiO2 nanostructures was observed at different substrate positioning. It was found that sample immersed with TiO2 layer facing down the vessel result in the formation of TiO2 nanowires and exhibit better memristive behavior.

Effect of TiO2 Seed Layer Thickness to the Growth of TiO2 Nanostructures by Immersion Method for Memristive Device Application

TiO2 nanostructures were successfully grown on TiO2 thin film by solution-based method at low temperature. TiO2 thin film as a seed layer for the nanostructures growth was deposited on ITO substrate by RF magnetron sputtering method at 40 and 60 nm thicknesses. Then the TiO2 nanostructures were synthesized on the samples by keeping them floating with TiO2 layer facing down the vessel in 10M NaOH solution at 80°C for 45 min. Effect of seed layer thickness to the growth of TiO2 nanostructure and its memristive behaviour were investigated. Surface morphology and current-voltage measurement for its memristive behaviour were measured by FESEM image and Keithley 4200 semiconductor characterization system. It was found that 60 nm-TiO2 thin film result in the formation of dandelion-like morphology of TiO2 nanowires and gives better memristive behavior with larger switching loops when positive voltage was applied to the sample.

Memristive behavior of HF-etched sputtered titania thin films

This paper demonstrates the fabrication method and reports the essential physical characterization of a memristive device with TiO2 or titania as an active layer. The memristive device was fabricated on glass substrate. Titania thin films were grown in two layers by RF-magnetron sputtering technique onto the substrates. The first layer is a titania layer etched by 1% HF (Hydrofluoric acid) before the deposition of the second layer. The etching time was varied; for 5 seconds and 7 seconds. Current-voltage (I-V) curves of the samples were measured from the voltage loop ranging from 0V to -5V, -5V to 5V then back to 0V and also from -5V to 5V then back to -5V. It was proven that the HF-etch give an improvement in the memristive behavior when it is etched at 7 s.

Switching behavior of lateral-structured zinc oxide-based memristive device

Lateral-structured zinc oxide (ZnO) based memristive device was studied. The effect of oxide and electrode size variations on the switching behavior was investigated. The lateral structure was formed by depositing the metal electrodes at the right and left ends of a glass substrate. The ZnO thin films were deposited right at the center of the metal coated substrate using sol-gel spin coating technique. The oxide and electrode widths were varied. It was observed that using the smallest oxide width in the combination with wide electrode size resulted in better memristive behavior. The values of both on and off resistances (RON and ROFF) were found to be decreased as the width of the electrode increasing. The hysteresis curve on the other hand became wider with the increases of electrode width. The ROFF/RON ratio was calculated to be 1.044.